WDXS32 PGTW 230300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (SEAN) WARNING NR 
021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.2S 107.8E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 536 NM SOUTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE 10S (SEAN) WITH A COMPLETELY EXPOSED AND SHALLOW LOW-LEVEL
CIRCULATION CENTER (LLCC). THE VORTEX IS BECOMING INCREASINGLY
ELONGATED IN THE NORTH-SOUTH AXIS AS WELL. THE ENVIRONMENT
CONTINUES TO BE HIGHLY UNFAVORABLE DUE TO THE HIGH VERTICAL WIND
SHEAR (VWS), COOL SEA SURFACE TEMPERATURES, AND SIGNIFICANT DRY AIR
ENTRAINMENT. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE EXPOSED LLCC IN THE ANIMATED MSI. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
PERSISTENCE FROM A 221837Z AMSR2 WIND SPEED IMAGE SHOWING 39-40 KTS
WITHIN THE SOUTHWESTERN PERIPHERY. AGENCY DVORAK AND OBJECTIVE
INTENSITY ESTIMATES ARE TOO LOW DUE TO THE LACK OF ASSOCIATED
CONVECTION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30-35 KTS
   SST: 23-24 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

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 IS FORECAST TO CONTINUE TRACKING
GENERALLY SOUTHEASTWARD ALONG THE WESTERN PERIPHERY OF THE STR TO
THE EAST OVER THE NEXT 24 HOURS. 10S WILL CONTINUE TO BE PLACED
WITHIN A HOSTILE ENVIRONMENT THROUGH THE REMAINDER OF ITS
EXISTENCE, CHARACTERIZED BY HIGH VWS, COOL SST, AND COPIOUS DRY AIR.
AS A RESULT, 10S IS FORECAST TO CONTINUE DEGRADING AND IS FORECAST
TO WEAKEN BELOW TROPICAL STORM STRENGTH NEAR TAU 24. 10S IS
SIMULTANEOUSLY TRANSITIONING INTO AN EXTRATROPICAL CYCLONE AND WILL
BECOME COLD-CORE AROUND THE SAME TIME AS IT DISSIPATES (TAU 24). 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
REGARDING THE TRACK OF 10S, WITH A 55 NM CROSS-TRACK SPREAD AT TAU
24. THE JTWC TRACK FORECAST IS PLACED CLOSE TO CONSENSUS WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT, WITH ALL
MEMBERS SUGGESTING STEADY WEAKENING. THE JTWC INTENSITY GUIDANCE IS
PLACED WITH HIGH CONFIDENCE AS WELL.

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