[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 172038
TCDAT2
TROPICAL DEPRESSION SEVENTEEN DISCUSSION NUMBER   2
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT SAT SEP 17 2005

AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT FOUND A BROAD AND
ELONGATED CIRCULATION CENTER ON THE NORTHEAST SIDE OF THE STRONG
CONVECTION OF TROPICAL DEPRESSION SEVENTEEN...WITH THE REPORTED
POSITION SOMEWHAT TO THE NORTH OF THE PREVIOUS ADVISORY POSITION.
THE LATEST MINIMUM CENTRAL PRESSURE IS 1006 MB AND THE MAXIMUM
FLIGHT-LEVEL WINDS AT 1500 FT SO FAR ARE 40 KT.  THIS SUGGESTS THAT
THE DEPRESSION IS NOT QUITE A TROPICAL STORM...BUT IT SHOULD REACH
THAT STATUS SOMETIME TONIGHT.

THE INITIAL MOTION IS A STILL SOMEWHAT UNCERTAIN 310/8.  STEERING
CURRENTS REMAIN UNUSUALLY WEAK FOR THAT PART OF THE ATLANTIC...AND
THE CYCLONE IS EXPECTED TO MOVE RATHER SLOWLY NORTHWESTWARD AROUND
THE SOUTHWEST SIDE OF A WEAK MID-LEVEL RIDGE FOR THE NEXT 3 DAYS...
WITH PERHAPS A MORE NORTHWARD MOTION AFTER THREE DAYS TOWARDS A
WEAKNESS IN THE RIDGE.  THE LARGE-SCALE MODELS CONTINUE TO FORECAST
THE SYSTEM TO PASS EAST OF THE LESSER ANTILLES...ALTHOUGH MOST OF
THEM STILL DO NOT NOT INITIALIZE THE SYSTEM VERY WELL.  THE
FORECAST TRACK IS SHIFTED SOMEWHAT TO THE NORTH OF THE PREVIOUS
TRACK BASED ON THE INITIAL POSITION...AND LIES ALONG THE LEFT SIDE
OF THE ENVELOPE OF MODEL GUIDANCE.

THE CYCLONE IS FORECAST TO BE OVER 30C WATER FOR THE NEXT 5 DAYS AND
THE SHEAR IS FORECAST TO BE LIGHT TO PERHAPS MODERATE.  THUS...
STEADY STRENGTHENING SHOULD OCCUR.  THE SHIPS MODEL HAS A LITTLE
LESS INTENSIFICATION THAN 6 HR AGO AS IT IS FORECASTING A LITTLE
MORE SHEAR.  HOWEVER...THE GFDL CONTINUES TO SHOW RAPID
INTENSIFICATION TO A MAJOR HURRICANE.  THE INTENSITY FORECAST
BRINGS THE DEPRESSION TO HURRICANE STRENGTH IN 48 HR AND TO 95 KT
BY 120 HR...IN BETWEEN SHIPS AND THE GFDL.

THE CURRENT FORECAST TRACK DOES NOT IMMEDIATELY REQUIRE WATCHES OR
WARNINGS.  WATCHES OR WARNINGS MAY BE REQUIRED FOR PORTIONS OF THE
LESSER ANTILLES LATER TONIGHT OR SUNDAY.

FORECASTER BEVEN


FORECAST POSITIONS AND MAX WINDS

INITIAL      17/2100Z 13.8N  55.2W    30 KT
 12HR VT     18/0600Z 14.6N  56.1W    35 KT
 24HR VT     18/1800Z 15.6N  57.1W    45 KT
 36HR VT     19/0600Z 16.6N  58.1W    55 KT
 48HR VT     19/1800Z 17.6N  59.1W    65 KT
 72HR VT     20/1800Z 19.5N  61.0W    75 KT
 96HR VT     21/1800Z 21.5N  62.0W    85 KT
120HR VT     22/1800Z 23.5N  63.0W    95 KT


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