WDXS31 PGTW 020300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 11S (IGGY) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.3S 109.5E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 495 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 11S (IGGY) WITH FLARING CONVECTION LOCATED OVER THE
LOW-LEVEL CIRCULATION CENTER. SINCE THE PREVIOUS WARNING, THE
SYSTEMS LLCC HAS BECOME COMPLETELY EXPOSED WITH ALL ASSOCIATED
CONVECTION SHEARED EASTWARD, HOWEVER, CONVECTION HAS BEGUN BUILDING
IN CLOSE PROXIMITY TO THE SYSTEMS CENTER. ALTHOUGH CONVECTION HAS
RETURNED OVER THE LOW-LEVEL VORTEX, INDIVIDUAL CONVECTIVE CELLS
REMAIN ISOLATED AND RELEGATED TO THE IMMEDIATE SOUTHEASTERN
QUADRANT. ALOFT, THE POLEWARD OUTFLOW CHANNEL HAS REMAINED,
ASSISTING IN MAINTAINING THE CYCLONES SURFACE INTENSITIES NEAR 40
KTS. THE ENVIRONMENT HAS ALSO REMAINED MARGINAL OVER THE LAST FEW
HOURS WITH VERTICAL WIND SHEAR (VWS) CONTINUING TO INTRODUCE DRY
AIR INTO THE SYSTEMS CORE. THE INITIAL POSITION HAS BEEN PLACED
WITH HIGH CONFIDENCE BASED ON THE AFOREMENTIONED FULLY EXPOSED
LOW-LEVEL CIRCULATION CENTER OBSERVED ON ANIMATED MSI. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A COMBINATION
OF SUBJECTIVE AGENCY ESTIMATES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A NEAR
EQUATORIAL RIDGE (NER) LOCATED TO THE NORTH, BECOMING A SUBTROPICAL
RIDGE (STR) OVER THE NEXT 12 HOURS

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   APRF: T2.5 - 35 KTS
   CIMSS ADT: 55 KTS AT 012030Z
   CIMSS AIDT: 43 KTS AT 012030Z
   CIMSS D-PRINT: 36 KTS AT 020030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: VWS IN EXCESS OF 15 KTS HAS LIMITED
FURTHER INTENSIFICATION PAST 45 KTS SINCE THE PREVIOUS FORECAST

FORECAST DISCUSSION: TC 11S IS FORECASTED TO TRACK SOUTH-SOUTHEAST
OVER THE NEXT FEW HOURS, ALONG THE SOUTHWESTERN PERIPHERY OF THE
NER LOCATED TO THE NORTH AND NORTHEAST. AFTER TAU 12, THE SYSTEM
WILL BEGIN A WEST-SOUTHWESTWARD TRACK ALONG THE NORTHEASTERN EXTENT
OF A STR BUILDING TO THE SOUTHWEST. THE AFOREMENTIONED STR WILL
CONTINUE BUILDING WESTWARD OVER THE NEXT 48 HOURS, DRIVING TC 11S
WEST-SOUTHWEST THROUGH THE REMAINDER OF THE FORECAST PERIOD.
REGARDING INTENSITY, AN EASTWARD PROGRESSING LONGWAVE TROUGH WILL
CONTINUE PROVIDING UPPER-LEVEL OUTFLOW SUPPORT, ASSISTING IN
HOLDING THE SYSTEM NEAR 40 KTS OVER THE NEXT 36 HOURS. DURING THIS
PERIOD, WESTERLY VWS WILL INCREASE TO OVER 20 KTS, ULTIMATELY
CAUSING A HOSTILE ENVIRONMENT DURING THE CYCLONES WESTWARD TERMINAL
TRACK. BETWEEN TAU 24 AND TAU 36, TC 11S IS FORECASTED TO BEGIN ITS
TERMINAL DISSIPATION PHASE. TC 11S IS FORECASTED TO WEAKEN IN
INTENSITY TO 25 KTS BY THE END OF THE FORECAST PERIOD AS THE
ENVIRONMENT BECOMES LARGELY NON-CONDUCIVE WITH EXCESSIVE DRY AIR
INTRUSION AND VWS ABOVE 40 KTS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE AND ARTIFICIAL
INTELLIGENCE (AI) MODELS CONTINUE TO ILLUSTRATE A SHORT
SOUTH-SOUTHEASTERLY TRACK OVER THE NEXT 6-12 HOURS, AND THEN
QUICKLY START TRACKING WEST-SOUTHWESTWARD. ALTHOUGH CROSS-TRACK
SPREAD AT TAU 72 IS JUST 68 NM, THE ALONG-TRACK SPREAD OF THE
MAJORITY OF MODEL SOLUTIONS VARY GREATLY, INCREASING THE TAU 72
ALONG-TRACK SPREAD TO 208 NM. THE JTWC FORECAST IS POSITIONED
CLOSELY TO THE MULTI-MODEL CONSENSUS AND AI MODEL CONSENSUS WITH
MEDIUM CONFIDENCE. INTENSITY GUIDANCE REMAINS IN GOOD AGREEMENT,
WITH THE MAJORITY OF INTENSITY SOLUTIONS CHARACTERIZING SUSTAINED
INTENSITIES BETWEEN 35-40 KTS OVER THE NEXT 36 HOURS. FOLLOWING TAU
36, EACH INTENSITY FORECAST AID SHOWS A STEADY TERMINAL DISSIPATION
PHASE THROUGH THE END OF THE FORECAST PERIOD, LENDING MEDIUM
CONFIDENCE TO THE INTENSITY FORECAST.

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