WDXS31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (NEVILLE)    
WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8S 108.8E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 403 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AS DEPICTED IN THE ANIMATED ENHANCED INFRARED AND PROXYVIS SATELLITE 
IMAGERY, TROPICAL CYCLONE (TC) 18S HAS CONTINUED TO CONSOLIDATE 
RAPIDLY WITH TIGHTLY-CURVED BANDING WRAPPING INTO A WELL-DEFINED LOW-
LEVEL CIRCULATION CENTER (LLCC). A 201122Z SSMIS 91 GHZ COLOR 
COMPOSITE MICROWAVE IMAGE REVEALS SPIRAL BANDING OVER THE SOUTHERN
SEMICIRCLE WRAPPING INTO A SMALL, WELL-DEFINED MICROWAVE EYE
FEATURE, WHICH SUPPORTS THE INITIAL POSITION WITH HIGH CONFIDENCE.
THE SSMIS 91 GHZ AND 37 GHZ IMAGERY SHOWS THAT THE SYSTEM IS NOW
VERTICALLY ALIGNED, WHICH IS ALLOWING THE SYSTEM TO COMMENCE A
RAPID INTENSIFICATION PHASE. UPPER-LEVEL CONDITIONS ARE HIGHLY
FAVORABLE, WITH LOW VERTICAL WIND SHEAR AND RADIAL OUTFLOW. THE
INITIAL INTENSITY IS ASSESSED AT 50 KNOTS BASED ON AN AVERAGE OF
THE BULK OF THE SUBJECTIVE DVORAK AND CIMSS OBJECTIVE INTENSITY
ESTIMATES RANGING FROM 41 TO 55 KNOTS. HOWEVER, RECENT EIR IMAGERY
FROM 201300-201400Z INDICATES A FORMATIVE EYE DEVELOPING, WHICH
WILL CONTINUE TO DRIVE THE ONGOING RAPID INTENSIFICATION TREND.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
POSITIONED TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   DEMS: T3.5 - 55 KTS
   APRF: T3.5 - 55 KTS
   CIMSS SATCON: 54 KTS AT 1330Z
   CIMSS ADT: 49 KTS AT 201200Z
   CIMSS AIDT: 41 KTS AT 201200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

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 18S WILL TRACK WESTWARD TO WEST-SOUTHWESTWARD 
ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH TAU 72 WHILE RAPIDLY 
INTENSIFYING TO A PEAK INTENSITY OF 90 KNOTS BY TAU 36. THE SYSTEM 
SHOULD MAINTAIN 90 KNOTS THROUGH TAU 48 WITH STEADY WEAKENING AFTER 
TAU 60 DUE TO INCREASING (15-25 KNOTS) NORTHWESTERLY VERTICAL WIND 
SHEAR (VWS) AND DRY AIR ENTRAINMENT. AFTER TAU 72, THE SYSTEM WILL 
BEGIN TO ROUND THE NORTHWESTERN PERIPHERY OF THE STR, INTERACTING 
WITH A SHARP SUBTROPICAL UPPER-LEVEL TROUGH. AS THE SYSTEM RECURVES 
AROUND THE STR, IT WILL TRACK UNDER THE LEADING EDGE OF THE 
AFOREMENTIONED SUBTROPICAL TROUGH, WITH HIGH (25-35 KNOTS) 
NORTHWESTERLY VWS, COOLING SEA SURFACE TEMPERATURES (24 TO 26 C) AND 
SIGNIFICANT DRY AIR ENTRAINMENT CONTRIBUTING TO RAPID WEAKENING. THE 
SYSTEM IS EXPECTED TO DISSIPATE BY TAU 120 PRIOR TO COMPLETING 
SUBTROPICAL TRANSITION.   
 
MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT 
THROUGH TAU 72, WITH A 130 NM CROSS-TRACK SPREAD AT TAU 72. AFTER
TAU 72, NUMERICAL GUIDANCE DIVERGES GRADUALLY, WITH A 250 NM CROSS-
TRACK SPREAD AT TAU 120. HAFS-A SUPPORTS RAPID INTENSIFICATION OVER 
THE NEXT 2 DAYS, WITH A PEAK INTENSITY OF 94 KNOTS AT TAU 48. 
ALTHOUGH NO RAPID INTENSIFICATION AIDS HAVE TRIGGERED YET, THE 
200600Z COAMPS-TC INTENSITY PROBABILITY PLOT INDICATES A 60 TO 70 
PERCENT PEAK PROBABILITY OF RAPID INTENSIFICATION OCCURRING OVER THE 
NEXT 36 HOURS.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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