[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 030846
TCDAT3
TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT WED AUG 03 2005

THERE HAS BEEN A SLIGHT INCREASE IN THE CURVATURE OF THE CONVECTIVE
BAND OVER THE NORTHERN PORTION OF THE CIRCULATION...BUT THE
LOW-LEVEL CENTER REMAINS EXPOSED TO THE SOUTH OF THE PRIMARY AREA
OF DEEP CONVECTION.  SUBJECTIVE DVORAK T-NUMBERS USING A SHEAR OR
CURVED BAND PATTERN ARE 2.0 FROM TAFB AND SAB..AND 1.5 FROM AFWA.
3- AND 6-HOURLY AVERAGE OBJECTIVE T-NUMBERS FROM THE UNIVERSITY OF
WISCONSIN CIMSS ARE NEAR 2.0.  THERE ARE NO SHIP OBSERVATIONS OF
SURFACE WINDS TO HELP ESTIMATE THE STRENGTH OF THE CYCLONE.  BASED
ON THE SATELLITE DATA...THE SYSTEM IS NOT BEING UPGRADED AT THIS
TIME.  AN UPPER-LEVEL LOW JUST TO THE SOUTHWEST OF THE DEPRESSION
CONTINUES TO PRODUCE SHEAR AND SUBSIDENCE.  200 MB GLOBAL MODEL
GUIDANCE INDICATES THAT THE INFLUENCE OF THE UPPER LOW WILL
DIMINISH...BUT THE GUIDANCE ALSO SHOWS MODERATE SHEAR CONTINUING TO
AFFECT THE DEPRESSION OVER THE NEXT FEW DAYS.  HISTORICALLY...
TROPICAL CYCLONES AT HIGHER LATITUDES HAVE BEEN MORE RESILIENT TO
SHEAR THAN THOSE IN THE DEEP TROPICS.  THIS IS PROBABLY WHY THE
STATISTICAL/DYNAMICAL SHIPS MODEL PREDICTS STRENGTHENING.  THE
OFFICIAL FORECAST...LIKE THE PREVIOUS ONE...SHOWS MODEST
INTENSIFICATION OVER THE NEXT DAY OR SO.

INITIAL MOTION ESTIMATE IS 020/8.  A MID-TROPOSPHERIC SHORTWAVE
TROUGH CURRENTLY NEAR THE CANADIAN MARITIMES IS EXPECTED TO MOVE
AHEAD OF THE TROPICAL CYCLONE AND THE NEXT...UPSTREAM...SHORTWAVE
SHOULD BE NEARING THE LONGITUDE OF THE CYCLONE IN ABOUT 72 HOURS.
ALTHOUGH NEITHER OF THESE TROUGHS HAVE SUFFICIENT AMPLITUDE TO PULL
THE DEPRESSION/STORM INTO THE MID-LATITUDES...THE GUIDANCE
INDICATES THAT THERE WILL BE ENOUGH WEST-SOUTHWESTERLY FLOW TO
STEER THE TROPICAL CYCLONE ON A NORTHEASTERLY TO EAST-NORTHEASTERLY
TRACK OVER THE FORECAST PERIOD.  GLOBAL MODELS HAVE A SLIGHTLY
BETTER INITIALIZATION OF THE DEPRESSION THAN THEY DID EARLIER...AND
THEIR TRACK FORECASTS ARE IN SOMEWHAT BETTER AGREEMENT.  THE
OFFICIAL FORECAST IS QUITE SIMILAR TO THE PREVIOUS ONE THROUGH 48
HOURS...BUT IT IS FASTER AND TO THE LEFT OF THE PREVIOUS OFFICIAL
FORECAST AT 3-5 DAYS.  IT SHOULD BE NOTED THAT THE LATEST DYNAMICAL
MODEL CONSENSUS AT 3-5 DAYS IS EVEN FASTER AND FARTHER TO THE LEFT
OF THE OFFICIAL TRACK FORECAST.

FORECASTER PASCH


FORECAST POSITIONS AND MAX WINDS

INITIAL      03/0900Z 29.9N  68.5W    30 KT
 12HR VT     03/1800Z 30.8N  67.5W    40 KT
 24HR VT     04/0600Z 32.1N  65.3W    45 KT
 36HR VT     04/1800Z 33.1N  62.7W    40 KT
 48HR VT     05/0600Z 33.7N  60.0W    35 KT
 72HR VT     06/0600Z 34.5N  55.5W    35 KT
 96HR VT     07/0600Z 36.0N  51.5W    30 KT
120HR VT     08/0600Z 38.0N  47.0W    30 KT


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