Tropical Storm Allison (1989)

Infobox Hurricane
Name=Tropical Storm Allison
Type=Tropical storm
Year=1989
Basin=Atl
Image location=Tropical Storm Allison (1989).jpg


Formed=June 24, 1989
Dissipated=June 28, 1989
1-min winds=45
Da

Inflated=0
Pressure=999
Fatalities=11 direct
Areas=East Texas, Louisiana
Hurricane season=1989 Atlantic hurricane season

Tropical Storm Allison was the first tropical cyclone, first named storm, and first tropical storm of the 1989 Atlantic hurricane season. The storm moved over Texas, producing heavy rain, and causing $560 million (1989 USD) dollars in damage.

On June 24, Tropical Depression two had formed, caused by a fusion of a tropical wave and the remains of what was Hurricane Cosme in that same pacific hurricane season. It moved south, and on the 26, became a tropical storm. It moved over Texas, and on the 27, it started to lose its tropical characteristics, weakening to a tropical depression, and on the 28, it had dissipated.

The storm caused heavy rainfall, amounting to convert|30|in|mm in some places. In total, 11 fatalities resulted from the storm.

Meteorological history

Three meteorological phenomena combined to produce Tropical Storm Allison. First, Hurricane Cosme moved northward through Mexico in response to a strong mid to upper-level ridge. Its remnants entered the Gulf of Mexico on June 22, when a westward moving tropical wave reached the area. Finally, a strong anticyclone over the Gulf allowed for the disturbed area to organize into Tropical Depression Two in the western Gulf of Mexico on June 24.

The depression continued to organize as it drifted to the north, and became Tropical Storm Allison on June 26 off the Texas coast. A ridge to Allison's north weakened in response to an approaching frontal trough, and the tropical storm accelerated to the north. Allison reached a peak of convert|50|mi/h|km/h|abbr=on winds just before hitting near Freeport, Texas on the 27th. It turned to the northeast with the front, weakened to a tropical depression on the 27th, and became extratropical on June 28th.

The frontal trough outran the system, and the building ridge to Allison's north forced the extratropical depression turned to the south and southwest. On June 30 Allison completed its loop over the rain-flogged area. The ridge to the north began to erode, allowing Allison to escape Texas by heading to the northeast. Its circulation dissipated on July 1, but the remnants retained some organization, and continued to the northeast.

On July 3 and 4th, the shortwave that was guiding the remnants outran the storm, causing Allison to stall over the Kentucky/Illinois/Indiana border. A second shortwave trough brought Allison, or what was left of it, southward into Alabama. It turned to the west, and completely lost its identity on July 7 over Arkansas, bringing more precipitation to the area.

Preparations

A tropical storm watch was issued on June 24 for Baffin Bay, Texas to Morgan City, Louisiana which were upgraded to Tropical Storm Warnings on June 26. All advisories were discontinued the next day.

Impact

While Allison's winds weren't overly strong, it caused tremendous flooding in Texas and Louisiana, with 20-25 inches of rain occurring in some locations. The local hardest hit by the flooding was Winnfield, Louisiana, which experienced almost 30 inches of rain from June 26 to July 1.

Rainfall from the storm extended eastward into the Mid-Atlantic States, producing flooding. [http://www-ks.cr.usgs.gov/Kansas/pubs/reports/wsp.2502.sum89.html] In Delaware, the rainfall led to record breaking discharge rates at three gauging stations, while one-third of the state's gauging stations reported significant discharges. [http://www-ks.cr.usgs.gov/Kansas/pubs/reports/wsp.2502.de.html#HDR2]

13.9 inches of rain fell at a site in Arkansas, the highest rainfall total from a tropical cyclone in the state. [http://www.hpc.ncep.noaa.gov/tropical/rain/tcstatemaxima.gif]

Eleven people were reported killed from the storm. Three deaths occurred in Texas, five in Mississippi and three in Louisiana. Two teenage boys were killed when their raft got sucked into a drainage pipe from the runoff of Allison in Beaumont, Texas. An eighteen-year-old was killed in Harris County, Texas from drowning during a swim. The eight final deaths in Louisiana and Mississippi were by drowning. The extreme flooding in turn led to heavy damage, amounting to around $560 million (1989 USD, $872 million 2005 USD).

Lack of retirement

Allison, having replaced Hurricane Alicia, a hurricane that brought heavy damage to southeast Texas, coincidentally caused great damage in the same area. Even more unlikely is that though Allison was not retired, another Tropical Storm Allison in 2001 again devastated southeast Texas, with its name retired in 2002 and replaced by Andrea for 2007.

ee also

*List of tropical cyclones
*List of wettest tropical cyclones in the United States

External links

* [ftp://ftp.nhc.noaa.gov/pub/storm_archives/atlantic/prelimat/atl1989/allison/ NHC Allison Report]