WDPN33 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 23W (NESAT)        
WARNING NR 019//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.0N 110.2E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 125 NM EAST-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 23 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM (TS) 23W IS EMBEDDED WITHIN A STRATOCUMULUS FIELD
ASSOCIATED WITH A STRONG NORTHEAST SURGE EVENT. SIGNIFICANTLY COOL,
DRY AIR IS PRESENT ACROSS HAINAN ISLAND AND THE GULF OF TONKIN WITH
DEW POINT TEMPERATURES RANGING FROM 14-18C. CONSEQUENTLY, ANIMATED
MULTISPECTRAL SATELLITE IMAGERY (MSI) REVEALS A RAPIDLY-DECAYING,
FULLY-EXPOSED LOW-LEVEL CIRCULATION WITH AN ISOLATED BURST OF DEEP
CONVECTION OVER THE NORTHERN QUADRANT. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED CENTER
EVIDENT IN MSI. AS INDICATED IN A 190232Z ASCAT-B WINDSPEED IMAGE,
THE SYSTEM HAS DEVELOPED A SYMMETRIC, SMALL (LESS THAN 60NM
DIAMETER) CORE OF GALE-FORCE WINDS, WHICH ARE NOW SEPARATED FROM
THE EXTENSIVE REGION OF GALE-FORCE WINDS PERSISTING EAST OF HAINAN
ISLAND TO NEAR TAIWAN. BASED ON THE ASCAT-B IMAGE, THE 34-KNOT WIND 
RADII HAVE BEEN REFINED AND DO NOT INCLUDE THE NORTHEAST SURGE WINDS
SINCE THERE IS A CLEAR GAP OF GREATER THAN 100NM BETWEEN THE TWO
WINDFIELDS. THE INITIAL INTENSITY OF 50 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON A BLEND OF THE DVORAK CURRENT INTENSITY
ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE NORTH AND NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T3.5 - 55 KTS
   CIMSS SATCON: 42 KTS AT 190551Z
   CIMSS ADT: 30 KTS AT 190540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TS 23W WILL TRACK SLOWLY WESTWARD TO WEST-
NORTHWESTWARD THROUGH TAU 36 AS IT TRACKS ALONG THE SOUTHWEST
PERIPHERY OF THE STR TOWARD VIETNAM. TS 23W IS FORECAST TO CONTINUE 
DECAYING STEADILY DUE TO PERSISTENT SOUTHERLY VERTICAL WIND SHEAR, 
DRY AIR ENTRAINMENT AND INTERACTION WITH LAND. AFTER TAU 36, THE 
SYSTEM WILL SLOW AND DISSIPATE OVER EASTERN VIETNAM OR JUST EAST OF 
VIETNAM.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, WHICH IS THE SOLE
OUTLIER ON THE NORTHERN EDGE OF THE AIDS ENVELOPE, NUMERICAL MODEL
GUIDANCE IS IN FAIR AGREEMENT SUPPORTING THE JTWC FORECAST TRACK
WITH MEDIUM CONFIDENCE. THE 190000Z GFS (GEFS) AND ECMWF (EPS)
ENSEMBLES ALSO SUPPORT THE LATEST TRACK FORECAST AND INDICATE
STEADY WEAKENING AND DISSIPATION. RELIABLE INTENSITY GUIDANCE
REMAINS IN GOOD AGREEMENT WITH A STEADY WEAKENING TREND OVER THE
NEXT TWO DAYS.  

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