WDXS31 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (CHENESO)    
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0S 42.9E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 201 NM NORTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 02 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 08S HAS RAPIDLY INTENSIFIED 35 KNOTS OVER THE
PAST 24 HOURS FROM 25 KNOTS TO THE CURRENT INTENSITY OF 60 KNOTS.
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
CLOUD-FILLED EYE, RAGGED EYE WITH TIGHTLY CURVED SPIRAL BANDING. A
241214Z GMI 89GHZ COLOR COMPOSITE MICROWAVE IMAGE REVEALS A MORE
ELONGATED MICROWAVE EYE FEATURE, HOWEVER, THE OVERALL CONVECTIVE
STRUCTURE HAS DEFINITELY IMPROVED SIGNIFICANTLY OVER THE PAST 12
HOURS. ENVIRONMENTAL CONDITIONS REMAIN HIGHLY FAVORABLE WITH STRONG
NEAR-RADIAL OUTFLOW ENHANCED BY A WESTERLY JET TO THE SOUTH, WARM
SST VALUES AND LOW VERTICAL WIND SHEAR. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE MSI AND GMI IMAGERY. THE
INITIAL INTENSITY OF 60 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AVERAGE OF DVORAK ESTIMATES RANGING FROM 55 TO 65
KNOTS. HOWEVER, THE QUICK FORMATION OF A RAGGED EYE HAS MADE THIS
DETERMINATION MORE CHALLENGING. ADT AND AIDT ESTIMATES ARE LAGGING
A BIT AT 51 AND 45 KNOTS, RESPECTIVELY, WHILE DMN AND OPEN-AIR
ESTIMATES ARE NEAR 60 KNOTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN WITH A
NEAR-EQUATORIAL RIDGE POSITIONED TO THE NORTH AND A SUBTROPICAL
RIDGE ENTRENCHED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   KNES: T3.5 - 55 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS SATCON: 50 KTS AT 241028Z
   CIMSS ADT: 47 KTS AT 241200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: NO MAJOR CHANGES BUT CHANGED
EXTRA-TROPICAL TRANSITION TO A MORE LIKELY SUBTROPICAL TRANSITION
IN THE EXTENDED PERIOD. 

FORECAST DISCUSSION: TC 08S SHOULD REMAIN QUASI-STATIONARY THROUGH
AT LEAST TAU 36 WITHIN THE COMPETING STEERING PATTERN, WHICH IS
EXPECTED TO UPWELL COOLER WATER SLOWING INTENSIFICATION TO A MORE
MODEST RATE. ADDITIONALLY, INTERACTION WITH LAND WILL ALSO HINDER
SIGNIFICANT INTENSIFICATION. AFTER TAU 36, THE STR TO THE SOUTH IS
EXPECTED TO GRADUALLY WEAKEN WITH THE APPROACH OF A DEEP
UPPER-LEVEL TROUGH WHICH WILL SHIFT THE STR TO THE EAST AND ALLOW
TC 08S TO ACCELERATE POLEWARD. TC 08S WILL PEAK AT 100 KNOTS NEAR
TAU 72 DUE TO ENHANCED POLEWARD OUTFLOW INTO THE WESTERLIES. THE
STR WILL GRADUALLY STRENGTHEN TO THE EAST DRIVING TC 08S SOUTHWARD
THEN EVENTUALLY SOUTHEASTWARD AFTER TAU 96 WHEN THE SYSTEM ROUNDS
THE STR AND BEGINS TO INTERACT WITH THE SUBTROPICAL WESTERLIES.    

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM AND AFUM, THE TWO
PRIMARY OUTLIERS, NUMERICAL GUIDANCE IS IN FAIR AGREEMENT
SUPPORTING THE INITIAL QUASI-STATIONARY PHASE AND EVENTUAL POLEWARD
ACCELERATION. THE 240600Z ECMWF ENSEMBLE (EPS) AND GFS ENSEMBLE
(GEFS) ARE IN FAIR AGREEMENT AS WELL BUT INDICATE INCREASING
ALONG-TRACK UNCERTAINTY DURING THE RECURVE PORTION OF THE TRACK
SOUTH OF MADAGASCAR. THE COAMPS-TC ENSEMBLE (240600Z) INDICATES A
30-60 PERCENT PROBABILITY OF RAPID INTENSIFICATION OVER THE NEXT 30
HOURS.       

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: MEDIUM//
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