WDXS31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 27P (NARELLE) WARNING 
NR 
026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.0S 123.4E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 133 NM NORTH-NORTHEAST OF BROOME,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS SPIRAL BANDS
OF DEEP CONVECTION RAPIDLY DEVELOPING AS THE LOW-LEVEL CIRCULATION
CENTER ASSOCIATED WITH TROPICAL CYCLONE (TC) 27P (NARELLE) HAS 
RECENTLY RE-EMERGED OVER WATER NORTHEAST OF THE DAMPIER PENINSULA, 
AUSTRALIA. ROBUST WESTWARD AND EQUATORWARD OUTFLOW IS AIDING WITH 
DEVELOPMENT AND OTHER ENVIRONMENTAL PARAMETERS ARE FAVORABLE FOR RAPID 
INTENSIFICATION OF THE SYSTEM. SEA SURFACE TEMPERATURES (SST) ARE WARM 
(29-30 C), VERTICAL WIND SHEAR (VWS) IS LOW (10-15 KTS) AND THERE IS 
PLENTY OF ATMOSPHERIC MOISTURE AVAILABLE THROUGHOUT THE VERTICAL 
COLUMN. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE ANIMATED MSI AND EXTRAPOLATION FROM A 240502Z GW1 AMSR2 PASS. THE 
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED 
ON THE AVAILABLE OBJECTIVE AND SUBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 240502Z GW1 AMSR2 PASS

CURRENT STEERING MECHANISM: DEEP LAYER SUBTROPICAL RIDGE (STR)
POSITIONED OVER CENTRAL AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   APRF: T2.5 - 35 KTS
   CIMSS SATCON: 46 KTS AT 240543Z
   CIMSS ADT: 35 KTS AT 240540Z
   CIMSS AIDT: 33 KTS AT 240540Z
   CIMSS D-MINT: 43 KTS AT 240544Z
   CIMSS D-PRINT: 37 KTS AT 240700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE DUAL-CHANNEL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 IS FORECAST TO CONTINUE TRACKING ALONG
THE NORTHWESTERN PERIPHERY OF A STR CENTERED OVER AUSTRALIA, WHILE
QUICKLY INTENSIFYING. PEAK WIND SPEEDS ARE EXPECTED TO REACH 95-100
KTS BETWEEN TAUS 48 AND 72, JUST PRIOR TO THE SYSTEM BEGINNING TO
ROUND THE AXIS OF THE STR AND APPROACH NORTH WEST CAPE, WESTERN
AUSTRALIA. RAPID INTENSIFICATION IS HIGHLY POSSIBLE AND EXPECTED,
DUE TO VERY FAVORABLE ENVIRONMENT UNTIL TAU 72. TC NARELLE IS
CURRENTLY FORECAST TO MAKE LANDFALL WEST OR SLIGHTLY SOUTHWEST OF
LEARMONTH, APPROACHING THE CORAL BAY AS IT EVENTUALLY ROUNDS THE
AXIS OF THE RIDGE AND STARTS TRACKING SOUTHEASTWARD SOON AFTER TAU
72. AFTER THAT, THE SYSTEM IS EXPECTED TO WEAKEN DUE TO THE FRICTIONAL 
EFFECTS OF LAND INTERACTION, INCREASING DRY AIR ENTRAINMENT AND 
RAPIDLY INCREASING VWS DRIVEN BY THE UPPER-LEVEL JET INTERACTION. 
AROUND TAU 96, THE SUBTROPICAL TRANSITION WILL BEGIN, WITH COMPLETION 
EXPECTED PRIOR OR BY TAU 120. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN OVERALL GOOD
AGREEMENT, PARTICULARLY WITHIN THE INITIAL 72 HOURS. CROSS-TRACK
SPREAD AT TAU 48 IS 45 NM AND EXPANDS TO 75 NM JUST PRIOR TO LANDFALL. 
IMPACTS TO NORTH WEST CAPE AREA EXPECTED EVEN IF THE TRACK SHIFTS 
SLIGHTLY WESTWARD AND LANDFALL WILL OCCUR TO THE SOUTHWEST OF THE 
PENINSULA. CROSS-TRACK SPREAD EXPANDS TO 190 NM BY THE END OF THE 
FORECAST PERIOD INDICATING SLIGHTLY INCREASED LONG-TERM TRACK 
PREDICTION UNCERTAINTY. IN TERMS OF INTENSITY GUIDANCE, ALL MODELS ARE 
IN GOOD AGREEMENT IN REGARD TO THE TIMELINE ASSOCIATED WITH THE 
INTENSIFICATION AND EVENTUAL LANDFALL AND WEAKENING, HOWEVER OFFICIAL 
JTWC OFFICIAL INTENSITY FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE, 
DUE TO THE MAXIMUM INTENSITY SPREAD OF 40 KTS. MULTI-MODEL CONSENSUS 
SHOWS PEAK INTENSITY OF 90 KTS, WHILE HAFS AND GFS ARE MOST 
CONSERVATIVE WITH MAXIMUM WINDS OF 75-80 KTS AND GFS-DRIVEN COAMPS-TC, 
RIDE AND COAMPS-TC RI AID PREDICTING PEAK OF 105-110 KTS. AS SUCH, 
JTWC FORECAST IS LAID SLIGHTLY HIGHER THAN THE MULTI-MODEL CONSENSUS
WITH MEDIUM CONFIDENCE.

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