a. Synoptic History
The origin of Tropical Storm Charley is unclear. It could have
been a large swirl of clouds that exited the coast of Africa on 9
August at rather high latitude, mainly to the north of Dakar,
Senegal. More definitely, the precursor consisted of a small
area of deep convection first noted a few hundred miles to the
northeast of the Leeward Islands on the 15th. Intermittent
convective activity continued while the system moved just west of
north for the following few days. On the 19th, animation of
satellite pictures showed a cyclonic rotation of the clouds over
the southeastern Gulf of Mexico.
The first formal position estimate from satellite analysts came
on the evening of the 19th and Dvorak T-numbers (1.5)
were first assigned the next day over the central Gulf. By the morning of
the 20th, surface winds had begun to increase, with NOAA's
central Gulf buoy 42001 measuring sustained winds as high as 31
kt and gusts to 45 kt at 1700 UTC. These stronger winds were
fleeting, however, and an investigation of the system late that
day by U.S. Air Force Reserves reconnaissance aircraft did not
indicate a closed low-level circulation center.
A center "fix" was made aboard reconnaissance aircraft
early in the following flight, near 1300 UTC the next day, and this is the
basis for indicating that the system became a tropical depression
around 0600 UTC on the 21st (Fig. 1 (9K GIF) and
Table 1). At that time, the depression was centered about 275 n mi off of the
south Texas coast. The tropical cyclone moved toward the west-northwest to
northwest at about 10 kt during its three-day lifetime.
Although the center was not well-formed initially, the amount of
deep convection steadily increased, particularly over the
northern semicircle. That part swept over the oil platforms of
the northern Gulf and data from them (e.g., Table 2) suggest that
tropical storm status was reached by 1800 UTC on 21 August.
Winds of hurricane force were noted in intense convection to the
northeast of the center at a flight level of 1500 feet early on the 22nd.
Charley was likely then at its peak strength, near 60
kt. The wind speeds measured aboard aircraft were considerably
lower thereafter and it is estimated from that data and other
observations that surface winds were closer to 40 kt
when Charley's center made landfall near Port Aransas about 1000 UTC
on the 22nd.
The surface circulation weakened further after landfall and
likely dissipated early on the 24th along the Rio Grande near Del
Rio, Texas. Although the winds diminished inland, and a closed
surface circulation could no longer be identified, a slow-moving
circulation aloft persisted in the Del Rio vicinity and generated
flooding rains that were most devastating in that area on the
23rd and 24th. By late on the 25th, most of the remnant cloud
system had deteriorated and precipitation had diminished.
b. Meteorological Statistics
The "best track" intensity was obtained from the data
presented in Figs. 2 (10K GIF) and
3 (12K GIF). Those figures show Charley's
estimated central pressure and maximum one-minute wind speed,
respectively, versus time. Position and intensity estimates were
obtained from analyses of satellite pictures by NOAA's Synoptic
Analysis Branch (SAB) and Tropical Analysis and Forecast Branch
(TAFB), and by the Air Force Weather Agency (AFGWC in figures).
Analyses also included surface observations, and radar and
aircraft data.
Charley's primary legacy will be the rainfall and associated
flooding it produced in the Del Rio vicinity. On 23 August,
16.83 inches of rain fell in Del Rio. This easily surpassed the
previous daily record of 8.79 inches on 13 June 1935. A nearby
site recorded 17.59 inches for the 24 hour period ending in the
morning hours of 24 August. Along the coast, maximum rainfall
totals were near 5 inches except for an unofficial report of 9
inches near the mouth of the San Bernard River in Brazoria
County.
River flooding along the Rio Grande occurred well downstream
from Del Rio, in the Laredo area.
Storm tides of 2 to 3.5 feet above normal astronomical levels
were reported from the coast.
The ASOS sites at Rockport (RKP) and Galveston (GLS), Texas were
the only two surface reporting stations on land to measure sustained tropical
storm force winds. They recorded two-minute winds of
36 kt and 34 kt, respectively.
A gust to 55 kt was reported from the Pt. O'Connor Coast Guard.
A minimum pressure of 1000 mb is estimated at landfall from the
observation of 1000.7 mb at RKP an hour later.
c. Casualty and Damage Statistics
The death toll currently stands at 13 in Texas, with 6 people
unaccounted. All were apparently flood victims located well
inland. The total consists of four people including two
toddlers whose pickup was swept away by rising water in Real
County on the 23rd. Seven other people from the truck were
rescued. Nine deaths due to drowning occurred in Del Rio (Val
Verde County) along the San Felipe Creek during the late night of
23 August. Some in the latter group could have expired after the
system was no longer classified as a tropical cyclone.
Emergency operations personnel in Mexico reported that as of
early October the number of fatalities in Ciudad Acuña, Mexico,
across the border from Del Rio, was seven. Media reports
indicate that three of these victims drowned while trying to
cross a flooded gully.
A preliminary estimate of the total loss due to the inland flood
is $50 million. Property losses were reported in several
counties and consisted of damages to residences, businesses,
roads, bridges and agriculture. About 1500 homes, 200 mobile
homes, and 300 apartments were damaged or destroyed in Val Verde
County, where about $40 million in losses occurred.
Minor beach erosion was reported.
d. Forecast and Warning Critique
Tropical Weather Outlooks
and Special Tropical Disturbance
Statements issued by the NHC correctly identified the incipient
disturbance as a candidate for development once it entered the
southeastern Gulf of Mexico.
Charley was a tropical storm for less than a day and this is too
short a period to obtain a meaningful quantitative evaluation of
forecast accuracy. Qualitatively, NHC forecasts showed the
correct motion and intensity trends.
The NHC issued a tropical storm warning
from Brownsville to High Island, Texas on its first advisory (as a tropical depression)
at 1500 UTC on the 21st, about 19 hours prior to landfall in that
area. The warning was extended eastward to Cameron, Louisiana
six hours later. When the center of Charley was about to come
ashore, the warning was discontinued northeast of Sabine Pass,
Texas at 0900 UTC on the 22nd. The remaining warning was
discontinued at 1500 UTC 22 August.
Acknowledgements
Some data for this report were furnished by National Weather
Service offices in Corpus Christi,
Lake Charles,
and Austin/San Antonio.
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