WDXS31 PGTW 232100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 024//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.5S 125.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 252 NM NORTHEAST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 27P OVER THE KIMBERLEY PLATEAU WITH DEEP CONVECTION
FORMING ALONG THE COAST AS THE NORTHWESTERN PERIPHERY OF THE STORM
BEGINS TO EMERGE OVER THE TIMOR SEA. THE ENVIRONMENT REMAINS
UNFAVORABLE FOR INTENSIFICATION WHILE 27P REMAINS OVER LAND. THE
INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON LOW-LEVEL
CLOUD WRAPPING PRESENT IN ANIMATED EIR. THE LOW LEVEL CIRCULATION
CENTER REMAINS FULLY OBSCURED BY DEEP CONVECTION, MAKING
POSITIONING DIFFICULT WITH A LACK OF SATELLITE AND RADAR DATA;
HOWEVER, AS 27P CONTINUES SOUTHWESTWARD INTO THE RANGE OF THE RADAR IN
BROOME, THE REMAINING POSITION UNCERTAINTY SHOULD BE SWEPT AWAY. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH LOW CONFIDENCE BASED
ON PERSISTENCE, SUPPORTED BY A SURFACE OBSERVATION FROM TROUGHTON
ISLAND READING 33 KTS FROM THE NORTHWEST AT 1900Z, WHICH ALSO LENDS 
SUPPORT
TO THE INITIAL POSITION.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 5-10 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE RADIAL
   OTHER FACTORS: TERRAIN INTERACTION

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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 27P (NARELLE) IS FORECAST TO CONTINUE
TRACKING SOUTHWESTWARD FOR THE NEXT 48 HOURS WHILE IT REMAINS UNDER
THE STEERING INFLUENCE OF THE STR CENTERED OVER AUSTRALIA.
BEGINNING AROUND TAU 72, NARELLE WILL BEGIN TO TRACK ALONG THE
WESTERN PERIPHERY OF THE STR AND ASSUME A SOUTHWARD TO
SOUTH-SOUTHEASTWARD TRACK THROUGH TAU 120 AS IT ROUNDS THE RIDGE
AXIS. REGARDING INTENSITY, 27P IS EXPECTED TO INTENSIFY SLIGHTLY
OVER THE NEXT 12 HOURS, WHILE IT REMAINS MOSTLY OVER LAND. ONCE
REEMERGING OVER WATER AROUND TAU 12, NARELLE IS FORECAST TO
INTENSIFY WITHIN THE HIGHLY FAVORABLE ENVIRONMENT, WITH A PERIOD
OF RAPID INTENSIFICATION FORECAST TO OCCUR BETWEEN TAU 24-48. 27P
IS FORECAST TO INTENSIFY UNTIL ITS FINAL LANDFALL, WITH THE
POTENTIAL FOR THE PEAK INTENSITY TO OCCUR JUST AFTER TAU 72 AT AN
INTENSITY HIGHER THAN 95KTS, WHICH IS UNABLE TO BE REPRESENTED ON
THE JTWC FORECAST DUE TO THE ESTABLISHED FORECAST INTERVAL. ONCE THE 
STORM MAKES LANDFALL BETWEEN TAU 72-96, IT IS EXPECTED TO WEAKEN 
SIGNIFICANTLY THROUGH THE REMAINDER OF THE FORECAST PERIOD DUE TO 
TERRAIN INTERACTION, DRY AIR ENTRAINMENT, AND HIGH VERTICAL WIND SHEAR 
INDUCED BY THE UPPER-LEVEL JET. 27P IS EXPECTED TO BEGIN SUBTROPICAL 
TRANSITION AROUND TAU 96 AND COMPLETE THE TRANSITION NO LATER THAN TAU 
120.

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 48, WITH MINIMAL ALONG-TRACK SPREAD AND A
100 NM CROSS-TRACK SPREAD DURING THE SAME PERIOD. TRACK GUIDANCE 
DIVERGES FROM THERE, AS MODELS DISAGREE OVER THE SPEED OF ADVANCE
AND THE TIMING OF 27P ROUNDING THE RIDGE AXIS AS IT HEADS POLEWARD.
AS A RESULT, THERE IS A 250 NM CROSS-TRACK SPREAD AT TAU 72 WHILE
THE STORM IS AT ITS CLOSEST POINT OF APPROACH (CPA) TO LEARMONTH. THE 
AI MODEL GUIDANCE CONSISTENTLY TRACKS 27P RIGHT OVER OR JUST SOUTH OF 
LEARMONTH, WHILE GLOBAL DETERMINISTIC MODELS KEEP 27P JUST OFFSHORE. 
THE JTWC TRACK FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS WITH 
MEDIUM CONFIDENCE FROM TAU 0-72 AND LOW CONFIDENCE FROM TAU 72-120.
RELIABLE INTENSITY GUIDANCE IS IN GOOD AGREEMENT THROUGHOUT THE
FORECAST PERIOD, WITH ALL AVAILABLE MODELS INDICATING A PEAK
INTENSITY AT TAU 60-72 BETWEEN 80-95 KTS. THE JTWC INTENSITY
FORECAST IS ALIGNED SLIGHTLY ABOVE THE MULTI-MODEL INTENSITY
CONSENSUS WITH OVERALL MEDIUM CONFIDENCE.

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