WDPS31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.4S 143.0E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 265 NM NORTHWEST OF CAIRNS, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KT

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A RAPIDLY
WEAKENING CONVECTIVE CANOPY OBSCURING THE LOW-LEVEL CIRCULATION
(LLCC) OF TROPICAL CYCLONE (TC) 27P (NARELLE). THE SYSTEM MADE
LANDFALL OVER THE CAPE YORK PENINSULA WITHIN THE LAST 3 HOURS AND
CONTINUES TRANSITING WESTWARD UNDER THE CONTINUOUS INFLUENCE OF A
DEEP-LAYER SUBTROPICAL RIDGE CENTERED OVER WESTERN AUSTRALIA. THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON WEIPA, 
AUSTRALIA RADAR IMAGERY AND VISIBLE SATELLITE IMAGERY LOOP. THE 
INITIAL INTENSITY IS ALSO ASSESSED WITH MEDIUM CONFIDENCE AND IS BASED 
ON LAND INTERACTION IMPACTS AND ASSOCIATED RAPID WEAKENING OF THE 
CONVECTIVE ACTIVITY, SUPPORTED BY 106 KTS DPRINT ESTIMATE. THE 
ENVIRONMENTAL ANALYSIS INDICATES A TEMPORARILY UNFAVORABLE STATE 
DRIVEN BY THE EFFECTS OF LAND INTERACTION AND LOW TO MODERATE (15-20 
KTS) VERTICAL WIND SHEAR (VWS). OF NOTE, AS THE SYSTEM IS EXPECTED TO
REEMERGE OVER THE WARM WATERS OF THE GULF OF CARPENTARIA WITHIN THE
NEXT 12 HOURS, THE SEA SURFACE TEMPERATURES (SST) ARE EXPECTED TO 
REMAIN VERY WARM (29-30 C) AHEAD OF TC NARELLE. RADIAL OUTFLOW REMAINS 
ROBUST WITH A STRONG WESTWARD COMPONENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE (STR)
CENTERED OVER WESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS ADT: 127 KTS AT 192030Z
   CIMSS AIDT: 122 KTS AT 192030Z
   CIMSS D-MINT: 125 KTS AT 191950Z
   CIMSS D-PRINT: 106 KTS AT 200000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: OVER LAND
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 NARELLE IS FORECAST TO INITIALLY TRACK
WESTWARD, FOLLOWED BY A WEST-SOUTHWESTWARD TURN AROUND TAU 36 AND
THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD. AS THE CYCLONE RE-
EMERGES OVER THE GULF OF CARPENTARIA JUST PRIOR TO TAU 12, THE 
INTENSITY IS FORECAST TO BE AROUND 85 KTS. AT THIS TIME, THE VORTEX 
CORE WILL BE SLIGHTLY BROADER THAN BEFORE LANDFALL, RESULTING IN THE 
SYSTEM REQUIRING A PERIOD OF REORGANIZATION BEFORE INTENSIFICATION CAN 
COMMENCE OVER THE THERMODYNAMICALLY FAVORABLE GULF WATERS. MAXIMUM 
WINDS ARE FORECAST TO REACH 90 KTS. RAPID INTENSIFICATION
DURING THIS PERIOD IS DEEMED UNLIKELY DUE TO PERSISTENT AND INCREASING 
EASTERLY VERTICAL WIND SHEAR, POTENTIALLY REACHING 30-35 KTS, 
PRECEDING A SECONDARY LANDFALL IN THE VICINITY OF GROOTE EYLANDT. 
SUBSEQUENTLY, THE SYSTEM WILL TRACK PRIMARILY OVER LAND, WITH A
BRIEF TRANSIT OVER THE JOSEPH BONAPARTE GULF AROUND TAU 72, LEADING
TO A STEADY DECAY TREND THROUGHOUT TAU 96. TC 27P IS THEN FORECAST
TO REEMERGE OVER THE TIMOR SEA AT INTENSITY OF AROUND 45-50 KTS. THE
ENVIRONMENTAL CONDITIONS OF THE TIMOR SEA WILL YET AGAIN BE FAVORABLE 
FOR DEVELOPMENT AND INTENSIFICATION RESULTING IN THE SYSTEM REACHING 
65 KTS BY TAU 120.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE EXHIBITS A HIGH
DEGREE OF CONSENSUS WITH ALL MODELS REMAINING WITHIN A 70-80 NM
CROSS-TRACK ENVELOPE THROUGHOUT THE FORECAST PERIOD. ALONG-TRACK
SPREAD INCREASES WITH TIME, PRIMARILY DUE TO MULTIPLE PERIODS OF
LAND INTERACTION, BUT THE LATEST TRACKERS ARE CONTAINED WITHIN A 170
NM DISTANCE ENVELOPE AT TAU 120. AS SUCH, THE OVERALL CONFIDENCE IN
THE JTWC OFFICIAL TRACK FORECAST IS ASSESSED AS HIGH. THE INTENSITY
FORECAST IS POSITIONED NEAR AND SLIGHTLY ABOVE THE CONSENSUS MEAN,
WITH MEDIUM CONFIDENCE. THE DETERMINISTIC GFS GUIDANCE CONTINUES TO
BE THE PRIMARY OUTLIER, OFFERING THE MOST CONSERVATIVE MAXIMUM WIND
SPEED ESTIMATE, WHILE THE JTWC INTENSITY PREDICTION IS LAID CLOSE TO
THAT OFFERED BY THE HAFS-A GUIDANCE. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: HIGH
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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