WDPN31 PGTW 180900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 28W (RAI) WARNING NR 022//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.2N 114.8E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 476 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SYMMETRIC 
SYSTEMS WITH DUAL OUTFLOW CHANNELS TO THE NORTH AND SOUTH THAT HAS 
BEEN DEVELOPING A RAGGED EYE OVER THE PAST SIX HOURS. A 180410Z GMI 
89GHZ IMAGE SHOWS HALF OF WHAT APPEARS TO BE A WELL-DEFINED MICROWAVE 
EYE. TY RAI IS IN A FAVORABLE ENVIRONMENT WITH STRONG EQUATORWARD AND 
POLEWARD OUTFLOW ALOFT, LOW (<15 KT) VERTICAL WIND SHEAR, AND WARM 
(28-29 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS BASED ON 
THE PREVIOUSLY MENTIONED RAGGED EYE FEATURE AND THE INITIAL INTENSITY 
OF 110 KTS IS HEDGED SLIGHTLY HIGHER THAN THE PGTW CURRENT INTENSITY 
ESTIMATE OF T5.5 (102 KTS).

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   CIMSS ADT: 122 KTS AT 180710Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG EQUATORWARD AND 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 IS EXPECTED TO CONTINUE A GENERALLY WEST 
NORTHWEST TRACK AS IT APPROACHES THE SUBTROPICAL RIDGE AXIS OVER THE 
NEXT 12 HOURS. THE SYSTEM WILL CONTINUE TO TRACK IN A FAVORABLE 
ENVIRONMENT AND MAINTAIN ITS CURRENT INTENSITY OF 110 KTS UP TO TAU 
12, AT WHICH POINT, IT WILL CROSS INTO SEA SURFACE TEMPERATUERES 
BELOW 26C AND WILL REMAIN OVER COOLER WATERS FOR THE REMAINDER OF THE 
FORECAST. BY TAU 24, TY 28W WILL BEGIN TO ROUND THE RIDGE AXIS AND W 
BEGIN TO EXPERIENCE INCREASED VERTICAL WIND SHEAR. BY TAU 48, THE 
SYSTEM WILL TURN NORTHEASTWARD BEGIN TO ENCOUNTER DRIER AIR FROM THE 
WEST DECREASING THE INTENSITY TO 50 KTS. FOR THE REMAINDER OF 
FORECAST, THE SYSTEM WILL TRACK UNDER THE INFLUENCE OF STRONG 
WESTERLIES AND DISSIPATE BY TAU 96.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN 
RELATIVELY GOOD AGREEMENT IN REGARDS TO TRACK FORECAST WITH ONLY A  
50 NM CROSS-TRACK SPREAD AT TAU 36. THE SPREAD INCREASES AFTERWARDS 
BUT ALL MODELS AGREE ON THE SAME GENERAL TRACK DIRECTION FOR THE 
REMAINDER OF THE JTWC FORECAST PERIOD. THEREFORE, THE JTWC FORECAST 
TRACK IS PLACED CLOSE TO CONSENSUS. INTENSITY GUIDANCE IS IN GOOD 
AGREEMENT WITH MOST MODELS SHOWING THE SYSTEM AT CURRENT PEAK 
INTENSITY FOLLOWED BY A STEADY DECREASE IN INTENSITY FROM NOW UNTIL 
TAU 96. GFS DEPICTS A SLIGHT INCREASE (5-10 KTS) OVER THE NEXT SIX 
HOURS BEFORE BEGINNING TO WEAKEN THE SYSTEM. THE JTWC FORECAST 
INTENSITY IS PLACED CLOSE TO CONSENSUS. 

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