WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 33W (KOTO) WARNING 
NR 028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.6N 111.5E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 203 NM EAST-SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: SOUTHWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION 33W (KOTO) WITH A FULY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC) THAT IS COMPLETELY VOID OF DEEP CONVECTION. THE
SYSTEM HAS REMAINED NEARLY STATIONARY OVER THE PAST 6 HOURS.
ENVIRONMENTAL ANALYSIS INDICATES THAT 33W IS IN A HIGHLY
UNFAVORABLE ENVIRONMENT CHARACTERIZED BY WEAK OUTFLOW ALOFT, LOW
(10-15 KTS) VERTICAL WIND SHEAR, EXTREME DRY AIR ENTRAINMENT, AND
WARMISH (26-27 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN ANIMATED
EIR IMAGERY. THE INITIAL INTENSITY OF 30 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: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS ADT: 25 KTS AT 011210Z
   CIMSS AIDT: 26 KTS AT 011210Z
   CIMSS D-MINT: 30 KTS AT 010811Z
   CIMSS D-PRINT: 24 KTS AT 011210Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

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
SOUTH-SOUTHWESTWARD THROUGH TAU 24 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 AROUND TAU 48.
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 AROUND TAU 48, 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 MORE
WESTWARD AND INLAND RATHER THAN SKIRTING THE COAST. EXCLUDING JGSM,
THERE IS A 60 NM CROSS-TRACK SPREAD AND 75 NM ALONG-TRACK SPREAD AT
TAU 48. OUT OF THE PRIMARY BULK OF GUIDANCE, EC-AIFS MAKES UP THE
EASTERNMOST MEMBER WHILE GALWEM MAKES UP THE WESTERNMOST MEMBER THIS 
MODEL RUN. THE JTWC TRACK FORECAST IS PLACED SLIGHTLY TO THE EAST OF 
THE MULIT-MODEL CONSENSUS, TO OFFSET JGMS, WITH HIGH CONFIDENCE.
INTENSITY GUIDANCE GENERALLY AGREES ON A GRADUAL WEAKENING TREND
THROUGH TAU 48, LENDING MEDIUM CONFIDENCE TO THE JTWC INTENSITY
FORECAST.

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