Tropical Storm ARLENE

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TROPICAL STORM ARLENE DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012011
1000 AM CDT WED JUN 29 2011
 
THE CLOUD PATTERN OF THE TROPICAL STORM IS GRADUALLY BECOMING BETTER
ORGANIZED THIS MORNING...WITH MORE EVIDENCE OF CONVECTIVE BANDING.
THE CURRENT INTENSITY IS SET AT 45 KT...WHICH IS IN CLOSE AGREEMENT
WITH SFMR-OBSERVED SURFACE WIND MEASUREMENTS FROM THE AIR FORCE
HURRICANE HUNTERS.  WATER VAPOR IMAGERY INDICATES THAT THE
UPPER-LEVEL WINDS ARE BECOMING MORE CONDUCIVE FOR STRENGTHENING.
THE CURRENT LACK OF A WELL-DEFINED INNER CORE WOULD ARGUE AGAINST
SIGNIFICANT STRENGTHENING OVER THE NEXT 24 HOURS.  HOWEVER...THE
SHIPS RAPID INTENSIFICATION INDEX SHOWS A SIGNIFICANTLY HIGH
PROBABILITY OF A 25 TO 30 KT INCREASE IN INTENSITY OVER THE NEXT 24
HOURS.  THEREFORE THE OFFICIAL INTENSITY FORECAST IS ABOVE MOST OF
THE GUIDANCE AND NOW SHOWS ARLENE APPROACHING HURRICANE STRENGTH AT
LANDFALL.  BASED ON THE NEW INTENSITY FORECAST...A HURRICANE WATCH
HAS BEEN ISSUED FOR A PORTION OF THE COAST OF NORTHEASTERN MEXICO.
 
CENTER FIXES FROM THE AIRCRAFT INDICATE THAT ARLENE WAS LOCATED
FARTHER SOUTH THAN PREVIOUSLY ESTIMATED...WHICH REQUIRES SOME
SOUTHWARD RELOCATION FOR THIS ADVISORY.  BASED ON THE LATEST
FIXES...THE INITIAL MOTION ESTIMATE IS NOW WEST OR 270/7.  A
DEEP-LAYER RIDGE TO THE NORTH AND NORTHWEST OF ARLENE SHOULD INDUCE
A WESTWARD OR SLIGHTLY SOUTH OF WESTWARD TRACK FOR THE NEXT DAY OR
TWO.  SOME OF THE MODEL GUIDANCE SUGGESTS EVEN MORE OF A TURN TO
THE LEFT AS THE CENTER NEARS THE COAST.  THE OFFICIAL TRACK
FORECAST IS MORE OR LESS BETWEEN THE GFS AND ECMWF TRACKS.
 
GIVEN THE LARGE SIZE OF THE CIRCULATION OF ARLENE...ONE SHOULD NOT
FOCUS ON THE EXACT FORECAST TRACK...AS IMPACTS WILL LIKELY BE FELT
OVER A LARGE PORTION OF NORTHEASTERN MEXICO WELL AWAY FROM THE
CENTER.
 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 21.2N  95.7W   45 KT  50 MPH
 12H  30/0000Z 21.2N  96.6W   50 KT  60 MPH
 24H  30/1200Z 21.2N  97.7W   60 KT  70 MPH...INLAND
 36H  01/0000Z 21.0N  98.8W   35 KT  40 MPH...INLAND
 48H  01/1200Z 20.8N 100.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  02/1200Z...DISSIPATED
 
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FORECASTER PASCH/BEVEN
 
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