WDPN31 PGTW 140300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR 27//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 22W (PRAPIROON), LOCATED APPROXIMATELY 295 NM SOUTH-
SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED NORTH-
NORTHEASTWARD AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY SHOWS THE LOW LEVEL CIRCULATION 
CENTER (LLCC) IS LOCATED UNDER A WEAKLY DEVELOPING BAND OF 
CONVECTION WITHIN THE BROADER OUTER BANDING ALONG THE WESTERN AND 
NORTHERN SIDES OF THE SYSTEM. A 132341Z SSMIS PASS SHOWS THE EYEWALL 
HAS BEEN BREAKING DOWN OVER THE PAST 12 HOURS, WITH THE STRONGEST 
CONVECTION LOCATED ALONG THE NORTHERN PERIPHERY. THE CURRENT 
INTENSITY OF 65 KNOTS IS BASED ON THE STEADY WEAKENING TREND 
OBSERVED IN DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD ALL RANGING 
FROM 65 TO 75 KNOTS. UPPER LEVEL ANALYSIS INDICATES 22W IS LOCATED 
IN A REGION OF WEAK (05-10 KNOTS) VERTICAL WIND SHEAR (VWS) WITH A 
POINT SOURCE ANTICYCLONE LOCATED DIRECTLY OVER THE LLCC. ANIMATED 
WATER VAPOR IMAGERY SHOWS AN UPPER-LEVEL SUBTROPICAL RIDGE (STR) 
LOCATED OVER NORTHERN TAIWAN IS CREATING PRESSURE ALONG THE WESTERN 
SIDE OF THE SYSTEM. STRONG ZONAL MID-LATITUDE FLOW OVER SOUTHERN 
JAPAN IS HELPING SUPPORT A RECENT INCREASE IN POLEWARD OUTFLOW. TY 
22W IS SLOWLY DRIFTING IN A WEAK STEERING ENVIRONMENT, UNDER THE 
INFLUENCE OF A WEAKENING NEAR EQUATORIAL RIDGE (NER).
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE 
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. TY 22W IS EXPECTED TO SLOWLY TRACK ALONG THE NORTHERN EXTENT 
OF THE NER AS THE STR LOCATED TO THE NORTHEAST SLOWLY BUILDS TOWARDS 
TY 22W. THE TRACK HAS BEEN KEPT SLOW WITH AN EXPECTED TURN TO THE 
NORTHWEST AS THE STR BECOMES THE DOMINANT STEERING INFLUENCE AROUND 
TAU 36. BETWEEN TAU 36 AND 72, THE STR IS EXPECTED TO BUILD AS AN 
APPROACHING MID-LATITUDE TROUGH REORIENTS THE STR HELPING TO SHIFT 
THE TRACK TO THE NORTHEAST AROUND THE STR AXIS. THE INTENSITY IS 
EXPECTED TO MAINTAIN OVER THE NEXT 36 HOURS AS THE SYSTEM SLOWLY 
TRACKS TOWARDS THE STR AXIS. INTENSITY GUIDANCE INDICATES A SLIGHT 
INCREASE BETWEEN TAU 36 AND 48 AS INCREASED VENTILATION INTO THE MID-
LATITUDE FLOW HELPS TO INTENSIFY THE SYSTEM. THIS IS EXPECTED TO BE 
SHORT-LIVED AS THE MID-LATITUDE FLOW BEGINS TO INCREASE VWS OVER THE 
LLCC ALONG THE NORTHWESTERN QUADRANT, STIFLING THE POLEWARD OUTFLOW 
CHANNEL. 
   C. AS THE STEERING RIDGE ERODES AFTER TAU 72, TY 22W IS EXPECTED 
TO ACCELERATE NORTHEASTWARD AND WEAKEN AS SEA SURFACE TEMPERATURES 
DECREASE AND VWS INCREASES. BY TAU 120 TY PRAPIROON WILL BEGIN TO 
INTERACT WITH THE BAROCLINIC ZONE AND BEGIN EXTRATROPICAL 
TRANSITION. DYNAMIC MODEL GUIDANCE HAS SHIFTED DRASTICALLY OVER THE 
PAST SIX HOURS, WITH ECMF, NGPS, JGSM, AND GFS SHOWING A SHARP 
WESTWARD TURN IN THE NEXT 12 HOURS. WBAR AND GFDN CONTINUE TO SHOW A 
GENERALLY NORTHWARD TRACK. LOOKING AT THE MODEL FIELDS SUGGESTS THE 
SYSTEM WILL MAKE A SLIGHT NORTHWESTWARD TURN ASSOCIATED WITH THE 
BUILDING STR, HOWEVER THE CURRENT FORECAST TEMPERS THE SEVERITY OF 
THIS TURN BASED ON THE DRASTIC SHIFT IN MODEL GUIDANCE OVER THE PAST 
SIX HOURS. THE FORECAST KEEPS TO THE EAST OF CONSENSUS AND FASTER IN 
THE LATER TAUS BASED ON THE STRONG SHIFT IN MODEL GUIDANCE TO THE 
WEST. THERE HAS BEEN A SLIGHT SHIFT WESTWARD FROM THE PREVIOUS 
FORECAST, AND BASED ON THE RECENT LARGE VARIATION IN GUIDANCE THE 
CONFIDENCE IN THE TRACK REMAINS LOW.//
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