WDPN31 PGTW 121500
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 04W WARNING NR 21//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
A. TYPHOON (TY) 04W (MAN-YI) HAS INTENSIFIED TO 125 KTS, WITH THE
EYE DIAMETER STEADY AT 30 NM. A 120934Z SSMI MICROWAVE IMAGE SHOWS
DEEP CONVECTION ASSOCIATED WITH THE EYE WALL, AND SPIRAL BANDING
ON THE SOUTHERN SIDE OF THE STORM, THIS IMAGE ALSO SHOWS A LACK OF DEEP
CONVECTION IN THE NORTHERN AND WESTERN QUADRANTS. ANALYSIS OF ANIMATED
WATER VAPOR IMAGERY INDICATES STRONG EQUATORWARD OUTFLOW WITH A WEAK
POLEWARD OUTFLOW CHANNEL. TY 04W TRACKED NORTHWESTWARD AT 15 KNOTS OVER
THE PAST SIX HOURS.
B. TYPHOON (TY) 04W (MAN-YI) IS LOCATED APPROXIMATELY 150 NM SOUTH-
SOUTH OF NAHA, OKINAWA, WITH HIGH CONFIDENCE IN POSITION DUE TO
THE WELL-DEFINED EYE. THE CURRENT INTENSITY OF 125 KNOTS IS BASED ON
DVORAK ESTIMATES OF 6.5/6.5. THE SYSTEM REMAINS SOUTH OF THE SUBTROPICAL
RIDGE (STR) AXIS, ALTHOUGH THE SYSTEM IS VERY CLOSE TO THE RIDGE AXIS.
A. THE FORECAST PHILOSOPHY FOR TY 04W REMAINS UNCHANGED: THE
STORM IS EXPECTED TO TRACK ALONG A STANDARD POLEWARD FLOW SYNOPTIC
PATTERN AROUND THE AXIS OF THE STR. ONCE NORTH OF STR AXIS THE STORM
WILL UNDERGO EXTRATROPICAL TRANSITION.
B. TY 04W IS TRACKING NORTH-NORTHWESTWARD TOWARD A BREAK IN THE STR
OVER OKINAWA. TY 04W WILL REACH THIS BREAK NEAR TAU 12, AND SUBSEQUENTLY
TURN NORTHEAST. THE TC WILL INTERACT WITH THE MIDLATITUDE BAROCLINIC ZONE
AND BEGIN EXTRATROPICAL TRANSITION (ET) SOUTH OF JAPAN NEAR TAU 48. THE
UPPER LEVEL MIDLATITUDE LOW CURRENTLY OVER THE KOREAN PENINSULA WILL
FURTHER CONTRIBUTE TO THE ET OF TY 04W AND WILL AID IN THE ACCELERATION
OF THE STORM TO THE NORTHEAST. THE DYNAMIC AIDS ARE IN GOOD AGREEMENT
THROUGH TAU 48, BUT THEN BEGIN TO DIVERGE AS ET BEGINS. THE FORECAST IS
CONSISTENT WITH CONSENSUS THROUGH TAU 48, BUT IS FASTER IN THE ALONG-TRACK
DIRECTION FROM TAU 48 ONWARD.
C. THE STORM SHOULD COMPLETE ET BY TAU 72 IN THE VICINITY OF THE
KANTO PLAIN AS IT ACCELERATES IN THE MIDLATITUDE WESTERLIES. WHILE UNDER
GOING ET, THE SYSTEM INTENSITY WILL WEAKEN DUE TO INCREASING VERTICAL
WIND SHEAR AND LAND INTERACTION. DESPITE THIS FACT, THE STORM WILL STILL
PRODUCE WINDS OVER 60 KTS AS AN EXTRATROPICAL SYSTEM.
FORECAST TEAM: CHARLIE//
Japan is in for a major storm system.
