Tropical Storm HANNA

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TROPICAL STORM HANNA DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL082008
1100 PM EDT THU SEP 04 2008
 
A RECONNAISSANCE AIRCRAFT MEASURED A MINIMUM PRESSURE OF 987 MB AND
60 KNOTS AT FLIGHT LEVEL ON ITS WAY HOME A FEW HOURS AGO. SINCE
THEN SATELLITE IMAGES HAVE SHOWN AN INCREASE IN THUNDERSTORM
ACTIVITY AND THERE ARE SOME INDICATIONS THAT THE CENTER COULD BE
UNDER THE CONVECTION OR VERY NEAR THE SOUTHERN EDGE. THE CLOUD
PATTERN ON IR IMAGES INDICATE THAT HANNA LOOKS A LITTLE MORE
TROPICAL THAN EARLIER TODAY BUT THE CYCLONE STILL HAS A LARGE WIND
FIELD AND LACKS AN INNER CORE. INITIAL INTENSITY IS KEPT AT 55
KNOTS AND ANOTHER PLANE WILL BE IN THE AREA IN A FEW HOURS TO CHECK
IF THE WINDS HAVE INCREASED.  NONE OF THE GUIDANCE INDICATE
SIGNIFICANT STRENGTHENING AND THE OFFICIAL FORECAST BRINGS HANNA TO
60 KNOTS BEFORE IT REACHES THE UNITED STATES COAST. PEOPLE ARE
REMINDED THAT THERE IS VERY LITTLE DIFFERENCE BETWEEN A STRONG
TROPICAL STORM AND A MINIMAL HURRICANE...ONLY A FIVE KNOT
DIFFERENCE.
 
SURFACE DATA AND EXTRAPOLATION FROM EARLIER RECONNAISSANCE FIXES
INDICATE THAT HANNA IS MOVING TOWARD THE NORTHWEST OR 320 DEGREES
AT 12 KNOTS...STEERED BY STRONG SUBTROPICAL RIDGE OVER THE WESTERN
ATLANTIC. THE WESTERN EDGE OF THE RIDGE IS FORECAST TO BE ERODED BY
AN APPROACHING SHORT WAVE. THIS PATTERN SHOULD FORCE HANNA TO MOVE
ON A MORE NORTHERLY TRACK DURING THE NEXT 24 TO 48 HOURS WITH AN
INCREASE IN FORWARD SPEED. THEREAFTER...HANNA IS EXPECTED TO BE
FULLY EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES AND RACE TO THE
NORTHEAST WHILE BECOMING EXTRATROPICAL.  THIS IS BASICALLY THE
SOLUTION PROVIDED BY MOST OF THE GUIDANCE.
 
IF HANNA BECOMES MORE TROPICAL AS SUGGESTED BY THE INCREASE IN
CONVECTION...THE WIND FIELD MOST LIKELY WILL CONTRACT A LITTLE BIT.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      05/0300Z 26.5N  76.3W    55 KT
 12HR VT     05/1200Z 28.5N  77.7W    55 KT
 24HR VT     06/0000Z 31.5N  78.5W    60 KT
 36HR VT     06/1200Z 35.0N  78.0W    50 KT...INLAND
 48HR VT     07/0000Z 39.0N  75.0W    40 KT...INLAND
 72HR VT     08/0000Z 46.0N  62.0W    40 KT...EXTRATROPICAL
 96HR VT     09/0000Z 50.5N  44.5W    40 KT...EXTRATROPICAL
120HR VT     10/0000Z 51.2N  27.0W    40 KT...EXTRATROPICAL
 
$$
FORECASTER AVILA
 
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