[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 040835
TCDAT3
TROPICAL STORM HARVEY DISCUSSION NUMBER   8
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT THU AUG 04 2005

AIR FORCE RECON FOUND A LOWER CENTRAL PRESSURE...995 MB...
BUT SO FAR THE HIGHEST 850 MB FLIGHT LEVEL WINDS MEASURED BY THE
AIRCRAFT DO NOT SUPPORT AN INCREASE IN STRENGTH.  CURRENT INTENSITY
IS HELD AT 50 KT.  DEEP CONVECTION ASSOCIATED WITH THE TROPICAL
CYCLONE HAS INCREASED OVER THE PAST FEW HOURS.  ALTHOUGH HARVEY IS
BEING AFFECTED BY ABOUT 20 KT OF WEST-SOUTHWESTERLY SHEAR...IT IS
HOLDING ITS OWN...AS IS TYPICAL OF THESE HIGHER LATITUDE SYSTEMS.
SOME SLIGHT INCREASE IN STRENGTH IS POSSIBLE OVER THE NEXT DAY OR
SO...BUT SIGNIFICANT INTENSIFICATION IS UNLIKELY.  THE CYCLONE
SHOULD BE WEAKENING OVER COOLER WATERS IN THE LATTER PART OF THE
FORECAST PERIOD.  THE GFS MODEL SHOWS HARVEY'S CIRCULATION BECOMING
ELONGATED IN 3-5 DAYS...SUGGESTING THAT IT MAY LOSE TROPICAL
CHARACTERISTICS LATE IN THE PERIOD.

HARVEY IS MOVING AT ABOUT 070/11.  A SHORTWAVE TROUGH NEAR 60W IS
MOVING AWAY FROM THE STORM SO THE STEERING CURRENT WILL PROBABLY
WEAKEN OVER THE NEXT COUPLE OF DAYS...UNTIL ANOTHER APPROACHING
TROUGH ACCELERATES THE WEST-SOUTHWESTERLY FLOW LATER IN THE PERIOD.
THIS NEXT TROUGH...HOWEVER...WILL NOT HAVE MUCH AMPLITUDE SO IT
SEEMS UNLIKELY TO BE ABLE TO CAUSE A BIG INCREASE IN HARVEY'S
FORWARD SPEED.  THE CONSENSUS OF THE TRACK GUIDANCE IS GENERALLY
SLOWER THAN IN THE EARLIER RUNS...SO THE OFFICIAL FORECAST IS A
LITTLE SLOWER THAN THE PREVIOUS ONE.  THIS IS A COMPROMISE BETWEEN
THE U.K. MET AND GFS...WHICH ARE SIGNIFICANTLY SLOWER THAN MY
FORECAST...AND THE NOGAPS AND GFDL...WHICH ARE CONSIDERABLY FASTER.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      04/0900Z 31.8N  64.6W    50 KT
 12HR VT     04/1800Z 32.2N  62.8W    55 KT
 24HR VT     05/0600Z 32.6N  60.8W    55 KT
 36HR VT     05/1800Z 32.9N  59.5W    50 KT
 48HR VT     06/0600Z 33.3N  58.3W    45 KT
 72HR VT     07/0600Z 35.0N  55.5W    40 KT
 96HR VT     08/0600Z 37.5N  51.5W    35 KT
120HR VT     09/0600Z 40.0N  47.0W    30 KT


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