Meteorological Analysis
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Allison originated from a tropical wave which moved off the coast of Africa on
May 21st. The wave raised little suspicion as it headed west under the
subtropical ridge. The wave impacted South America on May 26th and moved
over water again in the Caribbean by May 29th. The wave then moved into the
Pacific ocean by June 1st and developed a low level circulation about 200 nm
SSE of Salina Cruz, Mexico. On June 3rd the low level circulation moved inland
over Mexico and dissipated. The mid level circulation stayed intact however and
moved into the Bay of Campeche on June 5th. A low level jet and an upper low
then combined to form deep convection over the mid level circulation. The
mid level circulation then built down to the surface and the system became
tropical storm Allison on June 5th, about 120 nm south of Galveston, Texas.
Allison was partially subtropical at formation, although classified as tropical.
Allison's winds occurred over a very large area due to the pressure gradient,
and Allison quickly strengthened to its maximum winds of 60 mph on the 5th.
Allison made landfall with winds just below 60 mph on the 5th near Freeport,
Texas. Allison quickly weakened into a tropical depression once inland but, it
brought heavy and relentless rains to areas of Texas and Louisiana. Allison
dumped heavy rains over the same areas for nearly 5 days, causing
catastrophic flooding. Allison finally drifted back into the Gulf of Mexico on the
10th and didn't organize much due to dry air and shear. Allison became a
subtropical depression on the 10th as most convection was hundreds of miles
from the center. A new center eventually formed though under the deepest
convection on the 11th, and Allison became a subtropical storm. An eye like
feature was even apparent from radar although the wind field suggests the
storm was subtropical. Allison made a second landfall in Intracoastal City,
Louisiana on June 11th. Allison moved ENE over the southeast U.S. and
weakened into a subtropical depression. Allison then stalled over North Carolina
on the 14th and began to drift north. A trough eventually caught Allison though
and by the 17th Allison cleared the U.S. Allison became a subtropical storm
once over water but, became extra-tropical shortly afterwards on the 18th.
Extra-tropical Allison dissipated southeast of Nova Scotia on June 19th.
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Casualty and Damage Overview
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A staggering 41 deaths are attributed to Allison with 23 in Texas, 8 in Florida,
7 in Pennsylvania, 1 in Mississippi, 1 in Virginia, and 1 in Louisiana.
Allison brought catastrophic flooding to northeast Texas and southwest
Louisiana. Most of the damage occurred in Houston, where 14,000 homes were
destroyed and 34,000 more damaged. Total U.S. damage varies from estimate
to estimate but is around $5 billion.
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Allison Hurricane Research Division Products
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Imagery
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Tracking Data
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Tropical Storm Allison
Time Lat Lon Wind(mph) Pressure Storm type
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12 GMT 06/05/01 27.5N 95.0W 45 1007 Tropical Storm
18 GMT 06/05/01 28.5N 95.3W 60 1002 Tropical Storm
0 GMT 06/06/01 29.3N 95.3W 50 1003 Tropical Storm
6 GMT 06/06/01 30.1N 95.2W 35 1006 Tropical Depression
12 GMT 06/06/01 31.0N 95.2W 25 1005 Tropical Depression
18 GMT 06/06/01 31.5N 95.0W 25 1005 Tropical Depression
0 GMT 06/07/01 31.6N 95.0W 25 1005 Tropical Depression
6 GMT 06/07/01 31.8N 94.9W 25 1006 Tropical Depression
12 GMT 06/07/01 31.4N 94.9W 25 1006 Tropical Depression
18 GMT 06/07/01 31.1N 95.0W 15 1007 Tropical Depression
0 GMT 06/08/01 30.9N 95.6W 15 1002 Tropical Depression
6 GMT 06/08/01 30.7N 96.1W 25 1004 Tropical Depression
12 GMT 06/08/01 30.4N 96.2W 25 1007 Tropical Depression
18 GMT 06/08/01 30.2N 96.1W 25 1007 Tropical Depression
0 GMT 06/09/01 29.9N 95.9W 25 1007 Tropical Depression
6 GMT 06/09/01 29.6N 95.8W 25 1007 Tropical Depression
12 GMT 06/09/01 29.3N 95.8W 25 1007 Tropical Depression
18 GMT 06/09/01 28.9N 95.6W 25 1008 Tropical Depression
0 GMT 06/10/01 28.6N 95.2W 25 1008 Subtropical Storm
6 GMT 06/10/01 28.6N 94.7W 30 1007 Subtropical Storm
12 GMT 06/10/01 28.7N 94.3W 30 1006 Subtropical Storm
18 GMT 06/10/01 28.8N 93.5W 35 1006 Subtropical Storm
0 GMT 06/11/01 29.1N 92.3W 35 1005 Subtropical Storm
6 GMT 06/11/01 30.0N 90.5W 40 1003 Subtropical Storm
12 GMT 06/11/01 30.7N 89.4W 45 1000 Subtropical Storm
18 GMT 06/11/01 31.0N 88.4W 40 1002 Subtropical Storm
0 GMT 06/12/01 31.3N 87.4W 30 1004 Subtropical Storm
6 GMT 06/12/01 31.8N 86.1W 25 1005 Subtropical Storm
12 GMT 06/12/01 32.4N 84.7W 25 1006 Subtropical Storm
18 GMT 06/12/01 32.8N 83.6W 25 1006 Subtropical Storm
0 GMT 06/13/01 33.1N 82.6W 25 1006 Subtropical Storm
6 GMT 06/13/01 33.4N 81.6W 30 1004 Subtropical Storm
12 GMT 06/13/01 33.7N 80.7W 30 1005 Subtropical Storm
18 GMT 06/13/01 34.0N 79.6W 30 1006 Subtropical Storm
0 GMT 06/14/01 34.3N 78.5W 30 1006 Subtropical Storm
6 GMT 06/14/01 34.6N 77.9W 30 1006 Subtropical Storm
12 GMT 06/14/01 34.7N 77.7W 30 1007 Subtropical Storm
18 GMT 06/14/01 34.6N 77.6W 30 1008 Subtropical Storm
0 GMT 06/15/01 34.6N 77.2W 30 1008 Subtropical Storm
6 GMT 06/15/01 34.9N 77.0W 30 1008 Subtropical Storm
12 GMT 06/15/01 35.5N 76.9W 30 1008 Subtropical Storm
18 GMT 06/15/01 35.9N 76.8W 30 1009 Subtropical Storm
0 GMT 06/16/01 36.3N 76.6W 30 1007 Subtropical Storm
6 GMT 06/16/01 36.6N 76.2W 30 1007 Subtropical Storm
12 GMT 06/16/01 36.8N 75.9W 30 1007 Subtropical Storm
18 GMT 06/16/01 37.2N 75.5W 30 1006 Subtropical Storm
0 GMT 06/17/01 37.8N 75.4W 30 1006 Subtropical Storm
6 GMT 06/17/01 38.6N 74.5W 35 1005 Subtropical Storm
12 GMT 06/17/01 39.3N 73.4W 45 1004 Subtropical Storm
18 GMT 06/17/01 40.0N 72.1W 40 1005 Subtropical Storm
0 GMT 06/18/01 40.6N 70.8W 35 1006 Extratropical Storm
6 GMT 06/18/01 41.3N 69.4W 35 1008 Extratropical Storm
12 GMT 06/18/01 42.0N 67.4W 35 1009 Extratropical Storm
18 GMT 06/18/01 42.7N 64.6W 30 1011 Extratropical Storm
0 GMT 06/19/01 43.5N 61.0W 25 1012 Extratropical Storm
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Tracking maps courtesy of NHC
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Selected Satellite Image
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