WDPS31 PGTW 192100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.8S 144.0E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 213 NM NORTH-NORTHWEST OF CAIRNS,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 27P (NARELLE) WITH AN INCREASINGLY RAGGED EYE AND
CENTRAL DENSE OVERCAST (CDO) AS THE STORM IS SLIGHTLY WEAKENED BY
LOW TO MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS) WHILE 
APPROACHING THE COAST OF CAPE YORK, AUSTRALIA. ENVIRONMENTAL ANALYSIS 
INDICATES AN OVERALL FAVORABLE ENVIRONMENT, CHARACTERIZED BY WARM (28-
29 C) SEA SURFACE TEMPERATURES AND ROBUST OUTFLOW ALOFT, OFFSET 
SLIGHTLY BY THE 15-20 KTS VWS. THE INITIAL POSITION IS PLACED WITH 
HIGH CONFIDENCE BASED ON THE RAGGED EYE PRESENT IN ANIMATED EIR. THE 
INITIAL INTENSITY OF 120 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON 
THE AGENCY SUBJECTIVE DVORAK FIXES AND CIMMS INTENSITY ESTIMATES 
LISTED BELOW, CORROBORATED BY A 191535Z AMSR2 WIND SPEED IMAGE 
INDICATING 115 KTS ALONG THE SOUTHWESTERN QUADRANT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHEASTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED OVER WESTERN AUSTRALIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   ABRF: T5.5 - 102 KTS
   CIMSS SATCON: 135 KTS AT 191800Z
   CIMSS ADT: 127 KTS AT 191900Z
   CIMSS AIDT: 120 KTS AT 191900Z
   CIMSS D-MINT: 131 KTS AT 191556Z
   CIMSS D-PRINT: 132 KTS AT 191900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 27P IS FORECAST TO CONTINUE ITS GENERALLY
WESTWARD TRACK FOR THE NEXT 48-72 HOURS AS IT REMAINS UNDER THE
STEERING INFLUENCE OF THE DEEP-LAYER STR CENTERED OVER WESTERN
AUSTRALIA. BEGINNING AROUND TAU 72, THE NORTHWESTERN EXTENSION OF
THE RIDGE IS EXPECTED TO WEAKEN SLIGHTLY AND RETREAT, ALLOWING 27P
TO ASSUME A MORE WEST-SOUTHWESTWARD TRACK FOR THE REMAINDER OF THE
FORECAST PERIOD. REGARDING INTENSITY, TC NARELLE IS EXPECTED TO MAKE
LANDFALL IN CAPE YORK IMMINENTLY, AT AN INTENSITY OF ABOUT 120 KTS.
IT WILL SPEND ABOUT 12 HOURS OVER LAND, AND IS EXPECTED TO WEAKEN
SIGNIFICANTLY DUE TO THE MODERATE SHEAR ENVIRONMENT AND TERRAIN
INTERACTION. TC 27P IS FORECAST TO BE AROUND 95 KTS BY THE TIME IT
EMERGES INTO THE GULF OF CARPENTARIA AROUND TAU 12. WHILE OVER THE
GULF JUST AFTER TAU 12 UNTIL JUST PRIOR TO TAU 48, INTENSITIES ARE
EXPECTED TO REMAIN NEARLY STAGNANT AS THE SHEAR INHIBITS SIGNIFICANT 
REINTENSIFICATION. HOWEVER, IF THE VWS WEAKENS DURING THIS PERIOD, 
INTENSITIES GREATER THAN 85 KTS ARE POSSIBLE AS THE ENVIRONMENT IS 
EXPECTED TO BE OTHERWISE FAVORABLE. TC 27P IS FORECAST TO MAKE 
LANDFALL IN THE NORTHERN TERRITORY JUST BEFORE TAU 48 AND WILL
WEAKEN STEADILY AS IT CROSSES AUSTRALIA. TC 27P MAY BRIEFLY REEMERGE
OVER WATER IN THE JOSEPH BONAPARTE GULF, BUT THE LIMITED TIME OVER
WATER WILL INHIBIT ANY REINTENSIFICATION, TC NARELLE IS FORECAST TO
REEMERGE INTO THE TIMOR SEA NEAR TAU 96 AT 45 KTS. THE ENVIRONMENT
IN THE TIMOR SEA IS ANTICIPATED TO BE FAVORABLE FOR REDEVELOPMENT,
ALLOWING ANOTHER BOUT OF INTENSIFICATION AT THE END OF THE FORECAST
PERIOD.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN STRONG
AGREEMENT THROUGHOUT THE FORECAST PERIOD, WITH ONLY SLIGHT
DISCREPANCIES IN BOTH CROSS-TRACK AND ALONG-TRACK SPREAD IN THE
LATER FORECAST TAUS, SUPPORTING THE JTWC TRACK FORECAST WITH HIGH
CONFIDENCE FOR TAU 0-72 AND MEDIUM CONFIDENCE FROM TAU 72-120.
RELIABLE INTENSITY GUIDANCE REMAINS HIGHLY VARIABLE IN THE INITIAL
INTENSITY, CAUSING A LARGE DISCREPANCY IN WEAKENING RATE AND
INTENSITIES WHILE THE STORM IS OVER CAPE YORK AND AFTER IT
REEMERGES INTO THE GULF OF CARPENTARIA. FOR TAU 0-36, THE JTWC
INTENSITY FORECAST IS PLACED HIGHER THAN AVAILABLE GUIDANCE, AND THE 
MULTI-MODEL CONSENSUS DUE TO ANALYSIS THAT INDICATES THE STORM WILL
NOT WEAKEN AS DRAMATICALLY AS MODELS ARE DEPICTING. FOLLOWING TAU
36, THE JTWC INTENSITY FORECAST LIES IN LINE WITH INTENSITY GUIDANCE 
AS THE MODELS COME INTO BETTER AGREEMENT. AS A RESULT, THE JTWC 
INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE THROUGHOUT THE 
FORECAST PERIOD.

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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