WDXS31 PGTW 211500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (NEVILLE) 
WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.7S 104.9E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 587 NM WEST-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 18S (NEVILLE) HAS RAPIDLY INTENSIFIED OVER THE 
PAST 12 HOURS, VASTLY OVERSHOOTING GLOBAL NUMERICAL MODEL AND 
MESOSCALE MODEL GUIDANCE. ANIMATED ENHANCED INFRARED SATELLITE 
IMAGERY (EIR) DEPICTS TROPICAL CYCLONE (TC) 18S WITH AN IMPROVED, 
CLEAR AND SYMMETRIC PINHOLE EYE ALONG WITH A VERY TIGHT, COMPACT RING 
SURROUNDING THE EYEWALL. THERE APPEARS TO BE SOME SLIGHT PRESSURE 
INDUCED BY NORTHERLY VERTICAL WIND SHEAR (VWS) ON THE NORTHERN 
SEMICIRCLE OF THE SYSTEM, BUT DOES NOT SEEM TO BE IMPACTING THE 
COCOONED INNER STRUCTURE. THE EYE IS ASSESSED WITH A TEMPERATURE OF 
13.8 C AND A DIAMETER OF 11NM. THE CURRENT ENVIRONMENT IS ASSESSED AS 
HIGHLY FAVORABLE WITH STRONG POLEWARD OUTFLOW ALOFT, LOW (5-10 KTS) 
VWS, AND WARM (27-28 C) SEA SURFACE TEMPERATURES. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON A 211200Z HIMAWARI-9 
INFRARED IMAGE SHOWING A WELL-DEFINED EYE. THE INITIAL INTENSITY IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE SUBJECTIVE DVORAK 
ESTIMATES LISTED BELOW AND A 211127Z RCM-3 SYNTHETIC APERTURE RADAR 
IMAGE SHOWING A MAX WIND SPEED OF 102KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A SUBTROPICAL
RIDGE (STR) TO THE SOUTH. 


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   APRF: T5.5 - 102 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: PEAK INTENSITY HAS BEEN RAISED 
SIGNIFICANTLY (25 KTS RISE) SINCE THE PREVIOUS FORECAST TO FIT THE 
RECENT RAPID INTENSIFICATION (RI) TREND, WHICH WAS NOT PREVIOUSLY 
CAPTURED IN NUMERICAL MODEL GUIDANCE OR RAPID INTENSIFICATION AIDS.

FORECAST DISCUSSION: TC 18S IS FORECAST TO CONTINUE TRACKING
WESTWARD ALONG THE NORTHERN PERIPHERY OF THE STR THROUGH TAU 24.
AFTER TAU 24, THE SYSTEM IS FORECAST TO TRACK WEST-SOUTHWESTWARD AS
IT BEGINS TO ROUND THE NORTHWESTERN PERIPHERY OF THE STR THROUGH
TAU 72. AFTER TAU 72, THE SYSTEM IS ANTICIPATED TO INITIATE A
POLEWARD TURN AS IT COMPLETES THE TRACK AROUND THE SOUTHWESTERN
QUADRANT OF THE STR. TC 18S IS FORECAST TO CONTINUE TO INTENSIFY TO
120 KTS NEAR TAU 12 AND MAINTAIN THROUGH TAU 24 DUE TO AN INCREASE
IN OUTFLOW ALOFT AND A CONTINUATION OF LOW VWS VALUES. NEAR TAU 36,
VWS VALUES BEGIN TO INCREASE TO OVER 20 KTS AND THE SYSTEM IS
FORECAST TO WEAKEN TO 105 KTS. AS VWS CONTINUES TO INCREASE AND DRY
AIR STARTS TO ENTRAIN INTO THE SYSTEM, TC 18S IS FORECAST TO
FURTHER WEAKEN TO 85 KTS NEAR TAU 48 AND TO 55 KTS NEAR TAU 72. BY
TAU 96, THE SYSTEM IS FORECAST TO DISSIPATE TO 30 KTS AS VWS
INCREASES TO OVER 30 KTS AND DRY AIR ENTRAINS THE SYSTEM, RESULTING 
IN A DECOUPLING OF THE MID AND UPPER LEVEL SUPPORT FROM THE LOW LEVEL 
CIRCULATION. 

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN GOOD
AGREEMENT THROUGH TAU 72, WITH A 175 NM CROSS-TRACK SPREAD AT TAU
72. WITH THE EXCEPTION OF THE UKMET DETERMINISTIC MODEL, WHICH HAS
THE SYSTEM TRACKING WEST-SOUTHWESTWARD AND NOT TAKING THE
POLEWARD TURN NEAR TAU 96, GUIDANCE CONTINUES TO BE IN RELATIVELY 
GOOD AGREEMENT AFTER TAU 72 WITH A CROSS-TRACK SPREAD OF 260 NM. AS A
RESULT, THE JTWC TRACK FORECAST IS ASSESSED WITH HIGH CONFIDENCE
THROUGH TAU 72 AND MEDIUM CONFIDENCE THEREAFTER. INTENSITY GUIDANCE
IS IN RELATIVELY POOR AGREEMENT. THE JTWC INTENSITY FORECAST STAYS 
ABOVE CONSENSUS, WHICH IN ITSELF HAS A PEAK INTENSITY HIGHER THAN ALL 
SOLUTIONS OFFERED WITH THE EXCEPTION OF HAFS-A.  HAFS-A SEEMS TO BE 
THE ONLY MESOSCALE MODEL GRIPPING ONTO THE RECENT RI TREND, BRING THE 
SYSTEM TO A PEAK INTENSITY OF 135 KTS AT TAU 24.  OF TANGENTIAL NOTE, 
GLOBAL MODELS HAVE DRASTICALLY UNDER ANALYZED THE CURRENT SYSTEM 
INTENSITY, WITH THE GREATEST DEVIATION SHOWING IN ECMWF (210600Z) 
REFLECTING A MAX SURFACE WIND SPEED OF NEAR 35KTS AT TAU 00.

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