WDXS31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (CHENESO) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.9S 42.1E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 132 NM NORTHEAST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN INNER
CORE THAT CONTINUES TO DRAMATICALLY ERODE, WITH A NOW FRAGMENTED
COLD BAND SURROUNDING THE LOW-LEVEL CIRCULATION CENTER (LLCC)
CONTAINING NO CLOUD TOPS COLDER THAN -58 DEGREES CELSIUS. WHILE NO
REAL-TIME OCEANOGRAPHIC DATA IS AVAILABLE, THE EVOLUTION OF THE
SATELLITE PRESENTATION OVER THE PAST 24 HOURS IS TYPICAL OF
SIGNIFICANT DYNAMIC OCEAN COOLING OCCURRING BENEATH THE CYCLONE'S
INNER CORE, SHUTTING OFF DEEP CONVECTION. SATELLITE-BASED INTENSITY
ESTIMATES FROM A 261543Z RCM-1 SAR PASS, A 261930Z ASCAT-B PASS,
SUBJECTIVE DVORAK ESTIMATES, AND OBJECTIVE MICROWAVE-BASED
INTENSITY ESTIMATES HAVE ALL DECREASED DURING THE PAST 12 HOURS,
WITH SAR AND ASCAT DIRECTLY CONFIRMING SIGNIFICANT WEAKENING TO AN
INITIAL INTENSITY OF 50 KT. EUROPA ISLAND, ABOUT 125 NM SOUTHWEST
OF THE CYCLONE, HAS REPORTED SOUTHEASTERLY WINDS OF 24-27 KT DURING
THE 270000Z TO 270200Z PERIOD.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE TO THE SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 59 KTS AT 262149Z
   CIMSS ADT: 61 KTS AT 270000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: WEAK RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE CYCLONE TRANSITION SCENARIO HAS
BEEN CHANGED TO EXTRATROPICAL TRANSITION, AFTER PREVIOUSLY
INCLUDING A SUBTROPICAL TRANSITION PERIOD. DYNAMICAL MODEL GUIDANCE
NOW FORECASTS MORE DIRECT BAROCLINIC INTERACTION WITH AN
UPPER-LEVEL TROUGH AFTER 48 HOURS.

FORECAST DISCUSSION: TROPICAL CYCLONE 08S (CHENESO) CONTINUES TO BE
ERODED BY UPWELLED COOLER WATERS BENEATH ITS CORE. THE STORM HAS
BEGUN MOVING SOUTH-SOUTHWESTWARD, BUT ONLY SLOWLY. THIS MOTION WILL
EVENTUALLY CARRY CHENESO OVER A REGION OF WARMER WATERS OFF OF
SOUTHWESTERN MADAGASCAR, WITH OCEAN HEAT CONTENT VALUES OF UP TO 40
KJ PER SQUARE CENTIMETER. THIS SHOULD REVIVE DEEP CONVECTION WITHIN
CHENESO'S INNER CORE AND IGNITE REINTENSIFICATION, BUT ONLY FOR A
LIMITED TIME PERIOD. AN UPPER-LEVEL LONGWAVE TROUGH WILL ADVANCE
EASTWARD FROM SOUTHERN AFRICA AND BEGIN IMPACTING THE CYCLONE WITH
NORTHWESTERLY WIND SHEAR OF 15-20 KT IN ABOUT 24 HOURS. THIS IS
FORECAST BY DYNAMICAL GLOBAL MODELS TO PUSH AN AMBIENT DRY AIR MASS
OVER THE WESTERN MOZAMBIQUE CHANNEL INTO THE STORM'S INNER CORE,
LIKELY DISRUPTING THE REINTENSIFICATION TREND. ADDITIONALLY, AFTER
36 HOURS, CHENESO WILL BEGIN MOVING INTO PROGRESSIVELY COOLER SEA
SURFACE TEMPERATURES, REACHING WATERS COOLER THAN 27 DEGREES
CELSIUS BY 48 HOURS, FURTHER CAPPING ITS INTENSITY. THE JTWC
INTENSITY FORECAST IS FOR CHENESO TO REACH A SECONDARY PEAK OF 70
KT DURING THE 24-36 HOUR PERIOD, FOLLOWED BY GRADUAL DECAY AS THE
CYCLONE INTERACTS WITH THE LONGWAVE TROUGH AND MOVES OVER COLDER
WATERS, TURNING AND ACCELERATING SOUTHEASTWARD AS IT DOES SO. THIS 
INTENSITY PEAK IS LOWER THAN THE PREVIOUS FORECAST PEAK OF 90 KT,
LARGELY DUE TO THE INITIAL INTENSITY BEING 20 KT LOWER THAN
PREVIOUSLY EXPECTED, COUPLED WITH LIMITED TIME TO REINTENSIFY.
CHENESO WILL BEGIN EXTRATROPICAL TRANSITION AT 72 HOURS, COMPLETING
BY 96 HOURS. MAXIMUM WINDS AROUND THE CYCLONE MAY REMAIN ABOVE 50
KT DURING EXTRATROPICAL TRANSITION DUE TO FAVORABLE BAROCLINIC
INTERACTION MAINTAINING A STRONG AND EXPANSIVE WIND FIELD.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS VERY CLOSE TO THE
CONSENSUS OF DYNAMIC GLOBAL MODELS, SLIGHTLY FASTER THAN THE
PREVIOUS FORECAST BEYOND 48 HOURS. THE JTWC INTENSITY FORECAST IS
BELOW THE MULTI-MODEL CONSENSUS FOR THE FIRST 12 HOURS DUE TO
ONGOING SATELLITE TRENDS, THEN SLIGHTLY ABOVE THE CONSENSUS BEYOND
24 HOURS DUE TO SHIPS BEING AN ANOMALOUSLY WEAK OUTLIER. DYNAMICAL
MODELS UNCOUPLED TO THE OCEAN, SUCH AS THE GFS, CONTINUE TO BE
STRONG OUTLIERS.

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