Preliminary Report
Hurricane Allen
31 July - 11 August 1980

1980 PRELIMINARY REPORTS

Hurricane Allen (5)
Hurricane Bonnie (2)
Hurricane Charley (1)
Tropical Storm Danielle (TS)
Hurricane Earl (1)
Hurricane Frances (3)
Hurricane Georges (1)
Tropical Storm Hermine (TS)
Hurricane Ivan (2)
Hurricane Jeanne (2)
Hurricane Karl (1)

Hurricane Allen was the second most severe Atlantic hurricane in modern records and will be long remembered and studied. Allen was an unusual hurricane in a number of ways.

1)	A Cape Verde hurricane is rarely observed so early in August.
2)	The forward motion of Allen along most of its track was unusually fast...close to 23 mph ...except for a decrease in forward speed over the Gulf of Mexico, during the 2 days prior to landfall.
3)	The rapid development of Allen east of the Lesser Antilles, while moving westward at more than 23 mph, was unusual although similar to Hurricane Flora in 1963.
4)	The movement of Allen into the Caribbean, where strong westerly shear had prevailed, appeared likely to doom the hurricane. On the contrary, Allen used the strong shear to strengthen even further. The strong anticyclone in the upper atmosphere associated with Allen's outflow moved along with the same forward speed as Allen and converted the westerlies to southerlies. This helped accelerate the outflow and allowed the hurricane to reach record strength.
5)	Allen reached the top of the Saffir-Simpson Scale (Category 5) 3 times. This event had not been observed before. It obtained the lowest pressure ever recorded in the eastern Caribbean...911 mb...on 5 August while south of Puerto Rico. After weakening near Haiti and Jamaica, Allen again strengthened and a record minimum pressure of 899 mb was recorded by NOAA reconnaissance aircraft on 7 August. This is not only the lowest pressure ever observed in the western Caribbean, but the lowest ever observed in the western Caribbean, but the lowest ever observed by a reconnaissance aircraft in an Atlantic hurricane, and the second lowest ever recorded in the Atlantic, Caribbean and Gulf of Mexico according to modern records. Allen began losing strength for a second time as the center passed near the north coast of the Yucutan peninsula on 8 August. Regaining strength again over the open waters of the Gulf of Mexico, Allen's central pressure dropped to 909 mb as recorded by an Air Force reconnaissance aircraft on 9 August. This is the lowest pressure ever measured in the western Gulf of Mexico.
6)	The center of Allen did not cross land at any location until it moved inland north of Brownsville, Texas. It did a remarkable job of 'broken field running' through the Caribbean at speeds of 17 to 23 mph. The eye passed between Barbados and St. Lucia, Haiti and Jamaica, and Cuba and Jamaica. It then passed north of the Cayman Islands, and between Cuba and the Yucutan peninsula. Even after reaching the Texas coast, Allen hesitated long enough to weaken to 945 mb, and then moved inland north of Brownsville with the highest tides and winds over the least populated section of the Texas coast.

a. Synoptic History

A disturbance moved off the northwest African coast on 30 July. By 1 August the second tropical depression of the season had developed when satellite pictures indicated the consolidation of two circulation centers within the large cloud mass of the African disturbance.

Allen rapidly reached tropical storm strength in the early morning hours of 2 August and hurricane strength that evening. By the time the first reconnaissance aircraft was able to penetrate the center during the afternoon of 3 August, Allen had winds of 127 mph and a minimum pressure of 967 mb. The pressure had dropped to 951 mb by that evening as the eye passed just north of Barbados and south of St. Lucia.

The hurricane continued westward into the Caribbean a 17 to 23 mph, reaching its first milestone when the minimum pressure fell to 911 mb south of Puerto Rico during the evening of 4 August.

As the large circulation of Allen began to spread over Hispaniola on 5 August, a turn toward the west-northwest brough the center just south of Haiti's southwestern peninsula that evening. The same northward jog has been observed in a number of large hurricanes, and be due to pressure falls over Hispaniola as large heat releases occur in mountain cloudbursts. The hurricane weakened as its circulation interacted with mountainous terrain of Haiti and Jamaica.

Thereafter, Allen resumed a more westerly course passing just north of Jamaica and the Cayman Islands on 6 August. Central pressure began to fall rapidly again as the circulation moved over the warm waters of the northwestern Caribbean Sea. Allen's second milestone occurred on the afternoon of 7 August when a record breaking minimum pressure of 899 mb was observed in the Yucutan Channel.

When the southern portion of Allen's circulation moved over the Yucutan peninsula during the night of 7 August, the moist southerly inflow to the hurricane's center was cut off. The minimum pressure rose very rapidly again, reaching 961 mb on the morning of 8 August.

While the hurricane continued west-northwest across the warm waters of the Gulf of Mexico, rapidly falling pressures resulted in the third milestone as a minimum pressure was observed the night of 8 August.

Allen's course through the Atlantic and Caribbean was controlled by a large, warm high pressure system covering the western Atlantic and southern United States. This system was nearly stationary and may have been partially reinforced by the warm outflow from Allen. As the hurricane moved into the Gulf of Mexico, general pressure falls began over the southern United States, indicating that Allen should begin slowing its rapid forward speed and possibly turn more toward the north.

The expected decrease in forward speed did not occur until Allen approached the Texas coast on 9 August. Even though the ridge over the southern states weakened markedly, its main effect was so slow Allen's forward speed. The western portion of the ridge did not retreat far enough to allow the hurricane to turn northward. This spared the heavily populated sections of the middle and upper Texas coast from storm surge up to 15 feet.

After moving inland on 10 August, Allen continued slowly west-northwest with winds diminishing rapidly as the circulation encountered mountains of northern Mexico. By this time the major threat was flash floods in the mountains.

b. Meteorological Statistics

Reconnaissance flights by Air Force and NOAA crews were outstanding. There was a total of 72 center fixes made on Allen. Fifty-two were made by the Air Force and 20 by NOAA crews. Many of the flights were made under difficult circumstances. On a number of occasions, flights were made into Allen's circulation when it was very near the mountainous islands of the Caribbean, where areas of severe turbulence can develop.

Prior to landfall on the Texas coast, an Air Force plane made a fix each hour for 8 hours...most of them at night. Total flight time was well over 10 hours.

Record low pressures were measured by dropsonde for both the Caribbean and western Gulf of Mexico. During the NOAA aircraft flight when the 899 mb was measured, the aircraft measured sustained flight level winds of 190 mph and estimated surface winds of 196 mph.

North Windward and southern Leeward Islands strongest winds were on the north coast of Barbados and the south coast of St. Lucia. Heavy rains caused flash flooding on St. Lucia.

Allen passed a short distance south of the extreme southwest coast of Haiti producing extensive damage from winds and flash floods.

Allen passed north of Cayman Islands but Cayman Brac was raked by winds in excess of 115 mph and sustained considerable property damage.

The extreme northeast coast of the Yucutan peninsula was very near the center of Allen but remained on the weak side. The northeast Mexican Gulf coast was also on the weak side. Both of these areas are sparsely populated.

Allen did only a fraction of the damage that had been feared, because it weakened just prior to reaching the coast, and its path sent the highest storm surge and strongest winds over the sparsely populated coastal section between Brownsville and Corpus Christi, Texas.

While Allen was passing south of Cuba winds of gale force swept the lower Florida Keys. However, there was no significant damage.

The strongest measured winds were 138 mph gusts at Port Mansfield on the west side of Laguna Madre about 40 miles north of Brownsville. The peak gust was only 79 mph at Brownsville airport. An oil rig 50 miles east of Brownsville recorded 138 mph sustained winds. Elsewhere, gusts to 92 mph occurred at Corpus Christi Airport and 109 mph at nearby Aransas Pass.

1. Storm Surge Data

Tides reached levels of 3 to 5 feet above normal along the upper Texas and western Louisiana coasts, with higher levels in the area of maximum storm surge from Corpus Christi southward. There is no way of estimating and maximum storm surge, since it occurred over the unpopulated section of Padre Island between Brownsville and Corpus Christi. A survey by aircraft the day after Allen moved inland showed numerous cuts and washouts over a 50 mile stretch of Padre Island north of where the center moved inland. It is believed so much water crossed the Island that water levels in the Laguna Madre were much higher than might be expected.

2. Rainfall Data

Rainfall of 10 to 15 inches fell over south Texas along the track of Allen for up to 150 miles north and 50 miles south of the center. More than 16 inches was measured at Falfurrias, and over 15 inches at Raymondville and Alice. As the remnants of Allen moved through northern Mexico, orographic lifting produced 5 to 10 inch rains north of Del Rio. Dryden, Texas recorded over 10 inches. The satellite interpretation method for rainfall estimates, developed by Woodley and Griffith, was quite successful with Allen. Twenty four hours prior to landfall this system indicated a maximum rainfall of 16 inches.

3. Tornadoes

There were at least a dozen tornadoes reported around south and central Texas. Two were confirmed in Brownsville which damaged 30 houses. More than 8 tornadoes were observed over inland areas west and north of Corpus Christi. The only significant damage was in Bishop were several buildings sustained heavy damage and part of the high school roof was blown off. Tornadoes in central Texas injured about 20 people at campground near San Marcus and caused an estimated $50 Million damage at the Austin Airport, primarily to hangars and corporate jets.

c. Casualty and Damage Statistics

There were 249 deaths attributed to Allen; 220 in Haiti,18 in St. Lucia, 8 in Jamaica, 2 in Texas and 1 in Guadeloupe.

Preliminary damage estimates in Barbados total $1.5 Million. About 500 houses were damaged or destroyed. There were no reports of deaths. Eighteen people were killed on St. Lucia which sustained heavy damage. The only other death reported in the islands was on Guadeloupe.

Two hundred twenty people were reported killed and 835,000 left homeless. Damage was estimated to be more than $400 Million. About one half of the nation's coffee crop was destroyed.

There was extensive damage along the immediate northeast coast of Jamaica, but only minor damage elsewhere. Eight people were reported killed.

There were no reports of significant damage from Cuba although 3 people died.

No reports of significant damage have been received from Mexico.

There were only 2 deaths directly attributed to Allen, and these were drownings in the Corpus Christi area. The reported indirect deaths were: 13 in an oil company evacuation helicopter which crashed while taking workmen from the Louisiana offshore oil rigs. Four in an offshore oil rig collapse off the Louisiana coast, three fishermen swept off the jetties by large swells in Galveston area, and two victims of heart attacks. There were also several deaths in automobile accidents during the period of evacuation. Estimated total US damage caused by Allen was $300 Million.

The major damage in Louisiana was the destruction of two $30 Million oil drilling platforms and damage to other platforms off the Louisiana coast. It has been calculated that nearly 500,000 people evacuated the coastal sections of Texas and Louisiana.