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Still a Low Chance of Development for Two Lows

July 23, 2009

The two areas of thunderstorms in the Caribbean from yesterday, July 21, are on the move. One area is now moving into out of the Caribbean and into the eastern Atlantic Ocean while the other is now moving over the southeastern Bahamas and Hispaniola on a northwest track.

The Geostationary Operational Environmental (GOES) satellite, GOES-11 grabbed another satellite snapshot of the two areas of thunderstorms on Wednesday, July 22. The satellite image shows two comma-like cloud formations, one east of Florida's east coast, and the other with its "tail" over Hispaniola.

Showers and thunderstorms that are closest to the U.S. mainland are showing less of a chance of developing into something tropical. They're located from the northern Bahamas northward into the Atlantic Ocean and span several hundred miles. That group of storms is associated with a weak surface trough, that is, an elongated area of low pressure. The National Hurricane Center in Miami, Fla. says that there is a low chance of development, less than 30 percent now, of any further development into something tropical because the air pressure on the surface is high. This area of showers and thunderstorms is forecast to move along the U.S. East coast bringing showers to the coastline from Delaware north to New England before it moves to sea.

The second area of disorganized showers and thunderstorms has spread over the eastern Caribbean including southeastern Bahamas and Hispaniola. That group of storms is associated with a tropical wave. This tropical wave is moving northwest near 20-25 mph.

Tropical waves in the Atlantic Ocean are an elongated area of low pressure, also called a "trough." They consist of clouds and thunderstorms and stretch from north to south and move west across the Atlantic Ocean, originating off the African coast. They are generated or enhanced by the African Easterly Jet stream. They can lead to the formation of tropical cyclones in the north Atlantic and northeast Pacific basins.

The National Hurricane Center noted that upper-level winds remain unfavorable for this group of storms to develop into a tropical depression in the next day or two. Further, interaction with land also inhibits organization of a tropical cyclone, because they draw their power from warm tropical waters. There is less than 30 percent of this system becoming a tropical cyclone during the next 48 hours.

GOES is operated by the National Oceanic and Atmospheric Administration. NASA's GOES Project, located at NASA's Goddard Space Flight Center, Greenbelt, Md. creates some of the satellite images from the GOES satellites.

Elsewhere in the Atlantic Ocean, Caribbean and Gulf of Mexico, tropical cyclone formation isn't expected for another two days, but GOES-11 is watching.

NASA's Goddard Space Flight Center