WDPN32 PGTW 040300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR SUPER TYPHOON 18W (PHANFONE) WARNING 
NR 22//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   SUPER TYPHOON (STY) 18W (PHANFONE), LOCATED APPROXIMATELY 682 NM 
SOUTHWEST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD AT 11 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) SHOWS A 35-NM EYE WITH SPIRAL BANDING WRAPPING INTO THE LOW-
LEVEL CIRCULATION CENTER. A 032333Z SSMIS MICROWAVE IMAGE ALSO 
REVEALS A SYMMETRIC SIGNATURE WITH A WELL-DEFINED MICROWAVE EYE. THE 
CURRENT POSITION IS BASED ON THE EYE FEATURE ON MSI ANIMATION, 
MICROWAVE EYE WITH HIGH CONFIDENCE. THE INITIAL INTENSITY HAS 
INCREASED TO 130 KNOTS BASED ON DVORAK CURRENT INTENSITY ESTIMATES 
FROM PGTW AND KNES RANGING FROM 127 TO 140 KNOTS. UPPER-LEVEL 
ANALYSIS INDICATES STY 18W IS LOCATED IN AN AREA OF STRONG VERTICAL 
WIND SHEAR OFFSET BY VIGOROUS OUTFLOW, NAMELY THE IMPROVED POLEWARD 
CHANNEL AS IT TAPS INTO THE MIDLATITUDE WESTERLIES. THIS INCREASED 
POLEWARD OUTFLOW SUPPORTS THE PEAK INTENSITY OF 130 KNOTS OVER THE 
PAST SIX HOURS. STY 18W IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY 
OF THE SUBTROPICAL RIDGE (STR) TOWARD A LARGE BREAK IN THE STR, 
POSITIONED SOUTH OF WESTERN JAPAN.
3. FORECAST REASONING.
   A. DUE TO FAVORABLE UPPER-LEVEL CONDITIONS, THE SYSTEM HAS 
UPGRADED TO SUPER TYPHOON STRENGTH OVER THE PAST SIX HOURS. 
OTHERWISE, THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY 
FROM THE PREVIOUS PROGNOSTIC REASONING BULLETIN.
   B. STY 18W IS FORECAST TO TRACK NORTHWARD OVER THE NEXT 12 HOURS 
AS IT TRACKS ALONG THE WESTERN PERIPHERY OF THE STR THEN SHOULD TURN 
NORTHEASTWARD AS IT ROUNDS THE AXIS OF THE STR. BY TAU 36, THE 
SYSTEM WILL BEGIN EXTRA-TROPICAL TRANSITION (ETT) AS IT INTERACTS 
WITH THE MIDLATITUDE WESTERLIES. STY 18W IS EXPECTED TO RAPIDLY 
COMPLETE ETT AND GAIN FRONTAL CHARACTERISTICS NEAR THE KANTO PLAIN 
LENDING INCREASED UNCERTAINTY TO POSITIONING DUE TO A BROADENING LOW 
PRESSURE AREA. REGARDLESS OF WHETHER THE SYSTEM IS WARM-CORE OR COLD-
CORE, STORM FORCE WINDS ARE FORECAST DUE TO THE STRONG PRESSURE 
GRADIENT ENHANCED BY A STRONG BAROCLINIC ZONE OVER JAPAN. AVAILABLE 
MODEL GUIDANCE HAS CONTINUED TO IMPROVE AND IN GOOD AGREEMENT OVER 
THE PAST SIX HOURS; HOWEVER, DUE TO SIGNIFICANT MODEL TRACK SPEED 
DIFFERENCES AND TRACK UNCERTAINTY ASSOCIATED WITH THE RAPID ETT 
PROCESS, THE JTWC TRACK FORECAST LEVEL OF CONFIDENCE REMAINS LOW.//
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