[Tropical] Tropical Cyclone Discussion

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WTNT42 KNHC 181454
TCDAT2
TROPICAL DEPRESSION TWO DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022006
1100 AM EDT TUE JUL 18 2006

CONVENTIONAL AND MICROWAVE SATELLITE DATA...ALONG WITH INFORMATION
FROM SURROUNDING BUOYS...INDICATE THE LOW PRESSURE SYSTEM LOCATED
ABOUT 250 NMI SOUTHEAST OF THE NORTH CAROLINA COAST HAS BECOME MUCH
BETTER ORGANIZED THIS MORNING. BANDING FEATURES HAVE IMPROVED IN
THE SOUTHEASTERN SEMICIRCLE WHERE AN EARLIER QUIKSCAT OVERPASS
INDICATED SEVERAL 20-25 KT UNCONTAMINATED WIND VECTORS.
THEREFORE...THE SYSTEM AS BEEN UPGRADED TO TROPICAL DEPRESSION TWO.

THE INITIAL MOTION ESTIMATE IS A SOMEWHAT UNCERTAIN 360/04...MAINLY
DUE TO SOME UNCERTAINTY IN THE EXACT LOCATION OF THE LOW-LEVEL
CENTER RELATIVE TO THE DEVELOPING CONVECTIVE PATTERN. HOWEVER...
LONG TERM SATELLITE LOOPS AND MICROWAVE DATA SUGGEST THAT A GENERAL
SLOW NORTHWARD MOTION HAS BEEN OCCURRING FOR THE PAST 6-9 HOURS. THE
DEPRESSION IS CAUGHT IN A BREAK IN THE SUBTROPICAL RIDGE WHOSE AXIS
LIES ALONG ABOUT 35N LATITUDE. MOST OF THE GLOBAL MODELS HAVE KEYED
ON A WEAK LOW PRESSURE SYSTEM LOCATED ABOUT 200 NMI NORTHEAST OF
TD-2. THAT SYSTEM SHOWS NO SIGNS OF DEVELOPMENT. THE ONLY MODELS
THAT HAVE INITIALIZED THIS SYSTEM WITH ANY REASONABLE ACCURACY
DURING THE PAST 24 HOURS HAS BEEN THE NAM AND UKMET MODELS. THE 3
GFS-BASED BAM MODELS ARE ALMOST ON TOP OF EACH OTHER AND TAKE THE
CYCLONE INTO NORTH CAROLINA NEAR CAPE LOOKOUT IN 36-48 HOURS. THE
NAM AND UKMET MOVE THE SYSTEM OVER OR JUST EAST OF THE NORTH
CAROLINA OUTER BANKS IN ABOUT 48 HOURS. THE LATTER SCENARIO IS
PREFERRED AT THIS TIME DUE TO THE UNCERTAINTY IN JUST HOW FAR SOUTH
AN UPPER-LOW WILL DIG THAT IS CURRENTLY SITUATED WEST-SOUTHWEST OF
THE DEPRESSION. IF THE UPPER-LOW DIGS A LITTLE FARTHER SOUTH THAN
FORECAST BY THE MODELS...THEN A MORE NORTHWESTWARD MOTION SIMILAR
TO THE BAM MODELS COULD OCCUR. DUE TO THE THIS UNCERTAINTY...A
TROPICAL STORM WATCH HAS BEEN ISSUED FOR THE EASTERN PORTIONS OF
NORTH CAROLINA.

THE INTENSITY FORECAST IS SOMEWHAT TRICKY. THE SHIPS MODEL ONLY
BRINGS THE CYCLONE UP TO ABOUT 45 KT IN 48 HOURS. HOWEVER... THIS
CONSERVATIVE INTENSITY FORECAST APPEARS TO BE DUE IN PART TO POORLY
INITIALIZED SST CONDITIONS. THE SHIPS MODEL CURRENTLY INDICATES THE
SYSTEM IS OVER 80F SSTS...WHEREAS SURROUNDING SHIP AND BUOY DATA
INDICATE SSTS ARE 82-83F UNDER THE CORE OF THE CYCLONE. IN
ADDITION...THE SHIPS MODEL INDICATES THAT UPPER-LEVEL DIVERGENCE
WILL BE POOR AT BEST AND... THEREFORE... A NEGATIVE CONTRIBUTING
FACTOR. IN CONTRAST...LATEST SATELLITE IMAGERY INDICATES CIRRUS
OUTFLOW HAS BEEN EXPANDING TO THE NORTHWEST... WHILE AN UPPER-LEVEL
LOW TO THE SOUTHEAST OF THE CYCLONE IS BEGINNING TO ENHANCE THE
OUTFLOW TO THE SOUTH. GIVEN THIS FAVORABLE DEVELOPING OUTFLOW
PATTERN... THE INTENSITY FORECAST IS HIGHER THAN THE SHIPS MODEL.

FORECAST POSITIONS AND MAX WINDS

INITIAL      18/1500Z 32.5N  73.4W    30 KT
 12HR VT     19/0000Z 33.3N  73.7W    35 KT
 24HR VT     19/1200Z 33.9N  74.1W    40 KT
 36HR VT     20/0000Z 34.7N  74.8W    45 KT
 48HR VT     20/1200Z 35.5N  75.0W    55 KT
 72HR VT     21/1200Z 36.9N  74.7W    55 KT
 96HR VT     22/1200Z 38.5N  71.0W    50 KT
120HR VT     23/1200Z 42.0N  63.0W    40 KT...BECOMING EXTRATROPICAL

$$
FORECASTER STEWART

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