Tropical Storm FAXAI Advisory Sun Sep 08

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 14W (FAXAI) WARNING NR 023//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON (TY) 14W (FAXAI), LOCATED APPROXIMATELY 479 NM SOUTH-
SOUTHEAST OF YOKOSUKA, JAPAN, HAS TRACKED NORTHWESTWARD AT 19 KNOTS
(KTS) OVER THE PAST SIX HOURS. TY 14W HAS RAPIDLY INTENSIFIED (40
KNOTS) OVER THE PAST 24 HOURS FROM 45 KTS TO 85 KTS. ANIMATED
ENHANCED INFRARED SATELLITE IMAGERY SHOWS SYMMETRIC EYEWALL
SURROUNDING A CLOUD-FILLED 15 NM EYE FEATURE, SUPPORTING THE HIGH
CONFIDENCE OF THE INITIAL POSITION. THE INITIAL INTENSITY OF 85 KTS
IS ASSESSED WITH HIGH CONFIDENCE BASED ON MULTI-AGENCY DVORAK
CURRENT INTENSITY ESTIMATES OF T5.0/90KTS FROM PGTW AND T4.5/77KTS
FROM RJTD. ENVIRONMENTAL ANALYSIS DEPICTS FAVORABLE CONDITIONS OF
LOW (5-15 KT) VERTICAL WIND SHEAR (VWS) AND WARM (29-30 CELSIUS) SEA
SURFACE TEMPERATURE (SST) VALUES. HOWEVER, THESE ARE OFFSET SLIGHTLY
BY FAIR POLEWARD OUTFLOW WHICH IS BEING LIMITED BY THE DEVELOPMENT
OF A TRANSIENT UPPER-LEVEL ANTICYCLONE TO THE NORTHWEST. TY 14W IS
TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTHEAST.
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY SINCE THE
PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B. THROUGH TAU 12, TY 14W WILL MAINTAIN ITS NORTHWESTWARD TRACK
AROUND THE PERIPHERY OF THE AFOREMENTIONED DEEP-LAYER STR. BETWEEN
TAUS 24 AND 36, THE SYSTEM WILL SLOW AS IT TURNS NORTHWARD AND
ROUNDS THE STR AXIS PRIOR TO LANDFALL SOUTHEAST OF TOKYO AROUND TAU
30. FOLLOWING THIS, TY 14W WILL SHIFT TO A NORTHEASTWARD TRACK,
ACCELERATING AFTER TRANSITING BACK OVER WATER. THE ENVIRONMENT WILL
REMAIN FAVORABLE FOR THE NEXT 24 HOURS WITH LOW VWS AND WARM SST.
MODELS MAINTAIN DEVELOPMENT OF THE ANTICYCLONE TO THE NORTHWEST OF
THE SYSTEM WHICH WILL INDUCE A BRIEF BREAK IN THE POLEWARD OUTFLOW
AND RESULT IN A SLOWING OF THE SYSTEM'S INTENSIFICATION. OUTFLOW
WILL REESTABLISH AFTER THIS ANTICYCLONE TRANSITS TO THE NORTHEAST BY
TAU 12, ALLOWING FOR ANOTHER PERIOD OF ENHANCED INTENSIFICATION JUST
PRIOR TO LANDFALL. THERE IS SIGNIFICANT UNCERTAINTY IN THE PEAK
INTENSITY WITH THE HIGH POTENTIAL FOR A PROLONGED PERIOD OF RAPID
INTENSIFICATION THROUGH TAU 24. AFTER LANDFALL, THE SYSTEM EXITS
BACK OVER THE PACIFIC WHERE IT WILL ENCOUNTER COOLER SSTS AND
INCREASING VWS, WHICH WILL GRADUALLY WEAKEN THE SYSTEM AS IT BEGINS
EXTRATROPICAL TRANSITION (ETT) AT TAU 48. TY 14W WILL BECOME
EMBEDDED IN THE WESTERLY FLOW BY TAU 72 AND COMPLETE ETT. MODEL
GUIDANCE REMAINS IN TIGHT AGREEMENT THROUGH THE DURATION OF THE
FORECAST, WITH NAVGEM AS A NORTHERLY OUTLIER AND GFS AS A SOUTHERLY
OUTLIER, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.//
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