[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 062045
TCDAT1
TROPICAL DEPRESSION IDA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL112009
400 PM EST FRI NOV 06 2009

THERE HAS BEEN LITTLE CHANGE WITH IDA DURING THE DAY.  SATELLITE
IMAGES STILL SHOW A RATHER ASYMMETRIC SYSTEM...WITH MOST OF THE
SIGNIFICANT BANDING ACTIVITY TO THE NORTH OF THE CENTER.  THE
INITIAL INTENSITY WILL BE MAINTAINED AT 30 KT.  NOW THAT IDA IS
OFFSHORE OVER VERY WARM WATERS...THE SYSTEM HAS A CHANCE TO RE-
INTENSIFY.  THE BEST OPPORTUNITY FOR THE TROPICAL CYCLONE TO
STRENGTHEN IS OVER THE NORTHWESTERN CARIBBEAN SEA...WHERE VERTICAL
WIND SHEAR IS FORECAST TO BE MODERATE BY THE GLOBAL MODELS.  SHEAR
IS LIKELY TO GET RATHER STRONG BY THE TIME THE SYSTEM ENTERS THE
CENTRAL GULF OF MEXICO...WITH COOLER WATERS PRESENT...SO WEAKENING
WILL BE SHOWN AT THAT TIME.  WHILE THE DYNAMICAL GUIDANCE REMAINS
HIGHER THAN THE STATISTICAL GUIDANCE...THERE IS A LITTLE LESS
SPREAD THAN EARLIER.  THE NHC FORECAST SHOWS SLIGHTLY HIGHER WINDS
IN THE CARIBBEAN SEA THAN THE PREVIOUS FORECAST DID...AND REDUCES
THE INTENSITY AT THE END OF THE FORECAST PERIOD.

IDA CONTINUES MOVING TOWARD THE NORTH...360/7.  THE DEPRESSION
SHOULD MOVE TOWARD THE NORTH-NORTHWEST TOMORROW DUE TO SHORTWAVE
RIDGING OVER THE SOUTHEASTERN UNITED STATES.  MOST OF THE MODELS
ARE IN GOOD AGREEMENT ON THE SYSTEM PASSING OVER OR JUST TO THE
EAST OF THE YUCATAN PENINSULA IN A COUPLE OF DAYS.  AFTER IDA
ENTERS THE GULF OF MEXICO...IT WILL LIKELY TAKE A TRACK TOWARD THE
NORTH OR NORTHEAST AS IT BECOMES STEERED BY AN APPROACHING
MID-LEVEL TROUGH.  THE FORECAST TRACK IS VERY COMPLEX IN THE LONG
RANGE WITH SIGNIFICANT UNCERTAINTY IN HOW IDA WILL INTERACT WITH
THAT TROUGH.  MOST OF THE MODELS ARE SHOWING THE CYCLONE
APPROACHING THE NORTHERN GULF COAST...THEN TURNING EASTWARD OR EVEN
SOUTH OF EAST.  A COMPLICATING FACTOR IS THAT IDA WILL LIKELY BE
TRANSITIONING INTO AN EXTRATROPICAL CYCLONE AT THAT TIME...AND THE
GLOBAL MODELS HAVE QUITE VARYING SOLUTIONS FOR THIS TRANSITION.
THE NHC FORECAST IS ADJUSTED NORTHWARD AT THE LONG RANGE...BUT
REMAINS SOUTH OF THE MODEL 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      06/2100Z 15.7N  83.9W    30 KT
 12HR VT     07/0600Z 16.7N  84.1W    30 KT
 24HR VT     07/1800Z 17.9N  84.7W    35 KT
 36HR VT     08/0600Z 19.1N  85.4W    45 KT
 48HR VT     08/1800Z 20.6N  86.3W    50 KT
 72HR VT     09/1800Z 24.5N  88.0W    45 KT
 96HR VT     10/1800Z 27.5N  87.5W    45 KT
120HR VT     11/1800Z 27.5N  85.5W    35 KT...EXTRATROPICAL

$$
FORECASTER BLAKE



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