MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
AUGUST, 2003
Part 1
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
SPECIAL NOTE: The August summary is being disseminated in two install-
ments. This first part covers tropical cyclones forming during the
first half of the month in all basins, plus contains the Feature of the
Month. The second installment will cover storms forming during the
latter half of the month.
*************************************************************************
AUGUST HIGHLIGHTS
--> Bermuda struck by most intense hurricane in many decades (actually
in early September)
--> Strong tropical storm strikes northeastern Mexico
--> Category 2 hurricane strikes southern Baja California Peninsula
--> Hurricane threatens Hawaii but passes to south
--> Northwest Pacific active with four typhoons--several Asian nations
adversely affected
*************************************************************************
***** Feature of the Month for August *****
INDIVIDUAL MONTHLY FORECASTS
FOR SEPTEMBER AND OCTOBER
----------------------------
Last month I highlighted a technique developed by Eric Blake
for forecasting Atlantic tropical cyclone activity for the month
of August. This month's feature concerns similar forecasts for
the months of September and October developed by Philip Klotzbach,
a research associate at Colorado State University (CSU) and
currently a member of the CSU forecast team headed by Dr. William
Gray. Over the past 20 years Dr. Gray and his team have issued
seasonal forecasts for the Atlantic basin which have shown considerable
skill at predicting overall seasonal activity at lead times varying
from 3 to 10 months. However, significant month-to-month and multi-
week variability exists within most seasons. Very active hurricane
seasons may contain periods of 2-4 weeks with little activity, while
inactive years can exhibit short periods in which the tropics are
quite busy.
The monthly feature for July included several examples of this
intraseasonal variability, so those won't be repeated here. Also,
in the June summary's monthly feature, definitions can be found
for the terminology employed in the CSU forecasts (e.g., NS, H, IH,
NSD, HD, IHD, NTC).
The success of Eric's initial August forecast in 2000 prompted
Phil to investigate the feasibility of similar forecasts for the
months of September and October. No formal forecast was made
in 2001, but a statement was included in the early August, 2001,
CSU forecast release to the effect that September of 2001 would
likely experience above-normal activity. And since October tropical
cyclone activity tends to correlate well with September activity,
Phil indicated he felt that October, 2001, would also be an active
month in the tropics. Those general forecasts verified quite well:
September's NTC was 58% and October's was 28%, well above the average
NTC values for the two months of 48% and 17%, respectively. (See the
URL: <http://hurricane.atmos.colostate.edu/Forecasts/2001/aug2001/> )
September is the most active month for tropical activity in the
Atlantic basin with an average of almost 50% of the annual NTC
occurring during the month. Phil based his prediction scheme for
forecasting September tropical cyclone activity on reanalysis data
from the National Centers for Environmental Prediction and the National
Center for Atmospheric Research (NCEP/NCAR). Based on hindcasting
results from 1950-2000, from 30-75% of the variance of most tropical
cyclone parameters can be hindcast by the end of July, with this
hindcasting skill improving to 45-75% by the end of August. Simple
least-squares linear regression techniques were utilized to calculate
hindcast skill, and variables were selected that explained the
largest degree of variance when combined with the other predictors
in the scheme.
With regard to October-only forecasts, the approach is somewhat
different. Utilizing the NCEP/NCAR reanalysis data, four predictors
were found which, in combination, explained about 50% of the variance
of October NTC. However, no combinations of predictors has yet been
identified which can explain large amounts of variance in the
individual tropical cyclone parameters (NS, NSD, etc). So the
procedure for the October, 2003, forecast was to forecast the overall
NTC and then adjust the other parameters accordingly.
The predictors used tend to be global in nature and include zonal
and meridional winds at 200 and 1000 mb and sea level pressure
measurements at various global locations. Many of the predictors
are strongly correlated with global modes such as ENSO and the
Pacific Decadal Oscillation (PDO). As was the case in describing
Eric's August-only forecast scheme last month, the details of Phil's
prediction schemes are better described with graphics, and charts
and tables giving much more information may be found at the following
links on the CSU website:
<http://hurricane.atmos.colostate.edu/Forecasts/2002/aug2002/>
<http://hurricane.atmos.colostate.edu/Forecasts/2002/sep2002/>
<http://hurricane.atmos.colostate.edu/Forecasts/2003/aug2003/>
<http://hurricane.atmos.colostate.edu/Forecasts/2003/sep2003/>
<http://hurricane.atmos.colostate.edu/Forecasts/2003/oct2003/>
The full paper on the September-only forecast scheme will be
published sometime in 2004 in _Weather and Forecasting_. Phil
sent me a copy of this highly interesting document, which is very
detailed, in .pdf format, and he has indicated he would be happy
to e-mail a copy to any interested person who would like to have
one. Phil can be reached at: philk@atmos.colostate.edu .
The remainder of this article will focus on the specifics of
Phil's September forecast for 2002, and his September and October
forecasts for 2003. Since data through the end of July is needed
for the August forecast, only one August-only forecast can be
issued each year. However, two September-only forecasts are made,
the first utilizing data through the end of July, and the second
based upon data collected through August. In a similar fashion,
three October-only forecasts are issued: one in early August, one
around 1 September, and another around 1 October.
The forecasts issued for September, 2002, as well as the observed
statistics, are presented in the following table:
FORECASTS AND VERIFICATION FOR SEPTEMBER, 2002
Parameter 1 Aug Forecast 1 Sep Forecast Observed
------------------------------------------------------------------
NS 3 3 8
NSD 18 13 37.25
H 2 2 4
HD 6 7 8
IH 1 1 1
IHD 2 2 1.75
NTC 30 26 56
The activity was significantly underforecast, but September of
2002 presented a particularly difficult situation to have forecasted
accurately. With an El Nino in place and some additional negative
atmospheric variables present, the 2002 Atlantic season had been
rather quiet through the end of August (4 generally short-lived NS
and no hurricanes), and indications were that this quiet trend would
continue. However, things turned around abruptly in September. The
total of 8 NS was the highest ever observed to develop in any calendar
month, and conditions during the middle and latter portions of the month
resembled a more typically active Atlantic season with the formation of
intense Caribbean and Gulf of Mexico hurricanes Isidore and Lili.
Also, the extremely long-lived Kyle added more than 15 days to the
NSD total.
No forecast was made for October in 2002, but the early August
forecast release contained an implicit forecast for the October-
November period for an NTC of 12%. This was obtained by taking the
seasonal forecast parameters for the remainder of the season after
1 August, and simply subtracting the forecast values for August
and September. The NTC for the final two months of the hurricane
season was further reduced to 8% on 1 September. The NTC for October
of 2002 was 17%--exactly average--but the month produced no tropical
cyclones. All the NTC was generated by Hurricane Lili and Tropical
Storm Kyle, both inherited from September.
The following table contains the September-only forecasts and
verification for September, 2003 (based on operational intensities):
FORECASTS AND VERIFICATION FOR SEPTEMBER, 2003
Parameter 1 Aug Forecast 1 Sep Forecast Observed
------------------------------------------------------------------
NS 4 4 4
NSD 14 18 29
H 2 2 3
HD 6 11 22.25
IH 1 1 1
IHD 1.25 6.5 13.5
NTC 33 55 92
The September NTC was once again underforecast, but also once again
there was an anomalous occurrence which would have been very difficult
to have predicted. It is very unusual to see two intense hurricanes
exist for as long as did Fabian and Isabel. The two storms together
generated 14.75 IHD (Hurricane Fabian was an IH for 1.25 days in
August). Those two great hurricanes alone generated an NTC of 95%!
However, Phil's forecast for the numbers of storms (4 NS, 2 H, 1 IH)
was almost exactly on target, spoiled only by Kate's six hours of
hurricane intensity early on 30 September.
The following table summarizes the three October-only forecasts
along with the observed October activity (based on operational
intensities):
FORECASTS AND VERIFICATION FOR OCTOBER, 2003
Parameter 1 Aug Fcst 1 Sep Fcst 1 Oct Fcst Observed
------------------------------------------------------------------
NS 3 3 3 3
NSD 12 12 19 21.5
H 2 2 2 0
HD 6 6 7 5.5
IH 0 1 0 1
IHD 0 1 0 1.5
NTC 19 30 21 29
The situation in October was a little odd. None of the three
named storms which actually formed in the month reached hurricane
intensity, but Kate (which had briefly reached hurricane intensity
in September but weakened) regained hurricane intensity early in
October and was a hurricane for 5.5 days. However, under the rules,
Kate counts as a September hurricane. But since it initially
reached Category 3 status in October, it counts as an October IH.
So the 1 September forecast for October was right on target, but
the final update on 1 October was still fairly good in that it
forecast above-normal tropical cyclone activity for the month.
It is to be expected that as more experience is gained, the
quality of the individual monthly forecasts will improve. And if
the monthly forecasts for the three primary months of the Atlantic
hurricane season improve, then the overall seasonal forecasts should
correspondingly become better.
I'd like to thank Phil for giving me permission to feature his
work and for sending me a copy of his research paper. Again, as a
reminder, persons interested in receiving a copy of the September
forecast paper should contact Phil at the e-mail address given above.
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for August: 1 tropical depression
2 tropical storms
1 major hurricane
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida:
discussions, public advisories, forecast/advisories, tropical weather
outlooks, special tropical disturbance statements, etc. Some
additional information may have been gleaned from the monthly
summaries prepared by the hurricane specialists and available on
TPC/NHC's website. All references to sustained winds imply a
1-minute averaging period unless otherwise noted.
Atlantic Tropical Activity for August
-------------------------------------
Over the period 1950-2002, August has averaged 2.7 named storms, 1.5
hurricanes and 0.6 intense hurricanes. In terms of overall activity,
August, 2003, was a rather average month with 3 named storms, 1 hurricane
and 1 intense hurricane. Tropical Storm Erika formed on 14 August in the
eastern Gulf of Mexico from a disturbance of subtropical origin which
had traveled westward for several days from the Atlantic north of
Hispaniola. Erica sailed westward at an unusually rapid speed for a Gulf
of Mexico storm and made landfall in northeastern Mexico only two days
after its formation southwest of Tampa. Erica intensified fairly quickly
as it neared landfall and may possibly have been a minimal hurricane when
the center moved onshore.
Tropical Storm Grace formed in the western Gulf of Mexico on 30 August
and limped ashore in Texas as a minimal tropical storm the next day. The
main storm to form in August was mighty Hurricane Fabian. This large,
severe Cape Verde hurricane tracked westward for many days, eventually
recurving along a smooth, parabolic track which took the center just west
of Bermuda, bringing Category 3 hurricane conditions to the small island.
Fabian was the most intense hurricane to strike the British colony in
many decades and was rather destructive to the island.
One non-developing depression formed during August in the northeastern
Caribbean. A strong tropical wave entered the Caribbean on 20 August,
and the next day a ship reported a west wind south of the center. There-
fore, advisories were initiated on Tropical Depression 09 at 2100 UTC
with the poorly-defined center located approximately 225 nm south of San
Juan, Puerto Rico. The depression was expected to develop into a
tropical storm and be near hurricane strength in 96 hours. On the
morning of the 22nd, high-resolution visible satellite imagery indicated
that the depression was becoming better organized with a well-defined
cloud band to the north and east of the center and good outflow in all
quadrants except the west. However, a reconnaissance plane investigating
the system south of Santo Domingo in the afternoon could not find a
closed circulation, so the system was downgraded to a tropical wave.
Even so, the system had a vigorous mid-level circulation and a well-
defined cloud pattern in satellite imagery, and data T-numbers were 2.0
and 2.5 from the various satellite analysis agencies. Regeneration was
considered a possibility, but this never materialized.
NOTE: A short report on Tropical Depression 09, written by Lixion
Avila, can be found on TPC/NHC's website at the following URL:
<http://www.nhc.noaa.gov/2003nine.shtml?>
Also, additional reports on some of the other Atlantic tropical cyclones
of 2003 have already been placed on TPC/NHC's website:
<http://www.nhc.noaa.gov/2003atlan.shtml>
This installment of the August summary (Part 1) contains the report
on Tropical Storm Erika. Reports on major Hurricane Fabian and
Tropical Storm Grace will follow in Part 2.
TROPICAL STORM ERIKA
(TC-08)
12 - 17 August
----------------------------------------
A. Storm Origins
----------------
The precursor of Tropical Storm Erika can be traced back to an area
of disturbed weather which appeared in the central subtropical Atlantic
almost a week before the storm was named. On 8 August a small
circulation accompanied by showers and gusty winds formed in the Atlantic
between Bermuda and the Azores. By the morning of the 9th the system was
located about 800 nm east-southeast of Bermuda moving west-southwestward,
and appeared to have become slightly better organized. The motion
became more westward at a rather quick pace of 17 kts over the next
couple of days, but upper-level conditions had become less favorable and
further development was hindered for the time being. Tropical Weather
Outlooks issued by TPC/NHC on 11 August indicated that the disturbed
weather was due to the interaction of an upper-level LOW and a sharp
surface trough. By afternoon that day the disturbance was located about
350 nm north of Puerto Rico, moving west at 17 kts. The associated
convection was still not organized very well.
On 12 August satellite imagery indicated the formation of a weak
surface LOW about 240 nm east of the central Bahamas, accompanied by an
increase in shower activity near the center. Also, it was noted that
upper-level winds were becoming more favorable for tropical development.
During the afternoon, however, convection diminished near a small, low-
level swirl north of the Turks and Caicos, and a reconnaissance plane
investigating the system found a mid-level circulation 260 nm to the
northeast of the weak low-level swirl. On the afternoon of the 13th
a Special Tropical Disturbance Statement was issued by TPC/NHC. A
reconnaissance plane still found no closed surface circulation, but
did measure winds to near tropical storm force to the north and north-
east of the area of lowest pressure. Concurrent satellite imagery
indicated that the system's organization was improving.
Little change was noted as the 13th rolled over into the 14th. The
disturbance continued westward, passing over the southern tip of the
Florida Peninsula during the morning of 14 August. Satellite images
depicted a well-organized system, but surface observations from the
Keys indicated only a broad low-pressure area without a well-defined
closed circulation, and pressures were not falling significantly either.
However, a reconnaissance mission into the disturbance in the afternoon
found a small, poorly-defined circulation with 300-m winds of 47 kts to
the north of the developing center. A central pressure of 1011 mb was
measured along with a northwest wind about 100 m above the surface.
Based on this information, along with well-defined satellite and radar
signatures, the system was upgraded to Tropical Storm Erika at 2100 UTC,
located in the eastern Gulf of Mexico southwest of Ft. Myers, Florida,
and about 300 nm southeast of the mouth of the Mississippi River.
Erika was scooting rapidly westward at 18 kts, guided by a persistent
strong HIGH over the south-central United States. The initial advisory
predicted landfall in southern Texas or northeastern Mexico in 36 to 48
hours--a forecast which verified very well.
B. Storm History
----------------
A reconnaissance flight into the cyclone during the evening hours
found a much better defined system. The peak winds measured were about
the same as previously, but the central convection had increased
markedly. Based on the improved organization, the MSW was upped to
40 kts at 15/0300 UTC. At 0900 UTC on the 15th Erika's center was
located approximately 450 nm east of Brownsville, Texas, moving westward
at the unusually rapid translational speed of 21 kts--very rapid at least
for a westward moving system in the Gulf of Mexico. A reconnaissance
plane early in the morning found a CP of 1008 mb and a peak FLW of 50 kts
about 60 nm northwest of the center. A tropical storm warning had
been issued for the southern Texas coast, and a hurricane watch was in
effect for northeastern Mexico. The intensity was increased to 45 kts
at 1500 UTC, based on Dvorak ratings of T3.0 from the satellite analysis
agencies, plus a 40-kt ship report at 1200 UTC from a location north of
the center. There appeared to be some easterly shear, but conditions
overall favored some strengthening.
At 15/2100 UTC Erika's center was located about 215 nm east of Browns-
ville, moving west at 19 kts with the MSW now estimated at 50 kts. Erika
appeared to be better organized with large, curved bands, good outflow,
and very strong convection near the center. A reconnaissance plane found
that the pressure had fallen to 1000 mb with a maximum 850-mb FLW of
57 kts. This would normally correspond to a surface MSW of about 45 kts,
but with the fall in pressure, it was assumed that the plane had not
sampled the actual maximum winds. Erika was forecast to be a minimal
hurricane at landfall. During the evening of the 15th WSR-88D data from
Brownsville revealed that Erika was sporting a 30-nm wide eye with
asymmetric surrounding convection, primarily in the western semicircle.
The minimum pressure measured was 992 mb, and the peak FLW measured by
a reconnaissance plane was 67 kts at 700 mb. Satellite intensity
estimates were 65 kts from TAFB and SAB and 55 kts from AFWA, so the
intensity was increased to 60 kts at 16/0300 UTC.
At 16/0900 UTC the storm was centered only about 40 nm southeast of
Brownsville, moving slightly south of due west at 16 kts. The Browns-
ville radar depicted a well-organized system with the eyewall open toward
the northeast. Doppler winds were 80 kts to the north of the center and
almost as high to the south. By 1500 UTC Erika's center was located
inland in Mexico about 85 km southwest of Matamoros. The discussion
bulletin at 1500 UTC was very interesting, indicating that Erika possibly
briefly reached hurricane intensity at landfall. Dvorak ratings from the
satellite agencies were T4.0 and T4.5 (65 and 77 kts). Also, the high-
resolution radar at Brownsville reported peak winds of 91 kts at 750 m
in a small area to the southeast of the center along the coast. In the
opinion of the Hurricane Specialist who authored the discussion bulletin,
this corresponds to at least 65 kts at the surface. Minimal hurricane
intensity is also supported by a pressure of 987 mb and a closed eyewall
as reported by a reconnaissance aircraft.
(NOTE: I have learned from a telephone conversation with one of the NHC
Hurricane Specialists that the issue of Erika's intensity at landfall is
still being discussed, and there is a good possibility that in the Best
Track Erika will be upgraded to a minimal hurricane at landfall.)
Erika continued moving fairly quickly inland as it weakened. By 2100
UTC the cloud pattern was still quite organized with deep convection and
excellent outflow, but the latest available radar data indicated that the
central features were no longer well-defined. Thus, Erika was downgraded
to a 30-kt depression. By 17/0300 UTC the depression was breaking up
over the mountains of northeastern Mexico. Satellite imagery and radar
data from Brownsville showed a significant decrease in the intensity and
coverage of convection, and surface observations from Monterrey and
Saltillo indicated peak winds of 20 kts or less. The final advisory on
Erika, issued at 17/0300 UTC, placed the weakening depression about
85 km south-southwest of Monterrey, moving west at 12 kts, and forecast
to completely dissipate within the next 12-24 hours.
C. Damage and Casualties
------------------------
Even though Erika made landfall in northeastern Mexico as a strong
tropical storm (possibly as a minimal hurricane), I have been unable
to locate any reports of damage or casualties resulting from the
cyclone.
(Report written by Gary Padgett)
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for August: 1 tropical depression
2 tropical storms
2 hurricanes
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the
Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for
locations west of longitude 140W): discussions, public advisories,
forecast/advisories, tropical weather outlooks, special tropical
disturbance statements, etc. Some additional information may have
been gleaned from the monthly summaries prepared by the hurricane
specialists and available on TPC/NHC's website. All references to
sustained winds imply a 1-minute averaging period unless otherwise
noted.
Northeast Pacific Tropical Activity for August
----------------------------------------------
Over the period 1971-2002, August has averaged 4.0 named storms, 2.4
hurricanes and 1.2 intense hurricanes. August, 2003, was pretty close
to normal with 4 named storms, 2 hurricanes and no intense hurricanes.
Tropical Storm Ignacio reached hurricane intensity on 24 August--the
latest starting date for the first hurricane of the season since the
beginning of the modern satellite era. Tropical Storms Guillermo and
Hilda formed during the second week of the month well southwest of
Mexico and were rather insignificant. Ignacio strengthened into a
Category 2 hurricane and moved up into the Gulf of California, passing
east of Cabo San Lucas. The hurricane grazed the coast near La Paz
and later moved inland on the peninsula northwest of La Paz, subsequently
dissipating over the mountainous terrain. Hurricane Jimena, forming
far to the west, also became a Category 2 hurricane and was beginning to
pose a threat to the Big Island of Hawaii, but as it approached the
island, weakened and turned to the west-southwest.
The only non-developing depression during the month formed in the
Honolulu AOR west of 140W. A disturbance which had been followed for
several days had acquired enough convective organization to be classified
as a tropical depression by the 15th. Advisories were initiated on
Tropical Depression 01C at 2100 UTC, placing the center approximately
475 nm southeast of Hilo. Almost immediately after being classified,
convection died down rather significantly. The discussion bulletin at
16/0900 UTC noted that the depression was a marginal system with an
elongated shape and several vorticity centers. By 17/0000 UTC the
depression had become too weak to be properly classified and was down-
graded to a disturbance at 0300 UTC when located roughly 350 nm south-
southwest of Hilo. An exposed vortex center was visible, but there was
no evidence of westerly winds on the south side of the system. Deep
convection was located far to the east and the vortex was forecast to
move into an even more hostile environment.
Additional reports on some of the other Eastern Pacific tropical
cyclones of 2003 have already been placed on TPC/NHC's website:
<http://www.nhc.noaa.gov/2003epac.shtml>
This installment of the August summary (Part 1) contains reports on
Tropical Storms Guillermo and Hilda. Reports on Hurricanes Ignacio and
Jimena will follow in Part 2.
TROPICAL STORM GUILLERMO
(TC-07E)
7 - 13 August
--------------------------------------------
A. Storm Origins
----------------
An area of disturbed weather formed on 4 August about 630 nm south-
southeast of the southern tip of the Baja California Peninsula. The
system was moving west-northwestward, and a Tropical Weather Outlook
issued by TPC/NHC indicated that there was some potential for
development over the next couple of days. The disturbance was better
organized the next day as it continued moving west-northwestward, and
by the evening of the 6th had reached a point about 535 nm southwest
of the tip of the Baja Peninsula. Convection and upper-level outflow
had increased significantly during the afternoon, and it was expected
that a tropical depression would likely form later in the evening or
by the next day.
The first advisory on Tropical Depression 07E was issued at 1500 UTC
on 7 August, locating the center approximately 525 nm southwest of Cabo
San Lucas. Initially, the depression was not forecast to reach tropical
storm intensity before reaching colder waters. However, by 2100 UTC
TD-07E was better organized and near tropical storm strength. Outflow
was excellent, some banding features were evident, and the center
appeared to be near the northwest portion of the deepest convection. At
0300 UTC on 8 August the cyclone was located about 560 nm southwest of
Cabo San Lucas, and appeared much better organized than six hours
previously. A small CDO feature had formed over the LLCC, and TAFB and
SAB were both rating the system at T2.5+, or about 40 kts. Therefore,
TD-07E was upgraded to Tropical Storm Guillermo with an initial intensity
of 40 kts.
B. Storm History
----------------
For the remainder of the 8th Guillermo continued to intensify. By
1500 UTC the storm had developed a persistent cold overcast with cloud
top temperatures to -80 C near the center. During the afternoon SSM/I
data showed tightly-curved convective bands and a possible eye. However,
the cloud pattern as revealed in visible imagery had decayed slightly,
possibly due to southerly shear caused by an upper-level LOW to the
west of Guillermo. Nonetheless, the MSW was upped to 50 kts--the peak
for the storm's history. During the early morning of 9 August the
cloud pattern's appearance was not very impressive. Infrared imagery
showed irregularly-shaped bursts of deep convection and the banding
had become ill-defined. However, microwave data suggested that the LLCC
was still embedded in the deep convection, and a QuikScat pass supported
an intensity of 50 kts; therefore, the official MSW remained at 50 kts.
By 09/1500 UTC Guillermo's cloud tops had warmed, but the MSW was
maintained at 50 kts based on CI estimates of 55 kts from TAFB and 45 kts
from SAB. Some binary interaction with the large developing TD-08E
located about 575 nm to the east, which was moving 3-4 kts faster than
Guillermo, was considered a possibility. However, by afternoon the
convection had become disorganized and ragged-looking, and the outflow
pattern had become severely restricted in the eastern semicircle due to
outflow from TD-08E--soon to become Tropical Storm Hilda. The MSW was
decreased to 45 kts, based on CI estimates ranging from 45 kts to 30 kts.
A burst of deep convection near the center during the evening hours led
to the MSW being maintained at 45 kts in the 10/0300 UTC advisory. Also,
at 0300 UTC, TD-08E was upgraded to Tropical Storm Hilda. East-
southeasterly shear from Hilda's outflow continued to affect Guillermo,
and at 1500 UTC the intensity was reduced to 40 kts. A mid-level vortex
in the convective debris could be seen moving away from Guillermo to the
northwest.
By afternoon, in addition to the unfavorable effects of Hilda, upper-
level westerlies from a disturbance located to the southwest began to
impinge on Guillermo. The cyclone's intensity was reduced to 35 kts at
2100 UTC; it was still generating bursts of convection but no banding
nor any other signs of organization were evident. At 0300 UTC on the
11th Guillermo was downgraded to a tropical depression when centered
about 1175 nm west-southwest of Cabo San Lucas. The system was largely
devoid of any central deep convection. Tropical Storm Hilda was also
showing signs of weakening, so the likelihood of any interaction between
the two cyclones was considered slim. A QuikScat pass at 0300 UTC showed
winds still very close to tropical storm strength, but shortly afterward
convection began to decrease, and continued weakening was forecast as
Guillermo's predicted track would carry it into a cooler and more stable
environment.
Guillermo was maintained as a tropical depression for a couple more
days as it continued moving westward, mainly due to occasional small
bursts of deep convection. The system crossed 140W into Honolulu's
AOR shortly after 1800 UTC on the 12th, and at 13/0300 UTC the CPHC
issued the final advisory on Tropical Depression Guillermo, placing
the convection-free swirl about 800 nm east-southeast of Hilo.
C. Damage and Casualties
------------------------
No damage or casualties are known to have occurred as a result of
Tropical Storm Guillermo.
(Report written by Gary Padgett)
TROPICAL STORM HILDA
(TC-08E)
9 - 13 August
----------------------------------------
The Tropical Weather Outlook issued by TPC/NHC for the Eastern North
Pacific at 1600 UTC on 7 August noted that a broad area of disturbed
weather had developed about 460 nm south of Manzanillo, Mexico, and
was moving westward. Slow development of the system was considered
a possibility. By early on the 8th the disturbance was located about
475 nm south-southwest of Manzanillo, but had changed little during
the night. By 0900 UTC on 9 August a circular-shaped area of strong
convection had developed near or over the estimated center of
circulation with banding features present in the southern semicircle.
Impressive outflow was also observed over the western quadrants of
the system. Based on this improved structure, advisories were initiated
on Tropical Depression 08E at 0900 UTC with an initial intensity of
25 kts. The depression was then centered about 600 nm south-southwest
of Cabo San Lucas on the southern tip of the Baja California Peninsula.
The MSW was increased slightly to 30 kts at 1500 UTC, but during the
afternoon inner-core convection became less defined, and microwave and
conventional satellite imagery suggested that there were multiple
circulations rotating around a mean center. By 10/0300 UTC deep
convection had redeveloped to the south of the center, but the overall
cloud pattern had improved only slightly. However, Dvorak T-numbers
from TAFB and SAB had reached T2.5, so TD-08E was upgraded to Tropical
Storm Hilda at 0300 UTC, located roughly 575 nm south-southwest of
Cabo San Lucas. By 0900 UTC the outflow pattern was looking more
symmetrical, and vertical shear was forecast to remain light for the
next few days. Hilda was moving west-northwestward at 12 kts, but a
complication to the forecast track was anticipated if the cyclone began
to undergo an interaction with Tropical Storm Guillermo, then located
about 10 degrees to the west.
Hilda remained poorly-organized, and the MSW was never estimated any
higher than 35 kts. By 0300 UTC on 11 August the LLCC had become exposed
on the north side of the deep convection, but the convection to the south
of the center was strong enough to warrant CI estimates of 35 kts. By
0900 UTC the LLCC was located 75 nm to the north of the deep convection.
Hilda was moving away from its upper-level anticyclone and had become
isolated from any moist southerly inflow. Guillermo had by this time
been downgraded to a tropical depression, and with both systems
weakening, the possibility of any binary interaction between the two
cyclones seemed remote.
QuikScat and SSM/I data indicated that winds were still 35 kts prior
to 1600 UTC, but the cloud pattern had decayed considerably by 2100 UTC
with the LLCC completely-exposed well to the northwest of the remaining
deep convection. Hilda was downgraded to a tropical depression at this
time, located approximately 785 nm west-southwest of Cabo San Lucas.
Like Guillermo, Hilda continued to produce occasional bursts of deep
convection, usually not near the center, during its decaying phase.
By 1500 UTC on 13 August Hilda was a large swirl of low clouds with a
small area of convection well-removed from the center. Since upper-
level winds were forecast to remain quite hostile for the next couple
of days, re-intensification was considered very unlikely. The final
advisory from TPC/NHC was issued at 13/1500 UTC, placing the weak 25-kt
center about 1200 nm west-southwest of Cabo San Lucas.
No damage or casualties are known to have resulted from Tropical
Storm Hilda.
(Report written by Gary Padgett)
NOTE: After writing this report on Hilda, I discovered that the official
TPC/NHC storm report on this cyclone, authored by Lixion Avila, is now
available on NHC's webiste at the following link:
<http://www.nhc.noaa.gov/2003hilda.shtml?>
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for August: 4 tropical depressions **
1 tropical storm
4 typhoons ++
** - one classified as a tropical depression by some of the Asian TCWCs
but not by JTWC, and as a tropical storm by PAGASA; another
referred to as a tropical depression only in a CPHC satellite
bulletin; two others classified as depressions by CWBT (one of
these by JMA also)
++ - one of these classified as a typhoon by JTWC only
Sources of Information
----------------------
Most of the information presented below is based upon tropical
cyclone warnings and significant tropical weather outlooks issued
by the Joint Typhoon Warning Center of the U. S. Air Force and
Navy (JTWC), located at Pearl Harbor, Hawaii. In the companion
tropical cyclone tracks file, I normally annotate track coordinates
from some of the various Asian warning centers when their center
positions differ from JTWC's by usually 40-50 nm or more. All
references to sustained winds imply a 1-minute averaging period
unless otherwise noted.
Michael V. Padua of Naga City in the Philippines, owner of the
Typhoon 2000 website, normally sends me cyclone tracks based upon
warnings issued by the Japanese Meteorological Agency (JMA) and the
Philippines' Atmospheric, Geophysical & Astronomical Services
Administration (PAGASA). Also, Huang Chunliang of Fuzhou City, China,
sends me each month tracks obtained from warnings issued by the
National Meteorological Center of China (NMCC), the Central Weather
Bureau of Taiwan (CWBT) and the Hong Kong Observatory (HKO). A very
special thanks to Michael and Chunliang for the assistance they so
reliably provide.
In the title line for each storm I have referenced all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their
area of warning responsibility.
The report on Typhoon Morakot was written by Kevin Boyle, and
a significant amount of the information contained in the reports on
Morakot and Typhoon Etau was provided by Huang Chunliang. A special
thanks to Kevin and Chunliang for their assistance.
Northwest Pacific Tropical Activity for August
----------------------------------------------
August was a very active month in the Northwest Pacific basin. Five
tropical cyclones were named by JMA--four of these became typhoons per
JTWC's analysis. Another system was named by PAGASA and was upgraded to
a minimal tropical storm by that agency, although no other warning center
did so. Typhoon Morakot formed early in the month east of Luzon and
followed a northwesterly track which carried it across southern Taiwan
and into China. JTWC was the only agency which classified Morakot as a
typhoon. NMCC upgraded it to severe tropical storm status (winds > 47
kts), but none of the other TCWCs estimated the MSW any higher than 45
kts. Also during the first week of August, much-stronger Typhoon Etau
formed well to the east of the southern Philippines and followed a
typical recurving track to the east of Taiwan which carried it over
Okinawa and later over Japan, first striking Shikoku and later Honshu.
Typhoon Krovanh, known as Nina ("NEEN-yah") in the Philippines, took
shape very slowly around mid-month in the Philippine Sea. Once the
depression finally developed into a tropical storm, it followed a some-
what unusual west-southwesterly track before turning westward across
northern Luzon as a typhoon of moderate intensity. After emerging into
the South China Sea, Krovanh turned to the west-northwest and regained
intensity, passing just off northeastern Hainan Dao before striking
the Luichow Peninsula. Krovanh emerged into the Gulf of Tonkin and
made a final landfall in extreme northern Vietnam. Minor Tropical
Storm Vamco formed east of Taiwan and moved northwestward into China,
passing just off the northern tip of Taiwan.
Finally, late in the month, Typhoon Dujuan (named Onyok by PAGASA)
formed west of Guam and followed a fairly straight west-northwesterly
track which carried it through the Luzon Strait south of Taiwan and
into southern China near Hong Kong. Dujuan became a strong typhoon
and neared super typhoon intensity (per JTWC) as it passed just off
Taiwan's southern tip.
Another South China Sea system was classified as a tropical depression
by several of the Asian TCWCs--though not by JTWC--and was assigned the
name Lakay by PAGASA. Since Lakay was treated as a minimal tropical
storm by PAGASA, and since it caused some enhanced rainfall in China
as it dissipated, a short report will be included on this system.
Huang Chunliang has advised me of two additional tropical disturbances
which were treated as weak tropical depressions by some of the Asian
TCWCs. A disturbance which took shape during the final two days of
July several hundred miles east-northeast of Saipan was carried as a
weak tropical depression (MSW of 25 kts or less implied) by JMA in the
summary portion of that agency's High Seas Forecasts. JTWC gave this
system a fair potential for development, but dissipated it in their STWO
on 2 August. The CWB of Taiwan also upgraded this LOW to depression
status. Another disturbance located to the west of the pre-Etau system
was briefly classified as a tropical depression by CWBT on 2 August.
Apparently, at one point this system and the one which ultimately became
Etau were competing for inflow, but the eastern system won and developed
into Typhoon Etau.
This installment of the August summary (Part 1) contains reports on
Typhoons Morakot and Etau. Reports on Typhoons Krovanh and Dujuan,
Tropical Storm Vamco, and Tropical Depression Lakay will follow in
Part 2.
TYPHOON MORAKOT
(TC-10W / TS 0309 / JUANING)
1 - 5 August
------------------------------------------------
Morakot: contributed by Thailand, means 'emerald'
Juaning: PAGASA name, is a Filipino male nickname
A. Storm Origins
----------------
Typhoon Morakot began as an area of convection near 8.5N, 150.0E,
or approximately 130 nm northwest of Chuuk, and was noted in a STWO
issued at 0600 UTC on 30 July. Animated multi-spectral satellite
imagery revealed a broad region of cycling convection. Upper-level
analysis indicated marginal wind shear conditions over the area such
that the potential for development within the next 24 hours was regarded
as poor. This was upgraded to fair at 30/0800 UTC when multi-spectral
satellite imagery showed convection beginning to wrap and consolidate
around a well-defined LLCC. Numerous low-level cloud lines were also
observed. Upper-level analysis depicted a slightly more favourable
environment, i.e., weak vertical shear and moderate diffluence aloft.
The fair development potential was maintained in STWOs through the rest
of 30 July and into the 31st. Based on improving organisation of the
deep convection, which had increased and consolidated about the LLCC,
the potential for development was upgraded to good at 31/1400 UTC and
accordingly a TCFA issued. At this time, the disturbance was located
approximately 275 nm east of Luzon, Philippines (near 15.5N, 127.2E).
The 1st day of August saw several TCWCs opening their account in
quick succession on this system, beginning with PAGASA issuing their
initial warning on Tropical Depression Juaning at 01/0600 UTC. JTWC
followed suit at 01/1200 UTC, and NMCC at 1800 UTC. Six hours later,
at 02/0000 UTC, JMA started writing bulletins, HKO at 02/0600 UTC, and
finally CWB of Taiwan at 0900 UTC. (Note: Both HKO and CWB upgraded to
tropical storm status at 02/0600 UTC.) Tropical Depression 10W's
initial position was approximately 175 nm east of Luzon, Philippines
(near 16.6N, 125.5E), based on JTWC's first warning, with the storm
moving slowly north-northwestward at 3 kts. The Prognostic Reasoning
Message issued at 01/1200 UTC indicated that TD-10W was forecast to
continue north-northwestward during the near term toward a weakness
caused by a longwave trough over Japan, then turn more westward towards
China as the ridge rebuilt behind the trough. The depression was
embedded in an area of shearing easterlies, but these were not too
strong and some slow intensification was forecast.
B. Storm History
----------------
At 02/0000 UTC JTWC upgraded the system to a minimal tropical storm,
i.e. 35 knots. TS-10W was named Morakot at 02/0600 UTC when JMA raised
the MSW to 35 kts (10-min avg). By 02/0600 UTC all warning agencies
were classifying the system as a tropical storm. Tropical Storm
Morakot was then moving northwestward at 7 to 8 kts, accelerating to
14 kts late in the day while continuing to strengthen. The MSW was
upped to 45 kts at 02/0600 UTC. (JMA's 10-min avg at this time was also
45 kts, and this turned out to be their peak intensity.) Multi-spectral
and water vapour imagery showed good equatorward outflow aloft and
increasing amounts of cycling deep convection in the northern semi-
circle.
By 0000 UTC on 3 August Tropical Storm Morakot/Juaning had moved
northwestward to a position approximately 225 nm south of Taipei, Taiwan
(near 20.8N, 122.0E). The MSW was still 45 kts at this time. However,
animated multi-spectral satellite imagery at 03/0600 UTC revealed the
formation of a large, ragged eye. Based on this and CI estimates of 55
to 65 kts, Morakot was upgraded to a typhoon. (JTWC was the only agency
to rank Morakot as a typhoon. All the Asian warning agencies except
NMCC regarded Morakot as a 45-kt system. NMCC's peak MSW was 50 kts: a
severe tropical storm. All the intensity estimates from the Asian
centres represent a 10-min average.) Events began to unfold quite
quickly late on the 3rd and into the 4th. After a brief jog toward the
west-northwest, Typhoon Morakot turned back to the north-northwest and
made its first landfall near Taitung, Taiwan, at 03/1500 UTC. Prior to
landfall on the southern tip of Taiwan, a SSM/I pass at 03/0952 UTC
depicted a symmetrical 45-nm diameter eye.
At 0000 UTC on 4 August Typhoon Morakot was located approximately
145 nm southwest of Taipei, Taiwan (near 23.0N, 120.0E), and had
decelerated quite markedly to 6 kts as it turned to the west. (This
sudden change in heading to the west and sudden deceleration may possibly
have been due to the mountainous terrain of Taiwan.) The system had by
then moved beyond PAGASA's boundaries and the last warning was issued by
that agency. Animated water vapor imagery (and a 03/2223 UTC SSM/I pass)
indicated that dry air entrainment was evident in the northwestern
quadrant. The MSW was still estimated at 65 kts at 04/0600 UTC when the
typhoon was about to make landfall in the vicinity of Xiamen City, China,
moving northwestward at a faster pace of 14 kts. The 04/1200 UTC warning
(#13) indicated that the storm had made its second landfall to the north-
east of Xiamen, China, and was beginning to weaken rapidly overland. At
this time Morakot was downgraded to a tropical storm. The weakening
tropical cyclone continued to move northwestward and further inland, and
the final warning was issued at 05/0000 UTC. (NMCC and CWB issued their
final bulletins at 04/1500 UTC, and HKO likewise ended warning coverage
three hours later. JMA had ceased writing statements even earlier at
04/0900 UTC.)
C. Meteorological Observations
------------------------------
All the observations in this section were obtained from a report sent
by Huang Chunliang of Fuzhou City, Fujian Province, China. A special
thanks to Chunliang for compiling and sending the information.
(1) Landfalls
-------------
According to the CWB warnings, Tropical Storm Morakot made its first
landfall near Dawu Town, Taitung County, Taiwan, around 03/1350 UTC with
the MSW estimated at 45 kts and a pressure of 990 hPa. Afterward, the
storm entered the waters of Taiwan Strait from Jiangjyun Town, Tainan
County, around 03/2030 UTC.
According to the NMCC warnings, Tropical Storm Morakot made a second
landfall near Weitou Town, Jinjiang City (a sub-city of Quanzhou City),
Fujian Province, around 04/1130 UTC with a MSW of 35 kts and a pressure
of 998 hPa.
(2) Rainfall Observations
-------------------------
Province/ Station Period Rainfall
Region (UTC) (mm)
----------------------------------------------------------------------
Taiwan Ta-chi Mt, Taitung County 02/1600-03/1500 150
Taiwan Lanyu, Taitung County 02/1600-03/1500 140
Taiwan Chih Pen, Taitung County 02/1600-04/1500 653
Taiwan Che Chen, Taitung County 02/1600-04/1500 379
Taiwan Mu Cha, Hualien County 02/1600-04/1500 296
Taiwan Hengchun, Pingtung County 02/1600-04/1500 242
Taiwan Zuojhen, Tainan County 02/1600-04/1500 196
Taiwan Zuoying, Kaohsiung City 02/1600-04/1500 194
Fujian Nan'an, Quanzhou City 04/0000-05/0000 252
Fujian Nan'an, Quanzhou City 04/0000-05/0600 381.2
Fujian * Jinjiang, Quanzhou City 04/0000-05/0000 254
Fujian * Jinjiang, Quanzhou City 04/0000-05/0600 344.2
Fujian Licheng, Quanzhou City 04/0000-05/0600 244.4
Fujian Shishi, Quanzhou City 04/0000-05/0600 251.1
Fujian Anxi, Quanzhou City 04/0000-05/0600 229
Fujian Yongchun, Quanzhou City 04/0000-05/0600 186
Fujian Dehua, Quanzhou City 04/0000-05/0600 161
Zhejiang Wencheng 03/2100-05/0900 103
Guangdong Shantou 04/0000-05/0000 102.7
Note (*): Rains in the range of 233 to 544 mm fell on Jinjiang City,
where Morakot made its second landfall, during the 18-hr period ending
at 05/1000 UTC. This was the most torrential rainfall recorded since
meteorological records began in the city. Zimao Town, Jinjiang City,
reported an 8-hr total of 334 mm that day.
(3) Wind Observations
---------------------
(a) Taiwan Region
-----------------
Station Peak Gusts
-----------------------------------------------------
Lanyu, Taitung County Beaufort Force 14
Dawu, Taitung County Beaufort Force 11
Hengchun, Pingtung County Beaufort Force 11
Taitung City Beaufort Force 10
Tainan Beaufort Force 9
(b) Fujian Province
-------------------
The coastal county of Pingtan reported the maximum gusts among all the
stations in Fuzhou. A peak gust up to Beaufort Force 8 was recorded at
that station at 03/1921 UTC.
(c) Guangdong Province
----------------------
Affected by the peripheral convection, many places in eastern
Guangdong and the region of the Zhujiang River Delta also received some
rain and gusty winds from the thunderstorms triggered by Morakot. An
automatic weather station located in Guanyao Water Conservancy Bureau,
Nanhai District, Foshan City, reported a peak gust of 68 kts at 04/1342
UTC. Stations Yantian and Longgang, both located in Shenzhen City,
reported peak gusts to 49 kts and 45 kts, respectively. Guangzhou City,
the provincial capital, also recorded 33.4 mm of rains with a peak gust
to Beaufort Force 8.
D. Damage and Casualties
------------------------
A total of 99 towns of Quanzhou City, Fujian Province, where Morakot
made its second landfall, suffered from the storm, which caused 240
million yuan of losses to the city. At least one death and another
missing person were reported there.
In several districts of Heyuan City, Guangdong Province, which were
affected by the periphery of the storm, power was cut off due to the
torrential rain, which lasted about 27 minutes around 04/0900 UTC. In
addition, two workers were reported to have been blown down from a
45-meter high falsework and lost their lives.
E. Artificial Rain
------------------
The following paragraphs appear exactly as sent by Huang Chunliang,
with some very minor editorial changes.
"To stimulate more rains artificially from the mouth of a storm?
Sounds crazy, but it was definitely true in the provinces of Fujian,
Zhejiang and Jiangxi during the storm.
"Many southern provinces of China are suffering from the most severe
drought in decades this summer. Take Fuzhou for example. Little rain
had fallen in the City for more than a month before the storm! What's
worse, the long running heatwave also hit us with a peak temperature of
41.7 C being recorded in the afternoon of 26 July. (According to the
database, the urban area of Fuzhou had not recorded a temperature
exceeding 40 C since meteorological records began 120 years ago until
15 July, when a record value of 41.1 C was reported.) No wonder
Morakot was called a "long-awaited storm" here. Thanks to the storm,
we were brought a breath of fresh air in the grip of drought, though
the relief was fleeting.
"We had no choice but to fetch more rain on our own initiative from
the mouth of Morakot. So several missions were operated by the local
meteorological services of Fujian, Zhejiang and Jiangxi to trigger more
rainfall to the dry earth. As a result, the drought was effectively
relaxed in these provinces.
"After Morakot's landfall in Fujian, 703 artificial rainfall missions
were carried out in 120 cities/counties of the province with 1027 rockets
and 14,700 cannonballs carrying silver iodide cannisters being fired (as
of the 6th). As a result, 1350 towns received rainfall from the missions
which brought rainfalls in the 40-60 mm range over an area totaling
138,500 square kilometres in the province. The highest amounts measured
in Zhejiang Province were 103 mm in Wencheng, 86 mm in Yongjia, and 61 mm
in Yuhuan. The artificial rains in Zhejiang were triggered by silver
iodide dispensed from aircraft rather than by the firing of cannons and
rockets.
"All in all, what I want to emphasize in this part is that Morakot
turned out to be more of a beneficial tropical cyclone than a baleful
one, even for the city of Quanzhou, which 'suffered most badly' from
the storm."
(Report written by Kevin Boyle and Huang Chunliang)
TYPHOON ETAU
(TC-11W / TY 0310 / KABAYAN)
3 - 11 August
------------------------------------------------
Etau: contributed by the United States, is a Palauan word meaning
'storm cloud'
Kabayan: PAGASA name, is a Filipino term meaning 'same citizenship'
A. Storm Origins
----------------
The precursor to the large, severe Typhoon Etau was an area of
convection which developed on 31 July approximately 60 nm north-
northwest of Chuuk. An interim STWO issued by JTWC at 31/2300 UTC
noted that the convection had persisted for 12 hours, and that various
satellite sensors indicated the presence of a weak LLCC to the east
of the deepest convection. An upper-level analysis depicted weak
diffluence and weak to moderate vertical shear over the region. The
potential for development was upgraded to fair at 0600 UTC on 1 August.
A recent QuikScat pass depicted the weak LLCC to the east of the deep
convection, and vertical shear had lessened somewhat. By 1400 UTC the
disturbance was located around 400 nm east of Yap. The convective
organization had continued to improve with much energy being absorbed
from a weaker LLCC to the west. (This secondary system was briefly
classified as a tropical depression by the CWB of Taiwan.)
At 01/2300 UTC JTWC issued a TCFA for the system, which was by then
located approximately 375 nm east of Yap. The convection had become
better organized, and an upper-level analysis indicated favorable
outflow on the equatorward side. A QuikScat pass early on the 2nd
depicted a broad and elongated LLCC, but the CIMSS relative vorticity
product showed that the low-level vorticity was increasing. A second
TCFA was issued at 2200, followed by the first JTWC warning on Tropical
Depression 11W at 0000 UTC on 3 August. The warning placed the center
of the depression roughly 300 nm west-southwest of Guam, moving north-
westward at 11 kts. The MSW was estimated at 25 kts, and the system
displayed improving organization with the convection consolidating near
the LLCC. TD-11W was tracking northwestward around the southwestern
periphery of a low to mid-level ridge extending westward from the
Marianas. The cyclone was forecast to track toward a weakness in the
ridge south of the Ryukyu Islands.
B. Storm History
----------------
The depression's organization continued to improve, and at 03/0600 UTC
JTWC, NMCC and JMA all upgraded to tropical storm status with JMA naming
the system Tropical Storm Etau. Etau was located about 325 nm west of
Guam, moving northwestward at 11 kts. The system exhibited good outflow
to the south. By 04/0000 UTC the cyclone had reached a position about
510 nm west of Saipan. Animated multi-spectral imagery and a 03/2303 UTC
SSM/I image depicted the LLCC just to the north of the deep convection.
At 0600 UTC animated enhanced water vapor imagery indicated that Etau had
linked up with a TUTT cell to the northeast with enhanced poleward
outflow a good possibility for the next 12-24 hours. The MSW by this
time had increased to 55 kts as Tropical Storm Etau continued tracking
northwestward along the southern periphery of a mid-level ridge located
to the north over Japan.
By 04/1800 UTC satellite CI estimates were in the 65-90 kt range. At
this time all three warning centers upgraded Etau to typhoon status,
located approximately 600 nm south-southeast of Naha, Okinawa. The storm
was plodding northwestward at a slightly slower speed of 8 kts. Early
on 5 August enhanced outflow to the east-northeast and equatorward was
noted, and convection was increasing in organization. By 1800 UTC
Typhoon Etau had reached a position 350 nm south-southeast of Naha.
Winds had reached 90 kts, and the system appeared well-organized with a
banding eye feature evident. Motion was still northwestward, but the
typhoon was forecast to turn more poleward as the steering ridge weakened
with the approach of a shortwave trough currently located over Asia.
At 0000 UTC on 6 August Etau was located a little less than 300 nm
south-southeast of Naha and had turned to a north-northwesterly heading
at 13 kts. The MSW was upped to 95 kts based on CI estimates of 90 kts
and an improving trend noted in microwave imagery. Banding features were
becoming more tightly wrapped--indicative of continued intensification.
Twelve hours later (1200 UTC) Etau was located 140 nm south-southeast of
Okinawa and was by now moving northward along the western periphery of
the mid-level ridge to the east-northeast. The typhoon was passing the
ridge axis and was forecast to begin recurving toward Japan within the
next 12-18 hours. By 1800 UTC the storm was centered only about 65 nm
south-southeast of Naha, and peak winds had increased to 100 kts around
a 35-nm diameter eye.
A portion of Etau's large eye was over the island of Okinawa at 0000
UTC on 7 August with the storm moving northward at 12 kts. The MSW was
increased to its peak of 110 kts based on CI estimates of 102 kts. The
storm was also at its peak intensity per JMA's and NMCC's warnings at
this time: 100 kts per NMCC and 80 kts per JMA (both representing 10-min
averages). The minimum CP estimated by JMA was 945 mb. A QuikScat pass
at 06/2109 UTC revealed that the 35-kt and 50-kt wind radii were almost
twice as large as had been indicated in the previous warning. Etau was a
large severe typhoon with gales covering an area about 470 nm in diameter
and storm-force winds extending over a zone 170 nm in diameter. By 0600
UTC the typhoon was moving north-northeastward at 10 kts from a position
75 nm northeast of Kadena AB, Okinawa. It had by now linked up with a
shortwave trough approaching from Korea and had begun to recurve along
the Ryukyu Island chain. At 1800 UTC Typhoon Etau was located 215 nm
south-southeast of Sasebo, Japan, moving northeastward at 16 kts.
Animated water vapor imagery indicated that the system was experiencing
northwesterly shear.
By 0600 UTC on 8 August the slowly-weakening typhoon was centered
about 140 nm south-southeast of Iwakuni, Japan, with the MSW estimated
at 90 kts. A 08/0600 UTC synoptic observation at Murotomisaki on the
eastern shoreline of the island of Shikoku reported sustained winds of
82 kts (10-min avg) for two consecutive hours. Typhoon Etau made land-
fall on Shikoku around 1200 UTC about 15 nm west-northwest of Muroto-
misaki. The cape experienced sustained typhoon-force winds for eight
hours from 0400-1100 UTC with a minimum hourly SLP of 951.7 mb. The
storm made landfall on Honshu near the Osaka International Airport around
08/1900 UTC. Tokushima reported a surface pressure of 964 mb at 1620
UTC. The lowest SLP reported at the Osaka Airport was 973 mb. At
0000 UTC on 9 August Etau was inland about 330 km west of Tokyo with the
MSW down to 65 kts. Animated multi-spectral imagery depicted strati-
form clouds in the western semicircle with bands of deep convection east
of the LLCC.
JTWC downgraded Etau to a tropical storm at 09/0600 UTC--the storm was
then located approximately 165 km northwest of Tokyo, moving northeast-
ward at 20 kts. (JMA had downgraded Etau six hours earlier.) The storm
was beginning to transform into an extratropical cyclone as its forward
speed increased--at 1200 UTC it was centered over land 145 km south-
southwest of Misawa, racing northeastward at 31 kts. JTWC and NMCC
issued their final warnings on Etau at 1800 UTC with JTWC declaring the
cyclone extratropical. The storm had moved back over the Pacific and was
located about 90 nm (165 km) east-northeast of Misawa. Animated water
vapor imagery showed that Etau had completed transition to an extra-
tropical cold-core system. JMA followed suit and classified the storm
extratropical six hours later. The remnants of Etau continued moving
northeastward, turning to the north on 11 August. At 1200 UTC on the
11th the system was a stationary 35-kt gale in the western Bering Sea
just east of the Kamchatka Peninsula.
C. Meteorological Observations
------------------------------
(1) Landfalls
-------------
Based on JMA warnings, there were five distinct landfalls of Typhoon
Etau:
(a) Northern Okinawa Island, Okinawa Prefecture, around 07/0100 UTC
(b) Amami Oshima, Kagoshima Prefecture, around 07/1200 UTC
(c) Near Muroto City, Kochi Prefecture, around 08/1230 UTC with
a MSW (10-min avg) of 78 kts and a CP of 950 hPa
(d) Near Nishinomiya City, Hyogo Prefecture, around 08/2100 UTC
(e) Near Cape Erima, Hokkaido, around 09/1700 UTC
(2) Rainfall
------------
The following table contains the top ten storm totals for the
96-hour period 06/1500 through 10/1500 UTC.
Ranking Prefecture Station Rainfall (mm)
---------------------------------------------------------------
01 Tokushima Asahimaru 683
02 Kochi Yanase 639
03 Miyazaki Mikado 539
04 Tokushima Fukuharaasahi 533
05 Tokushima Kitou 507
06 Kochi Funato 500
07 Mie Miyagawa 494
08 Nara Mt. Hidegatake 483
09 Nara Kamikitayama 476
10 Miyazaki Nakagoya 446
(3) Peak Wind Observations
--------------------------
Prefect. Station MSW/Dir Date/ Pk Gust/Dir Date/
(kts) Time UTC (kts) Time UTC
----------------------------------------------------------------------
Okinawa Minami-daito Is. 40.8/S 07/0520 68.0/SSE 07/0519
Okinawa Nago 58.1/W 07/0320 94.7/W 07/0310
Okinawa Naha 53.3/WNW 07/0020 98.0/N 06/2044
Okinawa Kumejima 33.6/WNW 07/0050 70.6/NW 07/0147
Kagoshima Okinoerabu 64.0/SE 07/0410 94.1/ESE 07/0250
Kagoshima Naze 29.9/ESE 07/1000 78.1/E 07/0922
Kagoshima Tanegashima 38.9/NNW 07/2250 78.9/E 07/1803
Kagoshima Yakushima 42.2/E 07/1700 74.4/WNW 07/2302
Kagoshima Makurazaki 34.2/NNW 08/0200 66.3/NNW 08/0154
Miyazaki Aburatsu 54.8/ESE 07/2010 88.1/ESE 07/1950
Kochi Murotomisaki 96.8/SW 08/1340 134.5/WSW 08/1329
Kochi Shimizu 38.9/E 08/0330 86.5/E 08/0333
Ehime Uwajima 31.7/W 08/1600 66.7/SE 08/0146
Tokushima Tokushima 33.6/SE 08/1540 70.0/SE 08/0415
Wakayama Shionomisaki 42.0/SSE 08/1240 81.6/SSE 08/1056
Wakayama Wakayama 42.4/SSW 07/1930 72.9/SW 07/1920
Mie Yokkaichi 18.5/ESE 08/1250 71.5/SE 08/1323
Mie Owase 29.9/S 08/1600 72.9/S 08/1600
Mie Tsu 40.6/SSE 08/1420 68.0/SE 08/1338
Only stations which either reported sustained winds (10-min avg)
of gale force or greater, or else gusts greater than typhoon force, are
included in the above table.
Karl Hoarau sent me some information which included three stations
that recorded SLPs in the 950-952 hPa range while in the eye of Etau:
Okinoerabu (27.4N, 128.7E) - 950 hPa at 07/0600 UTC
Naze (28.2N, 129.5E) - 951.6 hPa at 07/1200 UTC
Murotomisaki (33.2N, 134.2E) - 951.7 hPa at 08/1200 UTC
NOTE: These SLPs are regular hourly observations. It cannot be said
with certainty that they represent the true minimum SLP.
(4) Focus on Murotomisaki, Kochi Prefecture (WMO 47899)
-------------------------------------------------------
The station on Murotomisaki (Cape Muroto) recorded the highest winds
in Japan associated with Typhoon Etau. The station's coordinates are
33.25N, 134.18E. The altitude of the station is 185 metres, so this
should be taken into account when trying to compare the winds recorded
there with other localities, or with the official MSW estimates. For
U. S. NWS and military tropical cyclone warnings, the standard height
above sea level for which the reported MSW values apply is 10 metres.
The Murotomisaki station recorded sustained winds (10-min avg)
exceeding gale force for an extended period, beginning at 07/2100 UTC
and continuing through 09/0800 UTC. Sustained typhoon-force winds
developed around 08/0400 UTC and continued unabated until after 1600
UTC except for a two-hour period (1200-1300 UTC) when the eye was
nearest the station. Winds remained in excess of gale force during
the closest approach of the eye. As noted in the table above, the
peak MSW of about 97 kts occurred at 08/1340 UTC, but the hourly
observation with the highest MSW was at 1400 UTC with a sustained
wind of 89 kts. Sustained winds exceeded 80 kts for two different
two-hour periods: 0500-0600 UTC and 1000-1100 UTC. The minimum hourly
pressure reported by the station was 931.8 hPa at 1200 UTC, which
equates to a SLP of 951.7 hPa. Also, as noted above, the peak gust
of 135 kts was measured at 08/1329 UTC, but according to one of the
local JMA warnings, the station also recorded a gust of 119 kts at
1132 UTC.
In the history of the Murotomisaki station, only three typhoons
have brought higher sustained winds, and only two storms have produced
gusts higher than Etau since January, 1961. These are tabulated below:
Sustained Wind (kts) Date Name
---------------------------------------------------
135.7 10 Sep 1965 Shirley
129.7 16 Sep 1961 Nancy
100.5 21 Aug 1970 Anita
96.8 08 Aug 2003 Etau
Peak Gust (kts) Date Name
---------------------------------------------------
164.3 16 Sep 1961 Nancy
149.9 10 Sep 1965 Shirley
134.5 08 Aug 2003 Etau
(5) Acknowledgements
--------------------
This report was a compilation based on a special report prepared
by JMA with translation and processing performed by Huang Chunliang.
Some information was also distilled, translated and edited from the
raw data on the official web pages of JMA (Japanese version):
The special JMA report mentioned above can be downloaded at the
following link:
<http://www.jma.go.jp/JMA_HP/jma/press/0308/13b/t0310.pdf>
(Size: 885 Kbytes Language: Japanese)
A very special thanks to Chunliang for compiling, translating and
sending along this report, and a thanks to Karl for the information
he sent.
D. Damage and Casualties
------------------------
No reports of damage or casualties from Okinawa have been received.
On the main Japanese islands, press reports indicate 3 persons were
killed as a result of Typhoon Etau with 3 additional persons missing.
A total of 57 people sustained injuries as a result of the storm. The
National Police Agency reported that 15 homes were damaged and 754
others were flooded. Torrential rains were responsible for 106 land-
slides. There were 464 cancelled airline flights with 58,000 people
inconvenienced as a result. In western Japan 18,000 homes were without
electrical power after the typhoon's passage.
(Report written by Gary Padgett and Huang Chunliang)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for August: 1 tropical depression **
** - classified as a tropical depression by IMD only
North Indian Ocean Tropical Activity for August
-----------------------------------------------
I received some information from Huang Chunliang regarding a system
in the Bay of Bengal which was classified as a depression by the Indian
Meteorological Department (IMD). This system was mentioned on 27 August
as a low-pressure area over the northwestern Bay of Bengal off the
Orissa-West Bengal coast. During the evening it strengthened into a
depression and moved in a westerly direction, crossing the Orissa coast
early on the 28th. The system continued moving farther inland and had
weakened into a low-pressure area by the 29th. The bulletins from the
IMD indicate that the axis of the monsoon trough at sea level passed
through the center of the depression, so the system is probably best
classified as a monsoon depression. No warnings were issued on this
system by JTWC; in fact, it was never mentioned in that agency's STWOs
for the North Indian Ocean. The depression did enhance monsoonal rain-
fall in portions of eastern India. (A special thanks to Chunliang for
sending me the relevant IMD bulletins.)
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for August: No tropical cyclones
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for August: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for August: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for August: No tropical cyclones
*************************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I first included in the July, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
*************************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, and
Chris Landsea):
<http://australiasevereweather.com/cyclones/>
<http://www.typhoon2000.ph> OR <http://64.235.42.210>
<http://mpittweather.com>
<ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
<http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the complete Annual Tropical
Cyclone Report (ATCR) for 2002 (2001-2002 season for the Southern
Hemisphere). ATCRs for earlier years are available also.
The URL is: <http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 2002 Atlantic and Eastern North Pacific
tropical cyclones; also, storm reports for all the 2002 Atlantic
and Eastern North Pacific cyclones are now available, as well as
track charts and reports on storms from earlier years.
The URL is: <http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: garyp@alaweb.com
Phone: 334-222-5327
Kevin Boyle (Eastern Atlantic, Western Northwest Pacific, South
China Sea)
E-mail: newchapelobservatory@btinternet.com
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: saclarke@iprimus.com.au
*************************************************************************
*************************************************************************
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