15Z Tropical Update

TROPICAL STORM IGOR FORECAST 2
TROPICAL FORECAST CENTER
11:00 AM EDT SATURDAY SEPTEMBER 11, 2010

AT 11:00 AM EDT/1500Z...THE CENTER OF TROPICAL STORM IGOR WAS LOCATED NEAR 17.4 N 39.5W OR 1470 MILES EAST OF THE LEEWARD ISLANDS. IGOR WAS MOVING TO THE WEST NEAR 20 MPH...AND THIS MOTION WITH A DECREASE OF FORWARD SPEED IS EXPECTED. MAXIMUM SUSTAINED WINDS ARE NEAR 70 MPH...AND IGOR STRENGTHENING IS FORECAST AND IGOR WILL LIKELY BECOME A HURRICANE BY TONIGHT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB/29.38 IN.

DESPITE THUNDERSTORMS HAVE DECREASED IN IGOR...AN EYE FEATURE IS SHOWN ON VISIBLE SATELLITE AND WHILE WE COULD TECHNICALLY CALL IGOR A HURRICANE...DVORAK ESTIMATES HAVE DECREASE SOMEWHAT...SO WILL KEEP IGOR A 60 KT STRONG TROPICAL STORM. THERE IS A BIT OF EASTERLY SHEAR IMPACTING IGOR AND THIS WILL DECREASE AS THE DAY GO ON AND ALL MODELS POINT TO SIGNIFICANT STRENGTHENING DURING THE FORECAST PERIOD...TO THE POINT THAT I HAVE IGOR AS A LARGE...CATEGORY 4 HURRICANE IN 4 DAYS. NHCS FORECAST IS SLIGHTLY WEAKER THAN MINE...AND I THINK IT WILL BECOME A CATEGORY 4 STORM WITHIN 4 DAYS BECAUSE SHEAR WILL DECREASE TO LESS THAN 10 KTS AND IGOR WILL BE MOVING THROUGH WATERS OF AT LEAST 28 TO 29 C. THERE IS A CHANCE THAT IGOR COULD BE EVEN STRONGER THAN WHAT I/M FORECASTING ESPECIALLY IF IGOR GOES THROUGH A RAPID INTENSIFICATION CYCLE...WHICH IS CERTAINLY POSSIBLE.

INITIAL IS A BIT SLOWER...275/17 KTS. FORECAST TRACK WITH IGOR WILL FOLLOW THE STEERING CURRENTS OF THE SUBTROPICAL RIDGE AND MOVE WESTWARD THROUGH MOST OF THE FORECAST PERIOD. HOWEVER TOWARDS DAYS 3 THROUGH 5...A WEAKNESS IN THE TROUGH COULD SLOW DOWN IGOR TO LESS THAN 10 KTS AND COULD ACTUALLY MOVE MORE ERRATIC THAN WHAT I/M SHOWING...BUT OVER A GENERAL WEST TO WEST-NORTHWEST MOTION IS EXPECTED DURING THE FORECAST PERIOD AND NHCS FORECAST IS FAIRLY SIMILAR TO MY FORECAST TRACK.

FORECAST POSITION AND INTENSITY:

11/15Z 17.4 N 39.5 W 60 KTS
12/03Z 17.8 N 41.7 W 65 KTS
12/15Z 18.3 N 44.7 W 75 KTS
13/03Z 18.9 N 47.6 W 85 KTS
13/15Z 19.1 N 50.2 W 90 KTS
14/15Z 19.0 N 54.5 W 110 KTS
15/15Z 19.5 N 56.5 W 115 KTS
16/15Z 22.0 N 58.0 W 115 KTS

JACKSON