WDPN32 PGTW 050300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 18W (PHANFONE) WARNING NR 26//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 18W (PHANFONE), LOCATED APPROXIMATELY 326 NM SOUTH 
OF IWAKUNI, JAPAN, HAS TRACKED NORTHWARD AT 08 KNOTS OVER THE PAST 
SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A 
35-NM RAGGED EYE WITH WEAKENED SPIRAL BANDING. A 042320Z SSMIS 
MICROWAVE IMAGE CONTINUES TO SHOW A ROUND SIGNATURE WITH A WELL- 
DEFINED MICROWAVE EYE. THE CURRENT POSITION IS BASED ON THE EYE 
FEATURE ON THE MSI AND SSMIS IMAGE WITH HIGH CONFIDENCE. THE INITIAL 
INTENSITY HAS DECREASED TO 100 KNOTS BASED ON AN OVERALL ASSESSMENT 
OF DVORAK CURRENT INTENSITY ESTIMATES FROM ALL REPORTING AGENCIES 
AND WEAKENING TREND. UPPER-LEVEL ANALYSIS INDICATES TY 18W IS 
LOCATED IN AN AREA OF STRONG (GREATER THAN 30 KNOTS) VERTICAL WIND 
SHEAR (VWS) OFFSET BY VIGOROUS OUTFLOW, ESPECIALLY ON THE POLEWARD 
SIDE THAT IS BEING ENHANCED BY THE MID-LATITUDE WESTERLIES. TY 18W 
IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A DEEP-LAYERED 
SUBTROPICAL RIDGE (STR) TO THE EAST.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY FROM 
THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 18W WILL CONTINUE TO ROUND THE WESTERN PERIPHERY OF THE STR 
AND ACCELERATE NORTHEASTWARD AS IT STARTS EXTRA-TROPICAL TRANSITION 
BY TAU 12. TY 18W IS EXPECTED TO BE QUICKLY ABSORBED INTO THE 
BAROCLINIC ZONE. INCREASING VWS AND COOLING SEA SURFACE TEMPERATURES 
WILL RAPIDLY ERODE THE SYSTEM BUT WILL STILL BE A VERY INTENSE STORM 
FORCE COLD-CORE LOW BY THE END OF THE FORECAST PERIOD. THE AVAILABLE 
NUMERIC GUIDANCE REMAINS IN TIGHT AGREEMENT LENDING HIGH CONFIDENCE 
TO THE JTWC TRACK FORECAST THAT IS LAID SLIGHTLY TO THE RIGHT OF AND 
FASTER THAN MULTI-MODEL CONSENSUS.//
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