WDPN31 PGTW 291500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (TWENTY) 
WARNING NR 006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.2N 111.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 182 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 12 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY DEPICTS A PARTIALLY 
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH DISORGANIZED DEEP 
CONVECTION FLARING OVER THE SOUTHWEST QUADRANT. ANIMATED RADAR 
IMAGERY REVEALS MULTIPLE CONVECTIVE BANDS WRAPPING TIGHTLY INTO A 
WELL-DEFINED CENTER. THE INITIAL POSITION IS PLACED WITH HIGH 
CONFIDENCE BASED ON THE RADAR IMAGERY. THE INITIAL INTENSITY OF 30 
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE PGTW, KNES AND 
DEMS ESTIMATES. CIMSS OBJECTIVE ESTIMATES RANGE FROM 27 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: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 291130Z
   CIMSS AIDT: 34 KTS AT 291130Z
   CIMSS D-MINT: 29 KTS AT 290820Z
   CIMSS D-PRINT: 27 KTS AT 291230Z

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 36.  

MODEL DISCUSSION: MODEL GUIDANCE REMAINS IN GOOD AGREEMENT WITH A
55NM 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 35 KNOTS THROUGH TAU 24.       

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