WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (BUALOI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.3N 128.1E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 460 NM EAST-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 26W (BUALOI) WITH BUILDING DEEP CONVECTION NOW OBSCURING THE
LOW-LEVEL CIRCULATION CENTER (LLCC) AND CLOUD TOPS MEASURING -90 C
IN MULTIPLE AREAS OF THE OVERSHOOTING TOPS. ENVIRONMENTAL ANALYSIS
CONTINUES TO INDICATE A MARGINALLY FAVORABLE ENVIRONMENT
CHARACTERIZED BY MODERATE OUTFLOW ALOFT, MODERATE TO HIGH (20-25
KTS) EAST-NORTHEASTERLY SHEAR, AND WARM (29-30 C) SEA SURFACE
TEMPERATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON THE ANIMATED MSI. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY DVORAK AND
OBJECTIVE INTENSITY ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE WITH SLIGHT ADJUSTMENTS BASED
ON THE OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYERED
SUBTROPICAL RIDGE (STR) CENTERED TO THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T4.5 - 77 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 56 KTS AT 250433Z
   CIMSS ADT: 57 KTS AT 250540Z
   CIMSS AIDT: 63 KTS AT 250540Z
   CIMSS D-PRINT: 48 KTS AT 250610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 20-25 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: FORECASTED TRACK SPEEDS HAVE
INCREASED COMPARED TO THE PREVIOUS FORECAST, NOW CALLING FOR
LANDFALL IN NORTHERN VIETNAM NEAR TAU 84. 

FORECAST DISCUSSION: 26W IS FORECAST TO TRACK WEST-NORTHWESTWARD,
ALONG THE SOUTHERN PERIPHERY OF THE LARGE SUBTROPICAL RIDGE TO THE
NORTH THROUGH TAU 72. AN INITIAL LANDFALL ALONG NORTHEASTERN SAMAR
IS EXPECTED NEAR TAU 12. NEAR TAU 72, 26W IS FORECAST TO TURN
SLIGHTLY MORE NORTHWESTWARD AS IT TRACKS ALONG THE SOUTHWESTERN
EXTENT OF THE RIDGE. A SECOND LANDFALL IS CURRENTLY FORECAST TO
OCCUR NEAR TAU 84, JUST NORTH OF VINH. REGARDING INTENSITY, 26W IS
FORECAST TO SLIGHTLY WEAKEN THROUGH TAU 24 AS THE EASTERLY VERTICAL
WIND SHEAR AND TOPOGRAPHIC INTERACTION WITH THE VISAYAS ISLANDS.
THE LOW ELEVATION AND CONTINUED SUPPLY OF WARM SEA WATER WILL ALLOW
26W TO STAY AROUND 50 KTS AS IT TRAVERSES THROUGH THE ISLANDS.
AFTER EMERGING WITHIN THE SOUTH CHINA SEA, THE ENVIRONMENT WILL
IMPROVE WITH LOWER VERTICAL WIND SHEAR, CAUSING 26W TO INTENSIFY AS
IT APPROACHES THE GULF OF TONKIN. THE ENVIRONMENT WITHIN THE GULF
OF TONKIN IS EXPECTED TO BE HIGHLY FAVORABLE, PARTICULARLY VERY
WARM SEA SURFACE TEMPERATURES. AS A RESULT, THE SYSTEM IS EXPECTED
TO PEAK NEAR TAU 72-84, SOUTHEAST OF HAINAN. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF JGSM, WHICH IS QUITE A BIT FURTHER
NORTH THROUGHOUT THE FORECAST PERIOD THAN THE REMAINDER OF GUIDANCE
IS. WITHOUT JGSM THERE IS A 160 NM CROSS-TRACK SPREAD AT TAU 72
WHICH OPENS UP TO AROUND 220 NM AT TAU 120. THE JTWC TRACK FORECAST
IS PLACED SLIGHTLY SOUTH OF THE MULTI-MODEL CONSENSUS WITH OVERALL
MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT ON
INTENSIFICATION AFTER TAU 24 WITH PEAK INTENSITIES RANGING FROM
65-100 KTS AT TAU 72. HAFS-A IS ON THE LOWER SIDE WHILE COAMPS-TC
IS ON THE HIGHER SIDE. THE JTWC INTENSITY FORECAST IS PLACED A BIT
CLOSER TO THE HAFS-A GUIDANCE WITH OVERALL MEDIUM CONFIDENCE AS
WELL.

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