Preliminary Report
Hurricane Bret
18 - 25 August 1999

1999 PRELIMINARY REPORTS

Tropical Storm Arlene (TS)
Hurricane Bret (4)
Hurricane Cindy (4)
Hurricane Dennis (2)
Tropical Storm Emily (TS)
Hurricane Floyd (4)
Hurricane Gert (4)
Tropical Storm Harvey (TS)
Hurricane Irene (2)
Hurricane Jose (2)
Tropical Storm Katrina (TS)
Hurricane Lenny (4)

Bret was a small hurricane that made landfall along a sparsely-populated section of the south Texas coast with sustained winds up to 115 mph. Bret was the first hurricane to strike the Texas coast since Hurricane Jerry in October 1989. It was the first hurricane to affect south Texas since Hurricane Allen in August 1980, and it was the strongest since Hurricane Celia in 1970

a. Synoptic History

Bret formed as a tropical depression over the Bay of Campeche on 18 August. Both a tropical wave and an upper-level low contributed to the formation of Bret. A tropical wave moved from Africa to the tropical Atlantic Ocean on 5 August. Continuity and soundings from Merida, Mexico place this weak tropical wave in the vicinity of the Yucatan Peninsula on the 18th. The second feature, an upper-level cyclonic circulation, appeared on water vapor imagery over the north central Caribbean moving westward on 15 August. The circulation initiated a thunderstorm complex on the night of the 17th over the Yucatan Peninsula and a weak surface low formed in the same location early on the 18th.

Later on the 18th, the surface low moved over the Bay of Campeche. Early morning visible satellite imagery showed a low level cloud circulation center and, a few hours later, a U.S. Air Force Reserve Unit reconnaissance mission confirmed the existence of a closed circulation. With some deep convection and banding present, the system was upgraded to a tropical depression at 1800 UTC on the 18th over the Bay of Campeche. The best track begins at this time, as shown in Table 1, which is a listing of Bret's best track positions, wind speeds, and central pressures, every six hours. Figure 1 shows a map of this track.

The depression did not strengthen right away due to vertical shear caused by an upper-level trough over the extreme western Gulf of Mexico. But the trough moved away and Bret reached tropical storm strength late on the 19th while beginning to move slowly northward. The vertical shear decreased. Bret rapidly became more organized and then steadily strengthened to a 144-mph category four hurricane on the Saffir/Simpson scale on the morning of the 22nd, while appproaching south Texas coast near Brownsville. Responding to the presence of a weak mid-tropospheric ridge over the northwest Gulf of Mexico and to a mid-tropospheric cyclonic circulation over the Rio Grande valley, Bret turned northwestward and slowed its forward speed down to about 6 mph. The forward speed had earlier been as high as 10 mph.

Bret's center crossed the Texas coast over the central portion of Padre Island, midway between Brownsville and Corpus Christi, at 0000 UTC, 23 August. It had weakened to a category three hurricane with 115 mph winds and a pressure of 951mb by the time of landfall. After moving inland, Bret's movement became more westward with a slow forward speed. Bret continued to weaken as it moved across south Texas and into the high terrain of north central Mexico where it dissipated on the 25th.

b. Meteorological Statistics

Aircraft reconnaissance coverage began at 2000 UTC 18 August and continued until just after the hurricane's landfall at 0100 UTC 23 August. The maximum 1-min surface wind speed of 144 mph at 0600 and 1200 UTC on the 22nd is based on GPS-sonde vertical wind speed profiles. Figure 4 shows one of these profiles and shows that winds reached near 173 mph within 1000 feet (300 meters) above the surface and were near 144 mph near the surface. Bret's pressure dropped 35 millibars to 944 millibars in the 24 hours ending at 1200 UTC on the 22nd and dropped 21 millibars in the six hours ending at 0000 UTC of the same day.

This episode of intensification coincides with the hurricane's track over a maximum in the sea surface temperature (SST) field over the west central Gulf of Mexico. Analyses from the Johns Hopkins University Applied Physics Laboratory shows 31C SST values along Bret's track during this intensification period. In addition, estimates of the upper oceanic heat content (described by Shay et al., 1999) under portions of the hurricane's circulation in the western Gulf of Mexico were rather high.

During the 12 hours prior to landfall, the hurricane weakened from 125 to 115 mph. It was also at this time that the western edge of the eyewall was coming into contact with Padre Island.

Bret was a small hurricane. At its peak, hurricane force winds were confined to a narrow radius of 30-40 miles from the center in the north semicircle and only 10-20 miles in the south semicircle. Thus only a small segment of the Texas coast was affected by the core of the hurricane. Kennedy County received most of the hurricane force winds which are estimated as high as 115 mph over a small portion of the coast of Padre Island. With the center moving inland over a sparsely populated area, few surface reports were available substantiating strong winds. Table 2 lists a selection of available surface observations, provided by the National Weather Service offices at Brownsville, Corpus Christi, and Houston/Galveston.

The Port Aransas C-MAN station reported maximum sustained winds of 47 mph as the center of the hurricane passed about 60 nautical miles to the south.

1. Storm Surge Data

2. Rainfall Data

A 24-hour rainfall total of over 14 inches was reported from the Mexican state of Nuevo Leon and the state of Tamaulipas is believed to have received similar rainfall.

3. Tornadoes

In Aransas County around 2145 UTC 22 August, a tornado reportedly destroyed a recreational vehicle, along with a barn and a shed, and uprooted trees. Other reports indicate that a tornado touched down in Kingsville around 2245 UTC on the 22nd and a tornado was reported in Alice, time unknown. Little damage was reported with the latter two.

c. Casualty and Damage Statistics

Despite Bret's intensity, damage was generally reported to be fairly light. Much of this owed to its landfall over a sparsely populated region in south Texas and its small size. The nearest population centers, Brownsville and Corpus Christi, were spared the brunt of the hurricane's core.

Property insurance damage claims total $30 Million as reported by the Property Claims Services Division of the Insurance Services Office. Multiplying by a factor of 2.0 gives an estimated damage total of $60 Million.

There have been no reports of loss of life.