WDPN33 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (FRANCISCO) WARNING NR 26//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 26W (FRANCISCO), LOCATED APPROXIMATELY 403 NM WEST-
SOUTHWEST OF IWO TO, HAS TRACKED NORTHWESTWARD AT 09 KNOTS
OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY (EIR) SHOWS A SLIGHT WEAKENING OF DEEP CONVECTION WITHIN THE 
EYEWALL AND THE EYE HAS STARTED TO BECOME CLOUD FILLED. THE 
INTENSITY HAS BEEN DECREASED TO 75 KNOTS BASED ON THE WEAKENING 
TREND OBSERVED IN THE EIR AND DVORAK ESTIMATES FROM PGTW AND 
RJTD RANGING FROM 65 TO 90 KNOTS. UPPER-LEVEL ANALYSIS INDICATES THE 
SYSTEM IS WITHIN 05 DEGREES SOUTH OF THE RIDGE AXIS AND IN AN AREA 
OF WEAK (5-10 KNOT) VERTICAL WIND SHEAR (VWS). A WEAK POLEWARD 
OUTFLOW CHANNEL IS ALSO APPARENT ON ANIMATED WATER VAPOR IMAGERY. 
THE CYCLONE HAS BEEN TRACKING STEADILY TO THE NORTH-NORTHWEST UNDER 
THE INFLUENCE OF A DEEP LAYERED SUBTROPICAL RIDGE (STR) LOCATED TO 
THE NORTHEAST OF THE SYSTEM.
3. FORECAST REASONING.
   A. NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING.
   B. IN THE NEAR TERM, TY 26W IS EXPECTED TO MAINTAIN A STEADY 
TRACK TO THE NORTH-NORTHWEST, WITH INCREASING INTERACTION WITH THE 
STR. AN APPROACHING MID-LATITUDE TROUGH, CURRENTLY OVER NORTH 
CENTRAL CHINA IS FORECAST TO TRACK EASTWARD WEAKENING THE WESTERN 
EXTENT OF THE STR. INTERACTION OF THE TROUGH AND STR WILL ALLOW TY 
26W TO TURN NORTHWARD BY TAU 36. DECREASING SEA SURFACE TEMPERATURES 
(SSTS) WILL SLOWLY WEAKEN THE LOW LEVEL STRUCTURE, KEEPING THE 
SYSTEM ON A WEAKENING TREND THROUGH TAU 72. VWS IS EXPECTED TO 
INCREASE AROUND TAU 48 AS THE UPPER LEVEL ENVIRONMENT SUFFERS FROM 
THE APPROACH OF THE JET ALONG THE LEADING EDGE OF THE MID-LATITUDE 
TROUGH.
   C. AFTER TAU 72, TY 26W WILL BEGIN TO ACCELERATE TO THE NORTHEAST 
UNDER THE INFLUENCE OF THE NORTHWESTERN QUADRANT OF THE STR. SSTS 
WILL QUICKLY DIMINISH BEYOND TAU 72 AS THE SYSTEM MOVES TO THE 
NORTHEAST. ADDITIONALLY, THE MID-LATITUDE TROUGH WILL CREATE HIGH 
LEVELS OF VWS (30 PLUS KNOTS) BEYOND TAU 72. THE INTERACTION WITH 
THE BAROCLINIC ZONE AROUND TAU 72 WILL BEGIN THE EXTRA-TROPICAL 
TRANSITION PROCESS, WITH THE COMPLETE TRANSITION TO A COLD-CORE 
SYSTEM EXPECTED BY TAU 96. DUE TO THE POSITIONING OF THE SYSTEM 
BEING SLIGHTLY TO THE EAST OF CONSENSUS OVER THE PAST 12 HOURS, THE 
FORECAST HAS BEEN KEPT SLIGHTLY TO THE EAST AND FASTER THAN 
CONSENSUS. DUE TO THE CONTINUED UNCERTAINTY IN THE TIMING OF THE 
SHIFT OF STEERING MECHANISMS, THE CONFIDENCE IN THE FORECAST TRACK 
REMAINS LOW.//
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