[Tropical] Tropical Cyclone Discussion

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WTNT44 KNHC 140234
TCDAT4
TROPICAL STORM IRENE DISCUSSION NUMBER  38
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 PM EDT SAT AUG 13 2005

IRENE HAS BECOME A LITTLE BETTER ORGANIZED DURING THE PAST 6 HOURS
WITH A STRONG BURST OF DEEP CONVECTION HAVING DEVELOPED OVER AND
SOUTH OF THE WELL-DEFINED LOW-LEVEL CENTER. A 13/2232Z SSMI
OVERPASS DEPICTED A LARGE BUT CLOSED EYE FEATURE IN THE LOW-LEVELS
...BUT THE MID- AND UPPER-LEVEL CIRCULATIONS WERE STILL OPEN TO THE
NORTH. THE LAST RECON FLIGHT-LEVEL WIND DATA SUPPORTED 55-60 KT...
SO WITH THE INCREASE IN DEEP CONVECTION SINCE THAT TIME...AN
INTENSITY OF AT LEAST 60 KT SEEMS... ALTHOUGH IT COULD BE STRONGER.
IF THE CURRENT CONVECTIVE TREND CONTINUES...THEN THE NEXT RECON
FLIGHT AT 06Z SHOULD FIND IRENE AS A HURRICANE.

THE INITIAL MOTION ESTIMATE IS 335/09. THERE IS NO SIGNIFICANT
CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING THROUGH 96
HOURS. IRENE APPEARS TO BE MOVING THROUGH A WEAKNESS IN THE BERMUDA
RIDGE AND IT SHOULD GRADUALLY TURN NORTHWARD ON SUNDAY AND THEN
TURN NORTHEASTWARD AND ACCELERATE BY MONDAY AS THE CYCLONE GETS
CAUGHT UP IN THE STRONG MID-TROPOSPHERIC WESTERLIES THAT LIE ACROSS
THE NORTHERN U.S. AND NORTH ATLANTIC. BY 96 HOURS...A DEEP-LAYER
MID-LATITUDE LOW PRESSURE SYSTEM IS EXPECTED TO RAPIDLY ACCELERATE
THE THEN EXTRATROPICAL IRENE NORTHEASTWARD INTO THE FAR NORTH
ATLANTIC. THE OFFICIAL TRACK IS SIMILAR TO THE NHC MODEL CONSENSUS
AND IS CLOSE TO THE PREVIOUS FORECAST THROUGH 96 HOURS...AND THEN
FASTER AND TO THE LEFT AFTER THAT.

GIVEN THE IMPRESSIVE LOW-LEVEL EYE FEATURE NOTED IN THE SSMI IMAGERY
AND THE RECENT INCREASE IN DEEP CONVECTION...IRENE COULD BECOME A
LITTLE STRONGER THAN WHAT IS INDICATED BY THE OFFICIAL FORECAST
ONCE THE CYCLONE MOVES ONTO AND NORTH OF THE BERMUDA RIDGE AXIS
WHERE THE STEERING FLOWS SHOULD BECOME MORE ALIGNED AND REDUCE THE
SHEAR. THE OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS
PACKAGE AND REMAINS ABOVE THE SHIPS AND GFDL INTENSITY MODELS.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      14/0300Z 32.0N  69.9W    60 KT
 12HR VT     14/1200Z 33.5N  70.0W    65 KT
 24HR VT     15/0000Z 35.6N  69.3W    65 KT
 36HR VT     15/1200Z 37.4N  67.3W    65 KT
 48HR VT     16/0000Z 38.7N  64.3W    60 KT
 72HR VT     17/0000Z 41.0N  58.0W    55 KT...BECOMING EXTRATROPICAL
 96HR VT     18/0000Z 45.0N  50.0W    45 KT...EXTRATROPICAL
120HR VT     19/0000Z 55.0N  38.0W    40 KT...EXTRATROPICAL

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