Saturday, September 24, 2005

And then came the rain...

Rita has now reached landfall. The good news is that hurricane has weakened to a category 1 and the wind damage, although extensive in some areas, has turned out not to be as bad as expected. Also, judging from early reports, the much feared destruction of oil refineries and chemical plants seems not to have materialized.

But the bad news is that the storm is expected to remain stationary, dumping rain over the coastal regions of Texas and Louisiana Louisiana for several days to come:

Wind currents in the upper atmosphere, steering Hurricane Rita toward Port Arthur, Texas, are so weak, the storm is expected to stall after having made landfall late Friday night and to drench coastal Texas and Louisiana with up to two feet of rain over the next several days, causing flooding.

Packing maximum sustained winds of 125 miles-per-hour, Rita is capable of generating a 15- to 20-foot storm surge, forecasters warn.

While the population centers of Houston and Galveston appear to have been spared a direct hit due to Rita's eastward shift, the major oil refinery and chemical industry centers of Beaumont and Port Arthur are directly in its path. Crude oil prices at close of market dropped yesterday, indicating traders believe the Category 3 storm is less likely to cause the damage earlier feared.

But sustained rains caused by a stalled storm, saturated with water picked up from the warm Gulf of Mexico, may prove to be the source of greatest damage to the region.

Winds in the upper atmosphere responsible for steering the storm system are not strong enough, forecast models predict, to keep Rita moving inland once it reaches the coast. While it has been traveling at approximately 11 miles-per-hour while crossing the Gulf, the storm is expected to stall at landfall. While winds should decrease, the cyclonic storm will continue to be supplied with water as its winds pass over the Gulf and return inland. Instead of intense rainfall over a relatively short period of time, the stalled system is predicted to drop eight to 15 inches of precipitation over a widespread area and up to 24 inches of rain in some locations.

Severe flash flooding is expected in low-lying areas and in urban areas where extensive concrete surfaces prevent water from being absorbed by the soil.

Houston, although mostly above sea level, has subsided five to ten feet over the past 50 years. The city's flat topography means water has no place to flow to. Houston's tunnel system was flooded in 2001 by a tropical storm that dropped three feet of rain on the city, resulting in underground rivers flowing through downtown. Since that catastrophe, flood doors that can block 15 feet of water have been installed at tunnel entrances and two reservoirs were built to protect the city center.

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