COMET Case Study 037:Tropical Storm Allison at UCAR/JOSS/NOAA/CODIAC

Allison spent 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.

For more information, see:
"http://www.joss.ucar.edu/cgi-bin/codiac/projs?COMET_CASE_037"

and

"http://www.comet.ucar.edu/resources/cases/c37_06jun2001/index.htm"