a. Synoptic History
A tropical wave was at the coast of
Africa on 27 July and was a well-defined system as it was tracked across the Atlantic and
Caribbean over a 12-day period. It moved into the western Gulf of
Mexico on 8 August.
A weak low-level cloud circulation was evident from visible
satellite imagery on the 9th of August and aircraft reconnaissance
on the 10th determined that a well-defined low-level wind circulation had formed. The
stage begins on the afternoon of the 10th about 160 n mi east of La Pesca, Mexico
and 225 n mi southeast of Brownsville, Texas. Gabrielle's track is
shown in Fig. 1 (50K GIF)
and six-hour track positions, maximum one-minute wind speeds and minimum sea-level pressure
are listed in Table 1.
The track from the 10th through the 12th was slow and
erratically westward with a sharp turn to the south on the 10th and
a turn to the northwest on the 11th. With sporadic periods of deep
convection, the depression strengthened to a storm on the 10th. The
storm gradually intensified to 60 knots by late on the 11th,
just prior to moving inland. Landfall was on the coast of Mexico
just south of La Pesca and about 150 n mi south of the U.S./Mexico
border. Gabrielle quickly weakened after moving inland.
b. Meteorological Statistics
The minimum sea-level pressure and flight-level wind speed
observations from reconnaissance aircraft are plotted in
Figs. 2 and 3 (49K GIF) respectively.
Wind speed estimates from satellite data
are plotted in Fig. 3
and the corresponding pressure from the Dvorak pressure-wind relation is plotted in
Gabrielle came close to hurricane
intensity just before landfall. The 73-knot aircraft wind speed measured
at a flight level of 1500 feet is the basis for estimating a maximum one-minute
surface wind of 60 knots for 1800 UTC on the 11th. The corresponding
central pressure from an aircraft fix was 990 mb,
but a little later, a 989-mb pressure was reported when the
too close to the coast for the aircraft to monitor. It is assumed
that the central pressure was 988 mb at this time.
There were no land or ship reports of 34 knots or higher in
association with this storm. The storm center was tracked with the
Brownsville WSR-88D radar
on the 10th and 11th of August. A few radar pictures showing the center were also
received from Mexico.
c. Casualty and Damage Statistics
No reports of death have been received and damage is estimated
to be minor. It is assumed that 35- to 60-knot winds affected the
La Pesca region. A newspaper reported up to 24 inches of
beneficial rain in the Mexican states of Tamaulipes and Nuevo Leon
and flash floods were likely over higher terrain.
flooding of a few feet above normal was likely along the Mexican
coast to the north of where the center crossed the coast and some
beach flooding occurred in southeastern Texas. Eight hundred
persons were evacuated in Soto la Marina and San Fernando on the
northeast coast of Mexico.
d. Forecast and Warning Critique
There were six official forecasts issued while Gabrielle was a
tropical storm. The official
track errors are mostly near normal as the general westward motion was correctly
forecast by most of the guidance models.
The official wind speed forecasts had a negative bias. A
forecast issued at 0900 UTC on the 10th under-forecast the maximum
wind speed by 30 knots at 36 hours. his forecast was issued just
before the erratic motion began and the center was expected to be
inland in 12 hours. The center actually remained offshore for 35
more hours, allowing Gabrielle to strengthen to 60 knots at the
time that it was forecast to be inland.
Tropical storm warnings
were issued for the west coast of the Gulf of Mexico at 2100 UTC on the 9th,
from Baffin Bay, Texas to La Pesca, Mexico, while Gabrielle was still a depression.
These warnings were extended southward to just north of Tampico at 0900
UTC on the 10th and extended southward again at 2100 UTC, to
Tuxpan. Warnings were discontinued north of Port Mansfield, Texas
at 1500 UTC on the 10th, for the remainder of Texas at 2100 UTC and
for Mexico at 0300 UTC on the 11th. The tropical storm warnings
were issued 47 hours before landfall for La Pesca and 35 hours was
the lead time south of there.