[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 070233
TCDAT1
TROPICAL DEPRESSION IDA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
1000 PM EST FRI NOV 06 2009

A 2302 UTC SSMIS MICROWAVE PASS INDICATED THAT THE LOW-LEVEL CENTER
OF IDA WAS LOCATED JUST OFF THE NORTHEASTERN COAST OF HONDURAS AND
WAS DISPLACED TO THE SOUTH AND SOUTHEAST OF THE DEEP CONVECTION.
NEW CONVECTION IS DEVELOPING CLOSE TO THE CENTER...AND DVORAK
ESTIMATES FROM TAFB AND SAB ARE 25 KT AND 30 KT...RESPECTIVELY.
NOAA BUOY 42057...LOCATED ABOUT 150 N MI EAST-NORTHEAST OF THE
CENTER...RECENTLY REPORTED A 1-MINUTE SUSTAINED WIND OF 35 KT...BUT
IT APPEARS THAT THIS OCCURRED WITH THE PASSAGE OF A SQUALL AND MAY
NOT BE REPRESENTATIVE OF THE OVERALL CIRCULATION.  THEREFORE...IDA
IS KEPT AS A TROPICAL DEPRESSION FOR THIS ADVISORY...BUT IT IS
PROBABLY VERY CLOSE TO REGAINING TROPICAL STORM STATUS.

IDA CONTINUES TO MOVE NORTHWARD AT 360/6.  A MID-LEVEL ANTICYCLONE
BETWEEN JAMAICA AND HISPANIOLA AND A DEEP-LAYER TROUGH OVER MEXICO
ARE EXPECTED TO STEER IDA NORTH-NORTHWESTWARD THROUGH THE NEXT 72
HOURS.  THE TRACK GUIDANCE IS IN GOOD AGREEMENT DURING THIS PERIOD
ALTHOUGH THE GFDL AND HWRF MODELS ARE THE EASTERNMOST MODELS AND
HAVE FORCED THE MODEL CONSENSUS A LITTLE MORE TO THE EAST.  THE
FORECAST BEYOND 72 HOURS IS STILL COMPLEX AND IS DEPENDENT ON HOW
IDA INTERACTS WITH THE FRONT AND SHORTWAVE TROUGH OVER THE GULF OF
MEXICO.  MOST OF THE GUIDANCE SHOWS IDA BECOMING EXTRATROPICAL BY
96 HOURS ONCE IT MERGES WITH THE FRONT...BUT THE SOLUTIONS VARY ON
WHERE THE LOW GOES NEXT.  ONLY THE 1200 UTC ECMWF AND UKMET SHOW
IDA BECOMING PICKED UP BY A SHORTWAVE TROUGH AND MOVING
NORTHEASTWARD OVER THE NORTHERN GULF.  THE OTHER MODELS INDICATE A
MORE PRONOUNCED SOUTHWARD MOTION AFTER 96 HOURS...AND THE OFFICIAL
FORECAST NOW SHOWS A SLOW SOUTHEASTWARD TURN AT 120 HOURS.

ALTHOUGH WATERS ARE WARM OVER THE NORTHWESTERN CARIBBEAN...VERTICAL
SHEAR IS EXPECTED TO HAMPER MUCH INTENSIFICATION OVER THE NEXT FEW
DAYS.  THE GFDL AND HWRF MAKE IDA A HURRICANE OVER THE CENTRAL GULF
OF MEXICO...A SCENARIO THAT DOES NOT SEEM PLAUSIBLE IN THE FACE OF
WESTERLY SHEAR THAT IS EXPECTED TO INCREASE TO 50 OR 60 KT BY DAY
4.  THE OFFICIAL FORECAST INDICATES SOME SLOW STRENGTHENING OVER
THE NEXT SEVERAL DAYS BUT PEAKS THE INTENSITY AT 45 KT...WHICH IS
JUST BELOW THE INTENSITY CONSENSUS.

IT IS OF NOTE THAT MOST OF THE GLOBAL MODELS ARE SHOWING A LARGE
PRESSURE GRADIENT BETWEEN A HIGH OVER THE SOUTHEASTERN UNITED
STATES AND THE TROPICAL CYCLONE.  THIS COULD CONTRIBUTE TO A LARGE
AREA OF STRONG WINDS OVER THE GULF OF MEXICO NOT DIRECTLY
ATTRIBUTABLE TO IDA.

FORECAST POSITIONS AND MAX WINDS

INITIAL      07/0300Z 16.2N  84.0W    30 KT
 12HR VT     07/1200Z 17.1N  84.2W    35 KT
 24HR VT     08/0000Z 18.4N  84.8W    35 KT
 36HR VT     08/1200Z 19.7N  85.5W    40 KT
 48HR VT     09/0000Z 21.4N  86.5W    45 KT
 72HR VT     10/0000Z 25.5N  88.0W    45 KT
 96HR VT     11/0000Z 27.5N  87.0W    45 KT...EXTRATROPICAL
120HR VT     12/0000Z 26.5N  85.6W    35 KT...EXTRATROPICAL

$$
FORECASTER BERG



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