WDXS32 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.2S 107.2E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 515 NM SOUTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED PROXY VISIBLE (PROXYVIS) SATELLITE IMAGERY DEPICTS
WELL-DEFINED, BUT SHALLOW LOW LEVEL CIRCULATION CENTER (LLCC), WITH
A BROAD AREA OF SMOOTH, STABLE, LOW-LEVEL CLOUDS WRAPPING AROUND
THE MAJORITY OF THE CIRCULATION. A 221218Z GMI 89GHZ IMAGE SHOWED
THE VERY SHALLOW NATURE OF THE CIRCULATION, WITH EVEN THE
HIGH-RESOLUTION 89GHZ BAND HAVING A HARD TIME PICKING UP ANY
SIGNIFICANT FEATURES IN THE BANDING FEATURES. THE INITIAL POSITION
IS ASSESSED WITH HIGH CONFIDENCE USING A BLEND OF THE LLCC IN THE
PROXY VISIBLE IMAGERY, AND THE MICROWAVE CENTER AS DETERMINED BY
THE CIMSS ARCHER TECHNIQUE. THE INITIAL INTENSITY IS ASSESSED
SLIGHTLY HIGHER THAN THE BULK OF THE OBJECTIVE AND SUBJECTIVE
INTENSITY ESTIMATES STRICTLY BASED ON THE IDEA THAT THE SYSTEM IS
WEAKENING AT A PACE OF ROUGHLY 5-10 KTS PER 12 HOURS, BUT IT COULD 
ACTUALLY BE CLOSER TO 35 KNOTS. THE ENVIRONMENT IS HIGHLY
UNFAVORABLE, CHARACTERIZED BY COOL SSTS, HIGH WESTERLY VWS, AND
RELATIVELY DEEP DRY AIR ABOVE ABOUT 700MB. POLEWARD OUTFLOW REMAINS
STRONG BUT EVEN WITH THIS STRONG EXHAUST MECHANISM, THE LACK OF
ENERGY FROM BELOW MEANS THERE IS NO SIGNIFICANT CONVECTION
ASSOCIATED WITH THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SYSTEM IS IN THE PROCESS OF
ROUNDING THE SUBTROPICAL RIDGE (STR) AXIS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 36 KTS AT 221000Z
   CIMSS ADT: 25 KTS AT 221130Z
   CIMSS AIDT: 31 KTS AT 221200Z
   CIMSS D-MINT: 36 KTS AT 221218Z
   CIMSS D-PRINT: 28 KTS AT 221200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 25-30 KTS
   SST: 21-22 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR OVER THE MAJORITY OF THE
CIRCULATION. 

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 10S HAS NOW ROUNDED THE STR AXIS AND IS
VERY SLOWLY STARTING TO TURN TOWARDS THE SOUTHEAST. A SLOW
ACCELERATION CAN BE SEEN IN THE ANIMATED VISIBLE AND PROXY VISIBLE
IMAGERY BUT THE SYSTEM IS OVERALL STILL MOVING FAIRLY SLOWLY, AT
ABOUT 3 KNOTS. OVER THE NEXT FEW HOURS, THE SYSTEM IS EXPECTED
STEADILY ACCELERATE AS IT MOVES FURTHER AWAY FROM THE RIDGE AXIS
AND TRACK SOUTHEASTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE STR
OVER AUSTRALIA. THE ENVIRONMENT, ALREADY HIGHLY UNFAVORABLE, WILL
NOT IMPROVE GOING FORWARD. THE ONLY THING KEEPING THE SYSTEM ALIVE
IS MOMENTUM CONSERVATION. TC 10S IS ALREADY UNDERGOING SUBTROPICAL
TRANSITION (STT) BASED ON THE FSU PHASE SPACE DIAGRAM AND MANUAL
PHASE CLASSIFICATION WORKSHEETS. HOWEVER, IT IS ALSO SIMULTANEOUSLY
WEAKENING AND THE CURRENT FORECAST CALLS FOR THE SYSTEM TO WEAKEN
BELOW WARNING CRITERIA, WITHIN THE NEXT 24 HOURS, PRIOR TO
COMPLETING STT. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN STRONG
AGREEMENT, THOUGH NAVGEM IS AN OUTLIER TAKING THE SYSTEM DUE SOUTH
THROUGH THE DURATION OF THE FORECAST WHILE THE OTHER CONSENSUS
MEMBERS ARE TIGHTLY CONSTRAINED NEAR THE CONSENSUS MEAN AND THE
JTWC FORECAST. IN TERMS OF INTENSITY, ALL AVAILABLE MODEL GUIDANCE
IS IN GOOD AGREEMENT THAT THE SYSTEM WILL STEADILY WEAKEN AND CROSS
BELOW 35 KNOTS WITHIN THE NEXT 18-24 HOURS. 

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