WDXS31 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.6S 134.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 198 NM EAST-SOUTHEAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A
WELL-DEFINED  BUT HEAVILY TILTED CIRCULATION OVER LAND IN THE TOP
END (LANDPHOON). ANALYSIS OF ANIMATED RADAR DATA, UPPER-LEVEL WIND
ANALYSES AND THE ANIMATED MSI SUPPORT THE FACT THAT THE VORTEX IS
BECOMING INCREASINGLY TILTED WESTWARD WITH HEIGHT, DUE TO THE
ADDITIVE COMBINATION OF MODERATE EASTERLY SHEAR AND FRICTIONAL
EFFECTS AS THE SYSTEM TRACKS OVER LAND. THE INITIAL POSITION IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE RADAR DATA AND ANALYSIS
OF THE WIND OBSERVATIONS FROM NEARBY SURFACE STATIONS (INCLUDING
BULMAN AND CENTRAL ARNHEM), WHICH PROVIDE GOOD OBSERVATIONS OF THE
PERIPHERAL WIND STRUCTURE. THE INITIAL INTENSITY IS ASSESSED WITH
LOW CONFIDENCE DUE TO THE LACK OF SUBJECTIVE DVORAK ESTIMATES OVER
LAND AND A LIMITED SUITE OF OBJECTIVE ESTIMATES NOTED BELOW.
ENVIRONMENTAL CONDITIONS ARE UNFAVORABLE PRIMARILY DUE TO THE
SYSTEM BEING OVER LAND.

INITIAL WIND RADII BASIS: PERSISTENCE 

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
   CIMSS D-MINT: 56 KTS AT 212136Z
   CIMSS D-PRINT: 59 KTS AT 220020Z

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 (TC) 27P IS FORECAST TO TRACK
WEST-SOUTHWESTWARD ALONG THE NORTHERN FLANK OF THE STR FOR THE NEXT
48 HOURS. THE SYSTEM WILL BRIEFLY MOVE OVER WATER, CROSSING THE
JOSEPH BONAPARTE GULF AROUND TAU 24 BEFORE MAKING A THIRD LANDFALL
ON THE KIMBERLY COAST AROUND TAU 30. THE SYSTEM THEN CROSSES THE
KIMBERLY COAST AND EMERGES BACK OVER WATER IN THE VICINITY OF ADELE
ISLAND BY TAU 48. BY TAU 72, THE TRACK BEGINS TO ARC OVER TO A MORE
SOUTHWESTWARD TRAJECTORY AS THE SYSTEM PASSES NORTH OF BROOME, THEN
AS THE UPPER-LEVEL STEERING RIDGE SHIFTS NORTH AND EAST, TC 27P
WILL ROUND THE RIDGE AXIS AND TUN POLEWARD AFTER TAU 96. THE
LONG-RANGE FORECAST REMAINS FUZZY, WITH LARGE DIFFERENCES IN HOW
THE GLOBAL DETERMINISTIC, ENSEMBLE AND AI MODELS HANDLE THE
MOVEMENT, AND ORIENTATION OF THE STEERING RIDGE, RESULTING IN A
WIDE ENVELOPE OF UNCERTAINTY. THE JTWC FORECAST REMAINS UNCHANGED
FROM THE PREVIOUS FORECAST CYCLE, CONSISTENT WITH THE MULTI-MODEL
CONSENSUS (TES1) AND HEDGED TOWARDS THE AI GUIDANCE. IN REGARDS TO
INTENSITY, THE GUIDANCE HAS BEEN VERY CONSISTENT IN INDICATING A
RAPID WEAKENING TO MINIMAL TROPICAL STORM STRENGTH WITHIN THE NEXT
12 TO 18 HOURS, THEN HOLDING THERE UNTIL THE SYSTEM MOVES BACK OVER
WATER AT TAU 48, AS IT CROSSES OF SATURATED GROUND AND BRIEFLY OVER
THE BONAPARTE GULF. DEPENDING ON THE EXACT TRAJECTORY AND TIME OVER
THE GULF, A BRIEF PERIOD OF INTENSIFICATION IS POSSIBLE, THOUGH NOT
EXPLICITLY EXPECTED IN THE FORECAST. UPON RETURNING OVER THE INDIAN
OCEAN, THE SYSTEM WILL RAPIDLY RECONSOLIDATE AND BEGIN TO RAPIDLY
INTENSIFY (RI) SHORTLY AFTER TAU 72 UNDER VERY FAVORABLE
ENVIRONMENTAL CONDITIONS. PEAK INTENSITY OF AT LEAST 115 KNOTS IS
FORECAST TO OCCUR BY TAU 120 OR SHORTLY THEREAFTER. 

MODEL DISCUSSION: MODEL GUIDANCE HAS BEEN VERY CONSISTENT OVER THE
PAST 24 HOURS, WITH NO SIGNIFICANT CHANGES IN EITHER THE DEPICTED
TRACK OR THE DIFFERENCES BETWEEN THE INDIVIDUAL MODELS. THE AI
MODELS CONTINUE TO DEPICT A LANDFALL JUST WEST OF DAMPIER, AND A
TRACK INLAND EAST OF THE EXMOUTH GULF, WHILE THE DETERMINISTIC
MODELS PERSISTS IN DEPICTING A SOUTHWESTWARD TRACK BEYOND TAU 120
BEFORE EVENTUALLY TURNING POLEWARD, MAINTAINING THE CORE WELL
OFFSHORE TO THE NORTHWEST OF LEARMONTH. THE MOST SIGNIFICANT CHANGE
WITH THIS MODEL RUN IN THE SHIFT OF THE USAF GALWEM MODEL TO A
POSITION RIGHT ON TOP OF LEARMONTH JUST PRIOR TO TAU 120. ENSEMBLE
GUIDANCE REMAINS MIXED, WITH A FAIRLY LARGE SPREAD AMONGST THE
MEMBERS. THE GEFS AND EPS MEANS REMAIN ON A FLATTER TRAJECTORY THAT
KEEPS THE SYSTEM OFFSHORE AND WEST OF LEARMONTH. THE GDM FNV3 MEAN
HOWEVER REMAINS PERSISTENT IN TRANSITING EAST OF EXMOUTH. THE
SUPER-ENSEMBLE MEAN IS POSITIONED ABOUT 60NM WEST OF LEARMONTH. THE
JTWC FORECAST IS PLACED NEAR THE TES1 CONSENSUS MEAN, AND THE
SUPER-ENSEMBLE MEAN. INTENSITY GUIDANCE REMAINS VERY CONSISTENT,
AND THE JTWC FORECAST IS PLACED SLIGHTLY ABOVE THE INTENSITY
CONSENSUS MEAN, BUT WELL BELOW THE AGGRESSIVE CTCX, WHICH REACHES A
PEAK INTENSITY OF 140 KNOTS. 

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