Tropical Storm PRAPIROON Advisory lun, 15.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON)
/WARNING NR 32//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 22W (PRAPIROON), LOCATED APPROXIMATELY 305 NM SOUTHEAST OF
KADENA AIR BASE, OKINAWA, JAPAN, HAS BECOME QUASI-STATIONARY (QS)
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY
(MSI) SHOWS A DEEP CONVECTIVE BAND THAT HAS PERSISTED ALONG THE
NORTHERN HALF OF THE SYSTEM HAS WRAPPED AROUND THE LOW LEVEL
CIRCULATION CENTER (LLCC) FORMING A BIG 60-NM EYE. THE INITIAL
POSITION IS BASED ON THE MSI LOOP AND EXTRAPOLATED FROM A 150409Z
AMSU-B MICROWAVE IMAGE WITH FAIR CONFIDENCE. THE INITIAL INTENSITY IS
AVERAGED FROM DVORAK ESTIMATES FROM PGTW, KNES AND RJTD. UPPER LEVEL
ANALYSIS INDICATES A POINT SOURCE ANTICYCLONE IS LOCATED DIRECTLY
OVER THE LLCC WITH LOW VERTICAL WIND SHEAR (VWS). ANIMATED WATER
VAPOR IMAGERY SHOWS THE SYSTEM HAS MAINTAINED GOOD RADIAL OUTFLOW
WITH AN IMPROVING POLEWARD OUTFLOW CHANNEL. THE CYCLONE IS NOW OUT OF
THE INFLUENCE OF THE WEAKENED NEAR EQUATORIAL RIDGE TO THE SOUTHEAST
AND IS IN A COL AREA WITH NO DOMINANT STEERING MECHANISM.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TY 22W IS EXPECTED TO REMAIN QS OVER THE NEXT 24-36 HOURS AS TS
23W AWAITS FOR THE SUBTROPICAL RIDGE (STR) TO THE EAST TO BUILD AND
EVENTUALLY EJECTS IT POLEWARD FROM THE COL AREA. THIS IS EXPECTED TO
OCCUR AFTER TAU 24. BUT SHORTLY AFTER TAU 48 JUST WHEN THE STR
ASSUMES SOLID STEERING, A MID-LATITUDE TROUGH APPROACHING FROM THE
NORTHWEST WILL WEAKEN THE STR AND CAUSE TY 22W TO RECURVE AND
ACCELERATE NORTHEASTWARD. WHILE THE SYSTEM IS IN A QS STATE AND WITH
CONTINUED FAVORABLE OUTFLOW, IT WILL SLIGHTLY INTENSIFY. THE NUMERIC
MODEL CONSENSUS CONTINUES TO BRING THE CYCLONE EXTREMELY WESTWARD
BEFORE RECURVING IT NORTHEASTWARD. THIS MAY BE A RESULT OF EXCESSIVE
DIRECT CYCLONE INTERACTION (E-DCI) WITH ANOTHER CYCLONE TO THE
SOUTHEAST. DUE TO THE UNCERTAINTY IN THE STEERING AND POSSIBLE E-DCI
FROM THE NUMERIC MODEL GUIDANCE, 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 DECREASE AND VWS INCREASES. BY TAU
120 TY 22W WILL BEGIN EXTRATROPICAL TRANSITION. MODEL GUIDANCE IS
UNIFIED IN A RECURVATURE SCENARIO AFTER TAU 72 BUT WIDELY DIFFER IN
LATERAL SPEED, LENDING POOR CONFIDENCE IN THE EXTENDED PORTION OF THE
TRACK FORECAST.   //
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