[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 251445
TCDAT5

TROPICAL DEPRESSION TEN DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102011
1100 AM EDT THU AUG 25 2011

AFTER BEING CLOSE TO A TROPICAL STORM OVERNIGHT...THE CLOUD PATTERN
OF THE DEPRESSION HAS BECOME LESS ORGANIZED WITH A DECREASE IN
CONVECTION AND CURVED BANDING. ALTHOUGH DVORAK ESTIMATES REMAIN AT
STORM STRENGTH...AN ASCAT PASS AT 1126 UTC SUGGESTED MAXIMUM WINDS
OF 25 TO 30 KT...WHICH WAS LESS THAN WHAT WAS MEASURED ON THE LAST
PASS.  THE INITIAL WIND SPEED WILL STAY AT 30 KT FOR THIS ADVISORY.

THE ASCAT DATA SHOWED THAT THE CIRCULATION OF THE DEPRESSION IS
ELONGATED FROM NORTHEAST TO SOUTHWEST...WHICH IS NOT EXACTLY A
FAVORABLE STRUCTURE FOR MUCH NEAR-TERM INTENSIFICATION.  IN
ADDITION...NORTHEASTERLY SHEAR IS FORECAST TO REMAIN MODERATE TO
STRONG TODAY.  THUS THE NHC FORECAST IS REDUCED FROM THE PREVIOUS
ONE IN THE SHORT-TERM.  SOME INTENSIFICATION SEEMS LIKELY ON FRIDAY
WITH LESS SHEAR WHILE THE CYCLONE REMAINS OVER WARM WATERS.
HOWEVER...THERE IS A BIG SPLIT BETWEEN THE DYNAMICAL AND
STATISTICAL GUIDANCE...WITH THE GFDL/HWRF MODELS SHOWING LITTLE
STRENGTHENING FOR THE NEXT SEVERAL DAYS WHILE THE SHIPS/LGEM MODELS
FORECAST THE DEPRESSION TO BECOME HURRICANE.  WITH SUCH A LARGE
SPREAD IN THE GUIDANCE...NO CHANGE IS MADE TO THE PREVIOUS FORECAST
BEYOND FRIDAY.  WEAKENING SHOULD COMMENCE BY DAY THREE DUE TO AN
INCREASE IN SHEAR AND DECREASE IN SSTS.

AN UNCERTAIN ESTIMATE OF INITIAL MOTION IS 290/10.  A MID-LEVEL
RIDGE TO THE NORTH OF THE DEPRESSION SHOULD BREAK DOWN AS A TROUGH
FORMS OVER THE EASTERN ATLANTIC OCEAN.  THIS SHOULD CAUSE THE
CYCLONE TO TURN TOWARD THE NORTHWEST AND NORTH-NORTHWEST DURING THE
NEXT FEW DAYS.  ALTHOUGH THE GUIDANCE HAS THIS GENERAL IDEA...THERE
ARE A VARIETY OF SOLUTIONS ON HOW QUICKLY THE MORE NORTHWARD MOTION
STARTS.  PART OF THE PROBLEM IS THAT THE TRACK FORECAST IS RATHER
DEPENDENT ON THE INTENSITY FORECAST WITH A DEEPER SYSTEM MORE
LIKELY TO BE PULLED MORE TO THE NORTH THAN A WEAKER ONE.  THE NHC
FORECAST WILL SHOW A NORTH-NORTHWEST MOTION BY DAY 3 AND ASSUMES
THE CYCLONE GAINS SOME STRENGTH.  THE NEW FORECAST IS TO THE RIGHT
OF THE PREVIOUS ONE DURING THE DAY OR SO...CLOSE TO A BLEND OF THE
ECMWF MODEL AND THE HURRICANE FORECAST IMPROVEMENT PROGRAM
EXPERIMENTAL CONSENSUS.  MOST OF THE MODELS SHOW A SHARPER LEFT
TURN IN THE LONGER-RANGE PERIOD...SO THE TRACK AT THAT TIME IS WEST
OF THE PREVIOUS FORECAST.

FORECAST POSITIONS AND MAX WINDS

INIT  25/1500Z 13.3N  31.8W   30 KT  35 MPH
 12H  26/0000Z 13.9N  32.9W   30 KT  35 MPH
 24H  26/1200Z 14.7N  34.1W   35 KT  40 MPH
 36H  27/0000Z 15.6N  35.2W   45 KT  50 MPH
 48H  27/1200Z 16.6N  35.9W   50 KT  60 MPH
 72H  28/1200Z 18.7N  37.0W   45 KT  50 MPH
 96H  29/1200Z 20.5N  38.0W   35 KT  40 MPH
120H  30/1200Z 22.0N  40.5W   30 KT  35 MPH

$$
FORECASTER BLAKE



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