WDPN31 PGTW 010300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 17W (SANVU) WARNING NR 
15//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
  TYPHOON 17W (SANVU), LOCATED APPROXIMATELY 6 NM NORTH OF CHICHI 
JIMA, JAPAN HAS TRACKED SOUTHEASTWARD AT 06 KNOTS OVER THE PAST SIX 
HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS A RAPIDLY 
INTENSIFYING SYSTEM WITH TIGHTLY WOUND BANDING WRAPPING INTO A 10 NM 
RAGGED EYE. A 312110Z 37GHZ COLOR COMPOSITE SSMIS IMAGE SHOWS A WELL 
DEFINED CYAN RING, INDICATIVE OF POTENTIAL RAPID INTENSIFICATION. 
THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE EYE 
FEATURE EVIDENT IN SATELLITE IMAGERY. THE INITIAL INTENSITY IS 
ASSESSED AT 90 KNOTS WHICH IS BASED ON IMPROVEMENTS IN THE 
CONVECTIVE STRUCTURE AND RECENT DVORAK ESTIMATES RANGING FROM T4.5 
TO T5.0 (77 TO 90 KNOTS) FROM ALL AGENCIES. UPPER-LEVEL ANALYSIS 
INDICATES ROBUST RADIAL OUTFLOW WITH LOW VERTICAL WIND SHEAR. A 
STRONG POLEWARD OUTFLOW CHANNEL IS WELL ESTABLISHED FEEDING INTO THE 
MIDLATITUDE JET. A TUTT CELL TO THE NORTHEAST IS ADVANCING WESTWARD 
SOMEWHAT IMPEDING OUTFLOW POTENTIAL ON THE NORTHEAST QUADRANT BUT 
REMAINS SOME DISTANCE AWAY TO ADVERSELY AFFECT OUTFLOW AT THIS TIME. 
SSTS IN THE REGION ARE ALSO SUPPORTIVE AROUND 29 TO 30 CELSIUS. TY 
17W IS CURRENTLY TRACKING NORTH-NORTHWESTWARD ALONG THE WESTERN 
PERIPHERY OF THE DEEP-LAYERED SUBTROPICAL RIDGE.
3. FORECAST REASONING.
   A. DUE TO THE RAPID IMPROVEMENT IN CONVECTIVE STRUCTURE AND 
SUPPORTIVE ENVIRONMENTAL CONDITIONS, THE FORECAST PEAK INTENSITY IS 
ELEVATED TO 115 KNOTS IN THE NEXT 12 HOURS. 
   B. TY 17W IS EXPECTED TO CONTINUE TRACKING GENERALLY NORTH-
NORTHEASTWARD OVER THE NEXT 72 HOURS UNDER THE INFLUENCE OF 
SUBTROPICAL RIDGING TO THE EAST BUT IS EXPECTED TO ACCELERATE 
POLEWARD AFTER TAU 36 AS IT BECOMES ABSORBED IN A MID-LATITUDE 
TROUGH APPROACHING FROM THE NORTHWEST. SLOW FORWARD MOTION IS 
ANTICIPATED IN THE NEXT 24 HOURS DUE TO CHANGES IN ORIENTATION OF 
THE STEERING RIDGE. ENHANCED POLEWARD OUTFLOW AND WARM WATERS WILL 
PERSIST FOR THE NEXT 24 HOURS SUPPORTING A CONTINUED INTENSIFICATION 
TREND PEAKING IN THE NEXT 12 HOURS AT 115 KNOTS. WHILE SSTS ARE 
SUBSTANTIALLY WARM OHC VALUES ARE LESS THAN IMPRESSIVE WITH A 
NOTABLE COOLER POCKET OF WATER UNDER THE TRACK IF TY 17W. UPWELLING 
WILL MITIGATE THE INTENSIFICATION TREND BY TAU 24. AROUND TAU 36 THE 
APPROACHING TROUGH WILL INTRODUCE INCREASED WIND SHEAR AND THE 
SYSTEM WILL BEGIN TO WEAKEN.  TY 17W IS EXPECTED TO INTERACT 
FAVORABLY WITH THE APPROACHING TROUGH, YIELDING A VERY INTENSE 
EXTRATROPICAL LOW BY TAU 72. NUMERICAL MODEL GUIDANCE IS IN GOOD 
GENERAL AGREEMENT, LENDING HIGH CONFIDENCE TO THE CURRENT 
TRACK FORECAST.//
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