WDXS31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 24S (JASMINE) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.4S 40.3E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 108 NM NORTH OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A TIGHTLY 
COMPACT SYMMETRICAL SYSTEM IN THE MOZAMBIQUE CHANNEL WITH THE MAIN
CONVECTION RESIDING ON THE SOUTHERN SIDE OF THE LLC. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE USING A MICROWAVE EYE
FEATURE INDICATED BY THE 250717Z GMI 37GHZ IMAGE. TC JASMINE ALSO 
SHOWS A SLIGHTLY POLEWARD TILT WHEN USING BOTH 89GHZ AND 37GHZ GMI 
IMAGES. THE INITIAL INTENSITY OF 45KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE OVERALL ASSESSMENT OF AGENCY AND AUTOMATED
DVORAK ESTIMATES AND A PARTIAL 250712Z METOP-B ASCAT IMAGE. THE 
OVERALL ENVIRONMENT IS MARGINALLY UNFAVORABLE WITH STRONG 20-25KTS 
VWS, AND WEAK RADIAL OUTFLOW, BEING OFFSET BY WARM (29-30C) SSTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA FROM A PARTIAL 250712Z
METOP-B ASCAT.

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE EAST.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS SATCON: 54 KTS AT 250436Z
   CIMSS ADT: 51 KTS AT 250615Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS FORECAST, HOWEVER, BEGINNING WITH
THE NEXT WARNING CYCLE, JTWC WILL BE REPACKAGING RSMC (LA REUNION)
FORECASTS FOR THIS SYSTEM DUE TO A PLANNED COOPEX. PROGNOSTIC
REASONING MESSAGES WILL NOT BE AVAILABLE. 

FORECAST DISCUSSION: TC JASMINE WILL CONTINUE GENERALLY SOUTH-
SOUTHEASTWARD UNDER THE STEERING INFLUENCE OF THE STR TO THE EAST. 
AROUND TAU 24, A MID-LATITUDE TROUGH TRANSITING FROM THE SOUTHWEST 
WILL WEAKEN THE STR. SHORTLY AFTER TAU 48 A MIGRATORY RIDGE WILL 
BUILD IN FROM THE SOUTHWEST, FORCING THE TRACK OF TC JASMINE 
EQUATORWARD TOWARD THE MADAGASCAR COAST. THE MARGINALLY UNFAVORABLE 
ENVIRONMENT WILL BECOME MORE UNFAVORABLE DUE TO INCREASING VWS AND 
THE INFLUX OF COLD DRY AIR IN THE LOWER LEVELS, LEADING TO A GRADUAL 
DISSIPATION TO 35KTS BY TAU 48. CONCURRENTLY, THE SYSTEM WILL BEGIN 
DISSIPATING IN THE HIGH SHEARED ENVIRONMENT AND COMPLETE DISSIPATION 
OVER THE RUGGED TERRAIN OF MADAGASCAR BY TAU 72. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GENERAL AGREEMENT WITH THE 
SOUTHEAST TRAJECTORY UNTIL TAU 24, THEN TURN EQUATORWARD WITH A 
GRADUAL SPREAD OF 143NM EXCLUDING GFS WHICH IS THE EXTREME RIGHT 
OUTLIER. BY INCLUDING GFS TRACK, THE SPREAD EXPANDS TO 290NM. THE 
DISPARITY IN THE CROSS-TRACK IS MOST LIKELY DUE TO THE PLACEMENT OF 
THE MID-LATITUDE TROUGH AND THE OVERALL TIMING OF THE BUILDING 
MIGRATORY HIGH SOUTH OF THE SYSTEM. GIVEN THIS, THE JTWC TRACK 
FORECAST IS LAID CLOSE TO THE MODEL CONSENSUS WITH MEDIUM 
CONFIDENCE. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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