WDPN31 PGTW 231500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGHT) 
WARNING NR 005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5N 112.7E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 356 NM EAST OF HO CHI MINH CITY, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
DEPRESSION (TD) 28W AS A STRUGGLING SYSTEM WITH A RAGGED AND FULLY 
EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC). THE SHALLOW VORTEX HAS
CONTINUED TO TRACK NORTHWARD AS ASSOCIATED CONVECTION HAS BEEN
SHORT-LIVED AND MINIMAL OVER THE CENTER. THROUGHOUT THE NORTHERN
SEMICIRCLE, FLARING CONVECTION HAS BEEN OBSERVED APPROXIMATELY 163
NM FROM THE MOST RECENT POSITION ASSESSMENT, HOWEVER, MODERATE TO
HIGH VERTICAL WIND SHEAR (VWS) OF GREATER THAN 20 KTS HAS KEPT THE
SYSTEM VOID OF ANY SIGNIFICANT UPPER-LEVEL OUTFLOW MECHANISM.
ADDITIONALLY, DRY AIR ASSOCIATED WITH AN ONGOING NORTHEAST COLD
SURGE EVENT HAS PERSISTED, WRAPPING INTO THE EASTERN SEMICIRCLE
FROM THE NORTHWEST, CREATING A HOSTILE ENVIRONMENT FOR SUSTAINED
TROPICAL CYCLONE DEVELOPMENT. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON THE AFOREMENTIONED RAGGED AND FULLY 
EXPOSED LLCC, OBSERVED ON ANIMATED EIR. THE INITIAL INTENSITY IS 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE DVORAK ESTIMATES 
AT T1.0 (25KTS) AND CIMSS OBJECTIVE INTENSITY ESTIMATES RANGING FROM 
27-28 KTS.

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

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) DIRECTLY TO
THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T1.0 - 25 KTS
   DEMS: T1.0 - 25 KTS
   CIMSS ADT: 27 KTS AT 231300Z
   CIMSS AIDT: 28 KTS AT 231300Z
   CIMSS D-PRINT: 27 KTS AT 231300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK POLEWARD

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 28W IS FORECASTED TO TRACK ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR POSITIONED DIRECTLY TO THE
NORTHEAST THROUGH TAU 12. AFTER TAU 12, THE STR LOCATED TO THE
NORTHEAST IS EXPECTED TO BUILD WESTWARD INTO THE END OF THE
FORECAST PERIOD. AS THE STR BUILDS WESTWARD, TD 28W IS EXPECTED TO
BEGIN A WEST-SOUTHWEST TRACK BETWEEN TAU 12 AND TAU 96. WITH REGARD
TO INTENSITY, THE SYSTEM IS EXPECTED TO SLOWLY INTENSIFY TO 30 KTS
OVER THE NEXT 12 TO 24 HOURS AS ENHANCED GRADIENT WINDS IN THE 
WESTERN QUADRANT WRAP AROUND THE TROPICAL DEPRESSIONS CENTRAL 
STRUCTURE. BETWEEN TAU 12 AND TAU 24, A STEADY INTENSITY OF 30 KTS IS 
EXPECTED AS DRY-AIR ENTRAINMENT AND MODERATE TO HIGH VWS IMPEDE 
FURTHER INTENSIFICATION. AFTER TAU 24, PERSISTENT VWS OF HIGHER THAN 
20 KTS, DRY AIR ENTRAINMENT, AND COOLER SEA SURFACE TEMPERATURES OF
LESS THAN 26 C WILL WEAKEN THE SYSTEM QUICKLY TO LESS THAN 25 KTS
BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE CONTINUES TO BE IN GOOD
AGREEMENT WITH REGARD TO THE TRACK AND INTENSITY FORECAST
THROUGHOUT THE NEXT 48 HOURS. ALTHOUGH THE SHALLOW SYSTEM PERSISTS
SLIGHTLY MORE NORTHWARD, TRACK GUIDANCE HAS IMPROVED OVER THE LAST
FEW HOURS, TO A CROSS-TRACK SPREAD OF 90 NM BY COMPLETE DISSIPATION
AT TAU 48. DUE TO THE SYSTEMS CONTINUED SLOW TRACK NORTHWARD, THE
JTWC FORECAST IS PLACED WITH MEDIUM CONFIDENCE AND CLOSELY ALIGNED
WITH THE JTWC MULTI-MODEL CONSENSUS AND PREVIOUS FORECAST TRACK.
WITH REGARD TO THE INTENSITY FORECAST, THERE IS HIGH CONFIDENCE
THAT TD 28W WILL EXPERIENCE A SLIGHT INTENSIFICATION OVER THE NEXT
12 TO 24 HOURS AND WEAKEN QUICKLY THEREAFTER. COAMPS-TC
EPS INTENSITY PROBABILITIES CONTINUE TO INDICATE A STEADY
INTENSITY THROUGHOUT THE REMAINDER OF THE FORECAST PERIOD.

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