Tropical Depression SEVENTEEN

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TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL172008
1000 PM EST WED NOV 05 2008
 
CONVECTION HAS INCREASED NEAR THE CENTER OF THE DEPRESSION OVER THE
PAST FEW HOURS...AND DVORAK T-NUMBERS FROM SAB AND TAFB AT 0000 UTC
SUPPORTED AN INTENSITY OF 30 AND 35 KT...RESPECTIVELY.  ANALYSIS OF
AMBIGUITIES FROM A QUIKSCAT PASS AT 2334 UTC SUGGESTS THAT THE
HIGHEST WINDS OUTSIDE OF RAIN NEAR THE CENTER WERE AROUND 25
KT...REASONABLY SUGGESTING THAT WINDS ARE NEAR 30 KT IN THE
CONVECTION.  ALSO...NOAA BUOY 42057 WELL NORTH OF THE CENTER
REPORTED A PEAK WIND OF 29 KT AT 2200 AND 2300 UTC...AND A GUST OF
33 KT.  BASED ON ALL OF THIS EVIDENCE...THE INITIAL INTENSITY IS
SET AT 30 KT.  AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT WILL
INVESTIGATE THE CYCLONE LATER TONIGHT AND MAY FIND THAT THE SYSTEM
HAS REACHED TROPICAL STORM STATUS.  

THE DEPRESSION HAS BEEN MOVING SLOWLY NORTHWEST OVER THE PAST FEW
HOURS.  A SLOW MOVEMENT TOWARD THE NORTHWEST IS EXPECTED TO CONTINUE
FOR THE NEXT 24 HOURS...WITH A GRADUAL TURN TOWARD THE NORTH
EXPECTED BY 48 HOURS AS THE CYCLONE ROUNDS THE WESTERN EDGE OF THE
UPPER-LEVEL ANTICYCLONE CENTERED TO ITS EAST.  LATER IN THE
PERIOD...AN UPPER-LEVEL TROUGH IS FORECAST TO DIG INTO THE GULF OF
MEXICO...AND WILL CAUSE THE CYCLONE TO TURN TOWARD THE NORTHEAST
WITH AN INCREASE IN FORWARD SPEED.  THE CURRENT TRACK FORECAST IS
SLIGHTLY FASTER THAN THE PREVIOUS ADVISORY THROUGH ABOUT 36
HOURS...BUT IS STILL SLOWER THAN MOST OF THE MODEL GUIDANCE.  AFTER
36 HOURS...THE FORECAST TRACK IS ADJUSTED TO THE LEFT OF THE
PREVIOUS FORECAST TOWARD THE DYNAMICAL MODEL CONSENSUS...TVCN. 

THE UPPER-LEVEL ENVIRONMENT AND WARM SEA-SURFACE TEMPERATURES ARE 
VERY FAVORABLE FOR INTENSIFICATION THROUGH ABOUT 72 HOURS.  THE
GFDL AND HWRF BOTH MAKE THE CYCLONE A HURRICANE WITHIN 36 TO 48
HOURS...AND FORECAST AN INTENSITY NEAR MAJOR HURRICANE STATUS BY 72
HOURS.  THE SHIPS MODEL FORECASTS THE SYSTEM TO BE NEAR HURRICANE
INTENSITY AT 48 HOURS BUT DOES NOT SHOW AS MUCH STRENGTHENING
BEYOND THAT TIME.  THE INTENSITY FORECAST WAS ADJUSTED UPWARD...AND
IS IN EXCELLENT AGREEMENT WITH THE ICON INTENSITY MODEL CONSENSUS. 
HOWEVER...IF THE CYCLONE IS ABLE TO ESTABLISH AN INNER CORE...MORE
RAPID INTENSIFICATION MAY OCCUR THAN IS FORECAST HERE.  BEYOND 72
HOURS...THE VERTICAL WIND SHEAR INCREASES RAPIDLY AS THE CYCLONE
INTERACTS WITH THE WESTERLIES...AND WEAKENING IS FORECAST AT THOSE
TIME PERIODS.  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      06/0300Z 14.3N  82.1W    30 KT
 12HR VT     06/1200Z 14.8N  82.5W    40 KT
 24HR VT     07/0000Z 15.6N  82.9W    50 KT
 36HR VT     07/1200Z 16.4N  83.1W    60 KT
 48HR VT     08/0000Z 17.3N  83.2W    70 KT
 72HR VT     09/0000Z 19.0N  82.0W    90 KT
 96HR VT     10/0000Z 20.5N  79.5W    70 KT
120HR VT     11/0000Z 23.5N  74.5W    50 KT
 
$$
FORECASTER BRENNAN/STEWART
 
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