WDPN31 PGTW 272100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 26W (BUALOI) WARNING NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.8N 110.6E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 133 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SLIGHTLY
ASYMMETRIC STRUCTURE, WITH A WEDGE OF RELATIVELY DRY AIR SEPARATING
TWO REGIONS OF DEEP CONVECTIVE ACTIVITY. THE DEEPEST CONVECTION
WITH THE COLDEST CLOUD TOPS ARE LOCATED SOUTHEAST OF THE ASSESSED
LOW LEVEL CIRCULATION CENTER (LLCC), WHILE THE AREA CLOSER TO THE
LLCC DEPICTS WARMER CLOUD TOP TEMPERATURES. RADAR DATA SHOWS A
RAGGED EYE FEATURE SURROUNDED BY WEAK TO MODERATE CONVECTION AND
WELL-DEFINED OUTER RAIN BANDS ALONG THE VIETNAMESE COASTLINE.
EARLIER MICROWAVE IMAGERY AND MODEL-DERIVED CROSS-SECTIONS AND
SOUNDINGS SUGGEST A MODERATE AMOUNT OF VORTEX TILT, TOWARDS THE
SOUTH-SOUTHEAST, SUPPORTING THE CIMSS SHEAR ANALYSIS OF 17KTS OF
SHEAR FROM THE NORTH. THE INITIAL POSITION IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON THE RADAR DATA. REANALYSIS OF EARLIER POSITIONS
RESULTED IN A REDUCTION OF THE INTENSITY ESTIMATES THAT BRINGS THEM 
MORE IN LINE WITH THE SUBJECTIVE ESTIMATES, AND A 271417Z
ASCAT-C PASS WHICH SHOWED MAXIMUM WINDS OF LESS THAN 55 KNOTS. THE
INITIAL INTENSITY IS THUS ASSESSED AT 65 KNOTS, WITH MEDIUM
CONFIDENCE, IN LINE WITH THE LOWER-END AGENCY FIXES AND THE BULK OF
THE OBJECTIVE ESTIMATES. THE ENVIRONMENT REMAINS FAVORABLE, WITH
VERY WARM SSTS, STRONG EQUATORWARD OUTFLOW AND MODERATE NORTHERLY
SHEAR.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A DEEP LAYER
SUBTROPICAL RIDGE (STR) CENTERED NEAR TAIWAN. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T4.0 - 65 KTS
   KNES: T5.0 - 90 KTS
   CIMSS ADT: 61 KTS AT 271730Z
   CIMSS AIDT: 69 KTS AT 271730Z
   CIMSS D-PRINT: 59 KTS AT 271730Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THE TRACK OF TY 26W HAS SHIFTED SLIGHTLY MORE
WESTWARD THAN PREVIOUSLY EXPECTED OVER THE PAST SIX HOURS, BUT THE
SYSTEM IS STILL TRUCKING ALONG THE SOUTHWESTERN SIDE OF THE STR
TOWARDS A LANDFALL ALONG THE VIETNAMESE COASTLINE. THE SYSTEM IS TO
PASS NORTH OF HUE CITY WITHIN THE NEXT 12 HOURS OR SO, THEN MAKE
LANDFALL NORTH OF DONG HAI, VIETNAM WITHIN THE NEXT 18 TO 24 HOURS.
THE SYSTEM IS STILL SUFFERING FROM SOME VORTEX MISALIGNMENT DUE TO
THE MODERATE NORTHERLY SHEAR, AND THE CYCLING CONVECTION HAS FAILED
TO PERSIST OR ORGANIZE AROUND THE VORTEX. THUS, WHILE THE
ENVIRONMENT IS STILL FAVORABLE, THE INTENSIFICATION TREND HAS
STAGNATED OVER PAST 24 HOURS. AVAILABLE MODEL GUIDANCE SUGGESTS A
REDUCTION IN DEEP-LAYER SHEAR OVER THE NEXT 12 HOURS OR SO, WHILE
ALL OTHER ENVIRONMENTAL FACTORS ARE EXPECTED TO REMAIN THE SAME. TY
26W IS THUS FORECAST TO INTENSIFY UP TO 80 KNOTS OVER THE NEXT 12
HOURS. WHILE NOT SPECIFICALLY CAPTURED IN THE FORECAST POINTS, THE
ACTUAL PEAK INTENSITY IS LIKELY TO BE 85-90 KNOTS, AS THE SYSTEM
MOVES OVER A POCKET OF VERY WARM, HIGH OHC WATERS, SITUATED JUST
OFF THE VIETNAMESE COAST. ONCE THE SYSTEM MOVES ASHORE, EXPECT
RAPID WEAKENING DUE TO TERRAIN INTERACTIONS, WITH THE SYSTEM
FORECAST TO DISSIPATE OVER NORTHERN LAOS BY TAU 48.  

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
TIGHT AGREEMENT, WITH MINIMAL CROSS- OR ALONG-TRACK SPREAD THROUGH
THE MAJORITY OF THE FORECAST PERIOD. THE JTWC FORECAST IS
POSITIONED ON THE SOUTHERN EDGE OF THE FORECAST ENVELOPE THROUGH
TAU 12, TO ACCOUNT FOR THE RECENT TRACK EVOLUTION. THEREAFTER, THE
JTWC FORECAST IS POSITIONED CLOSE TO THE CONSENSUS MEAN, WITH HIGH
CONFIDENCE. INTENSITY GUIDANCE IS GENERALLY IN GOOD AGREEMENT,
INDICATING A NEAR-TERM INTENSIFICATION TREND, FOLLOWED BY RAPID
WEAKENING AFTER LANDFALL. MODELS DISAGREE ON THE PEAK INTENSITY,
WITH THE HAFS-A BEING THE MOST AGGRESSIVE AND REACHING MAX
INTENSITY AT TAU 12 AT 75 KNOTS. THE COAMPS-TC MARKS THE LOWER END
OF THE ENVELOPE, REACHING MAX INTENSITY AT TAU 12 AT 65 KNOTS. THE
JTWC FORECAST POINTS ARE CONSISTENT WITH THE HAFS-A, BUT NONE OF
THE GUIDANCE SHOWS WHAT IS LIKELY TO BE THE ACTUAL PEAK WHICH IS
EXPECTED TO OCCUR BETWEEN TAU 12 AND TAU 18 AND THUS THE JTWC
FORECAST (AS DISCUSSED ABOVE) DEVIATES FROM THE GUIDANCE IN THIS
REGARD. 

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