WDPN31 PGTW 262100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 33W (KOTO) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.2N 114.8E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 413 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT, FAIRLY SYMMETRICAL CENTRAL DENSE OVERCAST (CDO) FEATURE
OBSCURING THE LOW-LEVEL CIRCULATION CENTER (LLCC) OF TYPHOON (TY)
33W (KOTO). THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON A 261733 GPM GMI 37 GHZ MICROWAVE EYE, CONSISTENT WITH THE
CENTER OF THE CDO SEEN IN THE ANIMATED SHORTWAVE INFRARED SATELLITE
IMAGERY LOOP. THE INITIAL INTENSITY IS PLACED WITH HIGH CONFIDENCE
BASED ON A COMBINATION OF AGENCY FIXES AND OBJECTIVE AIDS LISTED
BELOW. TY KOTO IS NOW FULLY INTERACTING WITH THE STRONG
NORTHEASTERLY SURGE FLOW, RESULTING IN GALE-FORCE WIND RADII
EXPANDING WITHIN THE NORTHERN AND WESTERN PORTIONS OF THE
CIRCULATION. ENVIRONMENTAL ANALYSIS REVEALS FAVORABLE CONDITIONS
CHARACTERIZED BY STRONG RADIAL OUTFLOW, LOW TO MODERATE (10-15 KTS)
VERTICAL WIND SHEAR AND WARM (28-29 C) SEA SURFACE TEMPERATURES AND
MOIST AIR THROUGHOUT THE ATMOSPHERIC COLUMN.

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: T4.5 - 77 KTS
   RJTD: T5.0 - 90 KTS
   RCTP: T4.5 - 77 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 64 KTS AT 261746Z
   CIMSS ADT: 63 KTS AT 261730Z
   CIMSS AIDT: 69 KTS AT 261730Z
   CIMSS D-MINT: 65 KTS AT 261801Z
   CIMSS D-PRINT: 61 KTS AT 261930Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 TRACK TOWARDS
THE COAST OF VIETNAM THROUGHOUT TAU 120, HOWEVER WEAK AND COMPETING
STEERING ENVIRONMENT WILL RESULT IS MEANDERING SOUTHWARD AND
NORTHWARD ALONG THE OVERALL WESTWARD DIRECTION. AROUND TAU 96, THE
SUBTROPICAL RIDGE (STR) CENTERED OVER SOUTHEAST ASIA WILL BEGIN TO
DOMINATE THE STEERING AND PUSH THE SYSTEM TOWARDS LANDFALL. IN
TERMS OF INTENSITY, TY 33W HAS A SHORT (12 HOURS) WINDOW OF
OPPORTUNITY FOR INTENSIFICATION AND IS EXPECTED TO REACH 75-80 KTS.
AFTER TAU 12 HOWEVER, TY KOTO WILL ENCOUNTER AN INCREASINGLY
STRONGER VWS. WITHIN THE NEXT 12 HOURS, DRY AIR ORIGINATING FROM THE
CONTINENTAL AIR MASS AND THE COLD, NORTHEASTERLY SURGE WILL BEGIN
TO ENTRAIN INTO THE CORE OF THE VORTEX FURTHER HALTING CHANCES AT
ADDITIONAL INTENSIFICATION AND RESULTING IN A BEGINNING OF A
WEAKENING TREND. ADDING TO THE COMPLEXITY OF THE FORECAST, AROUND
TAU 72, THE SURGE IS EXPECTED TO BEGIN RETREATING. THAT COMBINED
WITH THE SLIGHTLY LOWERED VWS WILL RESULT IN OPENING OF ANOTHER
WINDOW OF MORE FAVORABLE CONDITIONS. OFFSETTING THOSE POSITIVE
IMPACTS WILL BE REDUCED UPPER LEVEL OUTFLOW COMBINED WITH A
POTENTIAL IMPACT FROM THE UPWELLING BRINGING COLDER WATER TO THE
SURFACE BENEATH THE STORM. THAT LAST COMPONENT MAY BE 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 WESTWARD TRACK OVER THE
NEXT 12 HOURS, FOLLOWED BY A TURN TOWARDS THE SOUTHWEST. BEGINNING
AT TAU 24, WEAK STEERING PATTERN WILL RESULT IN SYSTEM SLOWING
DOWN, FOLLOWED BY A GRADUAL TURN TOWARD THE NORTHWEST. THE ONLY
MODEL NOT FOLLOWING THIS TREND IS DETERMINISTIC GFS, WHICH CAN BE
SEEN STALLING, OR EVEN VERY SLOWLY RETROGRADING
NORTH-NORTHEASTWARD. AFTER TAU 72, NEARLY ALL GUIDANCE INDICATE A
TURN TOWARDS VIETNAM, HOWEVER CROSS-TRACK SPREAD INCREASES TO
NEARLY 300 NM AT THAT STAGE, SIGNIFICANTLY INCREASING 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 48-72,
RESULTING IN HIGH CONFIDENCE. AFTERWARDS HOWEVER THE ALONG-TRACK
AND POSITION UNCERTAINTY RESULTS IN SOME MODEL INDICATING POTENTIAL
FOR INTENSIFICATION (HAFS, GFS), WHILE OTHERS PREDICT CONTINUOUS
WEAKENING (COAMPS-TS AND STATISTICAL-DYNAMICAL GUIDANCE). AS A
RESULT, LONG-TERM INTENSITY FORECAST IS ONLY ASSESSED WITH LOW
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: LOW//
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