From Jonathan Vigh:
In an amazing show of fury and action, the tropical atmosphere has certainly been living up to its full potential over the last 24 hours. Since yesterday's update, Hurricane Frances strengthened into a rare cat. 4 hurricane and has since weakened slightly, Tropical Storm Gaston strengthened and wallopped the South Carolina coast just shy of hurricane strength, and Tropical Storm Hermine formed from that disturbed area of weather southwest of Bermuda that was mentioned 2 days ago (but not yesterday). Just to recap the records being set -- Hermine is now the EIGHTH tropical storm to form in August, the first time that has ever happened in the modern era (beating out 1995's 7 tropical storms). In the last 29 days, there has been nearly as much activity as would be expected in an entire normal hurricane season. First, the low-down on Gaston. This system had a short, but active life, having been just upgraded to a tropical storm yesterday morning. Very low vertical shear and sea surface temperatures to 28 deg C provided favorable conditions for strengthening. Gaston was clearly on the upswing as it approached South Carolina and made landfall near McClenanville at 14Z (near where Hurricane Hugo made landfall in 1989). If it had had a few more hours over water, it most likely would have become a hurricane. Gaston's circulation (eyewall?) raked far western Charleston County and Berkley County with high winds and heavy rains. Some beach erosion was reported along the coast, as well as peak gusts to 82 mph in downtown Charleston and 81 mph at Isle of Palms. Trees were downed and other minor damage was reported (preliminary), but the main problems, as expected, came from the extremely heavy rains. Radar indicates that as much as 13-15" may have fallen in some areas, and considerable flash flooding was occurring this afternoon. As of 03Z, Gaston has weakened to a tropical depression, but is continuing to drop very heavy rains as its impressive rain shield moves northward through North Carolina. Heavy rains will continue as the remnants of Gaston track up the Eastern Seaboard over the next couple days. Hermine appeared on the scene today from that area of disturbed weather south of Bermuda that was mentioned a couple days ago. Deep convection has persisted with this storm, although the system is under some moderate vertical wind shear. Hermine is currently at 33.2N 71.3W with an estimated central pressure of 1005 mb. The system is moving towards the NNW at 13 kt, and should continue northward over the next couple of days with only slight strenghthening forecast. The remants of Gaston, a cold front, and Hermine may mix together to make for some stormy, wet weather for New England by Tuesday. Finally, onto Frances. Yesterday, Frances presented a spectacular eye which fulfilled every expectation of a major hurricane. With the impressive appearance, the storm was upgraded to the somewhat rare status of cat. 4, with winds of 115 kt. Overnight and today, the storm has looked somewhat less impressive at times. It seems that Frances has felt some southerly to southwesterly vertical wind shear. The first aircraft flew into the storm this afternoon and evening and verified that the storm weakend slightly this afternoon, to 110 kts (the upper end of cat. 3) and 954 mb (the pressure was 949 mb when the aircraft first arrived in the storm). With sea surface temperatures as warm as 29.5 deg C and a strong ridge building to the north, Frances could strengthen again, assuming that the wind shear is low enough to be a nonfactor. The official forecast is for Frances to remain a strong cat. 3 hurricane through the next five days. The track forecast is more problematic than the intensity forecast at the moment. Frances is now moving slowly westward at 7 kt. The storm size has increased over the last couple days, and with a track just north of due west, the storm is forecast to pass close enough to the northernmost Leeward Islands to bring some ill effects including tropical storm conditions. Thus, Tropical Storm Watches have been issued for Antigua, Barbuda, St. Maartan, Anguilla, Nevis, St. Kitts, St. Eustatius, and Saba. These are generally the northern islands of the U.S. and British Virgin Islands and Anguilla. With the inherent uncertainty of forecasting, a more threatening southward track cannot be ruled out at this time. Therefore, Hurricane Watches have also been issued for the British and Northern U.S. Virgin Islands including St. Thomas, St. John and environs, and the islands of Culebra and Vieques. Some of these islands took a beating several times during the past decade. To briefly summarize this area's recent hurricane history: in 1995, Luis hit Barbuda and St. Martin as a cat. 4 hurricane and later in the season, Marilyn caused tremendous damage to the St. Thomas (U.S. Virgin Islands). Hurricane Georges raked pretty much the entire area, including Puerto Rico, and caused large loss of life in the Dominican Republic in 1998. And in 1999, 'wrong-way Lenny' caused more trouble late in the season. In the longer time frame, the storm is expected to move west northwest and menace the Bahamas. A general threat now exists to the U.S. East Coast, but it is still too far in advance to even say which state(s) may be threatened. If the WNW track develops, the threat to South Florida may be reduced (and increased for areas further north), but it is too early to say. All residents of Florida, Georgia, South Carolins, and North Carolina should monitor and track the progress of Frances through the week. At 03Z, Frances was near 18.9N 56.2W, moving west at 7 kt, with maximum sustained winds to 110 kt and aircraft-measured central pressure of 954 mb.
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