Tropical Storm GAMMA

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TROPICAL STORM GAMMA DISCUSSION NUMBER  13...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
10 PM EST FRI NOV 18 2005

...CLARIFIED WORDING IN SECOND PARAGRAPH...
 
THE AIR FORCE HURRICANE HUNTER AIRCRAFT... ON ITS LAST LEG ALONG THE
NORTH-CENTRAL COAST OF HONDURAS EARLIER THIS EVENING JUST BEFORE
22Z... DID NOT MEASURE ANY WESTERLY WINDS. HOWEVER... SATELLITE
IMAGERY AND SURFACE OBSERVATIONS IN HONDURAS SUGGESTED WESTERLY
WINDS FARTHER SOUTH... SO THE LOW-LEVEL CENTER APPEARS TO HAVE BEEN
ALONG THE IMMEDIATE COAST AT THAT TIME. MORE RECENT IMAGERY
SUGGESTS THE LOW-LEVEL CENTER HAS EDGED NORTHWESTWARD OFF THE COAST
AT A FORWARD SPEED OF ABOUT 4 KT.  A MID-LEVEL CENTER IS APPARENT
IN THE COLDER INFRARED TOPS FARTHER NORTH... WITH THE TILTING
LIKELY CAUSED BY THE SOUTHERLY WIND SHEAR. ALSO ON ITS LAST LEG...
THE AIRCRAFT MEASURED 1500-FT FLIGHT-LEVEL WINDS OF 56 KT. 00Z
DVORAK INTENSITY ESTIMATES BASED ON THE CURVED BANDING IN THE
MID-LEVELS ARE ONLY 30 KT... BUT A SHEAR PATTERN USING A MORE
SOUTHERN CENTER LOCATION YIELDS A STRONGER ESTIMATE. THE ADVISORY
INTENSITY IS SET TO 40 KT MAINLY BASED ON THE EARLIER AIRCRAFT
DATA... BUT IT IS ALSO CONSISTENT WITH A 2330Z QUIKSCAT PASS.
 
THE DYNAMICAL MODELS ARE UNANIMOUS IN FORECASTING AN EXTRATROPICAL
LOW PRESSURE SYSTEM TO FORM OVER THE SOUTHEASTERN UNITED STATES IN A
LITTLE MORE THAN TWO DAYS... IN ASSOCIATION WITH A DEVELOPING
MID-LATITUDE TROUGH OVER THE EASTERN HALF OF THE U.S.  THE MODELS
ARE NOT IN AGREEMENT... HOWEVER... ON WHAT WILL BE LEFT OF GAMMA BY
THAT TIME.  MOST OF THEM FORECAST A TRACK THAT SEEMS TOO FAR TO THE
WEST OVER YUCATAN AND TOO SLOW... GIVEN THE SOUTHERLY MID- TO
UPPER-LEVEL STEERING FLOW THAT WILL ALSO SHEAR THE SYSTEM AND FORCE
THE LOW-LEVEL CENTER TO MOVE GENERALLY NORTHWARD JUST BEHIND THE
CONVECTION DURING THE NEXT COUPLE OF DAYS.  THE MODELS OFTEN DO NOT
FORECAST THE TRACK WELL FOR SHEARED SYSTEMS... AND THE OFFICIAL
FORECAST LEANS CLOSER TO THE DIRECTION IN WHICH THE SHEAR IS
POINTED.  BEYOND ABOUT 48 HOURS... ONCE THE EXTRATROPICAL SYSTEM
FORMS OVER THE SOUTHEASTERN U.S... THE NEW OFFICIAL FORECAST...
LIKE THE PREVIOUS ADVISORY... KEEPS GAMMA MOVING NORTHEASTWARD
ALONG WITH THAT SYSTEM EVEN THOUGH MOST OF THE MODELS ARE MUCH
SLOWER IN FORECASTING RECURVATURE.
 
THE WIND SHEAR WILL ONLY GET STRONGER AS THE TROUGH DEVELOPS OVER
THE SOUTHEASTERN U.S. AND GULF OF MEXICO DURING THE NEXT 2-3 DAYS. 
THEREFORE... CONDITIONS DO NOT APPEAR CONDUCIVE FOR SIGNIFICANT
STRENGTHENING... AND INTENSIFICATION TO A HURRICANE SEEMS RATHER
UNLIKELY IN THIS ENVIRONMENT.  THE GFDL NOW FORECASTS LITTLE CHANGE
IN THE INTENSITY FOR THE NEXT 2-3 DAYS AND PEAKS AT ABOUT 45 KT. 
THE SHIPS IS SIMILAR BUT FORECASTS A DECLINE AFTER 24 HOURS AS THE
SHEAR INCREASES.  THE OFFICIAL INTENSITY FORECAST IS ADJUSTED
DOWNWARD COMPARED TO THE PREVIOUS ADVISORY... ANTICIPATING THE
POSSIBILITY OF SOME SLIGHT STRENGTHENING IN THE SHORT TERM BUT
OVERALL LITTLE CHANGE UNTIL GAMMA BECOMES EXTRATROPICAL AND
EVENTUALLY IS ABSORBED INTO THE LARGER EXTRATROPICAL SYSTEM OVER
THE ATLANTIC.
 
 
FORECASTER KNABB
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      19/0300Z 16.4N  85.8W    40 KT
 12HR VT     19/1200Z 16.8N  86.3W    45 KT
 24HR VT     20/0000Z 17.4N  86.9W    45 KT
 36HR VT     20/1200Z 18.8N  87.0W    45 KT
 48HR VT     21/0000Z 20.8N  85.6W    45 KT
 72HR VT     22/0000Z 25.0N  81.0W    45 KT
 96HR VT     23/0000Z 34.0N  70.0W    40 KT...EXTRATROPICAL
120HR VT     24/0000Z...ABSORBED BY LARGER EXTRATROPICAL SYSTEM
 
 
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