WDXS31 PGTW 152100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL)      
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.9S 120.3E
   INITIAL INTENSITY: 60 KTS
   GEOGRAPHIC REFERENCE: 264 NM NORTH-NORTHWEST OF BROOME,
                         AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 29S HAS STEADILY CONSOLIDATED WHILE MAINTAINING 
A COMPACT, VERTICALLY ALIGNED CORE. ANIMATED ENHANCED INFRARED (EIR) 
SATELLITE IMAGERY DEPICTS A SYMMETRIC CENTRAL DENSE OVERCAST (CDO), 
WITH RAPIDLY CYCLING DEEP CONVECTION AND INTENSE CONVECTIVE BURSTS 
(CLOUD TOP TEMPERATURES AS HIGH AS -87C). ALTHOUGH EIR IMAGERY HAS 
HINTED AT EYE FORMATION, A CLEAR, DISTINCT EYE HAS YET TO FORM. 
ANIMATED WATER VAPOR IMAGERY INDICATES IMPROVED RADIAL OUTFLOW, WITH 
A ROBUST POLEWARD OUTFLOW CHANNEL. A TIMELY 151725Z AMSR2 89GHZ 
MICROWAVE IMAGE REVEALS TIGHTLY CURVED BANDING WRAPPING INTO A WELL-
DEFINED LOW-LEVEL CIRCULATION CENTER, SUPPORTING THE INITIAL POSITION 
WITH HIGH CONFIDENCE, AND EXTENSIVE SPIRAL BANDING OVER THE EASTERN 
AND SOUTHERN SEMICIRCLES. THE INITIAL INTENSITY OF 60 KTS IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON AN AVERAGE OF THE AGENCY DVORAK 
ESTIMATES. CIMSS SUBJECTIVE INTENSITY ESTIMATES HAVE INCREASED SLOWLY 
BUT REMAIN SIGNIFICANTLY LOWER THAN THE SUBJECTIVE DVORAK ESTIMATES, 
RANGING FROM 38 TO 51 KNOTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTH AND SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   APRF: T3.5 - 55 KTS
   CIMSS SATCON: 48 KTS AT 151454Z
   CIMSS ADT: 51 KTS AT 151730Z
   CIMSS AIDT: 38 KTS AT 151730Z
   CIMSS D-PRINT: 45 KTS AT 151900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 29S IS TRACKING SLOWLY WESTWARD ALONG THE
NORTHERN PERIPHERY OF THE STR AND IS FORECAST TO CONTINUE TRACKING
WESTWARD TO WEST-SOUTHWESTWARD THROUGH TAU 24. AFTER TAU 24, THE
SYSTEM WILL SLOW AND TURN SHARPLY SOUTHEASTWARD AS A MAJOR TROUGH
APPROACHES AND DEEPENS OVER WESTERN AUSTRALIA, QUICKLY BREAKING
DOWN THE STR. ENVIRONMENTAL CONDITIONS WILL REMAIN HIGHLY FAVORABLE
THROUGH TAU 24, WITH IMPROVED POLEWARD OUTFLOW ENHANCED BY THE
UPPER-LEVEL TROUGH AND SUBTROPICAL JET OVER NORTHWEST AUSTRALIA.
CONSEQUENTLY, RAPID INTENSIFICATION IS EXPECTED, WITH A PEAK
INTENSITY OF AT LEAST 100 KNOTS FORECAST BY TAU 24. NEAR TAU 36,
ENVIRONMENTAL CONDITIONS WILL RAPIDLY DEGRADE AS THE SYSTEM TRACKS
UNDER STRONG WESTERLIES ASSOCIATED WITH THE AFOREMENTIONED TROUGH.
TC ERROL WILL TRACK EAST-SOUTHEASTWARD THROUGH THE END OF THE
FORECAST PERIOD WITHIN WESTERLY STEERING FLOW BETWEEN THE NEAR-
EQUATORIAL RIDGE TO THE NORTH AND THE LONGWAVE TROUGH ENTRENCHED TO 
THE SOUTH. THE SYSTEM WILL WEAKEN RAPIDLY DUE TO EXTENSIVE DRY AIR 
ENTRAINMENT AND INCREASING (30-50 KNOTS) VERTICAL WIND SHEAR, WITH 
DISSIPATION EXPECTED BY TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN FAIR AGREEMENT 
DUE TO THE COMPLEX, RAPIDLY EVOLVING STEERING ENVIRONMENT. THE JTWC 
TRACK FORECAST, HOWEVER, REMAINS HIGHLY CONSISTENT WITH THE PREVIOUS 
FORECAST TRACK. RAPID INTENSIFICATION GUIDANCE CONTINUES TO TRIGGER 
SUPPORTING THE RI PHASE OF THE FORECAST. ENSEMBLE GUIDANCE FROM THE 
ECENS AND GEFS ENSEMBLES SUPPORT THE JTWC TRACK FORECAST AND ALSO 
SHOW UNCERTAINTY IN THE RECURVE POINT AND EAST-SOUTHEASTWARD TRACK 
TOWARD NORTHWEST AUSTRALIA.    

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