[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 170228
TCDAT4
HURRICANE IRENE DISCUSSION NUMBER  50
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT TUE AUG 16 2005

A WARM SPOT WITHIN THE DEEP CONVECTION HAS STILL BEEN APPARENT FOR
MUCH OF THE EVENING...ALTHOUGH OVERALL THE AMOUNT OF DEEP
CONVECTION HAS DECREASED MARKEDLY OVER THE LAST 12 HOURS...AND THE
PATTERN HAS DEGRADED DURING THE LAST COUPLE OF HOURS. IN
ADDITION...WATER VAPOR IMAGERY SHOWS AN EROSION OF THE MOISTURE IN
THE SOUTHWEST QUADRANT. DVORAK T-NUMBERS FROM TAFB AND SAB HAVE
COME DOWN TO 4.0...AND THE INITIAL INTENSITY IS LOWERED TO 80 KT
FOR THIS ADVISORY. IRENE CONTINUES TO BE LARGELY SHELTERED FROM THE
STRONG BELT OF UPPER-LEVEL WESTERLIES THAT LIE NORTH OF ABOUT 38N
LATITUDE. IT IS STILL EXPECTED THAT IRENE WILL BE IMPACTED BY MUCH
STRONGER SHEAR ASSOCIATED WITH THESE WESTERLIES WITHIN 12-24
HOURS...AND THIS SHOULD CAUSE WEAKENING. THE SHIPS 48 HOUR FORECAST
OF A 68 KT HURRICANE OVER 15C WATER IS DIFFICULT TO ACCEPT...AND
THE OFFICIAL FORECAST IS CONSIDERABLY BELOW THIS GUIDANCE. A
BAROCLINIC KICK FROM THE MID-LATITUDE TROUGH CURRENTLY OVER THE
PROVINCE OF QUEBEC IS EXPECTED TO KEEP THE EXTRATROPICAL REMNANTS
OF IRENE VIGOROUS UNTIL THE SYSTEM IS ABSORBED BY A LARGER
EXTRATROPICAL LOW AFTER 48 HOURS.

THE INITIAL MOTION IS 090/8.  IRENE CONTINUES TO SLIDE SLOWLY
EASTWARD SOUTH OF THE MAIN BELT OF THE WESTERLIES.  AS THE
AFOREMENTIONED MID-LATITUDE TROUGH APPROACHES IRENE'S
LONGITUDE...THE FLOW IS EXPECTED TO TURN SOUTHWESTERLY AND IRENE
SHOULD BEGIN TO ACCELERATE AHEAD OF THE TROUGH.  OVER THE PAST
COUPLE OF DAYS...THE GFDL HAS BEEN CONSISTENTLY...AND CORRECTLY...
TO THE RIGHT OF THE GLOBAL MODELS AND THE CURRENT FORECAST IS
ADJUSTED SOMEWHAT EASTWARD TO BE IN BETTER AGREEMENT WITH THE
GFDL...ESPECIALLY IN THE FIRST 24 HOURS.

FORECASTER FRANKLIN


FORECAST POSITIONS AND MAX WINDS

INITIAL      17/0300Z 36.6N  60.4W    80 KT
 12HR VT     17/1200Z 37.1N  58.7W    70 KT
 24HR VT     18/0000Z 39.0N  55.0W    65 KT
 36HR VT     18/1200Z 43.3N  49.3W    55 KT...EXTRATROPICAL
 48HR VT     19/0000Z 50.0N  42.0W    50 KT...EXTRATROPICAL
 72HR VT     20/0000Z...ABSORBED BY EXTRATROPICAL LOW


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