WDPN31 PGTW 280900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
015//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.5N 112.7E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 331 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 22 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPOSED,
WELL-DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH DEEP CONVECTION 
REBUILDING OVER THE WESTERN SEMICIRCLE. THE INITIAL POSITION IS PLACED 
WITH HIGH CONFIDENCE BASED ON THE MSI. DESPITE THE MARGINAL 
CONDITIONS, THE OVERALL CONVECTIVE STRUCTURE IS WELL-ORGANIZED AS 
INDICATED IN THE 280534Z AMSR2 36GHZ MICROWAVE IMAGE, WHICH SHOWS 
TIGHTLY-CURVED BANDING WRAPPING INTO A DEFINED LLCC. THE INITIAL 
INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE 
OVERALL STRUCTURE, CONSISTENT WITH THE BULK OF THE AGENCY DVORAK 
ESTIMATES RANGING FROM 45 TO 55 KNOTS. THE CIMSS OBJECTIVE INTENSITY 
ESTIMATES APPEAR TOO LOW LIKELY DUE TO THE LACK OF CENTRAL CONVECTION.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT, WITH A
SUBTROPICAL RIDGE (STR) TO THE EAST AND ANOTHER STR POSITIONED TO
THE NORTHWEST OVER SOUTHEAST ASIA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T4.0 - 65 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   CIMSS SATCON: 42 KTS AT 280615Z
   CIMSS ADT: 31 KTS AT 280530Z
   CIMSS AIDT: 34 KTS AT 280530Z
   CIMSS D-MINT: 34 KTS AT 280535Z
   CIMSS D-PRINT: 31 KTS AT 280630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: 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: TROPICAL STORM (TS) 33W IS FORECAST TO CHURN 
SLOWLY POLEWARD THROUGH TAU 48 ALONG THE WESTERN PERIPHERY OF THE STR 
POSITIONED TO THE EAST. THE SYSTEM WILL MAINTAIN INTENSITY NEAR 50 
KNOTS DUE TO DRY AIR ENTRAINMENT, PERSISTENT SOUTHERLY VERTICAL WIND 
SHEAR, AND POSSIBLY COOL UPWELLING WATER. AFTER TAU 48, THE SYSTEM IS 
FORECAST TO TRACK SOUTHWESTWARD UNDER THE STEERING INFLUENCE OF THE 
WESTERN STR, WITH STEADY WEAKENING AS THE SYSTEM APPROACHES VIETNAM.     

MODEL DISCUSSION: DETERMINISTIC GUIDANCE IS IN POOR AGREEMENT WITH A 
LARGE SPREAD THROUGH THE FORECAST PERIOD. IN GENERAL, THE BULK OF THE 
DETERMINISTIC GUIDANCE SHOWS A BRIEF 36-48 HOUR POLEWARD TRACK THEN A 
WESTWARD TO SOUTHWESTWARD TRACK AFTER TAU 48 TOWARD THE COAST OF 
VIETNAM. THE 280000Z EPS RUN SHOWS A SIMILAR TRACK AND SPREAD 
SUPPORTING THE JTWC TRACK FORECAST WITH MEDIUM CONFIDENCE. THE 280000Z 
GEFS RUN IS CHAOTIC WITH A LARGE SPREAD AND SOLUTIONS VARYING FROM A 
WESTWARD TRACK INTO CENTRAL VIETNAM TO A SOUTHWARD TRACK. RELIABLE 
INTENSITY GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU 48 WITH A FAIRLY 
FLAT INTENSITY TREND. AFTER TAU 48, THE GUIDANCE DIVERGES WITH COAMPS-
TC (GFS BOUNDARY CONDITIONS) AND GFS INDICATING A MODEST 
INTENSIFICATION FROM TAU 60 TO TAU 84. CONVERSELY, HAFS-A AND COAMPS-
TC (NAVGEM) SHOW SIGNIFICANT WEAKENING.         

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