WDPN31 PGTW 230900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 28W (TWENTYEIGH) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.0N 112.8E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 360 NM EAST OF HO CHI MINH CITY, VIETNA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 28W WITH A COMPLETELY EXPOSED LOW-LEVEL CIRCULATION
CENTER (LLCC). FRAGMENTED LOW-LEVEL CURVED CLOUD LINES HAVE BEEN
OBSERVED WRAPPING INTO THE CENTER OVER THE LAST FEW HOURS, HOWEVER,
THE TILTED VORTEX HAS POSITIONED SUPPORTIVE CONVECTIVE STRUCTURES
APPROXIMATELY 120 NM TO THE NORTH. ADDITIONALLY, EVIDENT AND 
PERSISTENT DRY AIR WRAPPING AROUND THE EASTERN SEMICIRCLE FROM THE 
WEST HAS CONTINUED TO CREATE AN OTHER THAN FAVORABLE ENVIRONMENT FOR 
TD 28W. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE AFOREMENTIONED AND FULLY EXPOSED LLCC, OBSERVED ON ANIMATED MSI.
THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
CIMSS OBJECTIVE INTENSITY ESTIMATES RANGING FROM 28-35 KTS AND
SUBJECTIVE DVORAK ESTIMATES AT 25 KTS.

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

CURRENT STEERING MECHANISM: AN EXTENSION OF A SUBTROPICAL RIDGE
(STR) TO THE NORTHEAST, WITH AN ADDITIONAL RIDGE TO THE
WEST-NORTHWEST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 35 KTS AT 230500Z
   CIMSS ADT: 31 KTS AT 230700Z
   CIMSS AIDT: 29 KTS AT 230700Z
   CIMSS D-PRINT: 28 KTS AT 230700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: WEAK 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: TD 28W IS FORECASTED TO TRACK ALONG THE
SOUTHWESTERN PERIPHERY OF THE STR POSITIONED DIRECTLY TO THE
NORTHEAST THROUGH TAU 12. FOLLOWING TAU 12, THE SYSTEM WILL BEGIN A
SLOW TRACK TO THE WEST-SOUTHWEST, ALONG THE SOUTHEASTERN PERIPHERY
OF A STR LOCATED DIRECTLY TO THE WEST. THE WEST-SOUTHWEST TRACK
WILL CONTINUE THROUGH DISSIPATION BY TAU 48. WITH REGARD TO
INTENSITY, THE SYSTEM IS FORECASTED TO SLOWLY INTENSIFY TO 35 KTS
OVER THE NEXT 24 HOURS AS GRADIENT INDUCED ENHANCED SURFACE WINDS
ASSOCIATED WITH AN ONGOING NORTHEASTERLY SURGE EVENT WRAP AROUND
THE CENTRAL VORTEX. FOLLOWING TAU 24, INCREASED DRY-AIR ENTRAINMENT
AND VERTICAL WIND SHEAR (VWS) FROM THE AFOREMENTIONED COLD SURGE
EVENT FROM THE NORTHEAST ARE EXPECTED TO INCREASE, RESULTING IN
COMPLETE DISSIPATION OVER WATER BY TAU 48.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN GOOD AGREEMENT
WITH REGARD TO THE TRACK AND INTENSITY FORECAST OVER THE NEXT 48
HOURS. TRACK GUIDANCE CONTINUES TO IMPROVE, AS A GENERALLY WESTWARD
TRACK IS EXPECTED OVER THE NEXT 48 HOURS, RESULTING IN JUST A 98 NM
CROSS-TRACK SPREAD BY COMPLETE DISSIPATION. DUE TO THE TIMING OF
COMPLETE DISSIPATION, THE JTWC FORECAST IS PLACED WITH MEDIUM
CONFIDENCE AND ALIGNED CLOSELY WITH THE JTWC MULTI-MODEL CONSENSUS.
WITH REGARD TO THE INTENSITY FORECAST, MEDIUM CONFIDENCE IS
ASSESSED AS A SLIGHT INTENSIFICATION WINDOW IS FORECASTED BETWEEN
TAU 12 AND TAU 24, WITH A QUICK WEAKENING PHASE THEREAFTER. LASTLY,
COAMPS-TC EPS INTENSITY PROBABILITIES INDICATE A STEADY INTENSITY
FOR TD 28W THROUGHOUT THE ENTIRETY OF THE FORECAST PERIOD.

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