#1
WDPN31 PGTW 281500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W WARNING NR 34//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TYPHOON (TY) 04W (SONGDA), LOCATED APPROXIMATELY 60 NM WEST OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 24 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS
INCREASING STRETCHING OF THE CLOUD SHIELD OVER THE NORTHEAST SIDE OF
THE STORM AND WARMING TOPS THROUGHOUT THE SYSTEM. A DRY SLOT
WRAPPING AROUND THE WESTERN QUADRANT AND INTO THE LOW LEVEL
CIRCULATION CENTER (LLCC) IS ALSO VISIBLE ON BOTH SATELLITE AND
MICROWAVE IMAGERY. A 280903Z CORIOLIS IMAGE SHOWS THAT DESPITE THE
INTRUSION OF DRY AIR, ABUNDANT CURVED BANDING IN THE LOW LEVEL CLOUD
FIELDS PERSISTS. MEANWHILE, A 280856Z SSMIS IMAGE REVEALS DEEP
CONVECTION CONTINUING AROUND MOST OF THE LLCC. KADENA AIR BASE
(RODN) BEGAN REPORTING SUSTAINED WINDS OVER 40 KNOTS WITH STORM
FORCE GUSTS AT 281129Z, AND IS NOW REPORTING STORM FORCE WINDS WITH
GUSTS AS HIGH AS 89 KNOTS. NORTHEASTWARD MOVEMENT HAS ACCELERATED
WITH EACH OF THE PAST THREE FIXES AS THE UPPER LEVELS OF THE STORM
BEGAN COUPLING WITH THE MID-LATITUDE WESTERLIES. THE LOWER LEVELS OF
THE STORM REMAIN WELL SOUTH OF THE BAROCLINIC ZONE, HOWEVER. AT
290600Z, THE BAIU BOUNDARY WAS NORTH OF AMAMI SHIMA (RJKA), WHICH
WAS REPORTING A DEW POINT OF 20 DEGREES CELSIUS. TY 04W IS RAPIDLY
TRACKING INTO A REGION OF UNFAVORABLY COOL SEAS AND INCREASING
VERTICAL WIND SHEAR (VWS).
3. FORECAST REASONING.
A. THERE ARE NO CHANGES TO THE FORECAST PHILOSOPHY.
B. SEVERE DROPS IN SEA SURFACE TEMPERATURE AND OCEAN HEAT CONTENT
COUPLED WITH SEVERE RISES IN VWS WILL STEADILY WEAKEN THE SYSTEM
OVER THE NEXT 24 HOURS. EXTRA-TROPCIAL TRANSITION (XTT) IN THE LOWER
LEVELS WILL BEGIN JUST NORTH OF AMAMI SHIMA. THE INTERACTION BETWEEN
TC 04W AND A VIGOROUS MID-LATITUDE SHORT WAVE IS RESULTING IN
EXCESSIVE DIRECT CYCLONE INTERACTION (E-DCI) IN THE MODEL FIELDS,
WHICH THEN STEER THE VORTEX INTO SHIKOKU AND THE KANSAI REGION. AS
THE MID-LATITUDES WESTERLIES PICK THE SYSTEM UP, THE TRAJECTORY WILL
VEER MORE EASTWARD THAN THE CURRENT BEARING OF 040, RESULTING IN A
TRACK WELL SEAWARD OF THE KANSAI AND KANTO PLAINS. THE HIGH ENERGY
REMAINING WITH TY 04W COMBINED WITH THE VIGOROUS NATURE OF THE POLAR
FRONT JET OVER SOUTHERN JAPAN WILL KEEP THE SYSTEM AT GALE TO NEAR-
STORM FORCE INTENSITY AS IT FINISHES XTT SOUTH OF THE KANTO PLAIN.
THE JTWC FORECAST REMAINS SOUTH OF AND FASTER THAN CONSENSUS IN
ORDER TO ACCOUNT FOR BOTH THE E-DCI AND KNOWN MODEL TENDENCIES FOR A
POLEWARD, SLOWER BIAS DURING RECURVATURE SCENARIOS.//
#2
WDPN31 PGTW 281500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W WARNING NR 34//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TYPHOON (TY) 04W (SONGDA), LOCATED APPROXIMATELY 60 NM WEST OF
KADENA AB, OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT 24 KNOTS
OVER THE PAST SIX HOURS. ANIMATED INFRARED SATELLITE IMAGERY SHOWS
INCREASING STRETCHING OF THE CLOUD SHIELD OVER THE NORTHEAST SIDE OF
THE STORM AND WARMING TOPS THROUGHOUT THE SYSTEM. A DRY SLOT
WRAPPING AROUND THE WESTERN QUADRANT AND INTO THE LOW LEVEL
CIRCULATION CENTER (LLCC) IS ALSO VISIBLE ON BOTH SATELLITE AND
MICROWAVE IMAGERY. A 280903Z CORIOLIS IMAGE SHOWS THAT DESPITE THE
INTRUSION OF DRY AIR, ABUNDANT CURVED BANDING IN THE LOW LEVEL CLOUD
FIELDS PERSISTS. MEANWHILE, A 280856Z SSMIS IMAGE REVEALS DEEP
CONVECTION CONTINUES AROUND MOST OF THE LLCC. KADENA AIR BASE (RODN)
BEGAN REPORTING SUSTAINED WINDS OVER 40 KNOTS WITH STORM FORCE GUSTS
AT 281129Z, AND IS NOW REPORTING STORM FORCE WINDS WITH GUSTS AS
HIGH AS 89 KNOTS. NORTHEASTWARD MOVEMENT HAS ACCELERATED WITH
SUCCESSIVE FIX DURING THE PAST 18 HOURS, FURTHER EVIDENCE THAT THE
UPPER LEVELS OF THE STORM ARE COUPLING WITH THE MID-LATITUDE
WESTERLIES. THE BOUNDARY LEVEL OF THE STORM REMAINS WELL SOUTH OF
THE BAROCLINIC ZONE, HOWEVER. AT 290600Z, THE BAIU BOUNDARY WAS
NORTH OF AMAMI SHIMA (RJKA), WHICH WAS REPORTING A DEW POINT OF 20
DEGREES CELSIUS. TY 04W IS RAPIDLY TRACKING INTO A REGION OF
UNFAVORABLY COOL SEAS AND INCREASING VERTICAL WIND SHEAR (VWS).
3. FORECAST REASONING.
A. THERE ARE NO CHANGES TO THE FORECAST PHILOSOPHY.
B. RAPID DROPS IN SEA SURFACE TEMPERATURE AND OCEAN HEAT CONTENT
COUPLED WITH SEVERE RISES IN VWS WILL STEADILY WEAKEN THE SYSTEM
OVER THE NEXT 24 HOURS. EXTRA-TROPCIAL TRANSITION (XTT) IN THE LOWER
LEVELS WILL BEGIN JUST NORTH OF AMAMI SHIMA. THE INTERACTION BETWEEN
TC 04W AND A VIGOROUS MID-LATITUDE SHORT WAVE IS RESULTING IN
EXCESSIVE DIRECT CYCLONE INTERACTION (E-DCI) IN THE MODEL TRACKERS,
WHICH STEER THE VORTEX INTO SHIKOKU AND THE KANSAI REGION. AS THE
MID-LATITUDE WESTERLIES PICK THE SYSTEM UP, THE TRAJECTORY WILL VEER
FURTHER EASTWARD THAN THE CURRENT BEARING OF 040, RESULTING IN A
TRACK WELL SEAWARD OF THE KANSAI AND KANTO PLAINS. THE HIGH ENERGY
REMAINING WITH TY 04W COMBINED WITH THE VIGOROUS NATURE OF THE POLAR
FRONT JET OVER SOUTHERN JAPAN WILL KEEP THE SYSTEM AT GALE TO NEAR-
STORM FORCE INTENSITY AS IT FINISHES XTT SOUTH OF THE KANTO PLAIN.
THE JTWC FORECAST REMAINS SOUTH OF AND FASTER THAN CONSENSUS IN
ORDER TO ACCOUNT FOR BOTH THE E-DCI AND KNOWN MODEL TENDENCIES FOR A
POLEWARD, SLOWER BIAS DURING RECURVATURE SCENARIOS.//