WDPN31 PGTW 131500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W WARNING NR 25//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS. A. TYPHOON (TY) 04W (MAN-YI) HAS BEGUN TO WEAKEN UNDER THE
INFLUENCE OF INCREASING VERTICAL WIND SHEAR FROM AN APPROACHING MID-
LATITUDE SYSTEM TO THE WEST AND DECREASING OCEAN HEAT CONTENT. TY 04W
HAS REACHED THE SUBTROPICAL RIDGE (STR) AXIS AND IS BEGINNING TO
TRACK TO THE NORTH-NORTHEAST UNDER THE INFLUENCE OF THE MIDLATITUDE
WESTERLIES.
B. TYPHOON (TY) 04W (MAN-YI) IS LOCATED APPROXIMATELY 310 NM
SOUTHSOUTHWEST OF SASEBO, JAPAN. TY 04W HAS TRACKED INTO A WEAKNESS
IN THE SUBTROPICAL RIDGE
CAUSED BY A MIDLATITUDE SYSTEM NOW LIFTING
OUT OVER THE KOREAN PENINSULA. THIS MIDLATITUDE SYSTEM INTRODUCED
DRY CONTINENTAL AIR INTO THE NORTHERN EAST CHINA SEA, WHICH TY 04W
HAS BEGUN TO INGEST, INDUCING THE FORMATION OF A DRY SLOT AND
REDUCING CONVECTION ON THE NORTHWESTERN QUADRANT OF THE SYSTEM.
HOWEVER, THE POLEWARD OUTFLOW INDUCED BY THE MIDLATITUDE SYSTEM
ALLOWED TY 04W TO REACH ITS PEAK INTENSITY OF 135 KNOTS.
3. FORECAST REASONING. A. THE FORECAST PHILOSOPHY FOR TY 04W REMAINS UNCHANGED, BUT THE
130600Z AND 131200Z FORECASTS REFLECT AN INCREASE IN FORWARD TRACK
SPEED AFTER RECURVATURE FROM THE PREVIOUS FORECASTS. THIS IS SUP-
PORTED BY AN INCREASE IN TRACK SPEED OF THE CONSENSUS AND SYNOPTIC
REASONING.
B. TY 04W WILL BEGIN RECURVE TO THE NORTHEAST BY TAU 12, AND
WILL INTERACT WITH THE MIDLATITUDE BAROCLINIC ZONE AND
START EXTRA-
TROPICAL TRANSITION (ET) BY TAU 36. THE TC WILL WEAKEN SLOWLY AFTER
TAU 36 WHILE UNDERGOING ET. A MIDLATITUDE SHORTWAVE TROUGH CURRENTLY
OVER CENTRAL CHINA WILL BE LOCATED OVER THE KOREAN PENINSULA BY TAU
24 AND
WILL HELP TO ACCELERATE THE TRANSITIONING SYSTEM. THE WIND
RADII AT TAUS 36 AND 48 REFLECT AN INCREASED WIND FIELD, ESPECIALLY
IN THE SOUTHEASTERN QUADRANT. CURRENT MODEL FIELDS INDICATE ET WILL
BE COMPLETE OVER THE KANTO PLAIN NEAR TAU 48. DESPITE ITS EXTRA-
TROPICAL STATUS,
THE SYSTEM COULD STILL PRODUCE WINDS NEAR 60 KTS.
THE DYNAMIC AIDS ARE IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD,
AND THEREFORE FORECAST CONFIDENCE IS HIGH.
FORECAST TEAM: CHARLIE//
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http://metocph.nmci.navy.mil/jtwc/warnings/wp0407prog.txt