WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
027//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.6N 111.5E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 203 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 33W (KOTO) WITH A FULLY EXPOSED LOW-LEVEL CIRCULATION CENTER
(LLCC) AND REMNANT CONVECTION DRIFTING OFF TO THE SOUTHWEST. DRY
AIR CAN BE SEEN STREAMING INTO THE CORE OF THE SHALLOW VORTEX FROM
THE NORTHWEST. A 010605Z AMSR2 89 GHZ MICROWAVE IMAGE REVEALED
LOW-LEVEL CLOUDS TIGHTLY WRAPPING INTO THE DEFINED LLCC. THE
INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
EXPOSED LLCC IN ANIMATED MSI AND THE AMSR2 MICROWAVE IMAGE. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE HIGHER END OF THE AGENCY DVORAK AND CIMSS OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW. THE DVORAK BASED ESTIMATES ARE
LIKELY SLIGHTLY UNDERESTIMATING INTENSITY DUE TO THE LACK ANY DEEP
CONVECTION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK INFLUENCE FROM A SUBTROPICAL RIDGE
(STR) CENTERED OVER THAILAND.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 37 KTS AT 010520Z
   CIMSS ADT: 25 KTS AT 010600Z
   CIMSS AIDT: 27 KTS AT 010600Z
   CIMSS D-MINT: 27 KTS AT 010605Z
   CIMSS D-PRINT: 28 KTS AT 010600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: WEAK EQUATORWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: 33W IS FORECAST TO TRACK SLOWLY SOUTHWESTWARD
THROUGH TAU 36 AS THE STEERING PATTERN REMAINS WEAKLY DEFINED.
AROUND TAU 36, THE STR OVER THAILAND IS EXPECTED TO MERGE WITH THE
STR OVER THE WEST PHILIPPINE SEA. AS THE RIDGING COMPLEX BUILDS TO
THE NORTH OF THE VORTEX, THE STEERING GRADIENT WILL STRENGTHEN,
CAUSING 33W TO ACCELERATE SOUTHWESTWARD. 33W IS FORECAST TO SKIRT
THE COAST OF SOUTHEASTERN VIETNAM FROM TAU 48 TO TAU 72. THE
UNFAVORABLE ENVIRONMENT THAT 33W IS CURRENTLY PLACED WITHIN IS
EXPECTED TO PERSIST THROUGHOUT THE FORECAST PERIOD. DRY AIR AND
INCREASING SOUTHEASTERLY VERTICAL WIND SHEAR WILL CONTINUE TO
STEADILY WEAKEN THE SYSTEM AS IT TRACKS SOUTHWESTWARD. DISSIPATION
IS FORECAST TO OCCUR NO LATER THAN TAU 72, POSSIBLY SOONER, JUST
OFF THE COAST OF VIETNAM.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF JGSM, WHICH TRACKS THE SYSTEM
INLAND RATHER THAN SKIRTING THE COAST. EXCLUDING JGSM, THERE IS A
105 NM CROSS-TRACK SPREAD AT TAU 48 WHICH OPENS UP TO 180 NM AT TAU
180. OUT OF THE PRIMARY BULK OF GUIDANCE, GDM MAKES UP THE
EASTERNMOST MEMBER WHILE THE GFS ENSEMBLE MEAN MAKES UP THE
WESTERNMOST MEMBER. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MULTI-MODEL CONSENSUS THROUGH TAU 48 AND THEN HEDGED CLOSER TO THE
GDM AND EC-AIFS MODELS THROUGH TAU 72 WITH OVERALL MEDIUM
CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES ON A GRADUAL
WEAKENING TREND THROUGH TAU 72, LENDING MEDIUM CONFIDENCE TO THE
JTWC INTENSITY FORECAST.

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