WDXS31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 040//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.1S 115.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 295 NM SOUTH-SOUTHEAST OF LEARMONTH,
   AUSTRALIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 20 KTS

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE (TC) 27P (NARELLE) AS A RAPIDLY DECAYING SYSTEM WITH
OBVIOUS EASTWARD VERTICAL TILT AND WEAKENING CIRCULATION, EVIDENT
VIA EIR IMAGERY. ALL CONVECTION HAS BEEN COMPLETELY DISLOCATED
EASTWARD OF THE NOW EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC).
THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON
ANIMATED EIR IMAGERY OF THE EXPOSED LLCC. THE INITIAL INTENSITY OF
40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON OBSERVED
WEAKENING VIA ANIMATED EIR IMAGERY AND STATISTICAL-DYNAMICAL MODEL
GUIDANCE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
ANTICYCLONE OVER WEST-CENTRAL AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: OVER LAND
   OUTFLOW: WEAK POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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 27P (NARELLE) WILL CONTINUE MOVING
SOUTH-SOUTHEASTWARD AROUND THE WESTERN PERIPHERY OF THE DEEP-LAYER
ANTICYCLONE OVER AUSTRALIA. INTERACTION WITH A PASSING UPPER LEVEL
TROUGH WILL CONTINUE TO SIGNIFICANTLY DEGRADE THE STORM STRUCTURE
AND FACILITATE SUBTROPICAL TRANSITION. THIS TREND WILL CONTINUE FOR
THE REMAINDER OF THE FORECAST PERIOD COINCIDING WITH INCREASING
WESTERLY VWS (35-40 KTS) AND ENHANCED DRY AIR ENTRAINMENT FROM THE
WESTERN SEMICIRCLE. SUBTROPICAL TRANSITION IS EXPECTED TO BE
COMPLETE BETWEEN TAU 12 AND TAU 24 AS THE CENTER REEMERGES OVER THE
SOUTHERN OCEAN WITHIN A HIGHLY UNFAVORABLE ENVIRONMENT. 

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN GOOD AGREEMENT ON
SOUTH-SOUTHEASTWARD MOTION THROUGH THE ENTIRE FORECAST PERIOD.
CROSS-TRACK SPREAD IS A MAXIMUM OF 30 NM AT TAU 24. THE JTWC
FORECAST TRACK IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS WITH
HIGH CONFIDENCE. RAPID WEAKENING IS INDICATED BY THE JTWC
MULTI-MODEL INTENSITY GUIDANCE OUTSIDE OF HWRF AND GFS. A 5 KTS
INTENSITY INCREASE IS DEPICTED BY HWRF AND GFS, VICE THE WEAKENING
TREND DEPICTED BY THE MAJORITY OF THE GUIDANCE. THE JTWC INTENSITY
FORECAST IS ALIGNED CLOSELY TO THE MULTI-MODEL CONSENSUS WITH
MEDIUM CONFIDENCE.

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