Tropical Storm Allison – June 4 – 18, 2001

Tropical Storm Allison brought intensive rainfall to the Gulf of Mexico states of Texas, Louisiana, and Mississippi. The first storm of the 2001 Atlantic hurricane season, Allison lasted an unusually long time, remaining a tropical or subtropical storm for 15 days. Allison reached Tropical Storm strength at 1200 UTC on June 5 with peak winds of 60 mph. Later in the day, Allison made landfall near Galveston, Texas with peak winds of 50 mph. Inland, the storm rapidly weakened with the National Hurricane Center discontinuing advisories early on June 6. From the NOAA Service Assessment, “Allison drifted back into the Gulf of Mexico on June 9, turned to the northeast, and made landfall again on June 10 near Morgan City, Louisiana. After causing 24 deaths in Texas and Louisiana, Allison moved across southern Mississippi, southern Alabama, southwest Georgia, and northern Florida, causing nine more deaths.”

Allison_2001_track

Tropical Storm Allison (2001) Track. The tracking data is from the National Hurricane Center.

Tropical Storm Allison caused more damage than any tropical storm in U.S. history, with estimates more than $5 billion. Because of this, the name Allison was retired from being used by the National Hurricane Center. Allison became the only Atlantic tropical storm to have its name retired without reaching hurricane strength. In 2015, Tropical Storm Erika joined this exclusive list.

Most of the damage and fatalities (22) occurred in Houston, Texas.

Allison_2001_Houston_Rain

Storm total rainfall for the Houston metropolitan area. Data was provided by Harris County, Texas Office of Emergency Management.

Allison_Flood_Houston

Severe flooding in downtown Houston, White Oak, and Buffalo Bayous at Main St. taken on June 9, 2001.

Allison_2001_Houston_Flood

A neighborhood near Interstate 10, Houston, Texas under water. Image courtesy of Harris County Flood Control District.

Allison_2001_Houston_Flood2

Interstate 10 North Loop, Houston, Texas. Image courtesy of the Harris County Flood Control District.

In Louisiana, Allison ranks among the worst storms to hit the state in the past 100 years. The most significant flooding occurred on June 6-7. Much of the city of Thibodaux was flooded when 15.16 inches of rain fell in 24 hours. In East Baton Rouge Parish, flooding resulted in the evacuation of 1,800 residents and flooded 1,000 homes. Over 2,000 homes were flooded in Livingston, Lafourche, St. Tammany, and Ascension Parishes.

Allison_2001_LA_rainfall_amounts

Rainfall amount on June 6-7, 2001. Image courtesy of the Midwestern Regional Climate Center.

Allison_2001_Radar_Image

This radar reflectivity image from Mobile, Alabama was taken on June 11, 2001, at 1227 UTC. The image is courtesy of the National Hurricane Center.

“By mid-week, Allison stalled over North Carolina and produced more heavy rainfall and flooding before tracking northeast along the DelMarVa Peninsula and moving off the New England coast on June 18. Seven additional deaths occurred in Pennsylvania and one in Virginia.”

Allison_2001_Total_Rainfall

Above is the storm total rainfall map of Tropical Storm Allison. The image is courtesy of the Weather Predication Center. 

Within weeks of this storm, 75 counties in Texas, southern Louisiana, southern Mississippi, northwest Florida, and southeastern Pennsylvania were declared disaster areas by President George Bush.

Sources:

NOAA NWS: Service Assessment of Topical Storm Allison.

National Hurricane Center’s Tropical Cyclone Report.

Weather Prediction Center.

Tropical Storm Allison, Prepared by John P. Ivey, PE, CFM

 

 

 

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