Tropical Depression THIRTEEN

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TROPICAL DEPRESSION THIRTEEN DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL132012
500 AM EDT TUE SEP 04 2012
 
SMALL BANDS OF DEEP CONVECTION CONTINUE TO WRAP AROUND THE EASTERN
SIDE OF THE DEPRESSION AND NIGHT VISIBLE IMAGES INDICATE THE CENTER
IS JUST WEST OF THE SOUTHERNMOST BAND. INTENSITY ESTIMATES WERE 35
KT AND 30 KT FROM TAFB/SAB RESPECTIVELY...AND GIVEN THE LACK OF ANY
SIGNIFICANT CHANGE IN SATELLITE IMAGERY DURING THE PAST FEW
HOURS...THE INITIAL WINDS ARE KEPT AT 30 KT. 

THE FUTURE STRENGTH OF THE DEPRESSION IS NOT AN EASY PREDICTION AS
IT IS VERY CLOSE TO SOME STRONG NORTHWESTERLY SHEAR. HOWEVER...THE
BULK OF THE MODEL GUIDANCE IS NOW INDICATING THAT THIS SHEAR WILL
STAY AWAY FROM THE CYCLONE...WITH LITTLE CHANGE IN THE ENVIRONMENT
PROBABLE FOR THE NEXT COUPLE OF DAYS WHILE THE CYCLONE REMAINS OVER
WARM WATERS. AN UPPER-LEVEL TROUGH IS FORECAST BY MANY GLOBAL
MODELS TO CUT OFF TO THE SOUTHWEST OF THE DEPRESSION IN A FEW
DAYS...WHICH COULD CREATE A FAVORABLE WIND PATTERN FOR
INTENSIFICATION. WITH THE CHANGE IN THE FORECAST LARGE-SCALE
ENVIRONMENT...IT DOES NOT SEEM AS LIKELY THAT THE DEPRESSION WILL
BECOME A REMNANT LOW ANYTIME SOON...AND THE NEW FORECAST NO LONGER
SHOWS THAT TRANSITION. THE LATEST PREDICTION IS CLOSE TO THE MODEL
CONSENSUS DURING THE FORECAST PERIOD...BUT IS MUCH LOWER THAN THE
SHIPS/LGEM GUIDANCE. IF THE DEPRESSION WERE TO TRACK FARTHER TO THE
LEFT THAN ANTICIPATED IN THE NEAR TERM...THEN MORE WEAKENING THAN
SHOWN BELOW IS LIKELY...WHICH COULD ALSO CAUSE THE SYSTEM TO
DEGENERATE INTO A REMNANT LOW.
 
BEST ESTIMATE OF INITIAL MOTION IS 310/5. THE CYCLONE SHOULD TURN
TOWARD THE NORTH-NORTHWEST AND NORTH OVER THE NEXT 24H OR SO AS IT
MOVES AROUND A WEAK SUBTROPICAL RIDGE OVER THE EASTERN ATLANTIC
OCEAN. STEERING CURRENTS ARE QUITE LIGHT AFTER THAT TIME...WITH THE
MIDDLE- TO UPPER-LEVEL LOW DROPPING TO THE SOUTH AND WEST OF THE
DEPRESSION IN A FEW DAYS THAT COULD CAUSE A SLOW NORTHWEST OR
NORTHWARD MOTION IN THE 3 TO 5 DAY PERIOD. THE LATEST NHC FORECAST
IS VERY CLOSE TO THE PREVIOUS ONE...BUT IS ADJUSTED A BIT TO THE
NORTH AND WEST AT LONG RANGE...ON THE LEFT SIDE OF THE TVCA MODEL.

FORECAST POSITIONS AND MAX WINDS
 
INIT  04/0900Z 26.5N  43.3W   30 KT  35 MPH
 12H  04/1800Z 26.9N  43.9W   30 KT  35 MPH
 24H  05/0600Z 27.6N  44.3W   30 KT  35 MPH
 36H  05/1800Z 28.3N  44.4W   30 KT  35 MPH
 48H  06/0600Z 28.8N  44.0W   30 KT  35 MPH
 72H  07/0600Z 30.0N  43.5W   30 KT  35 MPH
 96H  08/0600Z 31.5N  44.5W   35 KT  40 MPH
120H  09/0600Z 33.0N  44.5W   35 KT  40 MPH
 
$$
FORECASTER BLAKE
 
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