WDPN31 PGTW 120300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR
19//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 22W (PRAPIROON), LOCATED APPROXIMATELY 390 NM SOUTH 
OF KADENA AIR BASE, OKINAWA, JAPAN, HAS MADE A TURN TO THE NORTHEAST 
AND TRACKED AT 03 KNOTS OVER THE PAST SIX HOURS. ANIMATED 
MULTISPECTRAL SATELLITE IMAGERY (MSI) AND A 120006Z SSMIS 91GHZ 
MICROWAVE IMAGE DEPICT A WELL-DEFINED SYSTEM WITH TIGHTLY WRAPPED 
CONVECTIVE BANDING AND A RAGGED EYE. THE INITIAL INTENSITY IS BASED 
ON DVORAK INTENSITY ESTIMATES OF 102 KNOTS FROM PGTW AND RJTD. THERE 
IS HIGH CONFIDENCE IN THE INITIAL POSITION BASED ON THE EYE FEATURE 
IN THE MSI AND SSMIS IMAGERY. UPPER-LEVEL ANALYSIS AND ANIMATED 
WATER VAPOR IMAGERY INDICATE 22W IS LOCATED BENEATH A POINT SOURCE 
ANTICYCLONE IN AN AREA OF LOW (05 TO 10 KNOT) VERTICAL WIND SHEAR 
(VWS) WITH GOOD RADIAL OUTFLOW. TY 22W HAS NOW TAKEN ON A MORE 
NORTHEASTWARD TRACK UNDER THE INFLUENCE OF A WEAK 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 CONTINUE TRACKING SLOWLY NORTHEASTWARD 
DURING THE NEXT 48 HOURS AS THE SYSTEM STEERS ALONG THE NORTHWESTERN 
PERIPHERY OF THE NER TO THE SOUTHEAST. BETWEEN TAUS 48 AND 72 A 
BUILDING SUBTROPICAL RIDGE (STR) TO THE EAST OF TY PRAPIROON WILL 
BECOME THE PREDOMINANT STEERING FEATURE. A NORTHERLY TURN IS 
EXPECTED NEAR TAU 72 AS THIS STR BUILDS WESTWARD. WITH THE EXCEPTION 
OF JGSM AND EGRR, THE SLOWEST AND LEFTMOST OUTLIERS, DYNAMIC MODEL 
GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT THROUGH TAU 36. BY TAU 
72, MODELS BEGIN TO SPREAD CONSIDERABLY AS THE STEERING REGIME 
TRANSITIONS. TY 22W IS EXPECTED TO INTENSIFY SLIGHTLY DURING THE 
NEXT 12 HOURS IN A FAVORABLE ENVIRONMENT. AS OCEAN HEAT CONTENT 
BEGINS TO DECREASE NEAR 22 DEGREES NORTH INTENSITY IS EXPECTED TO 
GRADUALLY DECREASE AFTER TAU 36. CONFIDENCE IS HIGH IN THE JTWC 
TRACK AND INTENSITY FORECASTS UNTIL TAU 72, WITH NO SIGNIFICANT 
CHANGES FROM THE PREVIOUS FORECAST.
   C. AFTER TAU 72, TY 22W IS EXPECTED TO TURN NORTHWARD AS THE STR 
TO THE EAST BUILDS WESTWARD AND REORIENTS IN A MORE NORTH-SOUTH 
DIRECTION. THE WESTWARD EXTENSION OF THE STR WILL BE FAIRLY SHORT-
LIVED AS A VIGOROUS MID-LATITUDE TROUGH EMERGES EAST OF JAPAN. NEAR 
TAU 120 TY PRAPIROON IS EXPECTED TO SLOWLY TAKE ON A MORE EASTWARD 
TRACK AS THE STR ERODES. BY TAU 120, DYNAMIC MODEL GUIDANCE IS 
SPREAD UPWARDS OF 500NM, WITH EGRR TRACKING THE SYSTEM WESTWARD 
AFTER TAU 72 AND WBAR INDICATING A CONTINUOUS NORTHEASTERLY TRACK. 
MOST MODELS INDICATE A TURN TO THE NORTH AFTER TAU 72 IN RESPONSE TO 
THE BUILDING STR TO THE EAST. GRADUAL WEAKENING IS EXPECTED AS TY 
22W SLOWLY GAINS LATITUDE IN A LESS FAVORABLE ENVIRONMENT. FORECAST 
CONFIDENCE AFTER TAU 72 REMAINS LOW DUE TO HIGH VARIANCE IN TRACK 
SPEEDS AND DIRECTION.//
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