Tropical Storm CHANTAL

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TROPICAL STORM CHANTAL DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032013
1100 AM AST MON JUL 08 2013
 
CONVECTIVE ORGANIZATION OF HAS IMPROVED SLIGHTLY IN SATELLITE
IMAGERY SINCE THE PREVIOUS ADVISORY WITH FRAGMENTED CURVED BANDS
DEVELOPING IN THE NORTHERN SEMICIRCLE...ALTHOUGH THE CORE
CONVECTION HAS WEAKENED SOME. THE INITIAL INTENSITY OF 40 KT IS
BASED ON A BLEND OF TAFB...SAB...ADT...AND AMSU SATELLITE INTENSITY
ESTIMATES. VISIBLE AND WATER VAPOR IMAGERY ALSO INDICATE THAT
CHANTAL HAS DEVELOPED SOME WEAK ANTICYCLONIC OUTFLOW.
 
THE INITIAL MOTION ESTIMATE REMAINS A RATHER BRISK 280/23 KT. NO
CHANGES WERE MADE TO THE PREVIOUS FORECAST TRACK. CHANTAL IS
FORECAST TO MOVE QUICKLY WEST-NORTHWESTWARD TO THE SOUTH OF A
STRONG DEEP-LAYER SUBTROPICAL RIDGE FOR THE NEXT 48 HOURS. BY DAY 3
AND BEYOND...A VIGOROUS MID-/UPPER-LEVEL LOW CURRENTLY JUST EAST OF
THE BAHAMAS IS EXPECTED TO MOVE WESTWARD AND MERGE WITH A
MID-LATITUDE TROUGH...CREATING A BREAK IN THE SUBTROPICAL RIDGE
OVER THE SOUTHEASTERN U.S. AND THE BAHAMAS. CHANTAL IS FORECAST TO
SLOW DOWN AND TURN NORTHWESTWARD BY 72 HOURS AS IT APPROACHES THIS
DEVELOPING WEAKNESS IN THE RIDGE...AND THEN MOVE SLOWLY
NORTH-NORTHWESTWARD THROUGH THE WEAKNESS ON DAYS 4 AND 5. THE
OFFICIAL FORECAST TRACK IS A LITTLE TO THE LEFT OF THE MODEL
CONSENSUS AND LIES ALONG THE SOUTHERN EDGE OF THE GUIDANCE
ENVELOPE...CLOSE TO THE GFS AND FSSE MODELS.
 
OTHER THAN THE FAST FORWARD SPEED OF CHANTAL...ENVIRONMENTAL
CONDITIONS ARE FAIRLY FAVORABLE FOR AT LEAST SOME MODEST
STRENGTHENING TO OCCUR DURING THE NEXT 48 HOURS OR SO WHILE THE
CYCLONE REMAINS UNDERNEATH A 200 MB RIDGE AXIS. INTERACTION WITH
THE MOUNTAINOUS TERRAIN OF HISPANIOLA AND EASTERN CUBA IN ABOUT
THREE DAYS...COUPLED WITH INCREASING WESTERLY VERTICAL WIND
SHEAR...IS EXPECTED TO CAUSED TO CHANTAL TO WEAKEN CONSIDERABLY BY
DAY 3...AND CONTINUE INTO DAYS 4 AND 5 AS THE CYCLONE MOVES
UNDERNEATH AN UPPER-LEVEL TROUGH. THE OFFICIAL INTENSITY FORECAST
FOLLOWS THE ICON INTENSITY CONSENSUS MODEL AND THE FSSE MODEL.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/1500Z 10.9N  51.7W   40 KT  45 MPH
 12H  09/0000Z 12.0N  55.0W   45 KT  50 MPH
 24H  09/1200Z 13.6N  59.6W   50 KT  60 MPH
 36H  10/0000Z 15.2N  64.1W   55 KT  65 MPH
 48H  10/1200Z 16.8N  68.2W   60 KT  70 MPH
 72H  11/1200Z 19.8N  74.1W   50 KT  60 MPH
 96H  12/1200Z 23.3N  76.8W   35 KT  40 MPH
120H  13/1200Z 26.0N  78.1W   30 KT  35 MPH
 
$$
FORECASTER STEWART
 
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