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Tropical Storm DORIAN (Text)

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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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