WDPN31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (BUALOI) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.0N 131.8E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 690 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CONTINUOUSLY 
ORGANIZING SPIRAL BANDS OF DEEP CONVECTION WRAPPING INTO A LOW-LEVEL 
CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL STORM (TS) 26W 
(BUALOI). ENVIRONMENTAL ANALYSIS REVEALS CONDITIONS FAVORABLE FOR 
DEVELOPMENT WITH WARM (29-30 C) SEA SURFACE TEMPERATURES (SST), GOOD 
POLEWARD AND EQUATORWARD OUTFLOW CHANNELS AND LOW TO MODERATE (15-20 
KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION IS PLACED WITH 
MEDIUM CONFIDENCE BASED ON PARTIALLY EXPOSED OUTER REGIONS OF LOW-
LEVEL CLOUDS OBSERVED WITHIN THE NORTHEASTERN AND WESTERN SECTORS OF 
THE SYSTEM, IN CONJUNCTION WITH RECENT CENTRAL CONVECTIVE BURST. THE 
INITIAL INTENSITY OF 45 KTS IS ALSO ASSESSED WITH MEDIUM CONFIDENCE 
BASED ON INCREASING AGENCY DVORAK AND OBJECTIVE ESTIMATES LISTED 
BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 43 KTS AT 240540Z
   CIMSS AIDT: 36 KTS AT 240540Z
   CIMSS D-PRINT: 39 KTS AT 240740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TS 26W IS FORECAST TO TRACK GENERALLY
NORTHWESTWARD THROUGH THE CURRENT FORECAST PERIOD, UNDER THE
PRIMARY INFLUENCE OF A STR TO THE NORTH. LONG TERM MODEL GUIDANCE
SUGGESTS LANDFALL OVER NORTHERN VIETNAM NEAR OR SHORTLY AFTER TAU
120, HOWEVER NUMERICAL MODEL TRACK GUIDANCE IS DIVERGING FROM THE
CONSENSUS AFTER TAU 72, SO THE EXACT TIMELINE OF THAT INTERACTION
IS CURRENTLY ASSESSED WITH SOME UNCERTAINTY. IN TERMS OF INTENSITY,
TS 26W IS FORECAST TO CONTINUE INTENSIFYING OVER THE NEXT 36 HOURS
AS IT APPROACHES PHILIPPINES. AFTER THAT, A BENEFICIAL IN REGARD TO 
THE OUTFLOW, UPPER-LEVEL LOW IS EXPECTED TO RETROGRADE WESTWARD 
RESULTING IN DISAPPEARING POLEWARD CHANNEL. SIMULTANEOUSLY, BUILDING 
UPPER-LEVEL RIDGE WILL BEGIN TO INTRODUCE INCREASED SHEAR ON TS 26W, 
WHICH COMBINED WITH FRICTIONAL EFFECTS OF PASSAGE OVER LAND, WILL 
RESULT IN A BRIEF WEAKENING TREND. AFTER TS BUALOI RE-EMERGES OVER 
THE SOUTH CHINA SEA, WEST OF PHILIPPINES, IT IS EXPECTED TO YET AGAIN 
BEGIN INTENSIFYING DUE TO IMPROVING ENVIRONMENT, CHARACTERIZED MAINLY 
BY DECREASING VWS AND WARM SSTS.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT INITIALLY, AS WITNESSED BY A CROSS-TRACK SPREAD OF 75 NM,
AS TS 26W APPROACHES PHILIPPINES. CONSENSUS DECREASES NEAR TAU 72,
HOWEVER MAJORITY OF THE MODELS INDICATE A NORTHWESTWARD TRACK WITH
LANDFALL SPREAD BETWEEN DA NANG AND HANOI, VIETNAM. NAVGEM AND JGSM
ARE THE MAIN OUTLIERS PROJECTING A NORTH-NORTHWESTWARD TURN DRIVEN
BY THE STR POSITIONING FURTHER EAST. THEREFORE LONG-TERM TRACK
FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE, WHILE BEING LAID CLOSE 
TO THE MULTI-MODEL CONSENSUS, NEAR THE MAIN GROUPING OF THE GUIDANCE.
INTENSITY MODEL GUIDANCE IS ALSO CHALLENGING, PARTICULARLY FROM TAU
36 AND FORWARD. HOWEVER, NEARLY ALL MODELS SUGGEST INTENSIFICATION
TO A PEAK OF 50-65 KTS NEAR TAU 36, FOLLOWED BY BRIEF WEAKENING AND
RE-INTENSIFICATION TO A PEAK NEAR 70 KTS AROUND TAU 96. MAJOR
OUTLIERS ARE NAVGEM-DRIVEN AND GFS-DRIVEN COAMPS-TC, WHICH BOTH 
PREDICT PEAK SIGNIFICANTLY HIGHER THAN THE CONSENSUS. JTWC INTENSITY
FORECAST IS LAID WITH MEDIUM CONFIDENCE THROUGH TAU 72 AND LOW
AFTERWARDS, REFLECTING THE LONG-TERM INTENSITY ASSESSMENT 
UNCERTAINTY.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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