Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters , 11:26 PM GMT on May 09, 2007
Subtropical Storm Andrea has changed little since it was named at 11am today. The amount of thunderstorm activity has decreased on the storm's west side, but become a little more concentrated on the east side. The organization of the spiral bands of rainfall visible on the Jacksonville, FL long range radar has remained about the same, and winds at some of the offshore buoys have remained fairly constant. Andrea remains a sloppy, disorganized storm. The main threat from the storm is coastal erosion due to the pounding surf it is generating--plus a possible fanning of the fires burning in Florida and Georgia (see below).
Wind shear has increased from 10 knots this morning to about 25 knots this evening. Shear is expected to increase to over 30 knots late tonight. Given the unfavorable wind shear, and the fact that the storm is over waters of 24-25 degrees C, I don't expect any significant intensification of Andrea. A slow decay as forecast by NHC seems reasonable.
Andrea and the Florida/Georgia fires
As Andrea began to form on Tuesday off the Carolina coast, the counter-clockwise circulation of air around the center of low pressure brought northerly winds over northern Florida and southern Georgia, where significant fires are burning. These north winds blew the smoke from the fires into the Tampa/St. Petersburg area, where unhealthy levels of particulate matter air pollution were recorded (Figure 1). The storm moved far enough west and south today that a more westerly flow of air has been carrying the smoke out over the Atlantic. Rainfall from Andrea has been less than 0.3 inches across the fires zones, which is not enough to douse them; in fact, the storm's high winds have served to fan the flames.
Andrea is a very dry storm; peak rainfall rates are only about 0.25 inches per hour, in the storm's southeastern rainbands. These rainbands are not expected to hit the coast in the next two days. Maximum total rainfall observed by the Jacksonville radar has been less than 1.5 inches.
Figure 1. NASA MODIS image of fires burning over Florida on May 8, 2007. Image credit: NASA Earth Observatory.
The last time a named storm formed so early in the year was on April 18 2003, when Tropical Storm Ana formed near Bermuda. An unnamed subtropical storm also formed on April 21, 1992.
Longest period with a tropical cyclone ends
Andrea's formation brings to a close the longest period on record globally without a tropical cyclone. The last advisory issued on a tropical cyclone this year was at 06 GMT on April 6th, for Tropical Cyclone Cliff in the Southern Hemisphere. Today's 15 GMT advisory on Subtropical Storm Andrea ends the record longest period without a tropical cyclone at 33.4 days, besting the old record of 31.5 days set mid-April to mid-May in 1984. Reliable records of global tropical cyclone numbers go back to the beginning of the satellite era, about 1970.
I'll have an update in the morning. The next Quikscat pass is at about 8pm. The next Hurricane Hunter mission is not until 8am Thursday.
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