COMET_CASE_037: COMET Case Study 037:Tropical Storm Allison

Summary

Allison spent 5 days over Southeast and East Texas and dumped record amounts of rainfall across the area. Nearly 37 inches of rain was recorded at the Port of Houston during this time. Damage estimates in Harris County alone (includes the Houston Metro area) surpassed $4.88 billion. Allison will likely go down as the costliest tropical storm to ever effect the United States. On the morning of June 11, 2001, Tropical Storm Allison was moving into the marshes/bayous of southeast Louisiana. The maximum amounts of rainfall occurred in the Vermilion and Atchafalaya basins of south central Louisiana that saw heavy rains each day from the 5th through the 11th. The highest amount reported from Louisiana was 27.55 inches at salt point in St. Mary parish. On the 11th, the low that was once Tropical Storm Allison developed over land, which had never happened before. This was mainly due to a jet streak riding along the subtropical jet to its north and northeast enhancing its outflow, which in turn led to a stronger surface low. As it edged farther inland that afternoon, it finally weakened and lost the eye.Allison tracked out of Mississippi into southern Alabama on the afternoon on the 11th. Severe weather broke out in Georgia, South Carolina, and southern North Carolina on the 13th and 14th. As the system slowed in North Carolina,flooding became a major problem. As the remnants of Tropical Storm Allisonmoved north-northwest along the eastern edge of the DelmarvaPeninsula, a cold front moved in from the west. This allowed moisture from Allison to pool along the front. Southeast Pennsylvania saw torrents of rain during the afternoon and evening of June 16th. Ultimately, Willow Grove Naval Air Station received 10.16 inched while Chanfont recorded 10.17 inched for the 24-hour period ending the morning of the 17th. One June 18th, the last of the rain associated with Allison left eastern Maine during the early morning. The project objective is to allow in depth investigation of abnormal tropical storm behavior.