Tropical Storm PRAPIROON Advisory lun, 15.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR
35//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 22W (PRAPIROON), LOCATED APPROXIMATELY 300 NM SOUTH-
SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED
SOUTHWESTWARD AT 06 KNOTS OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) CONTINUES TO SHOW A TIGHTLY
WRAPPED, WELL DEFINED SYSTEM WITH WEAKENING DEEP CONVECTION. THE
INITIAL POSITION IS BASED ON THE MSI AND A 152317Z SSMIS 37GHZ
MICROWAVE IMAGE. THE INITIAL INTENSITY OF 65 KNOTS IS BASED ON AN
AVERAGE OF DVORAK ESTIMATES FROM PGTW, KNES AND RJTD AND IS
CONSISTENT WITH THE CURRENT WEAKENING TREND SEEN IN ENHANCED
INFRARED IMAGERY. UPPER LEVEL ANALYSIS AND ANIMATED WATER VAPOR
IMAGERY INDICATE A POINT SOURCE ANTICYCLONE IS SLIGHTLY DISPLACED
TO THE SOUTHEAST, GIVING THE SYSTEM GOOD POLAR AND EQUATORWARD
OUTFLOW IN A LOW (05-10 KNOT) VERTICAL WIND SHEAR (VWS)
ENVIRONMENT. THE CYCLONE IS IN A COL REGION BETWEEN TWO DEEP-
LAYERED SUBTROPICAL RIDGES WITH NO DOMINANT STEERING MECHANISM.
3. FORECAST REASONING.
   A. TY 22W IS NOW FORECASTED TO MAKE A WIDER TURN IN THE EARLIER
TAUS.
   B. TY 22W IS EXPECTED TO TRACK IN A SLOW RECURVE MOTION FOR THE
NEXT 48 HOURS AS THE SUBTROPICAL RIDGE (STR) TO THE EAST BUILDS IN.
THE STR IS CURRENTLY BEING WEAKENED BY TS 23W NORTHEAST OF TY 22W.
AFTER TAU 48, THE STR WILL BE THE DOMINANT STEERING INFLUENCE AS A
MID-LATITUDE TROUGH APPROACHES FROM THE NORTHWEST NEAR TAU 48,
WHICH WILL CAUSE TY 22W TO ACCELERATE NORTHEASTWARD. TY 22W WILL
SLOWLY WEAKEN FOR THE REMAINDER OF THE FORECAST PERIOD AS TY 22W
ENCOUNTERS DECREASING SEA SURFACE TEMPERATURES (SSTS). DYNAMIC
MODEL GUIDANCE IS IN FAIR AGREEMENT WITH SOME DISCREPANCIES IN
TRACK SPEED. THE OFFICIAL JTWC FORECAST IS BASED ON MULTI-MODEL
CONSENSUS. DUE TO THE UNCERTAINTY IN THE STEERING PATTERN AND SOME
DISAGREEMENT IN TRACK SPEED, THERE IS LOW CONFIDENCE IN THIS
PORTION OF THE TRACK FORECAST.
   C. AFTER TAU 72, TY PRAPIROON IS EXPECTED TO CONTINUE
ACCELERATING NORTHEASTWARD AND WEAKEN AS SSTS FURTHER DECREASE AND
VWS INCREASES. BY TAU 96, TY 22W WILL BEGIN EXTRATROPICAL
TRANSITION AND BECOME AN EXTRATROPICAL LOW BY TAU 120. DYNAMIC
MODEL GUIDANCE CONTINUES TO DIFFER IN TRANSLATIONAL SPEED IN THE
LATER TAUS. DUE TO THE DISAGREEMENT AMONGST THE MODELS, FORECAST
CONFIDENCE REMAINS LOW.//
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