WDXS31 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 29S (ERROL) WARNING NR 
020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.4S 118.9E
   INITIAL INTENSITY: 140 KTS
   GEOGRAPHIC REFERENCE: 283 NM NORTHWEST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 47 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 29S (ERROL) CUTS AN IMPRESSIVE LOOK IN THE
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY, WITH AN
APPROXIMATELY 8NM WIDE EYE SURROUNDED BY A SOLID CENTRAL DENSE
OVERCAST (CDO) FEATURE. THE EYE TEMP AT 161200Z WAS MEASURED A
WHOPPING POSITIVE 15C IN THE HIMAWARI-9 BD-ENHANCEMENT. TC 29S HAS
UNDERGONE AN AMAZING PERIOD OF EXTREME RAPID INTENSIFICATION (ERI),
INTENSIFYING 85 KNOTS IN THE LAST 24 HOURS, AND MORE THAN 50 KNOTS
IN JUST THE LAST 12 HOURS. A SERIES OF MICROWAVE PASSES BETWEEN
160741Z AND 1610005Z SUGGEST THAT TC ERROL COMPLETED A RAPID
EYEWALL REPLACEMENT CYCLE (ERC) DURING THAT TIMEFRAME, WHICH IS
BACKED UP BY THE CIMSS M-PERC PRODUCT WHICH PREDICTED A 96 PERCENT
PROBABILITY OF AN IMMINENT ERC AT 1000Z. THE MOST RECENT FRAMES OF
EIR SHOW THE EYE DIAMETER WIDENING EVER SO SLIGHTLY POTENTIALLY IN
RESPONSE TO COMPLETION OF THE SHORT-DURATION ERC. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE
DEPICTION IN THE EIR. TC 29S HAS LIKELY REACHED PEAK INTENSITY,
WITH THE INITIAL INTENSITY OF 140 KNOTS ASSESSED WITH MEDIUM
CONFIDENCE. DVORAK CURRENT INTENSITY ESTIMATES FROM BOTH PGTW AND
KNES WERE HELD AT T6.5 DUE TO CONSTRAINTS BUT BOTH AGENCIES
REPORTED DATA-T VALUES OF T7.5. OBJECTIVE ESTIMATES REMAIN BIASED
LOW DUE TO THE EXTREMELY SMALL SIZE OF THE SYSTEM. THE INITIAL
INTENSITY IS HEDGED UPWARDS TO TAKE INTO ACCOUNT THE HIGHER DATA-T
VALUES. THE ENVIRONMENT REMAINS FAVORABLE THOUGH SHEAR IS ALREADY
STARTING TO INCREASE SLIGHTLY. SSTS REMAIN VERY WARM AND THE
OUTFLOW ALOFT REMAINS STRONG.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   KNES: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   APRF: T5.5 - 102 KTS
   CIMSS SATCON: 117 KTS AT 161200Z
   CIMSS ADT: 119 KTS AT 161230Z
   CIMSS AIDT: 118 KTS AT 161230Z
   CIMSS D-MINT: 108 KTS AT 161039Z
   CIMSS D-PRINT: 112 KTS AT 161230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG RADIAL
   OTHER FACTORS: ENHANCED POLEWARD OUTFLOW CHANNEL. 

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 CURRENTLY DRIFTING SOUTHWARD IN A
WEAK STEERING PATTERN CAUSED BY A BREAK IN THE STR TO THE SOUTH
AHEAD OF AN APPROACHING DEEP UPPER-LEVEL TROUGH. OVER THE NEXT 12
TO 24 HOURS, THE SYSTEM WILL TURN SHARPLY TO THE SOUTHEAST ALONG
THE WESTERN SIDE OF A SMALL UPPER-LEVEL ANTICYCLONE OVER CAPE
TALBOT THAT RAPIDLY WEAKENS AND MOVES EQUATORWARD. THEREAFTER THE
PRIMARY STEERING INFLUENCE BECOMES THE DEEP TROUGH TO THE SOUTHWEST
WHICH WILL PULL TC 29S ALONG TOWARDS THE SOUTHEAST, EMBEDDED IN THE
DEEP NORTHWESTERLY FLOW AHEAD OF THE TROUGH. THE SYSTEM IS FORECAST
TO MAKE LANDFALL JUST PRIOR TO TAU 72 NEAR CAPE LEVEQUE, THEN
TURNING SOUTHWARD BEFORE DISSIPATING IN THE VICINITY OF DERBY BAY
THE END OF THE FORECAST. TC 29S IS LIKELY AT PEAK INTENSITY, THOUGH
IT IS POSSIBLE IT COULD SQUEEZE OUT ANOTHER FIVE KNOTS. HOWEVER,
THE MOST RECENT EIR IMAGERY AT 161340Z SHOWS THE EASTERN SIDE OF
THE EYEWALL STARTING TO WEAKEN FAIRLY DRAMATICALLY, WHICH MAY
INDICATE THE BEGINNING OF THE END FOR TC ERROL. SHEAR IS ALREADY UP
TO 14 KNOTS PER THE LATEST CIMSS ANALYSIS, UP FROM JUST 8 KNOTS SIX
HOURS AGO. THE GFS MODEL SOUNDINGS INDICATE A RAPID INCREASE IN
SHEAR TO NEAR 25 KNOTS BY TAU 12, INCREASING TO MORE THAN 35 KNOTS
BY TAU 24. THE SYSTEM WILL LIKELY MAINTAIN INTENSITY THROUGH TAU 12
BEFORE THE SHEAR REALLY STARTS TO TAKE EFFECT. HOWEVER, THE EFFECT
OF THE SHEAR WILL BE DRAMATIC FROM TAU 24 ONWARDS. HAFS-A
CROSS-SECTIONS DEPICT A RAPID AND DRAMATIC DECAPITATION EVENT, WITH
THE VORTEX BEING COMPLETELY DECIMATED BY TAU 24. WHILE THE RATE OF
INTENSIFICATION HAS BEEN INCREDIBLE, THE PACE OF THE WEAKENING
WILL LIKELY BE EQUALLY IMPRESSIVE. THE SYSTEM WILL BE DOWN TO
TROPICAL STORM STRENGTH WITHIN 48 HOURS AND WILL DISSIPATE ALONG
THE COAST NO LATER THAN TAU 96.   

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN FAIR AGREEMENT
THROUGH TAU 48, WITH ALL MEMBERS OF THE CONSENSUS CONCURRING ON A
SHORT PERIOD OF QUASI-STATIONARY OR SLOW SOUTHWARD MOVEMENT,
FOLLOWED BY A RAPID TRANSITION TO A SOUTHEASTWARD TRACK BY TAU 24.
MODELS BEGIN TO DIVERGE AFTER TAU 24, WITH CROSS-TRACK SPREAD
OPENING UP TO 155NM BY TAU 48 THOUGH AT THIS POINT IN THE FORECAST
ALL OF THE CONSENSUS MEMBERS ARE TRACKING THE SYSTEM RIGHT AT THE
COAST. BY TAU 72, CROSS-TRACK SPREAD OPENS UP TO 255NM BETWEEN THE
GFS-GEFS COMBO ON THE LEFT, TURNING THE SYSTEM SOUTHWEST JUST
NORTHWEST OF BROOME AND THE EC-AIFS TO THE RIGHT, TAKING THE SYSTEM
INLAND TO THE WEST OF WYNDHAM. BY THE END OF THE FORECAST THE
MAJORITY OF CONSENSUS MEMBERS BEGIN TO TURN THE SYSTEM
SOUTHWESTWARD THOUGH THEY ARE SPREAD OUT ACROSS A NEARLY 500NM
SWATCH FROM WEST OF BROOME TO THE NORTHERN KIMBERLY COAST. ENSEMBLE
GUIDANCE IS ALSO HIGHLY UNCERTAIN WITH A SPREAD OF MEMBERS BETWEEN
EXMOUTH AND BROOME FOR THE GEFS, AND BETWEEN CAPE TALBOT AND BROOME
FOR THE ECENS. THE JTWC FORECAST IS ROUGHLY CONSISTENT WITH THE
MULTI-MODEL CONSENSUS MEAN WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM WILL RAPIDLY WEAKEN
AFTER TAU 12, BUT DOES DIFFER SIGNIFICANTLY ON HOW QUICKLY THE
SYSTEM WILL ULTIMATELY DISSIPATE, AS EARLY AS TAU 48 FOR THE
COAMPS-TC AND HWRF, OR AS LATE AS TAU 120 FOR THE HAFS-A. THE JTWC
FORECAST IS SLIGHTLY LOWER THAN THE CONSENSUS MEAN AFTER TAU 48. 

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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