[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT44 KNHC 162127
TCDAT4
HURRICANE IRENE DISCUSSION NUMBER  49
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT TUE AUG 16 2005

THE EYE BECAME BETTER DEFINED AND ITS EMBEDDED DISTANCE WITHIN THE
COLD CLOUD TOPS WAS LARGE ENOUGH TO YIELD A T NUMBER OF 5.0 AT
18Z...CORRESPONDING TO 90 KNOTS.  SINCE THEN...THE CLOUD TOPS HAVE
WARMED SOMEWHAT AND THE EYE BECAME LESS DISTINCT.  THEREFORE THE
ADVISORY INTENSITY IS SET AT 85 KNOTS.  IRENE'S CONTINUED EASTWARD
TRACK HAS KEPT THE HURRICANE MOSTLY 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 GUIDANCE LOOKS SUSPECT...
SINCE IT KEEPS IRENE AT HURRICANE STRENGTH THROUGH 48 HOURS...BY
WHICH TIME THE SHEAR IS FORECAST TO INCREASE TO 37 KNOTS WITH A SEA
SURFACE TEMPERATURE OF 15 DEG C.  THE OFFICIAL FORECAST SHOWS A
MORE RAPID RATE OF WEAKENING THAN SHIPS...BUT MAINTAINS A VIGOROUS
EXTRATROPICAL STORM OUT TO 72 HOURS.  BEYOND THAT TIME...THE SYSTEM
IS LIKELY TO BECOME ABSOREBED BY...OR MERGE WITH...ANOTHER
BAROCLINIC CYCLONE.

IRENE HAS CONTINUED ITS UNEXPECTEDLY PROLONGED EASTWARD TRACK.
HOWEVER...A MID-TROPOSPHERIC TROUGH NEAR JAMES BAY WILL SOON BE
APPROACHING THE LONGITUDE OF THE HURRICANE.  THIS SHOULD INTRODUCE
A SOUTHWESTERLY COMPONENT TO THE STEERING FLOW...AND INDUCE A
LEFTWARD TURN IN LESS THAN 24 HOURS.  HOWEVER BECAUSE OF THE
CONTINUED EASTWARD MOTION...THE OFFICIAL FORECAST TRACK IS SHIFTED A
LITTLE MORE TO THE EAST OF THE PREVIOUS NHC TRACK.  THE OFFICIAL
TRACK FORECAST IS IN GOOD AGREEMENT WITH THE DYNAMICAL MODEL
CONSENSUS.  BY 72 HOURS...THERE IS A CONSIDERABLE SPREAD IN THE
INDIVIDUAL MODELS.  THEREFORE THERE IS LOW CONFIDENCE IN THE
LOCATION AT THAT FORECAST TIME.  BY THEN...HOWEVER...IRENE'S
EXTRATROPICAL REMNANT MAY NO LONGER HAVE RETAINED ITS IDENTITY.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      16/2100Z 36.5N  61.6W    85 KT
 12HR VT     17/0600Z 37.2N  60.1W    80 KT
 24HR VT     17/1800Z 38.8N  57.3W    70 KT
 36HR VT     18/0600Z 42.0N  52.5W    60 KT...BECOMING EXTRATROPICAL
 48HR VT     18/1800Z 47.0N  46.0W    50 KT...EXTRATROPICAL
 72HR VT     19/1800Z 56.0N  40.0W    50 KT...EXTRATROPICAL
 96HR VT     20/1800Z...ABSORBED


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