Tropical Cyclone Report
Tropical Storm Henri
3 - 8 September 2003
Henri was a tropical storm with maximum 1-min surface
winds of 50 kt in the eastern Gulf of Mexico. After weakening to a
depression, it moved across central Florida, where it dumped up to
ten inches of rainfall.
a. Synoptic History
Henri formed from a tropical wave that moved from
Africa to the tropical Atlantic Ocean on 22 August. The wave
reached the eastern Gulf of Mexico on 1 September where the
northern portion became nearly stationary, while the southern
portion continued westward. By 1800 UTC on 3 September, the
associated convection and low-level circulation became well-enough
organized about 260 n mi west of Tampa, Florida to become Tropical
Depression Twelve.
The "best track" chart of the tropical cyclone's path
starts on the 3 September and is plotted in Figure 1;
the wind and
pressure histories are plotted in Figure 2 and
Figure 3, respectively. The
complete best track positions and intensities are listed in
Table 1.
The depression was embedded in the southern portion
of a slow-moving mid-latitude trough and moved slowly eastward. The
depression became a tropical storm at 0600 UTC , 5 September and
the wind speed increased to its maximum value of 50 kt on 1800 UTC
on that day even though there was at least 20 kt of southwesterly
vertical shear affecting the circulation. The winds quickly
weakened to 30 kt before Henri, preceded and accompanied by heavy
rain, accelerated northeastward across north-central Florida on the
6 September. Over the southwestern North Atlantic Ocean, Henri
slowed its forward speed on 7 September when it became trapped to
the south of a shallow high pressure system. Strong vertical shear
finally led to its dissipation when the depression lost a
well-defined low-level circulation and simultaneously became
involved with a frontal zone resulting in a spreading out of the
wind field. The broad and disorganized extratropical low remained
nearly stationary off the coast of the Carolinas for several days
and moved inland over North Carolina on 12-13 September.
b. Meteorological Statistics
Wind speed estimates in Henri are based on
satellite-based Dvorak technique intensity estimates from the
Tropical Analysis and Forecast Branch (TAFB), the Satellite
Analysis Branch (SAB) and the U. S. Air Force Weather Agency
(AFWA), as well as flight-level and dropwindsonde observations from
flights of the 53rd Weather Reconnaissance Squadron of
the U. S. Air Force Reserve Command. These estimates and
observations are plotted in Figure 2. Minimum central pressure data
are plotted in Figure 3.
There were no ship reports of tropical storm force
winds. On 5 September, a reconnaissance aircraft reported an 850-mb
flight level wind speed of 46 kt at 1116 UTC, along with 997 mb
surface pressure. Data buoy 42036, located in the northeastern Gulf
of Mexico, reported a 10-min. mean wind speed of 45 kt with a gust
to 64 kt at 1720 UTC on the same day. This buoy also reported a
surface pressure of 1001.7 mb at 1750 UTC. Henri was centered about
25 n mi east-southeast of the buoy at the time of the 45-kt wind
speed. Based on these reports, Henri's highest 1-min wind speed is
estimated at 50 kt at 1800 UTC. Note in Figure 2 that subjective
Dvorak wind speed estimates based on satellite imagery were as high
as 55 to 65 kt. Based on aircraft data, as well as the buoy,
Henri's maximum wind speed quickly decreased to 30 kt during the
next six hours as the low level center became totally exposed. Then
Henri crossed over Florida as a tropical depression.
Henri's rain affected much of Florida. There were
five to ten inches of rain in portions of Charlotte County. There
was generally minor freshwater flooding in two areas: from Sarasota
through Lee Counties , and a small portion of southern Hernando and
extreme northern Pasco County. In southern Florida and in the
panhandle area, rainfall totals were generally less than two
inches.
c. Casualty and Damage Statistics
There were no deaths attributed to Henri. However, a
male in Lee County was injured when struck by lightning from a
thunderstorm in a feeder band. Also, an indirect injury occurred
when a vehicle driven by a Pinellas Park man hydro-planed into a
concrete wall on Interstate 275 in Tampa. Damage from flooding was
generally minor.
d. Forecast and Warning Critique
Average official track errors (with the number of cases in
parentheses) for Henri were 44 (18),73 (16), 83 (14), 97 (12), 82 (8), and
124 (4) n mi for the 12, 24, 36, 48, 72, and 96 h forecasts,
respectively1.
These errors are lower than the average official track
errors for the 10-yr period
1993-20022
(45, 81, 116, 150,
225, and 282, n mi, respectively). Henri did not last long enough to verify
any 120-h forecasts.
Average official intensity errors were 5, 8, 7, 8, 8,
and 3 kt for the 12, 24, 36, 48, 72, and 96 h forecasts,
respectively. For comparison, the average official intensity errors
over the 10-yr period 1993-2002 are 6, 10, 13, 15, 19, and 21 kt,
respectively.
Table 2 lists the watches and warnings issued for
Henri.
1
All forecast verifications in this report include the depression stage of the
cyclone. National Hurricane Center verifications presented in these reports
prior to 2003 did not include the depression stage.
2
Errors given for the 96 h periods are averages over the two-year
period 2001-2002.
Table 1: Best track for Tropical Storm Henri, 3-8 September
2003.
Date/Time (UTC) | Position | Pressure (mb) | Wind Speed (kt) | Stage |
Lat. (°N) | Lon. (°W) |
03 / 1800 | 27.4 | 87.7 | 1013 | 25 | tropical depression |
04 / 0000 | 27.6 | 87.8 | 1011 | 25 | " |
04 / 0600 | 27.8 | 87.6 | 1009 | 25 | " |
04 / 1200 | 27.8 | 87.2 | 1010 | 30 | " |
04 / 1800 | 27.8 | 86.3 | 1002 | 30 | " |
05 / 0000 | 27.6 | 85.8 | 1004 | 30 | " |
05 / 0600 | 27.7 | 85.1 | 1000 | 35 | tropical storm |
05 / 1200 | 28.1 | 84.4 | 997 | 40 | " |
05 / 1800 | 28.3 | 84.2 | 997 | 50 | " |
06 / 0000 | 27.9 | 83.9 | 1002 | 30 | tropical depression |
06 / 0600 | 27.7 | 83.5 | 1005 | 30 | " |
06 / 1200 | 28.4 | 81.8 | 1007 | 25 | " |
06 / 1800 | 29.2 | 80.4 | 1006 | 25 | " |
07 / 0000 | 30.0 | 79.5 | 1006 | 30 | " |
07 / 0600 | 30.5 | 79.2 | 1008 | 30 | " |
07 / 1200 | 30.8 | 78.5 | 1006 | 30 | " |
07 / 1800 | 31.3 | 77.9 | 1006 | 30 | " |
08 / 0000 | 31.7 | 77.1 | 1006 | 30 | " |
08 / 0600 | 32.1 | 76.5 | 1007 | 30 | " |
08 / 1200 | 32.5 | 75.9 | 1006 | 30 | " |
08 / 1800 | 32.9 | 75.3 | 1006 | 25 | extratropical |
09 / 0000 | | | | | dissipated |
05 / 1800 | 28.3 | 84.2 | 997 | 50 | minimum pressure |
06/0900 | 27.9 | 82.8 | 1006 | 30 | landfall near Clearwater, FL |
Table 2: Watch and warning summary for Tropical Storm
Henri, 3-8 September 2003.
Date/Time | Action | Location |
03/2100 | tropical storm warning
issued | Englewood to Indian Pass,
Florida |
05/0000 | tropical storm warning
discontinued | Aucilla River to Indian
Pass |
06/0300 | tropical storm warning
discontinued | Swannee River to
Aucilla |
06/0900 | all warnings
discontinued | |
Figure 1:
Best track positions for
Tropical Storm Henri, 3-8 September 2003.
Figure 2:
Selected wind
observations and best track maximum sustained
surface wind speed curve for Tropical Storm Henri, 3-8 September
2003. Aircraft observations, when available, have been adjusted for
elevation using 90%, 80%, and 80% reduction factors for
observations from 700 mb, 850 mb, and 1500 ft,
respectively.
Figure 3:
Selected pressure observations and best track
minimum central pressure curve for Tropical Storm Henri, 3-8
September 2003.
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