WDXS31 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (IGGY) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7S 108.9E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 446 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 11S HAS ENTERED ITS DISSIPATION PHASE, WITH
THE SYSTEM QUICKLY DETERIORATING UNDER THE INFLUENCE OF HIGH
VERTICAL WIND SHEAR AND DRY MID-LEVEL AIR PUSHING IN FROM THE WEST.
ANIMATED SHORTWAVE INFRARED (SWIR) SATELLITE IMAGERY DEPICTS A
FULLY EXPOSED, AND POORLY ORGANIZED LOW LEVEL CIRCULATION CENTER
(LLCC), WITH REMNANT CONVECTION DISPLACED WELL TO THE EAST. THE
LLCC IS SO SHALLOW AND WEAK THAT IT IS NOT READILY IDENTIFIABLE IN
A 021132Z SSMIS 36GHZ MICROWAVE IMAGE AND ONLY WEAKLY EVIDENT IN
THE 91GHZ BAND. THE INITIAL POSITION IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN THE ANIMATED SWIR IMAGERY.
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BIASED 
TOWARDS THE AIDT AND PGTW DVORAK CURRENT INTENSITY ESTIMATE, THOUGH
A LACK OF RECENT RELIABLE SCATTEROMETER DATA PRECLUDES A MORE 
DEFINITIVE ASSESSMENT. THE ENVIRONMENT IS HIGHLY UNFAVORABLE, WITH 
HIGH WESTERLY SHEAR AND SIGNIFICANT DRY AIR INTRUSION OFFSETTING THE
ROBUST POLEWARD OUTFLOW ALOFT AND MODERATELY WARM SSTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF THE LOW- TO
MID-LEVELS OF A DEEP SUBTROPICAL RIDGE (STR) FAR TO THE SOUTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS SATCON: 38 KTS AT 020900Z
   CIMSS ADT: 30 KTS AT 021200Z
   CIMSS AIDT: 33 KTS AT 021200Z
   CIMSS D-MINT: 29 KTS AT 020855Z
   CIMSS D-PRINT: 32 KTS AT 021200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: DUE TO THE RAPID DETERIORATION OF THE
SYSTEM, THE FORECAST HAS BEEN TRUNCATED TO 24 HOURS. 

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 11S CONTINUES TO
GRADUALLY TURN SOUTHWESTWARD AS THE STR TO THE SOUTHWEST BUILDS
NORTHWARD ALONG THE EASTERN FLANK OF THE SYSTEM. OVER THE SHORT
DURATION OF THE FORECAST, TC 11S WILL TURN ONTO A WESTWARD TRACK AS
THE RIDGE CONTINUES TO BUILD AND POSITIONS TC 11S ON THE NORTHERN
PERIPHERY OF IT. NO SIGNIFICANT CHANGES ARE ANTICIPATED IN THE
ENVIRONMENT, IN FACT CONDITIONS ARE LIKELY TO DETERIORATE FURTHER,
AND THE SYSTEM WILL STEADILY WEAKEN AS IT DISSIPATES. DISSIPATION
BELOW THE 35 KNOT WARNING THRESHOLD IS FORECAST NO LATER THAN TAU
24, AND IT IS LIKELY TO OCCUR AS EARLY AS TAU 12. 

MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE AND ARTIFICIAL
INTELLIGENCE (AI) TRACK GUIDANCE IS IN TIGHT AGREEMENT FOR THE
DURATION OF THE SHORT FORECAST PERIOD, LENDING HIGH CONFIDENCE TO
THE JTWC TRACK FORECAST. INTENSITY GUIDANCE IS ALSO IN GOOD
AGREEMENT ON ALL AVAILABLE MODELS INDICATING WEAKENING BELOW
WARNING THRESHOLD WITHIN 12 TO 24 HOURS, LENDING HIGH CONFIDENCE TO
THE JTWC INTENSITY FORECAST.  

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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