WDPN31 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR 29//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 22W (PRAPIROON), LOCATED APPROXIMATELY 295 NM SOUTH-
EAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED NORTHEASTWARD AT
03 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED
SATELLITE IMAGERY (EIR) SHOWS THE SYSTEM HAS MAINTAINED DEEP CENTRAL
CONVECTION EVEN AS THE EYE HAS BECOME OPEN AND RAGGED. ADDITIONALLY,
THE STORM MOTION HAS CONTINUED TO WOBBLE OVER THE PAST 12 HOURS. THE
INITIAL POSITION IS BASED ON THE EIR LOOP AND EXTRAPOLATED FROM A
SEMI-CLOSED EYE FEATURE ON A 141057Z 37 GHZ SSMIS MICROWAVE IMAGE
WITH HIGH CONFIDENCE. THE INITIAL INTENSITY IS BASED ON THE 141230Z
DVORAK ESTIMATE FROM PGTW. UPPER LEVEL ANALYSIS INDICATES 22W IS IN A
REGION OF WEAK (05-10 KNOTS) VERTICAL WIND SHEAR (VWS) WITH A POINT
SOURCE ANTICYCLONE LOCATED DIRECTLY OVER THE LOW LEVEL CIRCULATION
CENTER. ANIMATED WATER VAPOR IMAGERY SHOWS THE SYSTEM HAS MAINTAINED
GOOD RADIAL OUTFLOW. TY 22W IS SLOWLY DRIFTING IN A WEAK STEERING
ENVIRONMENT, UNDER THE INFLUENCE OF A WEAKENING NEAR EQUATORIAL RIDGE
(NER) TO THE SOUTHEAST.
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 NORTHWESTERN
EXTENT OF THE NER AS THE SUBTROPICAL RIDGE (STR) TO THE NORTHEAST
SLOWLY BUILDS AND BECOMES THE DOMINANT STEERING MECHANISM OVER THE
NEXT 12-24 HOURS. A MID-LATITUDE TROUGH APPROACHING FROM THE
NORTHWEST WILL WEAKEN THE STR AFTER TAU 36 AND REORIENTS THE TRACK TO
THE NORTHEAST. THE INTENSITY IS EXPECTED TO MAINTAIN OVER THE NEXT 36
HOURS AS THE SYSTEM SLOWLY TRACKS TOWARDS THE STR AXIS. DURING AND
SHORTLY AFTER THE RECURVATURE, THE INTENSITY WILL SLIGHTLY INCREASE
DUE TO IMPROVED OUTFLOW BROUGHT ON BY THE MID-LATITUDE TROUGH. THIS,
HOWEVER, WILL BE SHORT-LIVED AS VWS SUBSEQUENTLY INCREASES. DYNAMIC
MODEL GUIDANCE CONSENSUS SHOWS A
TRACK REVERSAL THEN A WESTWARD POLEWARD TURN OVER THE NEXT 12-24
HOURS APPARENTLY DUE TO EXCESSIVE DIRECT CYCLONE INTERACTION WITH A
DEVELOPING CYCLONE TO THE SOUTHEAST.
   C. AFTER TAU 72, TY PRAPIROON IS EXPECTED TO ACCELERATE 
NORTHEASTWARD AND WEAKEN AS SEA SURFACE TEMPERATURES DECREASE AND VWS
CONTINUES TO INCREASE. BY TAU 120 TY PRAPIROON WILL BEGIN
EXTRATROPICAL TRANSITION. THE MODEL GUIDANCE EVENTUALLY RE-CURVES THE
VORTEX NORTHEASTWARD BUT AT WIDELY VARYING TRACK SPEEDS. BASED ON THE
LARGE VARIATION IN THE MODEL GUIDANCE THE CONFIDENCE IN THE 120-HOUR
FORECAST TRACK REMAINS LOW.    //
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