[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 062045
TCDAT2

HURRICANE PHILIPPE DISCUSSION NUMBER  51
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL172011
500 PM AST THU OCT 06 2011

PHILIPPE HAS CONTINUED TO BECOME BETTER ORGANIZED THIS AFTERNOON AS
AN EYE IN THE VISIBLE IMAGERY HAS BECOME ESTABLISHED INSIDE A
RELATIVELY SMALL CENTRAL DENSE OVERCAST.  BOTH TAFB AND SAB
SUBJECTIVE DVORAK ANALYSES GIVE A CURRENT-INTENSITY NUMBER OF
4.5...OR ABOUT 77 KT.  A CIMSS AMSU ESTIMATE SUGGESTS 75 KT FROM A
1649Z POLAR-ORBITING SATELLITE PASS. THE CIMSS ADVANCED DVORAK
TECHNIQUE INDICATE A SLIGHTLY STRONGER 82 KT.  A BLEND OF THESE
GIVES AN INITIAL INTENSITY OF 75 KT...WHICH MAY BE SOMEWHAT
CONSERVATIVE. A 1228Z ASCAT SCATTEROMETER PASS PROVIDED THE WIND
RADII ANALYSIS...EVEN SMALLER THAN ESTIMATED EARLIER.

PHILIPPE IS BEING STEERED TOWARD THE NORTHEAST AT ABOUT 11 KT...
PRIMARILY DUE TO THE INFLUENCE OF A LARGE DEEP-LAYER
EXTRATROPICAL LOW CENTERED OVER THE CANADIAN MARITIMES.  THE
MULTI-MODEL CONSENSUS IS IN VERY GOOD AGREEMENT ON AN ACCELERATION
OF PHILIPPE IN THE SAME GENERAL DIRECTION DURING THE NEXT FEW DAYS.
THE MODELS INDICATE A SLOWING OF THE FORWARD SPEED AS THE CYCLONE
OCCLUDES AROUND DAYS THREE AND FOUR BEFORE ACCELERATING A FINAL
TIME IN THE FAR NORTH ATLANTIC AROUND DAY FIVE.  THE TRACK
PREDICTION IS VERY CLOSE TO BOTH THE CONSENSUS AND THE PREVIOUS
ADVISORY.

THE SHARP GRADIENT OF INFRARED CLOUD TOP TEMPERATURES ALONG THE
SOUTHWESTERN FLANK OF PHILIPPE MAY BE INDICATIVE OF THE EXPECTED
INCREASE IN VERTICAL SHEAR.  EVEN THOUGH PHILIPPE WILL BE PASSING
OVER A SUFFICIENTLY WARM SEA SURFACE TO SUSTAIN A TROPICAL
CYCLONE...THE COMBINATION OF STRONG VERTICAL SHEAR AND A DRY STABLE
ATMOSPHERE SHOULD LEAD TO GRADUAL WEAKENING DURING THE NEXT TWO
DAYS.  THE DYNAMICAL HURRICANE MODELS HAVE BACKED OFF FROM THEIR
EARLIER INSISTENCE OF CONTINUED INTENSIFICATION.  THE FORECAST IS
SLIGHTLY LOWER THAN THE INTENSITY CONSENSUS AND VERY SIMILAR TO THE
PREVIOUS ADVISORY.  AROUND 36 TO 48 HOURS...EXTRATROPICAL
TRANSITION SHOULD OCCUR AS A COLD FRONT WRAPS AROUND THE CYCLONE.

THE EXTRATROPICAL PORTION OF THE FORECAST IS BASED PRIMARILY ON
GUIDANCE FROM THE OCEAN PREDICTION CENTER.


FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 28.7N  59.0W   75 KT  85 MPH
 12H  07/0600Z 29.5N  57.7W   75 KT  85 MPH
 24H  07/1800Z 30.4N  55.2W   65 KT  75 MPH
 36H  08/0600Z 31.9N  51.4W   60 KT  70 MPH
 48H  08/1800Z 35.3N  47.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
 72H  09/1800Z 40.5N  44.5W   55 KT  65 MPH...POST-TROP/EXTRATROP
 96H  10/1800Z 45.0N  41.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
120H  11/1800Z 54.0N  34.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

$$
FORECASTER LANDSEA/PASCH


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