Subject: Pacific-NW: Subj/prognostic Reasoning For Typhoon 16w Warning Nr 19 Corrected//

From: SIU Weather Processor <[email-masked]>
Date: Mon, 25 Oct 2010 22:56:07 -0500

WDPN32 PGTW 260300 COR
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 16W WARNING NR 19 CORRECTED//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TYPHOON 16W (CHABA), LOCATED APPROXIMATELY 430 NM SOUTH-
SOUTHEAST OF KADENA AIR BASE, JAPAN, HAS TRACKED NORTH-NORTHWESTWARD
AT 5 KNOTS DURING THE PAST SIX HOURS. ANIMATED MULTI-SPECTRAL
SATELLITE IMAGERY SHOWS CONVECTION INTENSIFYING AND CONSOLIDATING
OVER THE LOW LEVEL CIRCULATION CENTER (LLCC). MARKEDLY IMPROVED
POLEWARD OUTFLOW DURING THE PAST SIX HOURS IS RESPONSIBLE FOR MUCH
OF THE INTENSIFICATION. A 252132Z 37GHZ MICROWAVE PASS SHOWS A
DEVELOPING MICROWAVE EYE AND INCREASINGLY WELL ORGANIZED CONVECTIVE
BANDING. INFRARED ANIMATION SHOWS A SHARP INCREASE IN COLD TOPS OVER
THE LLCC DURING THE PAST SIX HOURS. THE INTENSITY ESTIMATE IS BASED
ON A COMBINATION OF DVORAK ESTIMATES OF 65 KNOTS FROM PGTW AND 77
KNOTS FROM RJTD. IN ADDITION TO THE IMPROVING POLEWARD OUTFLOW, WELL
DEVELOPED EQUATORWARD OUTFLOW PERSISTS.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE TRACK FORECAST
PHILOSOPHY. TRACK SPEEDS AFTER TAU 72 HAVE BEEN INCREASED.
   B. TYPHOON CHABA IS EXPECTED TO CONTINUE A STEADY POLEWARD TRACK
AROUND THE PERIPHERY OF THE SUBTROPICAL RIDGE THROUGH TAU 48.
THE STORM WILL SUSTAIN INTENSIFICATION AS A MID-LATITUDE TROUGH
CURRENTLY MOVING OVER THE SEA OF JAPAN PROVIDES FURTHER ENHANCEMENT
TO THE POLEWARD OUTFLOW CHANNEL. A MID-LATITUDE SHORT WAVE TROUGH
CURRENTLY OVER THE SEA OF JAPAN WILL ACT TO SUSTAIN A VIGOROUS
POLEWARD OUTFLOW CHANNEL UNTIL IT PASSES EAST OF THE STORM. THIS
WILL INDUCE STEADY INTENSIFICATION AS TY 16W ROUNDS THE WESTERN EDGE
OF THE SUBTROPICAL RIDGE. GFDN, FORMERLY AN OUTLIER TO THE EXTREME
WEST, HAS NOW JOINED THE PACK AND IS TRACKING THE SYSTEM TO THE EAST
OF OKINAWA.
   C. A RECENT COLD SURGE OVER WESTPAC HAS BROUGHT CONTINENTAL POLAR
AIR DEEP INTO THE THEATER, THEREFORE EXTRATROPICAL TRANSISTION WILL
BEGIN BEFORE THE STORM REACHES 30N. TYPHOON CHABA IS EXPECTED TO
RECURVE AND TRACK ALONG THE EAST COAST OF HONSHU AFTER TAU 72 WHILE
UNDERGOING A RAPID EXTRA-TROPICAL TRANSITION. THE RECURVATURE WILL
NOT BE A DRAMATIC TURN AND ACCELERATION DUE TO A ZONAL ORIENTATION
OF THE POLAR FRONT JET DURING THAT PERIOD. THE ZONAL JET, HOWEVER,
WILL PRODUCE TREMENDOUS VERTICAL WINDSHEAR BETWEEN 30 AND 35 NORTH
LATITUDE. THEREFORE TYPHOON CHABA IS EXPECTED TO UNDERGO RAPID
DE-INTENSIFICATION DURING ITS PERIOD OF EXTRATROPICAL TRANSITION.
DURING THE SAME PERIOD,THE STORM WILL BE RIDING OVER A REGION OF
RAPIDLY DECREASING OCEAN HEAT CONTENT. NUMERICAL MODELS ARE COMING
INTO BETTER AGREEMENT WITH THIS SCENARIO. NOGAPS AND EGRR BOTH STEER
THE STORM OVER SHIKOKU AND INTO THE SEA OF JAPAN, PUNCHING IT
THROUGH A 100 KNOT POLAR FRONT JET AND OVER THE JAPANESE ALPS. THIS
SOLUTION IS INCOHERENT AND IS DISREGARDED. BECAUSE THE CONSENSUS
INCLUDES BOTH NOGAPS AND EGRR, THE FORECAST IS TO THE
RIGHT AND FASTER THAN CONSENSUS, WHICH IS SLIGHTLY SLIGHTLY SLOWER
BUT VERY CLOSE TO ECMWF. ECMWF HAS SHOWN THE BEST HANDLING OF THE
SYSTEM'S TRACK THUS FAR.
4. JUSTIFICATION FOR CORRECTION: CHANGED WEST OF TO EAST OF OKINAWA
IN LAST SENTENCE OF PARA 3.B.//

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