Tropical Storm CHANTAL

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TROPICAL STORM CHANTAL DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL032013
500 PM AST MON JUL 08 2013
 
LITTLE CHANGE IN THE CONVECTIVE ORGANIZATION OF CHANTAL HAS OCCURRED
TODAY...SO THE INTENSITY IS BEING MAINTAINED AT 40 KT. HOWEVER...AN
AIR FORCE RESERVE RECONNAISSANCE AIRCRAFT IS ENROUTE TO THE CYCLONE
AND IT WILL PROVIDE A BETTER ESTIMATE OF THE INTENSITY SHORTLY.
VISIBLE AND WATER VAPOR IMAGERY CONTINUE TO INDICATE AN INCREASE IN
THE UPPER-LEVEL ANTICYCLONIC OUTFLOW PATTERN.
 
THE INITIAL MOTION ESTIMATE IS NOW 290/23 KT. CHANTAL IS FORECAST TO
REMAIN SOUTH OF A STRONG DEEP-LAYER SUBTROPICAL RIDGE FOR THE NEXT
2 DAYS...SO A GENERAL WEST-NORTHWESTWARD MOTION IS EXPECTED DURING
THAT TIME. BY DAYS 3-5...A LARGE MID-/UPPER-LEVEL LOW CURRENTLY
MOVING WESTWARD THROUGH THE BAHAMAS IS FORECAST BY THE GLOBAL
MODELS TO MOVE ACROSS FLORIDA AND PHASE UP WITH A MID-LATITUDE
TROUGH...WHICH SHOULD CREATE A BREAK IN THE RIDGE AXIS AND PRODUCE
A WEAKER STEERING PATTERN OVER THE SOUTHEASTERN U.S. AND THE
BAHAMAS. AS A RESULT...CHANTAL IS EXPECTED TO SLOW DOWN AND TURN
NORTHWESTWARD BY 72 HOURS AS IT APPROACHES THE WEAKNESS IN THE
RIDGE...AND THEN MOVE SLOWLY NORTH-NORTHWESTWARD OR NORTHWARD ON
DAYS 4 AND 5 AS THE STEERING FLOW COLLAPSES. THE OFFICIAL FORECAST
TRACK HAS BEEN SHIFTED SLIGHTLY TO THE RIGHT OF THE PREVIOUS
ADVISORY TRACK...BUT NOT NEARLY AS FAR RIGHT AS THE MODEL CONSENSUS. 
 
ENVIRONMENTAL CONDITIONS AROUND AND AHEAD OF CHANTAL FAVOR AT LEAST
MODEST STRENGTHENING DURING THE NEXT 48 HOURS OR SO WHILE THE
CYCLONE REMAINS UNDER THE INFLUENCE OF UPPER-LEVEL RIDGING...AND
CHANTAL IS EXPECTED TO BE NEAR HURRICANE STRENGTH BEFORE IT REACHES
HISPANIOLA. AFTER CHANTAL MOVES PAST HISPANIOLA ON DAY 2/3...THE
CYCLONE SHOULD BE AFFECTED BY MODERATE TO STRONG WESTERLY VERTICAL
WIND SHEAR ASSOCIATED WITH AN UPPER-LEVEL TROUGH ACROSS FLORIDA...
WHICH IS EXPECTED TO FURTHER ENHANCE THE WEAKENING PROCESS. THE
OFFICIAL INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND
ESSENTIALLY FOLLOWS THE ICON CONSENSUS MODEL.

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/2100Z 11.8N  53.9W   40 KT  45 MPH
 12H  09/0600Z 13.0N  57.3W   45 KT  50 MPH
 24H  09/1800Z 14.6N  61.7W   50 KT  60 MPH
 36H  10/0600Z 16.2N  66.0W   55 KT  65 MPH
 48H  10/1800Z 17.8N  69.6W   60 KT  70 MPH
 72H  11/1800Z 21.0N  74.5W   45 KT  50 MPH
 96H  12/1800Z 24.3N  76.6W   30 KT  35 MPH
120H  13/1800Z 26.7N  78.0W   30 KT  35 MPH
 
$$
FORECASTER STEWART
 
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