Tropical Storm Andrea - Discussion 4

By: National Hurricane Center
By: National Hurricane Center

EVEN THOUGH THE RADAR PRESENTATION OF ANDREA HAS BEEN IMPROVING
DURING THE PAST FEW HOURS...CONVECTIVE CLOUD TOPS NEAR THE CENTER
OF CIRCULATION HAVE BEEN WARMING. THE STRONGEST CONVECTION REMAINS
LOCATED IN A BAND THAT IS MOVING ONSHORE THE WEST COAST OF FLORIDA
AT THIS TIME...AND THE TAMPA WSR-88D HAS BEEN SHOWING 65-70 KT AT
ABOUT 6500 FT. THE INITIAL INTENSITY IS BEING HELD AT 50 KT
PENDING THE NEXT AIR FORCE RECONNAISSANCE MISSION THIS AFTERNOON.

ANDREA HAS TURNED NORTHEASTWARD AND IS BEGINNING TO ACCELERATE WITH
AN INITIAL MOTION OF 035/13 KT. THE STORM IS LOCATED JUST TO THE
EAST OF A MID- TO UPPER-LEVEL TROUGH AXIS...AND IT IS GETTING
CLOSER TO FASTER MID-LATITUDE FLOW LOCATED OVER THE TENNESSEE
VALLEY. THIS FLOW IS EXPECTED TO CAUSE ANDREA TO RACE
NORTHEASTWARD ALONG THE EAST COAST OF THE UNITED STATES DURING THE
NEXT 48 HOURS OR SO. THERE IS VERY LITTLE SPREAD AMONG THE TRACK
GUIDANCE...AND ESSENTIALLY NO CHANGES WERE REQUIRED FROM THE
PREVIOUS OFFICIAL TRACK FORECAST.

GIVEN THE CONFLICTING SIGNALS IN RADAR AND SATELLITE DATA...THERE IS
NO STRONG EVIDENCE THAT ANDREA WILL STRENGTHEN MUCH BEFORE IT
REACHES THE COAST LATER TODAY. AFTER THE CENTER MOVES INLAND...
SOME WEAKENING IS EXPECTED...BUT MOST OF THE INTENSITY GUIDANCE
INDICATE THAT ANDREA WILL MAINTAIN TROPICAL-STORM INTENSITY THROUGH
THE FORECAST PERIOD. THE MAIN QUESTION IS WHEN EXTRATROPICAL
TRANSITION WILL BE COMPLETE. THE GLOBAL MODEL FIELDS DO NOT SHOW
STRONG BAROCLINICITY UNTIL ABOUT 48 HOURS...BUT THE FSU PHASE-SPACE
DIAGRAMS BASED ON THE GFS SUGGEST THAT THE TRANSITION COULD BE
COMPLETE BY 36 HOURS. FOR NOW...THE OFFICIAL FORECAST WILL KEEP
ANDREA AS TROPICAL UNTIL 36 HOURS.

THERE ARE NO CHANGES TO THE TROPICAL STORM WARNINGS ON THIS
ADVISORY. BASED ON THE ASSUMPTION THAT ANDREA WILL BECOME
POST-TROPICAL IN 36 TO 48 HOURS...WE DO NOT EXPECT TO EXTEND THE
TROPICAL WARNINGS ANY FURTHER NORTH ALONG THE COAST. OUR CURRENT
INTENTION IS THAT ANY HAZARDOUS WIND CONDITIONS FROM THE DELMARVA
PENINSULA NORTHWARD TO NEW ENGLAND WOULD BE HANDLED BY LOCAL
NATIONAL WEATHER SERVICE WARNING PRODUCTS.

REGARDLESS OF THE EXACT TRACK OF THE CENTER OF ANDREA...THE
PRIMARY EFFECTS ARE EXPECTED TO BE HEAVY RAINFALL ACROSS MUCH OF THE
FLORIDA PENINSULA AND INTO THE COASTAL SECTIONS OF THE SOUTHEASTERN
UNITED STATES...STORM SURGE FLOODING ALONG PORTIONS OF THE WEST
COAST OF FLORIDA...AND ISOLATED TORNADOES TODAY ACROSS THE FLORIDA
PENINSULA.


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