NOCK-TEN Discussion......

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WDPN32 PGTW 240300

MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//

SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W WARNING NR 41//

RMKS/

1. FOR METEOROLOGISTS.

2. PROGNOSTIC REASONING FOR 240000Z6 TO 290000Z1 OCT 2004.

A. TYPHOON (TY) 28W (NOCK-TEN), LOCATED APPROXIMATELY 380

NM SOUTH-SOUTHWEST OF OKINAWA, JAPAN, HAS TRACKED WEST-

NORTHWESTWARD AT 17 KNOTS OVER THE PAST 06 HOURS. THE WARNING

POSITION IS BASED ON 232330Z3 MULTISPECTRAL SATELLITE IMAGERY.

THE WARNING INTENSITY IS BASED ON SATELLITE CURRENT INTENSITY

ESTIMATES OF 102 AND 115 KNOTS.

B. TY 28W IS FORECAST TO TRACK NORTHWESTWARD FOR THE NEXT

24 HOURS ALONG THE SOUTHWESTERN PERIPHERY OF THE SUBTROPICAL

RIDGE LOCATED TO THE NORTHEAST. THE TRACK IS FORECAST TO TURN

POLEWARD AFTER TAU 24 AS THE SUBTROPICAL RIDGE IS WEAKENED BY

THE PASSAGE OF A RELATIVELY WEAK SHORTWAVE TROUGH EXITING ASIA,

AND THE STEERING RIDGE RETREATS EASTWARD. TY 28W IS FORECAST

TO RECURVE SHARPLY BY TAU 36 IN A HIGHLY ZONAL ENVIRONMENT,

AND WILL BEGIN THE INITIAL STAGES OF EXTRATROPICAL TRANSITION

AS IT INTERACTS WITH THE MID-LATITUDE BAROCLINIC ZONE BY TAU 72.

THE AVAILABLE DYNAMIC AIDS CONSISTING OF NOGAPS, COAMPS, GFDN,

NCEP GFS, JGSM, JTYM, UKMET, AFWA MM5, TCLAPS AND WBAR ARE IN

GOOD AGREEMENT WITH THIS SCENARIO THROUGH 36 HOURS. DISPARITY

EXISTS IN THE MODEL FORECASTS AFTER 36 HOURS DUE TO VARIATION

IN THE INTENSITY OF THE INTERACTION WITH THE BAROCLINIC ZONE

TO THE NORTH AND THE ONSET TIME OF EXTRATROPICAL TRANSITION.

THE POLEWARD CLUSTER, CONSISTING OF UKMET, NCEP GFS, AND WBAR,

FORECASTS INTERACTION WITH THE BAROCLINIC ZONE AND THE INITI-

ATION OF EXTRATROPICAL TRANSITION BY TAU 36. THE SECOND CLUSTER

FORECASTS A STRONGER BAROCLINIC INTERACTION THAT RESULTS IN A

DECOUPLING OF THE LOW LEVEL CIRCULATION CENTER (LLCC) AND THE

MID AND UPPER LEVELS OF THE SYSTEM. THESE MODELS THEN TRACK THE

LLCC IN A WEAK, LOW LEVEL STEERING ENVIRONMENT, WHILE THE MID

AND UPPER LEVELS CONTINUE TO INTERACT WITH THE MID-LATITUDE

WESTERLIES AND TRACK NORTHEASTWARD. THIS FORECAST IS BASED ON

A CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS WITH LESS EMPHASIS

PLACED ON THE MODELS FORECASTING A WEAKER STEERING ENVIRONMENT.

C. THE INTENSITY OF TY 28W IS FORECAST TO DECREASE THROUGH

TAU 72 AS THE SYSTEM ENCOUNTERS DRY AIR AND COOLER SEA SURFACE

TEMPERATURES. AFTER 12 TO 24 HOURS, INTERACTION WITH THE TERRAIN

OF TAIWAN AND THE MID-LATITUDE BAROCLINIC ZONE WILL ALSO WEAKEN

THE SYSTEM.

D. CURRENT WIND RADII ARE BASED ON 231835Z2 TRMM MICROWAVE

IMAGERY AND A 232131Z2 QUIKSCAT PASS. FORECAST WIND RADII ARE

BASED ON CLIMATOLOGY FOR AN AVERAGE SIZED SYSTEM.

E. THE EXTENDED FORECAST CALLS FOR TY 28W TO COMPLETE EXTRA-

TROPICAL TRANSITION SOUTH OF JAPAN BY TAU 120. GFDN FORECASTS

A SOUTHWESTWARD TURN AFTER TAU 72 FOR THE EXPOSED LLCC WHILE

ABSORBING THE MID AND UPPER LEVELS OF THE CIRCULATION INTO THE

BAROCLINIC ZONE. THE EXTENDED FORECAST TRACK IS BASED ON A CON-

SENSUS OF ALL AVAILABLE AIDS WITH LESS EMPHASIS ON GFDN. THE

INTENSITY OF TY 28W IS FORECAST TO RAPIDLY DECREASE AFTER TAU

72 AS THE SYSTEM ENCOUNTERS HIGHER VERTICAL WIND SHEAR ASSOC-

IATED WITH THE MID-LATITUDE WESTERLIES AND COOLER SEA SURFACE

TEMPERATURES.

FORECAST TEAM: BOWER/MENEBROKER/FUNK/JAYKOSKI//

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