WDXS31 PGTW 162100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 
021//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7S 118.8E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 274 NM NORTHWEST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS RAPIDLY
DETERIORATING CONVECTIVE STRUCTURE OF TROPICAL CYCLONE (TC) 29S
(ERROL). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON THE CLEARLY IDENTIFIABLE EYE FEATURE, WHICH HAS COOLED
APPROXIMATELY 17 DEGREES CELSIUS OVER THE LAST 6 HOURS. THE EYE
TEMPERATURE IS CURRENTLY ASSESSED AS NEGATIVE 2 DEGREES CELSIUS,
WHILE THE FEATURE IS BEGINNING TO FILL, WITH CURRENT DIAMETER OF 10
NM. NORTHEASTERLY SHEAR IS IMPACTING THE CONVECTIVE ENVELOPE,
MAKING THE CENTRAL DENSE OVERCAST (CDO) HIGHLY ASYMMETRICAL, WITH THE
MAJORITY OF THE CONVECTION CONTAINED WITHIN THE WESTERN PORTION OF
THE SYSTEM. OBSERVED RAPID DETERIORATION IS ALSO ASSESSED THROUGH
WARMING CLOUD TEMPERATURES THROUGHOUT THE STRUCTURE OF TC ERROL.
THE INITIAL INTENSITY OF 125 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE DVORAK ESTIMATES AND OBJECTIVE AIDS LISTED BELOW.
ENVIRONMENTAL ANALYSIS REVEALS UNFAVORABLE CONDITIONS, PARTICULARLY 
CONSIDERING THE COMPACT STRUCTURE OF THE SYSTEM, AND PRIMARILY DUE TO 
INCREASING DEEP-LAYER VERTICAL WIND SHEAR (VWS) AND DRY AIR INTRUSION 
FROM THE WEST. SEA SURFACE TEMPERATURES REMAIN WARM (29-30 C) AND THE 
POLEWARD OUTFLOW IS STRONG, AMPLIFIED BY THE UPPER-LEVEL TROUGH 
PASSING TO THE SOUTH.

INITIAL WIND RADII BASIS: 161357Z METOP-C ASCAT UHR DATA

CURRENT STEERING MECHANISM: WEAK STEERING BY A SUBTROPICAL RIDGE
(STR) TO THE EAST AND INFLUENCE FROM A PASSING LONG WAVE TROUGH TO
THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   DEMS: T7.0 - 140 KTS 
   CIMSS SATCON: 114 KTS AT 161730Z
   CIMSS ADT: 122 KTS AT 161730Z
   CIMSS AIDT: 118 KTS AT 161730Z
   CIMSS D-PRINT: 118 KTS AT 161730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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 FORECAST TO CONTINUE TRACKING SOUTH, 
ROUNDING THE AXIS OF A WEAK STR TO THE EAST THAT IS SLOWLY MOVING 
EQUATORWARD, RELEASING THE STORM FROM ITS INFLUENCE. SIMULTANEOUSLY, 
AN UPPER-LEVEL TROUGH TO THE SOUTH OF TC ERROL IS HEADING EAST. 
STRONG WESTERLY FLOW AHEAD OF THE TROUGH IS BEGINNING TO IMPACT THE
SYSTEM, WITH RAPIDLY INCREASING VWS, REACHING 40 KTS BY TAU 48, AS
WELL AS INTRODUCING VERY DRY AIR INTO THE CORE OF THE VORTEX. AS A
RESULT, TC 29S IS FORECAST TO CONTINUE TRACKING TOWARDS THE WEST
KIMBERLEY COAST, WHILE RAPIDLY WEAKENING. THE SYSTEM IS EXPECTED TO
MAKE LANDFALL NEAR DAMPIER PENINSULA AROUND TAU 48, FOLLOWED BY
COMPLETE DISSIPATION IN PROXIMITY OF DERBY, AUSTRALIA BY TAU 72.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN FAIR
AGREEMENT IN REGARD TO THE GENERAL STEERING AND MOVEMENT OF THE
SYSTEM TOWARD THE COAST OF AUSTRALIA, AS WITNESSED BY A 95 NM
CROSS-TRACK SPREAD BY TAU 36. AFTERWARD HOWEVER, THE GUIDANCE
DIVERGES SIGNIFICANTLY WITH GALWEM TAKING A MORE EASTERLY TRACK, 
CULMINATING WITH LANDFALL NEAR THE WALCOTT INLET. ON THE OTHER HAND,
DETERMINISTIC AND ENSEMBLE GFS ARE FORECASTING LANDFALL FURTHER
SOUTH, CLOSER TO BROOME, AND TRACKING THE VORTEX WESTWARD AND BACK
TOWARD THE INDIAN OCEAN BEYOND THE FORECAST 72 HOURS. JTWC TRACK
FORECAST IS LAID WITH MEDIUM CONFIDENCE AND IN CLOSE PROXIMITY TO
THE MULTI-MODEL CONSENSUS, CLOSER TO THE GFS AND ECMWF SOLUTIONS,
WITH COMPLETE DISSIPATION AT TAU 72. INTENSITY MODEL GUIDANCE
REMAINS IN GOOD AGREEMENT, WITH ALL AVAILABLE MODELS PREDICTING
RAPID WEAKENING OF THE SYSTEM. GFS AND HAFS ARE THE MOST AGGRESSIVE 
AND DISSIPATE THE SYSTEM PRIOR TO TAU 48. DECAY SHIPS MODELS ARE 
CURRENTLY MORE CONSERVATIVE IN REGARD TO THE RATE OF WEAKENING, BUT 
EVEN THOSE PREDICT FULL DISSIPATION BEFORE TAU 72. JTWC INTENSITY 
GUIDANCE IS THEREFORE LAID WITH HIGH CONFIDENCE AND THE RATE OF 
WEAKENING IS ASSESSED CLOSE TO THE MULTI-MODEL CONSENSUS THROUGHOUT 
THE FORECAST PERIOD.

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