TROPICAL STORM DEAN ADVISORY NUMBER 7 | Main | Tropical Depression 5
August 15, 2007
TROPICAL STORM DEAN DISCUSSION NUMBER 7
AFTER THE CONVECTION WANED THIS AFTERNOON...A NEW BURST HAS
REDEVELOPED OVER THE CENTER DURING THE PAST FEW HOURS. DESPITE THE
SOMEWHAT RAGGED SATELLITE APPEARANCE AROUND 2100 UTC...A QUIKSCAT
PASS AT THAT TIME DETECTED A RATHER WELL DEFINED CIRCULATION WITH
BELIEVABLE 45-50 KT WINDS. WITH A NOD TO THE SATELLITE
PRESENTATION...THE INITIAL INTENSITY IS SET AT A POSSIBLY
CONSERVATIVE 45 KT. RECENT MICROWAVE IMAGERY AND THE QUIKSCAT DATA
SUGGEST THAT THE CENTER IS SLIGHTLY NORTH OF THE EARLIER ESTIMATES.
THE INITIAL MOTION IS 270/16...A LITTLE SLOWER THAN THE PREVIOUS
ADVISORY. THE FORECAST PHILOSOPHY REMAINS UNCHANGED AS DEAN IS
EXPECTED TO BE STEERED WEST TO WEST-NORTHWESTWARD DURING THE NEXT
FEW DAYS...SOUTH OF A DEEP-LAYER RIDGE. THE MODEL GUIDANCE
GENERALLY AGREES ON THIS SCENARIO BUT WITH SOMEWHAT VARYING FORWARD
SPEEDS. THE OFFICIAL TRACK FORECAST REMAINS FASTER THAN THE NOGAPS
AND ECMWF SOLUTIONS...WHICH CONTINUE TO STRUGGLE INITIALIZING THE
FORWARD MOTION OF DEAN. THE NEW TRACK FORECAST IS CLOSER TO THE
CONSENSUS OF THE GFDL...HWRF AND GFS MODELS THROUGH 72 HOURS...BUT
IS A LITTLE SLOWER THAN THESE MODELS AT DAYS 4 AND 5.
IT APPEARS THAT THE EASTERLY SHEAR THAT HAS BEEN AFFECTING DEAN IS
BEGINNING TO DECREASE. THE GLOBAL MODELS FORECAST A FAVORABLE
ENVIRONMENT FOR STEADY STRENGTHENING AND THE AVAILABLE INTENSITY
GUIDANCE BRINGS DEAN TO A HURRICANE IN 36-48 HOURS...AND NEAR THE
MAJOR HURRICANE THRESHOLD BY DAY 5.
THE WIND RADII WERE ADJUSTED BASED ON THE QUIKSCAT DATA.
FORECAST POSITIONS AND MAX WINDS
INITIAL 15/0300Z 12.0N 42.3W 45 KT
12HR VT 15/1200Z 12.2N 44.8W 50 KT
24HR VT 16/0000Z 12.4N 48.2W 55 KT
36HR VT 16/1200Z 12.8N 51.7W 60 KT
48HR VT 17/0000Z 13.4N 55.2W 70 KT
72HR VT 18/0000Z 14.5N 61.0W 80 KT
96HR VT 19/0000Z 16.0N 66.5W 90 KT
120HR VT 20/0000Z 17.5N 71.5W 100 KT
