WDPN32 PGTW 222100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 21W (TWENTYONE) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.0N 112.4E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 299 NM SOUTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A POORLY
ORGANIZED SYSTEM WITH BROAD, DEEP FLARING CONVECTION OBSCURING THE
LOW LEVEL CIRCULATION. THE INITIAL POSITION AND INTENSITY ARE
PLACED WITH MEDIUM CONFIDENCE BASED ON A 221058Z SCATTEROMETER
DIRECT PASS AND SUPPORTED BY AGENCY AND AUTOMATED DVORAK FIXES. THE
SYSTEM IS IN A FAVORABLE ENVIRONMENT WITH LOW-MEDIUM VWS AND WARM
SSTS OFFSET BY WEAK OUTFLOW. THE CYCLONE IS TRACKING ALONG THE
SOUTHERN PERIPHERY OF THE LOW- TO MID-LEVEL REFLECTION OF THE  STR
TO THE NORTH.

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

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE LOW- TO
MID-LEVEL REFLECTION OF THE SUBTROPICAL RIDGE (STR) TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 27 KTS AT 221750Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: HIGH
   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: TD 21W IS EXPECTED TO CONTINUE ON ITS CURRENT
TRACK AND MAKE LANDFALL SOUTH OF DANANG AROUND TAU 18 AND DRAG
ACROSS RUGGED TERRAIN OF VIETNAM AND INTO CAMBODIA. THE FAVORABLE 
ENVIRONMENT WILL FUEL A SLIGHT INTENSIFICATION TO A PEAK OF 35KTS BY 
TAU 12 PRIOR TO LANDFALL. AFTERWARD, LAND INTERACTION WILL ERODE THE
SYSTEM TO DISSIPATION BY TAU 36 AS IT REACHES THE WESTERN BOUNDARY
OF CAMBODIA. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GOOD AGREEMENT; HOWEVER,
GIVEN THE FORMATIVE NATURE OF THE SYSTEM, THERE IS ONLY MEDIUM
CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM//
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