WDXS31 PGTW 210300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (NEVILLE) WARNING 
NR 034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.9S 106.7E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 493 NM WEST-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 24 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 19S (NEVILLE) CONTINUES TO INTENSIFY IN THE
OPEN WATERS NORTHWEST OF LEARMOUTH. ANIMATED MULTISPECTRAL
SATELLITE IMAGERY (MSI) DEPICTS A COMPACT STORM, WITH FLARING DEEP
CONVECTION PARTIALLY SURROUNDING A CYCLING EYE FEATURE. THE MOST
RECENT ENHANCED INFRARED (EIR) SATELLITE LOOP SHOWS THAT THE EYE
WAS VERY WELL-DEFINED AROUND 2230Z, WHEN THE OBJECTIVE FIX
ESTIMATES PEAKED, THEN FILLED IN BY THE 210000Z HOUR BEFORE ONCE
AGAIN STARTING TO APPEAR AS OF 210130Z. A 202237Z SSMIS 91GHZ
MICROWAVE IMAGE SHOWED A WELL-DEFINED MICROWAVE EYE FEATURE, WITH A
SEGMENTED EYEWALL, BROKEN IN THE NORTHEAST QUADRANT WHICH FACES THE
SHEAR VECTOR. THE INITIAL POSITION WAS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE RAGGED EYE FEATURE IN THE EIR AND
EXTRAPOLATION OF THE AFOREMENTIONED MICROWAVE EYE. THE INITIAL
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, HEDGED SLIGHTLY BELOW
THE CONSENSUS OF AGENCY FIXES AT T4.5 (77 KTS) IN LIGHT OF THE
SLIGHTLY LOWER DPRINT ESTIMATE OF 71 KTS. ADT AND AIDT VALUES HAVE
BEEN DISCOUNTED DUE TO THE LARGE VARIABILITY SEEN IN THE RAW
ESTIMATES WHICH ARE DRIVEN BY THE SMALL SIZE OF THE INNER CORE AND
THE VARIABILITY IN THE EYE STRUCTURE. ANALYSIS REVEALS A FAVORABLE
ENVIRONMENT, WITH LOW VWS, WARM SSTS AND GOOD RADIAL OUTFLOW. DRY
AIR SURROUNDS THE SYSTEM, BUT LIKE A JOEY, TC NEVILLE REMAINS
SAFELY TUCKED IN A POUCH OF MOISTURE, NURTURING AND SUPPORTING IT.
OUTFLOW IS GOOD OVERALL BUT REMAINS CONSTRAINED TO THE IMMEDIATE
SURROUNDINGS WITH NO OUTFLOW CHANNELS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.5 - 77 KTS
   KNES: T4.5 - 77 KTS
   APRF: T4.5 - 77 KTS
   CIMSS ADT: 55 KTS AT 202330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   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 19S IS FORECAST TO CONTINUE TRACKING
WESTWARD OVER THE NEXT 24 HOURS ALONG THE NORTHERN SIDE OF AN
EAST-WEST ORIENTED STR TO THE SOUTH. AFTER TAU 36, THE SYSTEM WILL
BEGIN TO TRACK WEST-SOUTHWEST, THEN SOUTHWEST THROUGH TAU 96,
BEFORE TURNING SOUTHWARD BY THE END OF THE FORECAST, AS IT ROUNDS
THE STR AXIS. IN TERMS OF INTENSITY, WHILE THE SYSTEM REMAINS
EXTREMELY COMPACT, OUTFLOW ALOFT IS LIMITED IN AREAL EXTENT AND THE
SYSTEM IS CUT-OFF FROM ANY SIGNIFICANT OUTFLOW MECHANISMS, IT IS
FORECAST TO CONTINUE INTENSIFYING STEADILY FOR THE NEXT 12 TO 24
HOURS. BY TAU 36, THE SYSTEM BEGINS TO TAP INTO A DIVERGENT
POLEWARD OUTFLOW CHANNEL, AHEAD OF 200MB TROUGH APPROACHING FROM
THE WEST. THIS WILL ALLOW FOR A BURST OF INTENSIFICATION UP TO THE
PEAK OF AT LEAST 95 KTS BY TAU 36. BY TAU 72, SHEAR AND CONVERGENCE
ALOFT IS FORECAST TO DRAMATICALLY INCREASE AS THE SYSTEM MOVES INTO
THE LEFT-REAR ENTRANCE REGION OF A 100 KT JET MAX TO THE SOUTH,
RESULTING IN A RAPID DECAPITATION OF THE VORTEX. THOUGH THE SYSTEM
WILL BEGIN THE EARLY PHASES OF SUBTROPICAL TRANSITION (STT) BY TAU
96, THE SYSTEM IS FORECAST TO RAPIDLY WEAKEN AND DISSIPATE BEFORE
COMPLETING STT. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GENERAL
AGREEMENT ON THE OVERALL TRACK SCENARIO, BUT DIFFERS IN THE TIMING
AND STRENGTH OF THE TURN SOUTHWARD. THE GFS AND THE GEFS ENSEMBLE
MEAN LEAD THE PACK IN TURNING THE SYSTEM SHARPLY SOUTHWARD AT TAU
96, THEN ACCELERATING SOUTHEASTWARD TO A POSITION NEAR 35S.
MEANWHILE THE GALWEM AND UKMET TRACK THE SYSTEM SLOWLY
WEST-SOUTHWEST, LEADING TO A 1100NM SPREAD IN POSSIBLE TRACK
SOLUTIONS BY TAU 120. THE REMAINDER OF THE CONSENSUS MEMBERS
INCLUDING NAVGEM, AND ECMWF ARE MUCH CLOSER TO THE CONSENSUS MEAN
TRACK. THE JTWC FORECAST LIES SOUTH AND EAST OF THE CONSENSUS, BUT
HEDGED TOWARDS THE ECMWF TRACK. THROUGH TAU 72, CONFIDENCE IS
FAIRLY GOOD BUT QUICKLY DEGRADES TO LOW DUE TO THE HIGH UNCERTAINTY
IN THE TRACKERS TO TAU 120. INTENSITY GUIDANCE IS BECOMING MORE
UNCERTAIN, WITH THE BULK OF THE GUIDANCE NOW SUGGESTING LIMITED
ADDITIONAL INTENSIFICATION THROUGH TAU 60, FOLLOWED BY RAPID
WEAKENING THEREAFTER. THE ONLY OUTLIER IS THE HAFS-A WHICH SHOWS A
PEAK OF 110 KTS AT TAU 48. THE JTWC FORECAST IS 10 KTS HIGHER THAN
THE CONSENSUS WITH MEDIUM CONFIDENCE. 

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