Major flooding disaster in Central America possible; severe weather outbreak today

Tropical Depression 1-E, in the Eastern Pacific off the coast of Costa Rica, is steadily organizing and appears likely to develop into Tropical Storm Alma later today or tomorrow. Satellite loops show that the low has developed a very large and expanding circulation. This circulation is likely to expand across Central America into the Western Caribbean, allowing the storm to tap moisture from the Atlantic and Pacific. Storms that are able to tap the moisture sources of both oceans can be extremely dangerous rainmakers, even if they are weak tropical depressions. Already, TD 1-E is generating very heavy rains in excess of six inches per day near its center. So far, satellite estimates of rainfall (Figure 1) indicate that 3-6 inches of rain has fallen over portions of Costa Rica and Nicaragua, and rainfall will continue to increase in these nations through Saturday. All of Central America is at risk of flash flooding that will create dangerous mud slides over the next three days, and TD 1-E has the potential to be a major disaster for Central America. Nicaragua, in particular, is at high risk of experiencing flash flooding and mud slides capable of causing heavy loss of life, due to its high mountainous terrain that will receive rains up to 20 inches.

Since TD 1-E now dominates the circulation pattern of the region, none of the computer models are predicting that a tropical depression will form in the Western Caribbean in the coming week. It is possible that TD 1-E could cross Central America and pop out in the Western Caribbean near the Yucatan Peninsula, or in the Gulf of Mexico's Bay of Campeche. However, the crossing of Central America will severely disrupt the storm, and the odds of the storm becoming a depression in the Atlantic basin are low. I am not expecting moisture from the storm to reach the U.S., although I expect Jamaica and western Cuba will get heavy downpours from the system over the next three days.


Figure 2. Observed precipitation for the 24 hours ending at 06Z (2am EDT) Thursday May 29, 2008. Rainfall amounts in excess of 150mm (six inches, green colors) occurred near the coast of Costa Rica. Image credit: U.S. Navy Monterey.

Major severe weather outbreak today in the Plains
The Storm Prediction Center is calling for a "High" risk of severe weather across Iowa and Nebraska this afternoon--the highest level of severe weather alert. Expect another significant tornado outbreak today in the Plains. The Weather Underground Severe Weather page and Tornado page are good places to go to follow the severe weather. Also, tune in to the chase accounts and awesome storm photos from Wunderblogger Mike Theiss. Mike is in Tornado Alley this week, performing his annual chase efforts.

I'll have an update Friday morning, or tonight if there's major tornado action to talk about.

Jeff Masters