WDXS31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.8S 132.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 140 NM SOUTHEAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: OVER LAND

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VORTEX
THAT IS CONTINUING TO SHALLOW WITH WARMING CLOUD TOPS AND
PERSISTENT EASTERLY SHEAR PUSHING CONVECTION TO THE WEST OF THE
LOW-LEVEL CIRCULATION CENTER (LLCC). A 220515Z AMSR2 89 GHZ
MICROWAVE IMAGE SHOWS THAT THE SYSTEM HAS MAINTAINED CURVED BANDING
OUTLINING THE NORTHERN PERIPHERY OF THE CIRCULATION. THE INITIAL
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON ANIMATED RADAR
IMAGERY FROM KATHERINE (TINDAL) AND THE AFOREMENTIONED AMSR2 IMAGE.
THE INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH LOW CONFIDENCE
BASED PRIMARILY ON A STEADY WEAKENING TREND OVER LAND.
ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE DUE TO THE SYSTEM BEING
OVER LAND.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) ANCHORED OVER CENTRAL AUSTRALIA.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: TERRAIN INFLUENCE

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TROPICAL CYCLONE NARELLE HAS CONTINUED ON A
WEST-SOUTHWESTWARD TRACK ACROSS THE TOP END OVER THE PAST 6 HOURS.
IT IS FORECAST TO CONTINUE ON THIS TRAJECTORY THROUGH TAU 96. TC
NARELLE WILL EMERGE OVER THE BONAPARTE GULF NEAR TAU 18 BEFORE
MAKING A THIRD LANDFALL NORTH OF WYNDHAM. THE SYSTEM WILL TRACK
ALONG THE KIMBERLY COAST THROUGH TAU 36 THEN EMERGE BACK OVER WATER
IN THE INDIAN OCEAN NEAR ADELE ISLAND AROUND TAU 42. TC NARELLE IS
EXPECTED TO CONTINUE ON A WEST-SOUTHWESTWARD TRACK PARALLELING THE
COAST THROUGH TAU 96, WHERE IT WILL APPROACH THE NORTHWESTERN
EXTENT OF THE STR AND TURN MORE SOUTHWESTWARD. THE CURRENT FORECAST
CALLS FOR A TRACK OVER THE NORTHWEST COAST OF THE EXMOUTH
PENINSULA, THOUGH THIS PORTION OF THE FORECAST REMAINS UNCERTAIN.
THE SYSTEM WILL CONTINUE TO WEAKEN AS IT TRANSITS OVER LAND, THEN A
BRIEF PERIOD OF INTENSIFICATION IS POSSIBLE WHILE IT MOVES THROUGH
THE BONAPARTE GULF. ANY INCREASE IN INTENSITY WILL THEN BE DEGRADED
AGAIN AS NARELLE MOVES OVER THE KIMBERLY REGION DUE TO FURTHER LAND
INTERACTION. ONCE THE SYSTEM REEMERGES OVER THE INDIAN OCEAN IN A
HIGHLY FAVORABLE ENVIRONMENT WITH LOW VERTICAL WIND SHEAR (VWS) AND
VERY WARM (30 C) SEA SURFACE TEMPERATURES, IT WILL QUICKLY
INTENSIFY. A PEAK INTENSITY OF 105-110 KNOTS IS FORECAST TO OCCUR
NEAR TAU 108 WHICH IS NOT CAPTURED BY THE WARNING. AFTER TAU 108
INTERACTION WITH THE WESTERN AUSTRALIAN COAST NEAR THE EXMOUTH
PENINSULA AND COOLING SEA SURFACE TEMPERATURES WILL INITIATE A
WEAKENING TREND.

MODEL DISCUSSION: MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT THROUGH
TAU 72 WITH A CROSS-TRACK SPREAD OF 100 NM AND MINIMAL ALONG-TRACK
SPREAD. AFTER TAU 72 MODELS BEGIN TO DIVERGE RESULTING IN A
SIGNIFICANT CROSS-TRACK (450 NM) SPREAD AT TAU 120. THE MODELS ARE
SPLIT BETWEEN TWO DISTINCT GROUPINGS - EC-AIFS, GOOGLE DEEPMIND
ENSEMBLE MEAN, UKMET, AND GALWEM MAKE UP THE SOUTHERN AND EASTERN
GROUPING, WHILE ECMWF AND GFS DETERMINISTIC AND ENSEMBLE MEANS MAKE
UP THE NORTHERN AND WESTERN GROUPING. THE FORMER GROUP OF MODELS
DEPICT A LANDFALL RANGING FROM DAMPIER TO THE EXMOUTH GULF AND THE
LATTER GROUPING REMAINS OFFSHORE BEFORE ROUNDING THE RIDGE. THE
JTWC TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS
THROUGH TAU 72, THEN HEDGED CLOSER TO THE EASTERN GROUPING DUE TO
THE STRONG PERFORMANCE OF THE AI MODELS. CONFIDENCE IN THE TRACK
FORECAST IS HIGH THROUGH TAU 72 AND LOW THEREAFTER. MODEL INTENSITY
GUIDANCE AGREES ON A STEADY INTENSITY THROUGH TAU 48 FOLLOWED BY
SIGNIFICANT REDEVELOPMENT OF TC NARELLE OVER THE INDIAN OCEAN.
NOTABLY, HAFS-A IS THE LEAST AGGRESSIVE MODEL, SUGGESTING A PEAK
INTENSITY OF JUST 55 KTS AT TAU 108. THE REMAINDER OF GUIDANCE
SHOWS PEAK INTENSITIES RANGING FROM 85-125 KTS. COAMPS-TC (GFS
BASED) IS THE MOST AGGRESSIVE MODEL WITH A PEAK INTENSITY OF 125
KTS AT TAU 108. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE
CONSENSUS THROUGH TAU 72, THEN SLIGHTLY HIGHER THROUGH TAU 120,
CLOSE TO THE HWRF SOLUTION DUE TO THE EXPECTED HIGHLY FAVORABLE
ENVIRONMENT.

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