[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 310250
TCDAT2
HURRICANE EARL DISCUSSION NUMBER  23
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL072010
1100 PM AST MON AUG 30 2010

THE INTENSITY OF EARL APPEARS TO HAVE LEVELED OFF FOR THE TIME
BEING.  DROPSONDE MEASUREMENTS FROM THE AIR FORCE RESERVE HURRICANE
HUNTERS INDICATE LITTLE CHANGE IN CENTRAL PRESSURE OVER THE PAST
FEW HOURS.  THERE WAS ALSO AN UNFLAGGED SFMR-MEASURED SURFACE WIND
OF 111 KT.  THE CURRENT INTENSITY IS HELD AT 115 KT FOR THIS
ADVISORY.  WSR-88D RADAR DATA FROM SAN JUAN SUGGEST THAT A
CONCENTRIC EYEWALL OR CONVECTIVE RING MAY BE FORMING.  THIS WOULD
AT LEAST TEMPORARILY HALT FURTHER INTENSIFICATION.  WATER VAPOR
IMAGERY CONTINUES TO DEPICT A BROAD UPPER-LEVEL TROUGH TO THE
NORTHWEST OF THE HURRICANE.  GLOBAL MODELS FORECAST AN UPPER-LEVEL
LOW TO CUT OFF FROM THE TROUGH AND MOVE SOUTHWARD...WHICH IS AN
UPPER-LEVEL FLOW EVOLUTION THAT IS USUALLY CONDUCIVE FOR
STRENGTHENING.  HOWEVER THE GFS PREDICTS AROUND 18-20 KT OF
SOUTH-SOUTHWESTERLY VERTICAL SHEAR OVER EARL IN 24-48 HOURS.  THE
OFFICIAL INTENSITY FORECAST HAS BACKED OFF SOME FROM THE PREVIOUS
ONE...AND SHOWS ONLY SLIGHT STRENGTHENING OVER THE NEXT DAY OR SO.
ALSO...SOME OSCILLATIONS IN INTENSIYY DUE TO EYEWALL REPLACEMENTS
OR OTHER INNER-CORE CONVECTIVE PROCESSES ARE ALSO POSSIBLE.

THERE HAVE BEEN SOME WOBBLES IN THE TRACK OF EARL BUT THE MEAN
MOTION HAS BEEN ABOUT 300/12 OVER THE PAST 6 HOURS.  A GRADUAL TURN
TOWARD THE NORTHWEST IS LIKELY IN 12 TO 24 HOURS AS EARL MOVES
AROUND THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL RIDGE.  BY DAY
3...A GENERALLY NORTHWARD TRACK IS EXPECTED AS THE HURRICANE MOVES
ALONG THE WESTERN SIDE OF THE RIDGE.  A STRONG MID-TROPOSPHERIC
TROUGH MOVING THROUGH THE GREAT LAKES SHOULD PROVIDE AN EASTWARD
COMPONENT OF STEERING BY DAY 4...AND EARL IS LIKELY TO ACCELERATE
NORTH-NORTHEASTWARD AHEAD OF THE TROUGH NEAR THE END OF THE
FORECAST PERIOD.   THE TRACK GUIDANCE SUITE IS IN RATHER CLOSE
AGREEMENT UP TO 72 HOURS...BUT BECOMES MORE DIVERGENT AFTER THAT
FORECAST TIME.  THE OFFICIAL TRACK FORECAST IS...ONCE AGAIN...
SHIFTED SLIGHTLY WESTWARD FROM THE PREVIOUS ONE AND IS VERY CLOSE
TO THE MULTI-MODEL CONSENSUS.

INTERESTS FROM THE CAROLINAS NORTHWARD TO NEW ENGLAND SHOULD MONITOR
THE PROGRESS OF EARL.  THERE IS STILL CONSIDERABLE UNCERTAINTY AS
TO HOW CLOSE THE HURRICANE WILL COME TO THE U.S. EAST COAST.

FORECAST POSITIONS AND MAX WINDS

INITIAL      31/0300Z 19.9N  65.8W   115 KT
 12HR VT     31/1200Z 20.9N  67.2W   120 KT
 24HR VT     01/0000Z 22.6N  69.2W   120 KT
 36HR VT     01/1200Z 24.6N  71.4W   120 KT
 48HR VT     02/0000Z 26.9N  73.4W   120 KT
 72HR VT     03/0000Z 32.5N  75.0W   110 KT
 96HR VT     04/0000Z 38.5N  70.5W    90 KT
120HR VT     05/0000Z 46.0N  62.0W    60 KT

$$
FORECASTER PASCH



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