Tropical Storm IN-FA Advisory ma, 19-07

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR
012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 24.0N 131.5E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 251 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY DEPICTS TIGHTLY CURVED
BANDING WRAPPING INTO AN INCREASINGLY WELL DEFINED LOW LEVEL
CIRCULATION CENTER (LLCC), WITH A BROAD SWATH OF DEEP CONVECTION
ALONG ITS SOUTHEASTERN FLANK. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON A BLEND OF AVAILABLE FIXES, AND
GENERALLY SUPPORTED BY AN 182148Z SSMIS PASS. THE INTENSITY WAS
HELD AT 50 KNOTS, WITH AGENCY FIXES RANGING FROM T2.5 TO T3.5 (35
TO 55 KNOTS), WITH ADT AT 37 KNOTS. NO NEW SATCON IS AVAILABLE. THE
RADIUS OF MAXIMUM WINDS HAS STEADILY DECREASED AS THE LLCC HAS
CONSOLIDATED.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: DEEP LAYER STR TO THE NORTHEAST
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS ADT: 37 KTS AT 182340Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD
   OTHER FACTORS: MID-LEVEL MOISTURE IS IMPROVING
ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.
FORECAST DISCUSSION: TS 09W (IN-FA) CONTINUES TO TRACK GENERALLY
NORTH-NORTHWESTWARD UNDER THE INFLUENCE OF THE STEERING STR, BUT IS
STILL EXPECTED TO SHIFT TO A MORE WEST-NORTHWESTWARD TO WESTWARD
TRACK OVER THE NEXT 12 HOURS AS THE STR BEGINS TO RE-ORIENT, AFTER
WHICH THE FORECAST CALLS FOR NEAR STEADY WESTWARD MOTION THROUGH
TAU 72. AT THAT TIME, A WEAKNESS IS FORECAST TO DEVELOP IN THE STR,
RESULTING IN A SLIGHT POLEWARD DEFLECTION AS IN-FA PASSES TAIWAN.
THE FORECAST INTENSITY TREND IS SLIGHTLY HIGHER THAN THE PRIOR
FORECAST, AS CONSOLIDATION HAS TAKEN PLACES AND ENVIRONMENTAL
FACTORS REMAIN FAVORABLE. INTENSITY GUIDANCE ALSO SUGGESTS THAT
CONDITIONS ARE POTENTIALLY FAVORABLE FOR A RAPID INTENSIFICATION
SCENARIO. THE PEAK INTENSITY WAS INCREASED SLIGHTLY TO 90 KNOTS AT
TAU 72 AFTER WHICH DECLINING SST SHOULD START A GRADUAL WEAKENING
TREND. THE FORECAST IS PLACED CLOSE TO THE PRIOR JTWC FORECAST AND
THE MULTI-MODEL CONSENSUS.
MODEL DISCUSSION: NUMERICAL GUIDANCE IS IN MODERATELY GOOD
AGREEMENT THROUGH TAU 72, AND CONSISTENTLY CALLS FOR THE WESTWARD
TURN THAT HAS BEEN ANTICIPATED FOR THE PAST 12 HOURS. THE SPREAD
INCREASES AFTER TAU 72 DEPENDING ON THE EXTENT OF THE WEAKNESS OF
THE STR, WITH SOME MODELS SUGGESTING A MUCH MORE AGGRESSIVE TURN TO
THE NORTHWEST. THERE IS STILL A WIDE VARIATION IN THE INTENSITY
MODEL GUIDANCE. THE FORECAST WAS INCREASED DUE TO RAPID
INTENSIFICATION INDICATORS, BUT REMAINS WITHIN THE GPCE SPREAD.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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