667  
WTNT44 KNHC 060849  
TCDAT4  
 
TROPICAL DEPRESSION NINETEEN DISCUSSION NUMBER 1  
NWS NATIONAL HURRICANE CENTER MIAMI FL AL192017  
500 AM AST MON NOV 06 2017  
 
GOES-16 NIGHT-TIME VISIBLE AND INFRARED SATELLITE IMAGERY INDICATE  
THAT CONVECTION ASSOCIATED WITH THE WELL-DEFINED LOW PRESSURE  
SYSTEM LOCATED OVER THE CENTRAL ATLANTIC OCEAN HAS INCREASED AND  
BECOME BETTER ORGANIZED DURING THE PAST SEVERAL HOURS. SATELLITE  
INTENSITY ESTIMATES WERE T1.5/25 KT FROM BOTH TAFB AND SAB AT  
0600Z. SINCE THAT TIME, HOWEVER, A BURST OF DEEP CONVECTION HAS  
DEVELOPED OVER THE PREVIOUSLY PARTIALLY EXPOSED LOW-LEVEL  
CIRCULATION CENTER, WHICH HAD BEEN LOCATED NEAR THE NORTHWESTERN  
EDGE OF THE LARGE CONVECTIVE CLOUD MASS. GIVEN THAT THE CENTER IS  
NOW LOCATED FARTHER INTO THE DEEP CONVECTION, NHC OBJECTIVE  
INTENSITY ESTIMATES HAVE INCREASED TO MORE THAN 30 KT. AS A RESULT,  
ADVISORIES HAVE BEEN INITIATED ON THE NINETEENTH TROPICAL DEPRESSION  
OF THE 2017 ATLANTIC HURRICANE SEASON.  
 
THE INITIAL MOTION ESTIMATE IS 095/05 KT. THE CENTER OF THE CYCLONE  
HAS BEEN MOVING SLOWLY EASTWARD WITHIN THE LARGER CYCLONIC GYRE FOR  
THE PAST 12-18 HOURS, MOST LIKELY DUE TO THE DEEP CONVECTION BEING  
SHEARED TOWARD THE EAST. HOWEVER, THE LATEST NHC MODEL GUIDANCE  
INDICATES THAT THE RECENT EASTWARD MOTION SHOULD BE SHORT-LIVED  
SINCE THE LARGER GYRE IS FORECAST TO BEGIN MOVING NORTHWARD WITHIN  
THE NEXT 6 H OR SO. AS THE WIND FIELD CONTRACTS OVER THE NEXT 24  
HOURS, THE MOTION OF THE CYCLONE SHOULD STABILIZE AND BECOME LESS  
ERRATIC AS DEEP-LAYER SOUTHERLY STEERING FLOW BECOMES ESTABLISHED  
ON THE WEST SIDE OF A LARGE-SCALE SUBTROPICAL RIDGE. BY 48 H AND  
BEYOND, SOUTHWESTERLY FLOW AHEAD OF MID-LATITUDE TROUGH IS FORECAST  
TO ACCELERATE THE SYSTEM TOWARD THE NORTHEAST THROUGH 96 H. BY  
120 H, THE CYCLONE SHOULD HAVE MERGED WITH A FRONTAL SYSTEM OR HAVE  
DISSIPATED OVER THE COLD WATERS OF THE FAR NORTH ATLANTIC. THE  
OFFICIAL TRACK FORECAST LIES CLOSE TO A BLEND OF THE TVCN, TVCX,  
AND GFEX CONSENSUS TRACK MODELS.  
 
THE CYCLONE IS CURRENTLY EMBEDDED WITHIN A LOW-SHEAR ENVIRONMENT IN  
THE COL REGION BETWEEN A WEAKENING UPPER-LEVEL LOW LOCATED TO THE  
SOUTHEAST AND A TROUGH TO THE NORTHWEST. THE VERTICAL WIND SHEAR IS  
FORECAST BY THE GFS AND ECMWF MODELS TO REMAIN RELATIVELY LOW FOR  
THE NEXT 36 H OR SO, WHICH SHOULD ALLOW FOR SOME MODEST  
STRENGTHENING TO OCCUR DESPITE SEA-SURFACE TEMPERATURES ONLY BEING  
AROUND 25-26 DEG C. TEMPERATURES OF 2-3 DEG C COLDER-THAN-NORMAL  
IN THE MID- AND UPPER-LEVELS OF THE TROPOSPHERE, HOWEVER, SHOULD  
ACT TO OFFSET THE COOLER SSTS, PROVIDING SUFFICIENT INSTABILITY TO  
ALLOW FOR DEEP CONVECTION TO CONTINUE TO DEVELOP. MODEL SOUNDINGS  
AND THE FSU CYCLONE PHASE-SPACE DIAGRAM INDICATE THAT EXTRATROPICAL  
TRANSITION SHOULD BEGIN SHORTLY AFTER 48 H WHEN THE CYCLONE REACHES  
ABOUT 40N LATITUDE AND MOVES OVER MUCH COOLER WATER. THE NHC  
INTENSITY CLOSELY FOLLOWS THE HCCA AND IVCN CONSENSUS MODELS.  
 
FORECAST POSITIONS AND MAX WINDS  
 
INIT 06/0900Z 28.9N 50.2W 30 KT 35 MPH  
12H 06/1800Z 30.0N 49.9W 35 KT 40 MPH  
24H 07/0600Z 32.0N 49.6W 40 KT 45 MPH  
36H 07/1800Z 35.4N 49.4W 45 KT 50 MPH  
48H 08/0600Z 39.4N 48.2W 45 KT 50 MPH  
72H 09/0600Z 49.0N 38.0W 45 KT 50 MPH...POST-TROP/EXTRATROP  
96H 10/0600Z 59.0N 15.0W 40 KT 45 MPH...POST-TROP/EXTRATROP  
120H 11/0600Z...DISSIPATED  
 

 
FORECASTER STEWART  
 
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