Tropical Storm RAI Advisory dom, 19-12

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
WILL BEGIN TO EXPERIENCE INCREASED VERTICAL WIND SHEAR. BY TAU 48,
THE SYSTEM WILL TURN NORTHEASTWARD AND 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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