http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1488Posted by: JeffMasters, 8:40 PM GMT on May 21, 2010
An extratropical low pressure system has developed a few hundred miles northeast of the Bahamas today, and has been designated as the first "Invest" of the year (90L) by the National Hurricane Center. (For those of you who were wondering, a discussion of what an "Invest" is can be found in the Tropical Cyclone FAQ). This low has the potential to develop into the season's first named storm--Alex--and could be a threat to the Southeast U.S. coast by Tuesday. Wind shear is currently 40 knots over the low, and the high shear ripped apart a low level circulation that was attempting to form this morning. Water vapor loops show a large amount of dry, continental air exists to the west of the storm, and this dry air will hamper transition of 90L to a subtropical storm. This system is expected to move slowly northwestward towards the Southeast U.S. coast, and could bring 20 - 30 mph winds and heavy rain to the coast of North Carolina by Tuesday. While the storm will initially form in a region of high wind shear and be entirely extratropical, it will move into a region of lower wind shear in a gap between the polar jet stream to the north and the subtropical jet stream to its south early next week. At that time, the low will be positioned near the warm waters of the Gulf Stream, and will have the opportunity to develop a shallow warm core and transition to a subtropical storm.
The models are divided on whether the storm will eventually make landfall on the Southeast U.S. coast 5 - 7 days from now, and it is too early to offer odds on this occurring. The counter-clockwise flow of air around this low will probably lead to northeasterly winds over the oil spill region Tuesday through Wednesday, keeping oil away from the coasts of Alabama and the Florida Panhandle, but pushing oil southwards towards the Loop Current.Wunderbloggers Weather456 and StormW have more detailed discussions of the potential development of 90L.