WDXS31 PGTW 261500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (CHENESO) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.1S 42.8E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 192 NM NORTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE 10S (CHENESO) HAS REMAINED GENERALLY
QUASI-STATIONARY OVER MOST OF THE PAST 12 HOURS, BUT OVER THE LAST
COUPLE OF HOURS, BEGUN TO MOVE SOUTHWARD. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) REVEALS A SIGNIFICANTLY WEAKENED SYSTEM,
WITH THE UPWELLING OF MUCH COOLER WATERS NEGATIVELY IMPACTING THE
SYSTEM. THE MSI ALSO SHOWS THE IMPACT OF SOME NORTHERLY SHEAR, WITH
THE A RELATIVELY LARGE TILT EVIDENT BETWEEN THE UPPER-LEVEL EYE
FEATURE AND THE LOW-LEVEL CIRCULATION CENTER (LLCC) DISPLACED TO
THE NORTH. A 261051Z AMSR2 MICROWAVE IMAGERY SERIES SHOWED WEAK
SPIRAL BANDING WRAPPING INTO THE WELL-DEFINED LLCC, WHICH IS DEVOID
OF SIGNIFICANT CONVECTIVE ACTIVITY ACROSS THE NORTHERN HEMISPHERE.
THE UPPER-LEVEL STEERING ENVIRONMENT HAS BEGUN TO SLOWLY CHANGE, AS
THE SUBTROPICAL RIDGE (STR) TO THE SOUTH HAS STARTED MOVING OFF TO
THE EAST. IN RESPONSE, TC 10S HAS STARTED TO SLOWLY DRIFT TO THE
SOUTH, THOUGH THE STEERING GRADIENT REMAINS RELATIVELY WEAK. THE
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AMSR2 IMAGE NOTED ABOVE. THE INITIAL INTENSITY MEANWHILE IS
ASSESSED WITH LOW CONFIDENCE, BELOW THE MAJORITY OF THE OBJECTIVE
AND SUBJECTIVE DVORAK CURRENT INTENSITY ESTIMATES, HEDGED TOWARDS
RECENT OPEN-AIIR AND DEEP MICRONET (DMN) ESTIMATES WHICH
SUBJECTIVELY APPEAR TO BE MORE REPRESENTATIVE. ENVIRONMENTAL
CONDITIONS ARE IMPROVING AND ARE GENERALLY FAVORABLE FOR
INTENSIFICATION, WITH LOW (5-10 KNOTS) VWS, AND STRONG POLEWARD
OUTFLOW. THE UPWELLED WATERS ARE CURRENTLY THE ONLY HINDRANCE ON
THE SYSTEM, AND AS IT MOVES SOUTHWARD, THIS HINDRANCE WILL BE
REMOVED.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN WITH A
NEAR-EQUATORIAL RIDGE (NER) TO THE NORTH AND A SUBTROPICAL RIDGE
(STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   FMEE: T3.5 - 55 KTS
   CIMSS SATCON: 76 KTS AT 261038Z
   CIMSS ADT: 87 KTS AT 261200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: UPWELLING OF COOL WATER AND LOW-LEVEL DRY AIR
ENTRAINMENT OFF MADAGASCAR. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: LOW
   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 10S REMAINS WITHIN THE COMPETING AND WEAK
STEERING ENVIRONMENT, STUCK BETWEEN THE NER TO THE NORTH AND THE
STR TO THE SOUTH. THE LATEST UPPER-LEVEL ANALYSIS SUGGESTS THE STR
IS BEGINNING TO MOVE OFF TO THE EAST AHEAD OF A STRONG, DEEP-LAYER
MID-LATITUDE TROUGH MOVING IN FROM THE WEST, AND RECENT SATELLITE
IMAGERY INDICATES TC 10S HAS STARTED TO MOVE SOUTHWARD IN RESPONSE.
FREE TO MOVE AWAY FROM THE LIMITING INFLUENCES OF THE RELATIVELY
COOL UPWELLED WATER AND LAND INTERACTION, THE SYSTEM IS EXPECTED TO
QUICKLY INTENSIFY UP TO A PEAK OF 90 KNOTS BY TAU 36, AS IT PASSES
TO THE EAST OF EUROPA ISLAND. THE SYSTEM THEN ROUNDS THE RIDGE AXIS
AND ACCELERATES POLEWARD ALONG THE STRONG GRADIENT BETWEEN THE DEEP
RIDGE TO THE EAST AND THE STRONG TROUGH APPROACHING FROM THE WEST.
THE SYSTEM WILL CROSS THE 26C ISOTHERM AND BEGIN INTERACTING WITH
THE SUBTROPICAL WESTERLIES ALOFT BETWEEN TAUS 48 AND 60, WITH
SUBTROPICAL TRANSITION (STT) IN FULL THROAT NO LATER THAN TAU 60.
THE SUBTROPICAL PHASE WILL BE SHORT-LIVED HOWEVER. EXTRATROPICAL
TRANSITION (ETT) WILL BEGIN IN EARNEST BETWEEN TAUS 72 AND 96 AS
THE SYSTEM CONTINUES TO ACCELERATE POLEWARD, BECOMES EMBEDDED IN A
STRONG BAROCLINIC ZONE, TAKES ON FRONTAL CHARACTERISTICS AND MOVES
UNDER A 70 KNOT JET MAX. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
ON THE OVERALL FORECAST SCENARIO, WITH SOME MARGINAL CROSS AND
ALONG-TRACK SPREAD DEVELOPING AFTER TAU 48 WHEN THE SYSTEM STARTS
TO ACCELERATE. THE JTWC FORECAST TRACK IS PLACED WITH HIGH
CONFIDENCE THROUGH TAU 72 AND MEDIUM THEREAFTER DUE TO THE
INCREASED SPREAD IN THE GUIDANCE AFTER THE POLEWARD TURN. INTENSITY
GUIDANCE IS MIXED, WITH THE COAMPS-TC (NAVGEM VERSION AND THE DECAY
SHIPS (NAVGEM) SHOWING LITTLE IN THE WAY OF INTENSIFICATION THROUGH
THE FIRST 72 HOURS, WHILE THE HWRF IS DEPICTED RAPID
INTENSIFICATION, TO A PEAK OF 105 KNOTS OVER THE NEXT 24 HOURS. THE
CONSENSUS AND GFS DETERMINISTIC SHOW A MORE REASONABLE, FLAT
INTENSITY TREND THROUGH TAU 12, FOLLOWED BY A FAIRLY QUICK RAMP UP
TO A PEAK OF ABOUT 80 KNOTS BY TAU 36. THE JTWC FORECAST IS BASED
ON A BLEND OF THE AVAILABLE GUIDANCE AND LIES ABOVE THE CONSENSUS
MEAN BUT BELOW THE HWRF PEAK, WITH MEDIUM CONFIDENCE THROUGH TAU
72. CONFIDENCE INCREASES IN THE LONG TERM AS THE BULK OF THE
GUIDANCE CONCURS ON A SLOW WEAKENING TREND AFTER TAU 72. 

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