WDPN31 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (TWENTY) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.4N 112.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 226 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 14 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 FLARING OVER THE SOUTHWEST QUADRANT. ANIMATED RADAR
IMAGERY REVEALS BROAD CONVECTIVE BANDING OVER THE NORTHERN AND
WESTERN PERIPHERIES WRAPPING INTO THE SOUTHWEST QUADRANT OF THE
SYSTEM, WITH WEAKER BANDING WRAPPING INTO A WELL-DEFINED CENTER.
THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE
MSI AND RADAR IMAGERY. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON THE PGTW, KNES AND DEMS T2.0 (30
KNOTS) ESTIMATES. CIMSS OBJECTIVE ESTIMATES RANGE FROM 24 TO 35
KNOTS. ENVIRONMENTAL CONDITIONS ARE MARGINALLY FAVORABLE WITH
NORTHERLY TO NORTHEASTERLY UPPER-LEVEL FLOW HINDERING CONVECTIVE
DEVELOPMENT OVER THE EASTERN SEMICIRCLE WHILE MODERATE WESTWARD AND
ROBUST POLEWARD OUTFLOW ARE SUSTAINING THE CONVECTIVE BANDING OVER
THE WESTERN SEMICIRCLE.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR) TO
THE NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 35 KTS AT 290532Z
   CIMSS ADT: 34 KTS AT 290540Z
   CIMSS AIDT: 34 KTS AT 290540Z
   CIMSS D-MINT: 25 KTS AT 290532Z
   CIMSS D-PRINT: 24 KTS AT 290540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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: TROPICAL DEPRESSION (TD) 20W WILL TRACK WEST-
NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR THROUGH THE 
FORECAST PERIOD, WITH LANDFALL EXPECTED NEAR TAU 24. SLIGHT 
INTENSIFICATION IS POSSIBLE OVER THE NEXT DAY DUE PRIMARILY TO THE
ROBUST POLEWARD OUTFLOW AND WARM SEA SURFACE TEMPERATURES BUT
LIMITED BY THE PERSISTENT VWS OVER THE EASTERN SEMICIRCLE. AFTER
TAU 24, THE SYSTEM WILL TRACK OVER VIETNAM, LAOS AND THAILAND WITH
RAPID WEAKENING AND DISSIPATION BY TAU 48.     

MODEL DISCUSSION: MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH A
50NM CROSS-TRACK SPREAD AT TAU 24. THE RECENT ECEPS AND GEFS 
ENSEMBLES ALSO REMAIN IN GOOD AGREEMENT SUPPORTING THE JTWC TRACK
FORECAST WITH HIGH CONFIDENCE. RELIABLE INTENSITY GUIDANCE SUPPORTS
THE SHORT-TERM INTENSIFICATION WITH GUIDANCE RANGING FROM A PEAK OF
30 TO 40 KNOTS THROUGH TAU 24.       

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