WDPN31 PGTW 212100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 25W (TWENTYFIVE) 
WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.2N 119.8E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 155 NM NORTH-NORTHWEST OF VIGAN,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 18 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS A SMALL
SYSTEM WITH A DEEP, FLARING, COMPACT CENTRAL CONVECTION OBSCURING A 
WEAK AND ILL-DEFINED LOW LEVEL CIRCULATION (LLC). RAIN BANDS ARE
FRAGMENTED AND WRAPPING IN VERY LOOSELY TOWARD THE LLC. LONG
STRATOCUMULUS CLOUD LINES, ASSOCIATED WITH THE NORTHEAST COLD SURGE
IN THE LUZON STRAIT AND INTO THE SOUTH CHINA SEA, ARE FEEDING IN
FROM THE NORTHWEST. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE USING LOW CLOUD TRACING INTO THE OBSCURED LLC. THE
INITIAL INTENSITY OF 25KTS IS BASED ON AN OVERALL ASSESSMENT OF
AGENCY AND AUTOMATED DVORAK ESTIMATES AND TRENDS AND EXTRAPOLATED
FORM NEARBY SURFACE OBSERVATIONS.

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

CURRENT STEERING MECHANISM: EASTERN EXTENSION OF THE SUBTROPICAL
RIDGE (STR) TO THE NORTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 33 KTS AT 211740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: TD 24W WILL CONTINUE WESTWARD UP TO TAU 12
THEN BEGIN TO TRACK MORE SOUTHWESTWARD ALONG THE SOUTHEASTERN
PERIPHERY OF THE STR TOWARD CENTRAL VIETNAM AND MAKE LANDFALL
AROUND TAU 78 NEAR DANANG. THE MARGINALLY FAVORABLE ENVIRONMENT
WILL FUEL A MODEST INTENSIFICATION TO 45KTS BY TAU 24. AFTERWARD
THE ENVIRONMENT WILL BECOME UNFAVORABLE MOSTLY DUE TO THE
INCREASING IMPACT OF PERSISTENT COLD DRY AIR ASSOCIATED WITH THE
NORTHEASTERLY SURGE IN THE SOUTH CHINA SEA, LEADING TO A GRADUAL
DECAY AND EVENTUAL DISSIPATION BY TAU 96 AS THE SYSTEM TRACKS
DEEPER INTO THE RUGGED TERRAIN OF THE INDOCHINA PENINSULA. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A
GRADUAL AND EVEN SPREAD TO 110NM BY TAU 72 THEN MORE PRONOUNCED
SPREAD TO 212NM BY TAU 96. IN VIEW OF THIS, THERE IS HIGH
CONFIDENCE IN THE JTWC TRACK FORECAST UP TO TAU 72 THEN LOW
CONFIDENCE AFTERWARD.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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