WDPN31 PGTW 270300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 33W (KOTO) WARNING NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.2N 113.9E
   INITIAL INTENSITY: 80 KTS
   GEOGRAPHIC REFERENCE: 366 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 32 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS CENTRAL
DENSE OVERCAST (CDO) FEATURE OBSCURING THE LOW-LEVEL CIRCULATION
CENTER (LLCC) OF A COMPACT TYPHOON (TY) 33W (KOTO). THE INITIAL
COORDINATES ARE PLACED WITH MEDIUM CONFIDENCE BASED ON THE
CONVECTIVE WRAPPING SEEN IN VISIBLE SATELLITE LOOP. THE INITIAL
MAXIMUM SUSTAINED WIND SPEED IS ALSO ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A CONSENSUS OF AGENCY FIXES, WHILE OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW APPEAR TO BE UNDERWHELMING. TY KOTO 
IS NOW FULLY ENGAGED WITH THE MONSOONAL NORTHEASTERLY SURGE FLOW, 
RESULTING IN GALE-FORCE WIND RADII EXPANDING WITHIN THE NORTHERN AND 
WESTERN QUADRANTS OF THE CIRCULATION. ENVIRONMENTAL ANALYSIS REVEALS 
MARGINAL THERMODYNAMIC AND KINEMATIC CONDITIONS CHARACTERIZED BY 
ROBUST POLEWARD OUTFLOW AND WARM (28-29 C) SEA SURFACE TEMPERATURES 
(SST), OFFSET BY MODERATE TO HIGH (20-25 KTS) VERTICAL WIND SHEAR 
(VWS) AND BEGINNING OF DRIER AIR ENTERING THE CORE OF THE VORTEX.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT WITH RIDGING
TO THE EAST AND WEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T5.0 - 90 KTS
   KNES: T4.5 - 77 KTS
   DEMS: T4.5 - 77 KTS
   CIMSS ADT: 63 KTS AT 262030Z
   CIMSS AIDT: 59 KTS AT 262030Z
   CIMSS D-MINT: 66 KTS AT 262016Z
   CIMSS D-PRINT: 60 KTS AT 262300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TY KOTO IS FORECAST TO GENERALLY TRANSLATE
TOWARDS THE COAST OF VIETNAM THROUGH TAU 120, HOWEVER WEAK AND
COMPETING SYNOPTIC STEERING MECHANISMS WILL RESULT IN ERRATIC
MEANDERING SOUTHWARD AND NORTHWARD ALONG THE OVERALL WESTWARD
TRAJECTORY. SHORTLY BEFORE TAU 96, THE SUBTROPICAL RIDGE (STR)
CENTERED OVER SOUTHEAST ASIA WILL BEGIN TO DOMINATE THE STEERING AND 
PROPEL THE SYSTEM TOWARDS LANDFALL. IN TERMS OF INTENSITY, IT IS 
LIKELY THAT THE WINDOW OF OPPORTUNITY FOR INTENSIFICATION HAS ALREADY 
PASSED WITH TY KOYO REACHING 80-85 KTS. THE SYSTEM IS NOW ENCOUNTERING 
INCREASINGLY STRONGER VWS. WITHIN THE NEXT 12 HOURS, DRY AIR 
ORIGINATING FROM THE CONTINENTAL AIR MASS AND THE NORTHEASTERLY SURGE 
WILL FURTHER ENTRAIN INTO THE CORE OF THE VORTEX, INHIBITING CHANCES 
AT ADDITIONAL INTENSIFICATION AND RESULTING IN THE INITIATION OF A 
WEAKENING TREND. ADDING TO THE COMPLEXITY OF THE FORECAST, SHORTLY 
AFTER TAU 48, THE SURGE IS EXPECTED TO BEGIN DISSIPATING. THAT 
COMBINED WITH LOWER VWS WILL RESULT IN THE OPENING OF ANOTHER WINDOW 
OF MORE FAVORABLE CONDITIONS. OFFSETTING THOSE POSITIVE IMPACTS WILL 
BE REDUCED UPPER LEVEL OUTFLOW, COMBINED WITH A POTENTIAL IMPACT FROM
UPWELLING BRINGING COLDER WATER TO THE OCEAN SURFACE BENEATH THE
STORM. THAT LAST COMPONENT WILL REMAIN PARTICULARLY IMPORTANT, IF
THE STEERING ENVIRONMENT REMAINS WEAK AND THE SYSTEM REMAINS
QUASI-STATIONARY FOR PROLONGED PERIODS OF TIME.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN FAIR
AGREEMENT, WITH NEARLY ALL MODELS DEPICTING A MIRRORED-S, OF A 
GENERALLY WESTWARD TRACK OVER THE NEXT 12 HOURS. THE ONLY MAJOR 
OUTLIER TO THIS GUIDANCE IS NAVGEM, WHICH TAKES THE STORM 
SIGNIFICANTLY FURTHER NORTH OF THE GUIDANCE ENVELOPE. WITHIN THE NEXT 
12 HOURS, A WEAK STEERING PATTERN WILL RESULT IN THE SYSTEM 
DECELERATING, FOLLOWED BY A GRADUAL TURN TOWARD THE NORTHWEST. THE 
ONLY MODEL NOT FULLY ON BOARD WITH THIS TREND IS DETERMINISTIC GFS, 
WHICH CAN BE SEEN STALLING, OR EVEN VERY SLOWLY RETROGRADING NORTH-
NORTHEASTWARD. AFTER TAU 72, NEARLY ALL GUIDANCE INDICATES A TURN 
TOWARDS VIETNAM, HOWEVER CROSS-TRACK SPREAD INCREASES TO OVER 200 NM 
AT THAT STAGE, SIGNIFICANTLY INCREASING POSITION UNCERTAINTY. 
THEREFORE, THE OFFICIAL JTWC TRACK IS ASSESSED WITH MEDIUM CONFIDENCE 
THROUGHOUT THE FORECAST. IN TERMS OF INTENSITY, ALL MODELS PREDICT A 
STEADY WEAKENING TREND THROUGH TAU 48, RESULTING IN HIGH CONFIDENCE. 
AFTERWARDS HOWEVER THE ALONG-TRACK AND POSITION UNCERTAINTY LEADS TO 
HAFS INDICATING POTENTIAL FOR RE-INTENSIFICATION, WHILE THE REST OF 
THE CONSENSUS MEMBERS PREDICT CONTINUOUS WEAKENING, WITH A POTENTIAL 
FOR A PERIOD OF MAINTAINED INTENSITY BETWEEN TAUS 72 AND 96. AS A 
RESULT, LONG-TERM INTENSITY FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE, WHILE THE OFFICIAL JTWC INTENSITY IS LAID WITHIN 5 KTS OF 
THE MULTI-MODEL CONSENSUS THROUGHOUT THE FORECAST.

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