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Tropical Depression NINE (Text)

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TROPICAL DEPRESSION NINE DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
1100 PM AST SUN SEP 08 2013
 
SATELLITE IMAGES SHOW THAT DEEP CONVECTION ASSOCIATED WITH THE
DEPRESSION HAS INCREASED OVER THE WESTERN PORTION OF THE
CIRCULATION THIS EVENING.  RECENT ASCAT DATA WAS EXTREMELY HELPFUL
IN LOCATING THE CENTER OF THE CYCLONE...WHICH IS STILL LOCATED NEAR
THE EASTERN EDGE OF THE MAIN CONVECTIVE CLUSTER DUE TO SOME
NORTHEASTERLY SHEAR.  THE ASCAT DATA AND SUBJECTIVE DVORAK
INTENSITY ESTIMATES FROM TAFB AND SAB SUGGEST THAT THE MAXIMUM
WIND SPEED HAS INCREASED TO NEAR 30 KT.   

THE DEPRESSION IS MOVING WESTWARD AT ABOUT 10 KT. THE CYCLONE IS
FORECAST TO CONTINUE MOVING WESTWARD TO WEST-NORTHWESTWARD DURING
THE NEXT DAY OR SO...AROUND THE SOUTH SIDE OF A DEEP-LAYER RIDGE
OVER THE EASTERN ATLANTIC. AFTER THAT TIME...A MID- TO UPPER-LEVEL
LOW...CURRENTLY WELL TO THE NORTHWEST OF THE DEPRESSION IS FORECAST
TO DROP SOUTHWARD...CREATING A BREAK IN THE RIDGE ALONG 30W. THIS
SHOULD CAUSE THE DEPRESSION TO TURN NORTH-NORTHWESTWARD IN 36 TO 48
HOURS AND THE SYSTEM SHOULD REMAIN ON THAT GENERAL HEADING THROUGH
MUCH OF THE REMAINDER OF THE FORECAST PERIOD. THE TRACK GUIDANCE IS
IN A LITTLE BETTER AGREEMENT DURING THE FIRST 72 HOURS...BUT AFTER
THAT TIME...THERE IS A BIT MORE SPREAD THAN NOTED IN THE PREVIOUS
CYCLE. THE GFS...HWRF...AND GFS ENSEMBLE MEAN KEEP THE CYCLONE ON A
NORTH OR NORTH-NORTHWEST TRACK ALONG OR EAST OF 30W...WHILE THE
ECMWF SHOWS A FASTER NORTHWESTWARD OR WEST-NORTHWESTWARD MOTION AT
DAYS 4 AND 5. FOR NOW...THE OFFICIAL FORECAST SPLITS THESE
DIFFERENCES AND REMAINS NEAR THE MULTI-MODEL CONSENSUS. 

THE MODERATE NORTHEASTERLY SHEAR OVER THE DEPRESSION IS EXPECTED TO
DECREASE WITHIN THE NEXT 12 TO 24 HOURS.  DURING THAT TIME...THE
DEPRESSION WILL BE IN A MOIST AIRMASS AND OVER WARM WATERS.  THIS
SHOULD ALLOW FOR STEADY STRENGTHENING...AND THE UPDATED NHC
FORECAST SHOWS A FASTER RATE OF INTENSIFICATION DURING THE NEXT
DAY OR SO.  THE NHC FORECAST REMAINS MORE CONSERVATIVE THAN THE
STATISTICAL GUIDANCE AND IS CLOSE TO THE INTENSITY CONSENSUS.  LATE
IN THE PERIOD... INCREASING SOUTHWESTERLY SHEAR AND COOLER WATERS
ARE LIKELY TO CAUSE SOME WEAKENING. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  09/0300Z 13.2N  21.9W   30 KT  35 MPH
 12H  09/1200Z 13.4N  23.5W   35 KT  40 MPH
 24H  10/0000Z 13.7N  25.6W   45 KT  50 MPH
 36H  10/1200Z 14.2N  27.6W   55 KT  65 MPH
 48H  11/0000Z 15.2N  28.6W   60 KT  70 MPH
 72H  12/0000Z 18.5N  30.0W   70 KT  80 MPH
 96H  13/0000Z 22.0N  31.5W   70 KT  80 MPH
120H  14/0000Z 23.7N  33.0W   60 KT  70 MPH
 
$$
FORECASTER BROWN
 
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