WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 23W (TWENTYTHREE) 
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.8N 118.9E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 303 NM EAST-SOUTHEAST OF HONG KONG
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A LOW LEVEL
CIRCULATION CENTER (LLCC) ASSOCIATED WITH TROPICAL DEPRESSION (TD)
23W TRACKING NORTHWESTWARD ACROSS THE SOUTH CHINA SEA. THE CENTER
REMAINS PARTIALLY OBSCURED BY THE ASSOCIATED CONVECTIVE ACTIVITY,
WHICH HAS BEEN PERSISTING OVER THE LAST 6 HOURS. THE INITIAL
POSITION IS THEREFORE PLACED WITH MEDIUM CONFIDENCE BASED ON THE
AVAILABLE VISIBLE AND INFRARED IMAGERY. AGENCY FIXES ARE IN GOOD
AGREEMENT WITH THE CURRENT POSITION. INITIAL INTENSITY OF 25 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY AND OBJECTIVE
INTENSITY ESTIMATES LISTED BELOW.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 172030Z
   CIMSS AIDT: 34 KTS AT 172030Z
   CIMSS D-MINT: 24 KTS AT 172153Z
   CIMSS D-PRINT: 25 KTS AT 180020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

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: A SHORTWAVE TROUGH TO THE NORTH HAS GIVEN TD
23W ROOM TO CONTINUE TRACKING NORTHWESTWARD ACROSS THE SOUTH CHINA
SEA WHILE ATTEMPTING TO REGAIN A MORE WELL-DEFINED CIRCULATION. AS
IT APPROACHES LAND, THE SUBTROPICAL RIDGE WILL BUILD BACK IN
CAUSING THE SYSTEM TO PROCEED ALONG A MORE WESTWARD TRACK.
CONDITIONS CONTINUE TO LOOK MARGINALLY FAVORABLE WITH WARM (29-30
C) SEA SURFACE TEMPERATURES (SST), LOW (10-15 KTS) VERTICAL WIND
SHEAR (VWS) AND MODERATE POLEWARD AND EQUATORWARD OUTFLOW. WHILE TD
23W IS NOT EXPECTED TO REDEVELOP INTO A WELL-DEFINED FEATURE, IT IS
EXPECTED TO REACH A PEAK OF 40-45 KTS WITHIN THE NEXT 12-24 HOURS.
LANDFALL IS EXPECTED TO OCCUR JUST NORTHEAST OF HONG KONG, WITHIN
36-48 HOURS, AND TD 23W IS FORECAST TO DISSIPATE OVER LAND BY THE
END OF THE CURRENT FORECAST PERIOD.

MODEL DISCUSSION: MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON A
CONTINUED NORTHWESTWARD TRACK AND A PEAK INTENSITY OF 35-45 KTS.
CROSS-TRACK SPREAD AT TAU 12 IS MEASURED AT 75 NM AND EXPANDS TO
APPROXIMATELY 190 NM AT THE TIME OF LANDFALL, CONTRIBUTING TO
INCREASED UNCERTAINTY, ALTHOUGH MOST MEMBERS ARE NOW COMING TO A
CONSENSUS ON LANDFALL NORTHEAST OF HONG KONG. INTENSITY GUIDANCE
REMAINS FAIR WITH MINIMAL VARIATION AMONG THE
MULTI-MODEL CONSENSUS MEMBERS. MOST MODELS INDICATE A POTENTIAL FOR
SLIGHT INTENSIFICATION IN THE NEAR FUTURE, FOLLOWED BY RAPID
WEAKENING BEGINNING AROUND TAU 24-36, ASSOCIATED WITH THE TIMELINE
OF THE LANDFALL. THE ONLY OUTLIERS ARE DETERMINISTIC GFS AND HWRF,
WHICH PREDICT A SHARPER INCREASE IN INTENSITY OVER THE NEXT 12
HOURS, WITH MAXIMUM WIND SPEEDS OF 45-50 KTS. 

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