[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT43 KNHC 130302
TCDAT3
HURRICANE CHARLEY DISCUSSION NUMBER  15
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT THU AUG 12 2004

REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INDICATE
THAT WHILE THE CENTRAL PRESSURE HAS FALLEN TO 975 MB...WINDS FROM
DROPSONDES AND AT THE AIRCRAFT FLIGHT LEVEL ARE SO FAR NO HIGHER
THAN ON THE PREVIOUS FLIGHT.  THE AIRCRAFT AND LAND BASED RADAR
FROM KEY WEST FLORIDA AND CIENFUEGOS CUBA HAVE SHOWN THE 15-20 NM
DIAMETER EYEWALL SPORADICALLY BREAKING OPEN.  IN CONTRAST...
INFRARED SATELLITE IMAGERY SHOWS THE EYE BECOMING BETTER DEFINED...
ALTHOUGH CHARLEY HAS THUS FAR NOT BEEN ABLE TO MAINTAIN STRONG
SYMMETRIC CONVECTION AROUND IT.  ALL THESE SIGNS POINT TO A SYSTEM
THAT IS SLOWLY STRENGTHENING AT THIS TIME.  BASED ON THE AIRCRAFT
DATA AND SATELLITE INTENSITY ESTIMATES...THE INITIAL INTENSITY
REMAINS 90 KT.

THE INITIAL MOTION IS NOW 340/12...A LITTLE SLOWER THAN EARLIER.
RADAR TRACKING SHOWED A DUE NORTHWARD MOTION FOR A TIME THIS
EVENING...WHICH RAISES THE QUESTION OF WHETHER CHARLEY IS TURNING
NORTHWARD A LITTLE PERMATURELY.  ASIDE FROM THAT...THE TRACK
FORECAST IS FAIRLY STRAIGHT FORWARD.  CHARLEY IS ON THE WEST SIDE
OF THE SUBTROPICAL RIDGE OVER THE WESTERN ATLANTIC WHICH HAS ITS
AXIS AT ABOUT 25N.  A DEEP LAYER TROUGH COVERS THE CENTRAL AND
EASTERN UNITED STATES.  CHARLEY SHOULD MOVE GENERALLY NORTHWARD FOR
12-24 HR...THEN ACCELERATE NORTH-NORTHEASTWARD AHEAD OF THE TROUGH.
ALL MODEL GUIDANCE AGREES WITH THIS BASIC SCENARIO...ALTHOUGH THERE
IS SOME SPREAD IN BOTH SPEED AND DIRECTION.  THE OFFICIAL FORECAST
IS ALONG THE SAME LINE AS THE PREVIOUS FORECAST FOR THE FIRST 48 HR
BUT SOMEWHAT SLOWER.  IT IS ALONG THE EASTERN EDGE OF THE MODEL
GUIDANCE IN BEST AGREEMENT WITH THE GFS AND GFDL.  AFTER 48
HR...THE FORECAST IS SHIFTED SOMEWHAT TO THE LEFT TO COMPROMISE
BETWEEN THE GFS AND NOGAPS POSITIONS OF EXTRATROPICAL CHARLEY.

WHILE CHARLEY IS CURRENTLY STRENGTHENING SLOWLY...THERE IS STILL
POTENTIAL FOR RAPID STRENGTHENING OVER THE SOUTHEASTERN GULF OF
MEXICO GIVEN THE FAIRLY WELL-DEFINED EYE...THE WARM WATER AND THE
GOOD TO EXCELLENT OUTFLOW IN THE NORTHERN SEMICIRCLE.  ONE
POTENTIAL NEGATIVE FACTOR IS A DRY SLOT WHICH HAS WRAPPED ALL THE
WAY AROUND INNER CORE.  THE SHIPS MODEL TAKES CHARLEY TO 97 KT IN
24 HR...WHILE THE GFDL BEINGS IT TO 112 KT.  THE LATTER IS
CERTAINLY POSSIBLE IF THE INTENSIFICATION RATE INCREASES.  THE
INTENSITY FORECAST CALL FOR CHARLEY TO PEAK AT 105 KT PRIOR TO
LANDFALL...BUT IT COULD BE STRONGER.  AFTER LANDFALL...PASSAGE OVER
LAND AND INCREASING SHEAR SHOULD WEAKEN THE CYCLONE AND EVENTUALLY
CAUSE EXTRATROPICAL TRANSITION.

THE POSSIBILITY OF A PREMATURE NORTHWARD MOTION AND THE FORECAST
SIZE OF THE STORM REQUIRES TROPICAL STORM WATCHES TO BE EXTENDED
SOUTHWARD ALONG THE SOUTHEAST FLORIDA COAST.  THE FORECAST TRACK
REQUIRES EXTENSION OF HURRICANE WARNINGS UP THE FLORIDA WEST COAST
AND TROPICAL STORM WATCHES INTO SOUTH CAROLINA.

SINCE THE REST OF THE ADVISORY WAS TRANSMITTED...THE AIRCRAFT HAS
FOUND THAT THE CENTRAL PRESSURE HAS DROPPED TO 973 MB.

FORECASTER BEVEN

FORECAST POSITIONS AND MAX WINDS

INITIAL      13/0300Z 22.2N  82.4W    90 KT
 12HR VT     13/1200Z 24.0N  82.8W   100 KT
 24HR VT     14/0000Z 26.8N  82.8W   105 KT
 36HR VT     14/1200Z 31.0N  81.7W    65 KT...INLAND
 48HR VT     15/0000Z 35.0N  79.4W    45 KT...INLAND
 72HR VT     16/0000Z 43.5N  74.0W    35 KT...INLAND EXTRATROPICAL
 96HR VT     17/0000Z 48.5N  66.5W    30 KT...INLAND EXTRATROPICAL
120HR VT     18/0000Z...ABSORBED BY FRONTAL SYSTEM


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