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Subtropical Storm MELISSA Forecast Discussion Number 4
2013-11-19 09:49:35| National Hurricane Center (Atlantic)
Issued at 500 AM AST TUE NOV 19 2013 000 WTNT44 KNHC 190849 TCDAT4 SUBTROPICAL STORM MELISSA DISCUSSION NUMBER 4 NWS NATIONAL HURRICANE CENTER MIAMI FL AL142013 500 AM AST TUE NOV 19 2013 MELISSA APPEARS TO HAVE STRENGTHENED A LITTLE OVERNIGHT. ALTHOUGH THE CYCLONE IS NOT PRODUCING WIDESPREAD DEEP CONVECTION...A FEW BANDS HAVE BECOME BETTER ESTABLISHED TO THE NORTH OF THE CENTER DURING THE LAST FEW HOURS. THE INITIAL WIND SPEED IS NUDGED UPWARD TO 55 KT...IN AGREEMENT WITH THE LATEST SATELLITE INTENSITY ESTIMATE FROM TAFB. THE CIRCULATION OF THE CYCLONE IS GRADUALLY BECOMING MORE CIRCULAR AND THE CLOUD PATTERN APPEARS TO BE CONTRACTING WHILE IT SEPARATES FROM THE NEARBY FRONTAL BOUNDARY. A DECREASE IN SHEAR DURING THE NEXT 12 TO 24 HOURS COULD ALLOW MELISSA TO STRENGTHEN A LITTLE AND TRANSITION TO A TROPICAL CYCLONE. ANY STRENGTHENING SHOULD COME TO AN END IN 24 TO 36 HOURS WHEN THE STORM IS EXPECTED TO MOVE OVER SIGNIFICANTLY COLDER WATER AND INTO A DRIER AIRMASS. MELISSA IS ANTICIPATED TO BECOME POST-TROPICAL IN ABOUT 48 HOURS WHEN IT IS FORECAST TO BE OVER SEA SURFACE TEMPERATURES OF ABOUT 18 C. THE SUBTROPICAL STORM HAS TURNED TO THE NORTH...WITH THE LATEST INITIAL MOTION ESTIMATE BEING 360/8 KT. A DEEP-LAYER TROUGH AND ASSOCIATED COLD FRONT LOCATED OVER THE WESTERN ATLANTIC WILL BE MOVING CLOSER TO MELISSA...AND WILL HELP ACCELERATE THE CYCLONE NORTHEASTWARD DURING THE NEXT COUPLE OF DAYS. BEYOND A COUPLE OF DAYS...THERE IS A NOTABLE DISAGREEMENT IN HOW THE POST-TROPICAL REMNANT OF MELISSA INTERACTS WITH THE DEEP-LAYER TROUGH. THE GFS CONTINUES TO SHOW THE CYCLONE ROTATING AROUND THE EASTERN SIDE OF THE TROUGH OR LOW...WHILE THE ECMWF AND UKMET SHOW THE CYCLONE MOVING MORE EASTWARD IN THE WESTERLIES. THE NHC FORECAST IS ADJUSTED A LITTLE TO THE EAST OF THE PREVIOUS ONE...AND LIES CLOSE TO THE FLORIDA STATE SUPERENSEMBLE...WHICH IS IN BETWEEN THE AFOREMENTIONED SCENARIOS. FORECAST POSITIONS AND MAX WINDS INIT 19/0900Z 31.2N 54.6W 55 KT 65 MPH 12H 19/1800Z 32.6N 53.5W 60 KT 70 MPH 24H 20/0600Z 35.3N 50.3W 60 KT 70 MPH 36H 20/1800Z 38.4N 45.5W 55 KT 65 MPH 48H 21/0600Z 41.3N 39.5W 55 KT 65 MPH...POST-TROPICAL 72H 22/0600Z 46.5N 30.0W 45 KT 50 MPH...POST-TROP/EXTRATROP 96H 23/0600Z 52.0N 27.0W 40 KT 45 MPH...POST-TROP/EXTRATROP 120H 24/0600Z...DISSIPATED $$ FORECASTER CANGIALOSI
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