WDXS31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (CHENESO) WARNING NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 24.1S 41.5E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 135 NM SOUTH-SOUTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TC 08S HAS INTENSIFIED OVER THE PREVIOUS 12 HOURS AS THE SYSTEM
CONTINUES TO TRANSIT GENERALLY SOUTHWARD INTO A FAVORABLE
ENVIRONMENT. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
INDICATES THAT THE SYSTEM HAS BECOME BETTER ORGANIZED WITH DEEP
CONVECTIVE TOWERS FIRING ON THE WESTERN SIDE, WHILE VIGOROUS
CONVECTION IS DEVELOPING OVER THE NORTHERN QUADRANT OBSCURING THE
LOW LEVEL CIRCULATION CENTER (LLCC). A 272231Z AMSR2 36GHZ
MICROWAVE IMAGE SHOWS A WELL-DEFINED LOW-LEVEL EYE FEATURE. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
LOW-LEVEL MICROWAVE EYE IN THE AMSR2 IMAGE AND CLOSE TO AGENCY
POSITION FIXES. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A COMBINATION OF SUBJECTIVE AND OBJECTIVE
INTENSITY ESTIMATES, HEDGED TOWARDS OBJECTIVE INTENSITY ESTIMATES
FROM SATCON, ADT AND AIDT WHICH APPEAR TO BE MORE REPRESENTATIVE.
ENVIRONMENTAL CONDITIONS CONTINUE TO BE GENERALLY FAVORABLE, WITH
WARM SEA SURFACE TEMPERATURES (28-29C), MODERATE (10-15 KNOTS) VWS,
AND STRONG POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER NEAR EQUATORIAL RIDGE (NER)
CENTERED TO THE NORTHEAST AND A DEEP-LAYER SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T4.5 - 77 KTS
   FMEE: T4.5 - 77 KTS
   CIMSS SATCON: 67 KTS AT 272017Z
   CIMSS ADT: 72 KTS AT 270100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TC 08S IS FORECAST TO TRACK
SOUTH-SOUTHEASTWARD IN RESPONSE TO A NER TO THE NORTHEAST AND A STR
TO THE SOUTH, WHICH IS SHIFTING TO THE EAST AHEAD OF A STRONG
MID-LATITUDE LONGWAVE TROUGH MOVING IN FROM THE WEST. OVER THE NEXT
24 HOURS THE SYSTEM IS EXPECTED TO QUICKLY TURN AND TRACK TOWARD
THE SOUTHEAST AS IT PASSES THE SOUTHERN TIP OF MADAGASCAR. BY TAU
36, THE SYSTEM ROUNDS THE RIDGE AXIS AND WILL BEGIN TO ACCELERATE
POLEWARD BETWEEN THE DEEP RIDGE TO THE EAST AND THE STRONG
MID-LATITUDE LONGWAVE TROUGH APPROACHING FROM THE WEST. THE JTWC
INTENSITY FORECAST SHOWS A GRADUAL DECAY AS TC 08S INTERACTS WITH
THE STRONG MID-LATITUDE LONGWAVE TROUGH WHICH WILL INDUCE HIGH
NORTHWESTERLY WIND SHEAR IN ADDITION TO COLDER WATERS. BY TAU 48,
THE SYSTEM WILL BEGIN EXTRATROPICAL TRANSITION, COMPLETING BY TAU
72. THE SYSTEM’S MAXIMUM WINDS WILL REMAIN AT 45 KNOTS WITH AN EXPANDING WIND FIELD DURING THE EXTRATROPICAL TRANSITION PHASE DUE TO FAVORABLE BAROCLINIC INTERACTION WITH THE LONGWAVE TROUGH. 

MODEL DISCUSSION: THE JTWC TRACK FORECAST CONFIDENCE REMAINS HIGH
AND FOLLOWS CLOSE TO THE MULTI-MODEL CONSENSUS AS THE DETERMINISTIC
TRACK GUIDANCE IS IN OVERALL GOOD AGREEMENT THROUGHOUT THE FORECAST. THE JTWC INTENSITY GUIDANCE IS SLIGHTLY ABOVE THE MULTI-MODEL CONSENSUS FOR THE FIRST 12 HOURS DUE TO THE IMPROVED CONVECTIVE STRUCTURE AND THE INCREASE IN THE INTENSITY TRENDS. THEN AFTER TAU 24 THE FORECAST FOLLOWS CLOSE TO THE CONSENSUS THROUGHOUT THE FORECAST PERIOD. 

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