WDXS31 PGTW 171500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 
024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4S 120.3E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 186 NM NORTHWEST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 29S (ERROL) WITH A LARGE CENTRAL DENSE OVERCAST (CDO)
FEATURE OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC). A
171025Z SSMIS 91 GHZ MICROWAVE IMAGE SHOWS THE DEEP CONVECTION
BEING SHEARED TOWARD THE SOUTHEAST AS THE STRONG NORTHWESTERLY
SHEAR ACTS ON THE SYSTEM. ENVIRONMENTAL ANALYSIS INDICATES THAT 29S
IS IN AN UNFAVORABLE ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD
OUTFLOW AND WARM (29-30 C) SEA SURFACE TEMPERATURES GREATLY OFFSET
BY THE NORTHWESTERLY SHEAR AND DRY AIR ENTRAINMENT WITHIN THE
WESTERN PERIPHERY. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON THE MENTIONED SSMIS MICROWAVE IMAGE AND
ANIMATED EIR IMAGERY. THE INITIAL INTENSITY OF 80 KTS IS ASSESSED
WITH LOW CONFIDENCE BASED ON THE RAPIDLY LOWERING AGENCY DVORAK FIXES 
AND OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: A GENERAL EASTWARD STEERING PATTERN 
INFLUENCED BY THE LONGWAVE TROUGH TO THE SOUTH OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T5.5 - 102 KTS
   APRF: T4.5 - 77 KTS
   CIMSS ADT: 82 KTS AT 171200Z
   CIMSS AIDT: 74 KTS AT 171200Z
   CIMSS DMINT: 52 KTS AT 171025Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE WEST

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: LOW
   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 29S IS FORECAST TO TRACK EAST-SOUTHEASTWARD
THROUGHOUT THE FORECAST PERIOD DUE TO THE INTERACTION WITH THE
LONGWAVE TROUGH TO THE SOUTH. LANDFALL IS FORECAST TO OCCUR JUST
AFTER TAU 24, ABOUT 40 NM NORTH OF DERBY AFTER PASSING OVER THE
DAMPIER PENINSULA. REGARDING INTENSITY, 29S IS FORECAST TO CONTINUE
RAPIDLY WEAKENING OVER THE NEXT 36 HOURS AS SHEAR VALUES REACH
30-35 KTS AT TAU 24 AND UPWARDS OF 40 KTS AT TAU 36. SIGNIFICANT
DRY AIR ENTRAINMENT FROM THE WEST WILL ALSO AID IN ERODING THE
VORTEX. THIS WILL CAUSE 29S TO HAVE WEAK TROPICAL STORM STRENGTH
WINDS AS IT MAKES LANDFALL. A DROP TO BELOW 35 KTS IS FORECAST TO
OCCUR NO LATER THAN TAU 36 AS THE SYSTEM TRACKS INLAND AND TERRAIN
INTERACTION FURTHER DIMINISHES THE SYSTEM. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT WITH A 95 NM CROSS-TRACK SPREAD AT TAU 24, NEAR THE TIME
OF LANDFALL. AFTER TAU 24, ALONG-TRACK SPREAD INCREASES SLIGHTLY,
BUT REMAINS IN OVERALL CONCURRENCE ON A CONTINUED EAST-SOUTHEASTWARD 
TRACK. AS A RESULT, THE JTWC TRACK FORECAST IS PLACED WITH HIGH 
CONFIDENCE THROUGHOUT THE FORECAST PERIOD. INTENSITY GUIDANCE AGREES 
ON A RAPID WEAKENING TREND, AND THE JTWC INTENSITY FORECAST IS PLACED 
CLOSE TO THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE AS WELL.

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