[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 160858
TCDAT1
TROPICAL STORM FAY DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL062008
500 AM EDT SAT AUG 16 2008

EVEN THOUGH WE CANNOT DETERMINE EXACTLY WHERE THE CENTER OF FAY IS
LOCATED...SATELLITE IMAGERY AND DATA FROM AN AIR FORCE
RECONNAISSANCE AIRCRAFT SUGGEST IT IS STILL INLAND...OVER
SOUTH-CENTRAL HISPANIOLA NEAR THE BORDER BETWEEN THE DOMINICAN
REPUBLIC AND HAITI.  THE AIR FORCE PLANE CIRCUMNAVIGATED THE ENTIRE
ISLAND OF HISPANIOLA DURING THE PAST FEW HOURS...ENDURING SOME
RATHER TURBULENT CONDITIONS...ESPECIALLY WITHIN THE STRONGEST
THUNDERSTORMS NEAR THE SOUTHERN COAST...AND WE APPRECIATE THE HARD
WORK OF THE CREW.  FLIGHT-LEVEL AND SFMR DATA FROM THE AIRCRAFT
SUPPORT MAINTAINING THE INTENSITY AT 40 KT.  FAY REMAINS BENEATH A
LARGE UPPER-LEVEL ANTICYCLONE RESULTING IN WELL-ESTABLISHED OUTFLOW
ALOFT...AND DESPITE THE INTERACTION WITH MOUNTAINOUS TERRAIN...THE
STORM HAS A RELATIVE WELL-ORGANIZED APPEARANCE IN SATELLITE
IMAGERY.

THE SYSTEM APPEARS TO BE CONTINUING WESTWARD AT ABOUT 270/12 TO THE
SOUTH OF A NARROW MID-LEVEL RIDGE OVER THE WESTERN ATLANTIC.  THE
SYNOPTIC REASONING...DYNAMICAL MODEL TRACKS...AND THE OFFICIAL
FORECAST TRACK ARE NOT SIGNIFICANTLY CHANGED FROM THE PREVIOUS
ADVISORY.  ALL OF THE MODELS FORECAST THE MID- TO UPPER-LEVEL TROUGH
OVER THE EASTERN U.S. TO GRADUALLY ERODE THE RIDGE DURING THE NEXT
COUPLE OF DAYS...ALLOWING FAY TO TURN TO THE RIGHT INTO THE
WEAKNESS...EVENTUALLY LEADING TO A NORTH-NORTHWESTWARD MOTION IN
3-5 DAYS.  THE NEW OFFICIAL TRACK IS VERY CLOSE TO THE PREVIOUS ONE
AND TO THE MODEL CONSENSUS...BUT THERE ARE RELIABLE MODELS ON BOTH
SIDES OF THAT TRACK.  THE GFDL AND HWRF TRACKS HEAD UP THE WESTERN
PORTION OF THE FLORIDA PENINSULA IN A FEW DAYS...WHILE THE GFS AND
UKMET ARE FARTHER WEST OVER THE EASTERN GULF OF MEXICO.  IN THE
SHORTER TERM...THE MODELS ALSO DO NOT AGREE ON WHETHER THE CENTER
OF FAY WILL PASS OVER OR JUST SOUTH OF SOUTHEASTERN CUBA BEFORE
TURNING NORTHWESTWARD.  THESE DIFFERING SOLUTIONS AGAIN HIGHLIGHT
THE PITFALLS OF FOCUSING TOO MUCH ON THE EXACT OFFICIAL FORECAST
TRACK...ESPECIALLY AT THE LONGER RANGES.

INTENSITY FORECASTING IS ALWAYS DIFFICULT...BUT IN THIS CASE IS MADE
EVEN MORE COMPLICATED BY THE LIKELY INTERACTIONS WITH LAND DURING
THE NEXT FEW DAYS.  ATMOSPHERIC AND OCEAN CONDITIONS ALONG THE
FORECAST TRACK APPEAR RATHER CONDUCIVE FOR STRENGTHENING...SO THE
MORE TIME FAY SPENDS OVER WATER...THE STRONGER IT IS LIKELY TO
BECOME...AND VICE VERSA.  DYNAMICAL MODEL FIELDS INDICATE THAT THE
WEAK-SHEAR ENVIRONMENT AROUND FAY SHOULD PERSIST THROUGHOUT MOST OF
THE FIVE-DAY FORECAST PERIOD...WITH PERHAPS A MODEST BUT TEMPORARY
INCREASE IN SHEAR IN ROUGHLY 48 HOURS.  WHEN FAY IS OVER
WATER...THOSE WATERS WILL BE VERY WARM.  SINCE THE OFFICIAL TRACK
IMPLIES AMPLE AMOUNT OF TIME OVER WATER...STEADY STRENGTHENING IS
FORECAST...IN A MANNER SIMILAR TO THE GFDL MODEL.  FAY COULD BE
WEAKER THAN FORECAST IF ITS STAY OVER HISPANIOLA HAS SUBSTANTIALLY
DISRUPTED THE CIRCULATION...OR IF IT MOVES FARTHER NORTH AND EAST
AND SPENDS MORE TIME OVER CUBA.  A TRACK FARTHER SOUTH AND
WEST...HOWEVER...COULD ALLOW FAY TO GET STRONGER THAN WHAT IS
SHOWN BELOW.


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/0900Z 18.7N  72.0W    40 KT
 12HR VT     16/1800Z 19.0N  74.0W    40 KT
 24HR VT     17/0600Z 19.6N  76.4W    50 KT
 36HR VT     17/1800Z 20.5N  78.3W    55 KT
 48HR VT     18/0600Z 21.8N  79.9W    65 KT...NEAR S COAST OF CUBA
 72HR VT     19/0600Z 25.0N  82.0W    70 KT
 96HR VT     20/0600Z 28.5N  83.5W    80 KT
120HR VT     21/0600Z 32.0N  84.5W    35 KT...INLAND

$$
FORECASTER KNABB
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