[Tropical] Tropical Cyclone Discussion

EMWIN Server emwin at nashvilleweather.net
Thu Jun 6 21:35:57 CDT 2013


WTNT41 KNHC 070235
TCDAT1

TROPICAL STORM ANDREA DISCUSSION NUMBER   6
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012013
1100 PM EDT THU JUN 06 2013

ANDREA HAS WEAKENED CONSIDERABLY SINCE MOVING INLAND EARLIER THIS
EVENING. THE ONLY REPORT OF TROPICAL-STORM-FORCE WINDS ON LAND OR
OVER WATER HAS COME FROM A SHIP OBSERVATION EAST OF SAINT
AUGUSTINE...AND THE INITIAL INTENSITY HAS BEEN LOWERED TO 40 KT.
ANY WINDS THIS STRONG ARE LIKELY OCCURRING IN RANBANDS OFFSHORE TO
THE EAST OF THE CENTER. THE SATELLITE PRESENTATION OF ANDREA BEARS
LITTLE RESEMBLANCE TO A TROPICAL CYCLONE...WITH A PRONOUNCED DRY
INTRUSION NOTED OVER AND SOUTHWEST OF THE CENTER AND THE DEEP
CONVECTION IN A BAND WELL REMOVED TO THE EAST AND SOUTHEAST. GIVEN
THAT ONLY SHALLOW CONVECTION IS OCCURRING NEAR THE CENTER...
INTERACTION WITH BAROCLINIC FEATURES WILL INCREASINGLY BECOME THE
MECHANISM SUPPORTING THE CYCLONE THROUGH THE FORECAST PERIOD. AS
ANDREA IS ABSORBED BY A LIFTING MID/UPPER-LEVEL TROUGH...GLOBAL
MODEL GUIDANCE SHOWS LITTLE CHANGE IN INTENSITY DURING THE FORECAST
PERIOD. THE NEW NHC FORECAST FOLLOWS THIS THINKING...AND SHOWS
ANDREA BECOMING POST-TROPICAL BY 24 HOURS. HOWEVER...THIS COULD
OCCUR SOONER IF THE CONVECTIVE STRUCTURE DOES NOT IMPROVE.

THE INITIAL MOTION IS 045/13...AS THE CENTER SLOWED A LITTLE WHILE
MOVING ONSHORE. THE TRACK MODEL GUIDANCE REMAINS IN VERY GOOD
AGREEMENT SHOWING THE CYCLONE ACCELERATING NORTHEASTWARD ALONG THE
U.S. EAST COAST AHEAD OF THE AFOREMENTIONED TROUGH AND THEN TURNING
QUICKLY EASTWARD OVER THE NORTH ATLANTIC. THE NEW NHC FORECST IS
A LITTLE TO THE RIGHT OF THE PREVIOUS ONE FOR THE FIRST 24 HOURS DUE
TO THE INITIAL MOTION AND IS LARGELY AN UPDATE OF THE PREVIOUS
PACKAGE AFTERWARD. THE NHC TRACK IS CLOSE TO A BLEND OF THE GFS AND
ECMWF AND ALSO LIES NEAR THE FSU SUPERENSEMBLE.

BASED ON THE ASSUMPTION THAT ANDREA WILL BECOME POST-TROPICAL IN
ABOUT 24 HOURS...WE DO NOT EXPECT TO EXTEND THE TROPICAL WARNINGS
ANY FARTHER 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.


FORECAST POSITIONS AND MAX WINDS

INIT  07/0300Z 30.3N  82.4W   40 KT  45 MPH...INLAND
 12H  07/1200Z 33.0N  80.2W   40 KT  45 MPH...INLAND
 24H  08/0000Z 36.8N  76.3W   40 KT  45 MPH...POST-TROPICAL
 36H  08/1200Z 41.0N  70.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
 48H  09/0000Z 44.7N  63.3W   35 KT  40 MPH...POST-TROP/EXTRATROP
 72H  10/0000Z 45.5N  46.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  11/0000Z 45.5N  24.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
120H  12/0000Z...DISSIPATED

$$
FORECASTER BRENNAN



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