WDXS31 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 
025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0S 121.6E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 119 NM NORTH-NORTHWEST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-SOUTHEASTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
HEAVILY SHEARED TROPICAL CYCLONE (TC) 29S (ERROL), WITH THE
LOW-LEVEL CIRCULATION CENTER (LLCC) STILL FULLY OBSCURED BY THE
EDGE OF A CIRRUS CANOPY. THE INITIAL POSITION IS THEREFORE PLACED
WITH LOW CONFIDENCE, BASED ON THE EXTRAPOLATION OF THE LLCC
POSITION FROM LOW-LEVEL CLOUD TRACING OVER THE WESTERN PORTION OF
THE CIRCULATION. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED WITH
LOW CONFIDENCE BASED ON A HIGHLY SPREAD COMBINATION OF AGENCY
DVORAK AND OBJECTIVE ESTIMATES LISTED BELOW. AS THE SYSTEM IS
APPROACHING THE KIMBERLEY COAST, STRONG WEST-NORTHWESTERLY SHEAR,
COMBINED WITH THE INTRUSION OF DRY AIR THROUGHOUT THE WESTERN
SEMICIRCLE OF THE SYSTEM IS CAUSING RAPID WEAKENING AND EROSION OF
TC ERROL, DESPITE THE STRONG POLEWARD OUTFLOW, AS WELL AS THE SEA
SURFACE TEMPERATURES (SST) REMAINING WARM (29-30 C).

INITIAL WIND RADII BASIS: 171248Z METOP-B ASCAT

CURRENT STEERING MECHANISM: EAST-SOUTHEASTWARD FLOW ASSOCIATED WITH
A PASSING LONG WAVE TROUGH TO THE SOUTH OF THE SYSTEM

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T5.0 - 90 KTS
   DEMS: T5.5 - 102 KTS
   CIMSS SATCON: 66 KTS AT 171336Z
   CIMSS ADT: 69 KTS AT 171730Z
   CIMSS AIDT: 59 KTS AT 171730Z
   CIMSS D-MINT: 33 KTS AT 171714Z
   CIMSS D-PRINT: 37 KTS AT 171830Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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 EXPECTED TO MOVE EAST-SOUTHEASTWARD
THROUGHOUT THE FORECAST PERIOD DUE TO ITS INTERACTION WITH A
LONGWAVE TROUGH TO THE SOUTH. LANDFALL IS PROJECTED TO OCCUR AROUND
TAU 12, SOON AFTER THE SYSTEM PASSES THE DAMPIER PENINSULA. IN
TERMS OF INTENSITY, 29S IS ANTICIPATED TO CONTINUE WEAKENING
RAPIDLY THROUGHOUT THE FORECAST PERIOD, ENHANCED BY VWS INCREASING
TO 35-40 KTS BY TAU 24. MAXIMUM WINDS AT THE TIME OF LANDFALL ARE
FORECAST TO BE AROUND 40-45 KTS, WITH TC ERROL DISSIPATING SHORTLY
AFTER, WHILE THE CIRCULATION INTERACTS WITH TERRAIN.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN FAIR
AGREEMENT, WITH A CROSS-TRACK SPREAD OF 75 NM AND ALONG-TRACK
SPREAD OF 90 NM AT LANDFALL. WITH ALL AVAILABLE GUIDANCE SUGGESTING
INLAND DIRECTION, JTWC TRACK FORECAST IS LAID WITH MEDIUM CONFIDENCE, 
ALONG THE MULTI-MODEL CONSENSUS. INTENSITY GUIDANCE SUPPORTS A RAPID 
WEAKENING TREND AMONG ALL MEMBERS, AND THE JTWC INTENSITY FORECAST
IS CLOSELY ALIGNED WITH THE MULTI-MODEL CONSENSUS, WITH HIGH
CONFIDENCE.

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