WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 20W (TWENTY) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.1N 113.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 283 NM EAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL DEPRESSION (TD) 20W HAS MAINTAINED INTENSITY WHILE
TRACKING WEST-NORTHWESTWARD UNDER THE STEERING INFLUENCE OF
SUBTROPICAL RIDGING TO THE NORTH OVER THE PAST SIX HOURS. ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP CONVECTIVE
BANDING PERSISTING ALONG THE WESTERN PERIPHERY OF A PARTIALLY
EXPOSED LOW-LEVEL CIRCULATION. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE WITHIN THE EXPOSED LOW-LEVEL CIRCULATION CENTER,
FURTHER SUPPORTED BY FIXES FROM PGTW, KNES, AND RJTD. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A 
CONSENSUS OF AVAILABLE SUBJECTIVE DVORAK AND AUTOMATED FIX ESTIMATES 
LISTED BELOW.

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: T1.0 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 43 KTS AT 282232Z
   CIMSS ADT: 35 KTS AT 282030Z
   CIMSS AIDT: 34 KTS AT 282030Z
   CIMSS D-MINT: 23 KTS AT 282231Z
   CIMSS D-PRINT: 24 KTS AT 282300Z

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: TD 20W WILL TRACK WEST-NORTHWESTWARD INITIALLY
AND GRADUALLY TURN TOWARD A WESTWARD TRACK UNDER THE CONTINUED
STEERING INFLUENCE OF ENTRENCHED SUBTROPICAL RIDGE TO THE NORTH.
ALTHOUGH EASTERLY VERTICAL WIND SHEAR IS EXPECTED TO IMPACT THE
SYSTEM THROUGHOUT THE FORECAST PERIOD, MODERATE POLEWARD OUTFLOW
ALOFT AND RECENT STRUCTURAL IMPROVEMENTS INCLUDING CONSOLIDATION OF
THE LOW-LEVEL CIRCULATION AND DEVELOPMENT OF PERSISTENT CONVECTIVE
BANDING ALONG THE WESTERN PERIPHERY ARE EXPECTED TO DRIVE SLOW
INTENSIFICATION OVER THE NEXT 24 HOURS. LANDFALL AS A TROPICAL
STORM IS ANTICIPATED BETWEEN TAU 24 AND TAU 36, FOLLOWED BY FULL
DISSIPATION OVER LAND BY TAU 72. 

MODEL DISCUSSION: DETERMINISTIC CONSENSUS AND ENSEMBLE MODEL TRACK
FORECAST SOLUTIONS REMAIN IN TIGHT AGREEMENT REGARDING BOTH THE
ANTICIPATED DIRECTION AND SPEED OF MOTION, WITH NO NOTEWORTHY
DEVIATIONS IN THE GUIDANCE. THE CURRENT JTWC TRACK FORECAST IS
CONSISTENT WITH MULTI-MODEL CONSENSUS, THOUGH VERY SLIGHTLY FASTER
IN TERMS OF FORWARD TRACK SPEED AND SLIGHTLY SOUTH OF CONSENSUS AT 
TAU 72, BOTH ASPECTS CONSISTENT WITH PREVIOUS FORECASTS. MODEL 
INTENSITY FORECASTS ARE ALSO IN GOOD AGREEMENT, WITH ALL PRIMARY 
MODELS INDICATING A STEADY INTENSITY OR SLOW INTENSIFICATION OVER THE 
NEXT 24 HOURS FOLLOWED BY WEAKENING OVER LAND. THE CURRENT INTENSITY 
FORECAST LIES SLIGHTLY ABOVE THE INTENSITY FORECAST CONSENSUS, 
CONSISTENT WITH PREVIOUS JTWC FORECASTS AND ENVIRONMENTAL ASSESSMENT 
INDICATING A MARGINALLY FAVORABLE SCENARIO FOR NEAR-TERM 
INTENSIFICATION.

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