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Tropical Storm DORIAN Forecast Discussion Number 5
2013-07-25 10:37:55| National Hurricane Center (Atlantic)
Issued at 500 AM AST THU JUL 25 2013 000 WTNT44 KNHC 250837 TCDAT4 TROPICAL STORM DORIAN DISCUSSION NUMBER 5 NWS NATIONAL HURRICANE CENTER MIAMI FL AL042013 500 AM AST THU JUL 25 2013 DORIAN HAS BECOME A LITTLE BETTER ORGANIZED THIS MORNING...WITH STRONGER CONVECTION OCCURRING NEAR THE CENTER. A RECENT AMSU OVERPASS SHOWED A MID-LEVEL EYE ASSOCIATED WITH THIS CONVECTION... ALTHOUGH IT WAS UNCLEAR IF THIS FEATURE WAS DIRECTLY OVER THE LOW-LEVEL CENTER. SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM SAB AND 45 KT FROM TAFB...AND A RECENT AMSU-BASED INTENSITY ESTIMATE FROM CIMSS WAS 48 KT. BASED ON THIS THE INITIAL INTENSITY IS INCREASED TO 50 KT. THE INITIAL MOTION IS 290/15. DORIAN IS ON THE SOUTH SIDE OF A DEEP-LAYER RIDGE THAT COVERS THE CENTRAL AND EASTERN ATLANTIC. THIS FEATURE SHOULD STEER THE CYCLONE QUICKLY WEST-NORTHWESTWARD TO WESTWARD FOR THE NEXT 72 HOURS OR SO. AFTER THAT...DORIAN SHOULD APPROACH A WEAKNESS IN THE RIDGE...WHICH SHOULD LEAD TO A WEST-NORTHWESTWARD MOTION AT A DECREASED FORWARD SPEED. THE GUIDANCE ENVELOPE HAS SHIFTED A BIT TO THE NORTH SINCE THE PREVIOUS ADVISORY. BASED ON THIS...THE NEW FORECAST TRACK WILL BE NUDGED A LITTLE TO THE NORTH...BUT IT LIES SOUTH OF THE CENTER OF THE GUIDANCE ENVELOPE AND THE MODEL CONSENSUS. THE INTENSITY FORECAST IS COMPLEX AND OF LOW CONFIDENCE. DORIAN SHOULD MOVE OVER WARMER SEA SURFACE TEMPERATURES DURING THE NEXT 2-3 DAYS...BUT DURING THIS TIME IT ALSO MAY ENCOUNTER SOUTHWESTERLY VERTICAL WIND SHEAR AND DRIER AIR AT THE MID-LEVELS. IN ADDITION...THE UPPER-LEVEL WIND FORECASTS FROM THE DYNAMICAL MODELS BECOME QUITE DIVERGENT BETWEEN 72-120 HOURS...WITH THE POSSIBILITIES RANGING FROM CONDITIONS FAVORABLE FOR INTENSIFICATION TO SHEAR STRONG ENOUGH TO CAUSE DORIAN TO WEAKEN. OVERALL...THE INTENSITY GUIDANCE FORECASTS LITTLE CHANGE IN STRENGTH DURING THE NEXT FIVE DAYS...AND THUS THE NEW FORECAST IS THE SAME AS THE PREVIOUS FORECAST. THE NEW FORECAST IS IN BEST AGREEMENT WITH THE SHIPS MODEL AND IS STRONGER THAN THE INTENSITY CONSENSUS. FORECAST POSITIONS AND MAX WINDS INIT 25/0900Z 15.6N 34.5W 50 KT 60 MPH 12H 25/1800Z 16.3N 37.0W 50 KT 60 MPH 24H 26/0600Z 17.0N 40.5W 50 KT 60 MPH 36H 26/1800Z 17.8N 44.4W 50 KT 60 MPH 48H 27/0600Z 18.3N 48.3W 50 KT 60 MPH 72H 28/0600Z 19.5N 55.5W 55 KT 65 MPH 96H 29/0600Z 20.5N 62.0W 55 KT 65 MPH 120H 30/0600Z 21.5N 67.0W 55 KT 65 MPH $$ FORECASTER BEVEN
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