045
WTNT41 KNHC 071500
TCDAT1
TROPICAL STORM IDA DISCUSSION NUMBER 13
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL112009
1000 AM EST SAT NOV 07 2009
RECENT MICROWAVE IMAGERY SUGGESTS THAT THE STRUCTURE OF
IDA HAS CONTINUED TO IMPROVE THIS MORNING...WITH A COUPLE OF
HOOKING BANDS NEAR THE CENTER. VISIBLE IMAGERY SHOWS AN EXPANDING
CENTRAL DENSE OVERCAST FEATURE AND NO OBVIOUS SIGNS OF SIGNIFICANT
SHEAR. THE LATEST DVORAK INTENSITY ESTIMATES ARE 45 KT FROM BOTH
AGENCIES...BUT GIVEN THE INCREASE IN ORGANIZATION SINCE THAT TIME
THE INITIAL INTENSITY HAS BEEN RAISED TO 50 KT. AN AIR FORCE
RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY EN ROUTE TO
INVESTIGATE THE STORM.
IDA IS MOVING NORTHWARD OR 355/8. IDA IS EXPECTED TO MOVE
NORTH-NORTHWESTWARD BETWEEN A MID-LEVEL ANTICYCLONE OVER THE
NORTH-CENTRAL CARIBBEAN SEA AND A DEEP-LAYER TROUGH OVER SOUTHERN
MEXICO. THE TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH 36 TO 48
HOURS AND THE NHC FORECAST REMAINS IN LINE WITH THE MODEL CONSENSUS
DURING THAT TIME. THEREAFTER...THERE IS A LARGE SPREAD AMONG THE
MODELS AS TO HOW IDA INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH
DIGGING INTO THE NORTHERN GULF OF MEXICO. THE GFS...ECMWF...AND
HWRF ALL MOVE THE CYCLONE QUICKLY NORTHWARD AND SHOW IT REACHING
THE NORTHERN GULF COAST IN ABOUT 3 DAYS AS IT BECOMES AN
EXTRATROPICAL CYCLONE. THE REMAINDER OF THE GUIDANCE HAS TRENDED
NORTHWARD...BUT TURNS THE SYSTEM GENERALLY EASTWARD BEFORE REACHING
THE NORTHERN GULF COAST. FOR NOW...THE OFFICIAL FORECAST IS
BETWEEN THESE TWO SCENARIOS...BUT HAS BEEN ADJUSTED NORTHWARD TO
ACCOUNT FOR THE LATEST TRENDS.
ENVIRONMENTAL CONDITIONS...WHILE NOT IDEAL...APPEAR CONDUCIVE ENOUGH
FOR STRENGTHENING DURING THE NEXT DAY OR SO AS THE CYCLONE
TRAVERSES THE NORTHWEST CARIBBEAN SEA. THE OFFICIAL FORECAST HAS
BEEN ADJUSTED UPWARD FROM THE PREVIOUS ONE BASED ON RECENT TRENDS.
ONCE IDA REACHES THE GULF OF MEXICO...SHEAR IS FORECAST TO INCREASE
AND WATERS BEGIN TO COOL. THESE FACTORS SHOULD CONTRIBUTE TO
WEAKENING...HOWEVER THE INTERACTION WITH THE UPPER-TROUGH AND AN
EXPECTED EXTRATROPICAL TRANSITION WILL LIKELY RESULT IN LESS
WEAKENING THAN TYPICAL...GIVEN THE STRONG SHEAR.
MOST OF THE GLOBAL MODELS SHOW A LARGE PRESSURE GRADIENT BETWEEN
A HIGH PRESSURE RIDGE OVER THE SOUTHEASTERN UNITED STATES AND THE
TROPICAL CYCLONE. THIS IS ALREADY CONTRIBUTING TO A LARGE AREA OF
STRONG WINDS OVER THE SOUTHERN GULF OF MEXICO WHICH IS NOT DIRECTLY
ATTRIBUTABLE TO IDA.
FORECAST POSITIONS AND MAX WINDS
INITIAL 07/1500Z 17.9N 84.1W 50 KT
12HR VT 08/0000Z 18.9N 84.6W 55 KT
24HR VT 08/1200Z 20.3N 85.5W 60 KT
36HR VT 09/0000Z 22.2N 86.8W 55 KT
48HR VT 09/1200Z 24.6N 88.0W 45 KT
72HR VT 10/1200Z 28.5N 88.0W 45 KT...EXTRATROPICAL
96HR VT 11/1200Z 29.0N 86.5W 40 KT...EXTRATROPICAL
120HR VT 12/1200Z 28.0N 85.0W 35 KT...EXTRATROPICAL
FORECASTER BROWN/CANGIALOSI/BLAKE
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page