Tropical Storm PRAPIROON Advisory Çar, 10.10.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 22W (PRAPIROON) WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 22W (PRAPIROON), LOCATED APPROXIMATELY 530 NM SOUTH-
SOUTHEAST OF KADENA AIR BASE, OKINAWA, JAPAN, HAS TRACKED NORTH-
NORTHWESTWARD AT 04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED
INFRARED SATELLITE IMAGERY (EIR) SHOWS THE DEEP CONVECTIVE BANDING
CONTINUES TO WRAP TOWARDS THE DEEP CENTRALLY LOCATED CONVECTION.
THERE HAS BEEN A RECENT DRIFT NORTHWARD OVER THE PAST SIX HOURS, BUT
APPEARS TO BE SHORT LIVED AS THE EIR IMAGERY SHOWS THE SYSTEM
BEGINNING TO MOVE MORE WESTWARD IN THE PAST FEW HOURS. A RECENT
091215Z ASCAT PASS INDICATES THE LOW LEVEL CIRCULATION CENTER (LLCC)
WIND FIELD HAS IMPROVED OVER THE PAST 24 HOURS. THE CURRENT LOCATION
IS BASED ON A POSITION FIX FROM PGTW AND A 1701Z TRMM 37H MICROWAVE
IMAGE SHOWING A DEVELOPING EYE FEATURE. THE INTENSITY IS BASED ON A
4.0/4.0 DVORAK FROM PGTW. THE SYSTEM CONTINUES TO TRACK ALONG THE
WEAKENING SOUTHWESTERN EDGE OF THE SUBTROPICAL RIDGE (STR). UPPER
LEVEL ANALYSIS INDICATES THE LLCC IS SLIGHTLY WEST OF A POINT SOURCE
ANTICYCLONE, WHICH IS PROVIDING GOOD RADIAL VENTILATION AND LOW
VERTICAL WIND SHEAR (VWS) OVER THE SYSTEM.
3. FORECAST REASONING.
   A. THERE HAS BEEN A SHIFT IN THE TRACK SPEED PHILOSOPHY FROM THE
PREVIOUS PROGNOSTIC REASONING MESSAGE, SLOWING THE OVERALL SPEED OF
THE SYSTEM IN THE EXTENDED FORECAST AND SHIFTING THE RECURVATURE
POSITION MORE WESTWARD.
   B. TY 22W IS EXPECTED TO TRACK SLOWLY WEST-NORTHWESTWARD OVER THE
NEXT 36 HOURS ALONG THE SOUTHWESTERN QUADRANT OF THE STR AS A MID-
LATITUDE TROUGH IS WEAKENING THE STR. FAVORABLE UPPER LEVEL OUTFLOW
AND SURFACE CONDITIONS WILL ALLOW THE SYSTEM TO INTENSIFY THROUGH
TAU 72. THIS IS A SHIFT FROM THE PREVIOUS PROGNOSTIC MESSAGE, AS
TRACK SPEEDS HAVE BEEN DECREASED ALLOWING GREATER TIME FOR THE
SYSTEM TO DEVELOP.
   C. AFTER TAU 72, TY PRAPIROON WILL MOVE INTO A LESS FAVORABLE
UPPER LEVEL ENVIRONMENT WITH DECREASING SEA SURFACE TEMPERATURES.
THESE SLIGHT CHANGES WILL START TO HINDER DEVELOPMENT BEYOND TAU 72,
LEADING TO A WEAKENING TREND THROUGH TAU 120. MODEL GUIDANCE REMAINS
CONSISTENT WITH A RECURVATURE SCENARIO IN THE NEXT 24 TO 48 HOURS,
HOWEVER THE TIMING OF THIS REMAINS IN TWO GROUPINGS. THE FIRST GROUP
IS WITH ECMF AND GFS SHOWING THE TURN LATER, FURTHER WEST AND WITH
SLOWER TRACK SPEEDS, WHILE THE SECOND GROUP IS NGPS, WBAR AND GFDN
SHOWING A SHARPER TURN, EARLIER, WITH GREATER TRACK SPEEDS. THIS
FORECAST FAVORS THE GFS AND ECMF SOLUTIONS BY KEEPING THE TRACK
SPEED SLOWER THAN CONSENSUS THROUGHOUT THE FORECAST WITH A
RECURVATURE POINT TO THE WEST OF CONSENSUS. BASED ON THE SHIFTING
DYNAMIC MODEL GUIDANCE AND THE TIMING OF THE RECURVATURE, THERE IS
LOW CONFIDENCE IN THE FORECAST TRACK.//
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