WDXS31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.7S 128.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 390 NM EAST-NORTHEAST OF BROOME, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SLIGHLTY
REORGANIZED VORTEX THAT HAS MAINTAINED SOME CONVECTION OVER WARM
WATER FOLLOWING A BRIEF PERIOD OVER THE BONAPARTE GULF OVER THE
PAST 6 HOURS. THE INITIAL POSITION JUST ONSHORE, NORTH OF WYNDHAM,
IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE ANIMATED MSI. THE
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE CIMMS OBJECTIVE INTENSITY ESTIMATES RANGING FROM 39-46
KTS.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: DEEP-LAYER SUBTROPICAL RIDGE OVER
CENTRAL AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS SATCON: 46 KTS AT 230500Z
   CIMSS ADT: 41 KTS AT 230500Z
   CIMSS AIDT: 34 KTS AT 230500Z
   CIMSS D-MINT: 39 KTS AT 230513Z
   CIMSS D-PRINT: 39 KTS AT 230600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: TERRAIN INTERACTION

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 27P (NARELLE) CONTINUES ON A
WEST-SOUTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF THE STR TO
THE SOUTH. IT IS FORECAST TO CONTINUE WEST-SOUTHWESTWARD ALONG THE
KIMBERLEY COAST THROUGH TAU 18 WHERE IT WILL REEMERGE OVER THE
SOUTHERN INDIAN OCEAN, SOUTHEAST OF ADELE ISLAND. THE
WEST-SOUTHWESTWARD TRAJECTORY CONTINUES THROUGH TAU 72, THEN THE
SYSTEM BEGINS TO ROUND THE RIDGE AXIS INITIATING A POLEWARD TURN.
NARELLE IS FORECAST TO SKIRT THE WESTERN AUSTRALIA COASTLINE,
TRACKING JUST WEST OF LEARMONTH SHORTLY BEFORE TAU 96. AFTER TAU 96
THE SYSTEM WILL TRACK SOUTHWARD AND ACCELERATE TOWARD GERALDTON
THROUGH TAU 120. IN TERMS OF INTENSITY, TC NARELLE IS FORECAST TO
WEAKEN SLIGHTLY OVER THE NEXT 12 HOURS AS IT TRANSITS OVER LAND IN
THE KIMBERLEY REGION. ONCE THE SYSTEM EMERGES BACK OVER WATER, THE
ENVIRONMENT WILL QUICKLY IMPROVE AND SUPPORT REDEVELOPMENT. A
STEADY RATE OF INTENSIFICATION WILL OCCUR THROUGH TAU 48 AS THE
SYSTEM RECOVERS FROM ITS TIME OVER LAND. AFTER TAU 48 A RAPID RATE
OF INTENSIFICATION IS FORECAST TO OCCUR THROUGH TAU 72 AS IT
APPROACHES THE EXMOUTH PENINSULA. A PEAK INTENSITY OF 100-105 KTS
IS LIKELY TO OCCUR NEAR TAU 84, WHICH IS NOT DIRECTLY CAPTURED BY
THE CURRENT WARNING. COOLING SEA SURFACE TEMPERATURES, INCREASING
WESTERLY VERTICAL WIND SHEAR, AND DRY AIR ENTRAINMENT AFTER TAU 84
WILL CAUSE THE SYSTEM TO WEAKEN THROUGH THE REMAINDER OF THE
FORECAST PERIOD. TC NARELLE IS FORECAST TO BEGIN SUBTROPICAL
TRANSITION AT TAU 120 WHERE IT BEGINS TO INTERACT WITH MIDLATITUDE
WESTERLY WINDS AND CROSSES THE 26 C SST ISOTHERM.  

MODEL DISCUSSION: MODEL TRACK GUIDANCE REMAINS IN GOOD AGREEMENT
THROUGH TAU 72 WITH A CROSS-TRACK SPREAD OF 160 NM AND MINIMAL
ALONG-TRACK SPREAD. MODELS BEGIN TO DIVERGE AFTER TAU 72 WITH
CROSS-TRACK SPREAD QUICKLY INCREASING TO 380 NM AT TAU 96. AI
MODELS MAINTAIN A SHARPER TURN AROUND THE RIDGE AXIS WHILE THE
PHYSICS-BASED MODELS DEPICT A WIDER TURN. THE ECMWF DETERMINISTIC
MODEL IS THE WESTERNMOST SOLUTION AND THE EC-AIFS COMPRISES THE
EASTERNMOST. AFTER TAU 96 THE MODELS ARE IN VERY POOR AGREEMENT
REGARDING TRACK SPEED, WITH THE EC-AIFS AND GOOGLE DEEPMIND
ENSEMBLE MEAN ACCELERATING THE VORTEX WELL TO THE SOUTHEAST OF
PERTH AT TAU 120. ON THE OTHER HAND, THE GFS AND ECMWF ENSEMBLE
MEANS ARE NEAR SHARK BAY AT THE SAME TIME, CREATING AN ALONG-TRACK
SPREAD OF NEARLY 700 NM. THE JTWC TRACK FORECAST CLOSELY FOLLOWS
THE CONSENSUS THROUGH TAU 72, THEN FOLLOWS CLOSER TO THE TES1
CONSENSUS THROUGH TAU 96, WHICH ACCOUNTS FOR THE AI MODELS. THE TAU
120 POSITION IS PLACED WITH EXTREMELY LOW CONFIDENCE - SLIGHTLY
FASTER THAN THE GFS AND ECMWF ENSEMBLE MEANS. MODEL INTENSITY
GUIDANCE IS NOW IN BETTER AGREEMENT THAN PREVIOUS RUNS. THE MODELS
AGREE ON A STEADY INTENSITY THROUGH TAU 24 FOLLOWED BY RAPID
REDEVELOPMENT THROUGH TAU 84, WITH PEAK INTENSITIES RANGING FROM
70-100 KTS. COAMPS-TC AND HAFS-A ARE THE MOST AGGRESSIVE WHILE HWRF
MAKES UP THE LOW END OF GUIDANCE. MODELS ALSO AGREE ON STEADY
WEAKENING AFTER TAU 84. THE JTWC INTENSITY FORECAST IS PLACED NEAR
THE MULTI-MODEL CONSENSUS THROUGHOUT THE ENTIRE FORECAST PERIOD
WITH MEDIUM CONFIDENCE. 

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