WDPN31 PGTW 190300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.1N 111.4E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 250 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 35 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
AFTER A PERIOD OF RAPID INTENSIFICATION, TY RAI IS NOW SHOWING SIGNS OF WEAKENING ALTHOUGH STILL A VERY POWERFUL TROPICAL CYCLONE. ANIMATED MULTI-SPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN ASYMMETRIC SYSTEM WITH AN EYE FEATURE THAT HAS FILLED OVER THE PAST 6 HOURS. TY 28W IS NOW IN A MARGINALLY UNFAVORABLE ENVIRONMENT WITH STRONG POLEWARD OUTFLOW ALOFT, OFFSET BY MODERATE (20-25 KTS) 200-850MB VERTICAL WIND SHEAR (VWS), AND RELATIVELY COOLER (25-26 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED VISIBLE SATELLITE IMAGERY AND A 182304Z SSMIS 91GHZ PASS. THE INITIAL INTENSITY OF 125 KTS IS SET WITH MEDIUM CONFIDENCE BASED ON DECAYING STRUCTURE NOTED IN AFOREMENTIONED MSI. IN ADDITION, THE INITIAL INTENSITY IS AVERAGED BETWEEN MULTI-AGENCY AND AUTOMATED DVORAK ESTIMATES. 

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER 
SUBTROPICAL RIDGE (STR) TO THE EAST-NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   KNES: T6.0 - 115 KTS
   RJTD: T6.5 - 127 KTS
   CIMMS SATCON: 126 KTS AT 182304Z
   CIMSS ADT: 149 KTS AT 190010Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY UNFAVORABLE
   VWS: 20-25 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TY 28W CONTINUES TO APPROACH THE STR AXIS AND IS HEADING MORE NORTHWESTWARD. HAVING PASSED OVER THE 25 C ISOTHERM, TY RAI WILL REMAIN OVER RELATIVELY COOLER WATERS FOR THE REMAINDER OF THE FORECAST PERIOD. THE EYE FEATURE HAS SPENT THE PAST COUPLE OF HOURS FILLING AND THE STRONG CONVECTIVE ACTIVITY AROUND THE CENTER HAS WANED OVER THE PAST 6 HOURS. BY TAU 12, THE SYSTEM WILL CROSS THE STR AXIS AND HEAD NORTHWARD WHERE 200-850MB VWS IS EXPECTED TO INCREASE TO 35-40 KTS. FROM TAU 24 TO TAU 36, TY RAI WILL MAKES ITS TURN NORTHEASTWARD AND WILL BE INTRODUCED TO DRIER AIR FROM THE WEST, FURTHER DECREASING THE INTENSITY. BY TAU 48, THE SYSTEM WILL FALL UNDER THE INFLUENCE OF STRONG WESTERLIES AND COMPLETELY DISSIPATE ON OR BEFORE TAU 72.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN
VERY GOOD AGREEMENT, LENDING HIGH CONFIDENCE TO THE JTWC FORECAST TRACK. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT WITH ALL MODELS SHOWING THE SYSTEM RAPIDLY DECREASING IN INTENSITY THROUGH TAU 72. THE JTWC INTENSITY FORECAST IS SET WITH MEDIUM CONFIDENCE DUE TO THE RAPID WEAKENING OF THE SYSTEM AND HEDGED SLIGHTLY HIGHER THAN MODEL CONSENSUS.

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