WDPN31 PGTW 241500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (BUALOI) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4N 131.0E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 638 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 26W (BUALOI) CONTINUING TO INTENSIFY AS IT TRANSITS
WEST-NORTHWESTWARD. PERSISTENT CENTRAL CONVECTION HAS REACHED PEAK 
CLOUD TOPS TEMPERATURE OF -89 C AND DEVELOPED IRREGULAR, PULSATING 
CIRRUS CANOPY. ENVIRONMENTAL ANALYSIS INDICATES FAVORABLE DEVELOPMENT 
CONDITIONS, CHARACTERIZED BY WARM (29-30 C) SEA SURFACE TEMPERATURES 
(SST), STRONG POLEWARD AND EQUATORWARD OUTFLOW CHANNELS, AND LOW TO
MODERATE (15-20 KTS) VERTICAL WIND SHEAR (VWS). THE INITIAL POSITION 
IS ESTIMATED WITH MEDIUM CONFIDENCE, BASED ON EXTRAPOLATION FROM A 
240838Z WSFM MWI COLOR37 MICROWAVE IMAGE DEPICTING LOWER-LEVEL 
CONVECTIVE BANDING. THE INITIAL INTENSITY OF 50 KTS IS ALSO ASSESSED 
WITH MEDIUM CONFIDENCE, SUPPORTED BY INCREASING AGENCY DVORAK AND 
OBJECTIVE ESTIMATES INDICATED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.0 - 45 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 42 KTS AT 240920Z
   CIMSS ADT: 53 KTS AT 241140Z
   CIMSS AIDT: 42 KTS AT 241140Z
   CIMSS D-MINT: 35 KTS AT 240920Z
   CIMSS D-PRINT: 44 KTS AT 241210Z

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: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 26W IS EXPECTED TO TRACK GENERALLY
NORTHWESTWARD THROUGH THE CURRENT FORECAST PERIOD, UNDER THE
INFLUENCE OF A STR TO THE NORTH. LONG-TERM MODEL GUIDANCE STILL
SUGGESTS LANDFALL OVER NORTHERN VIETNAM AROUND OR SHORTLY AFTER TAU
120. HOWEVER, NUMERICAL MODEL TRACK GUIDANCE NOW BEGINS TO DIVERGE
FROM THE CONSENSUS AS EARLY AS TAU 48, LEADING TO UNCERTAINTY IN
THE TRACK OVER SOUTH CHINA SEA, AS WELL AS THE TIMING OF THE LAND
INTERACTION. IN TERMS OF INTENSITY, TS 26W IS FORECAST TO CONTINUE
INTENSIFYING OVER THE NEXT 12 HOURS. SUBSEQUENTLY, A BENEFICIAL
UPPER-LEVEL LOW IS EXPECTED TO RETROGRADE WESTWARD, AND AT A FASTER
RATE THAN PREVIOUSLY OBSERVED ON THE MODEL FIELDS. THIS WILL LEAD
TO A SIGNIFICANT REDUCTION OF THE POLEWARD OUTFLOW CHANNEL.
SIMULTANEOUSLY, A BUILDING UPPER-LEVEL RIDGE TO THE NORTH WILL RESULT 
IN INCREASED VERTICAL WIND SHEAR ON TS 26W, WITH IMPACTS AS EARLY AS
TAU 12. AROUND TAU 36, FRICTIONAL EFFECTS FROM LAND PASSAGE, WILL
FURTHER CONTRIBUTE TO A BRIEF WEAKENING TREND. AFTER RE-EMERGING
OVER THE SOUTH CHINA SEA WEST OF THE PHILIPPINES, TS BUALOI IS
EXPECTED TO RESUME INTENSIFICATION DUE TO IMPROVED ENVIRONMENTAL
CONDITIONS, PARTICULARLY DECREASING VWS AND WARM SSTS. THE SYSTEM IS 
EXPECTED TO REACH PEAK INTENSITY OF 60-65 KTS AROUND TAU 96. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE SHOWS GOOD
AGREEMENT INITIALLY, AS EVIDENCED BY A CROSS-TRACK SPREAD OF 80 NM,
AS TS 26W APPROACHES THE PHILIPPINES. AS THE SYSTEM RE-EMERGES OVER
WATER, JGSM AND NAVGEM PREDICT A SHARPER NORTHWESTWARD TURN THAT
THE REMAINDER OF THE CONSENSUS MEMBERS, RESULTING IN OVERALL LOWER 
TRACK PREDICTION CONFIDENCE. HOWEVER, THE REMAINING MODELS INDICATE A
NORTHWESTWARD TRACK WITH LANDFALL BETWEEN DA NANG AND HANOI, VIETNAM. 
THEREFORE, THE LONG-TERM TRACK FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE, PLACED CLOSE TO THE MULTI-MODEL CONSENSUS, NEAR THE MAIN 
CLUSTER OF GUIDANCE. INTENSITY GUIDANCE IS GENERALLY IMPROVING, AS 
NEARLY ALL MODELS PREDICT POTENTIAL FOR INTENSIFICATION OVER THE NEXT 
12 HOURS, FOLLOWED BY SLIGHT WEAKENING THROUGH TAU 48, AND FINALLY 
RE-INTENSIFICATION AFTERWARDS AND PRIOR TO LANDFALL. MAJOR SOURCE OF 
UNCERTAINTY, AND THE REASON THAT THE JTWC INTENSITY FORECAST IS 
ASSESSED WITH MEDIUM CONFIDENCE, IS ASSOCIATED WITH THE TRACK 
GUIDANCE AMBIGUITY, PARTICULARLY TOWARDS THE END OF THE FORECAST 
PERIOD. IF THE STEERING MECHANISM WEAKENS AND TS 26W SLOWS DOWN, IT 
MAY HAVE ENOUGH TIME TO INTENSIFY BEYOND CURRENT PEAK OF 60 KTS. 
HOWEVER, WITH THE STEERING PATTERN REMAINING STRONG AND TRANSLATION 
SPEED OF THE SYSTEM HIGH, EARLY LANDFALL AND QUICKER DISSIPATION ARE 
POSSIBLE. 

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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