WDPN31 PGTW 100300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (LIONROCK) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.5N 107.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 89 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS AN EXPANSIVE
SYSTEM WITH THE MAIN CONVECTION OVER NORTHERN VIETNAM AND SOUTHWEST
CHINA, SLIGHTLY OFFSET FROM THE LOW-LEVEL CIRCULATION (LLC) THAT
REMAINS JUST OFFSHORE OF VIETNAM. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON AN LLC FEATURE IN A COMPOSITE RADAR
LOOP FROM CMA. THE INITIAL INTENSITY OF 35KTS IS ASSESSED WITH
MEDIUM CONFIDENCE FROM THE MULTIPLE AGENCY AND AUTOMATED DVORAK
ESTIMATES. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH LOW
(05-10KT) VWS, WEAK RADIAL OUTFLOW, AND WARM (27-29C) SSTS. THE
CYCLONE IS TRACKING ALONG THE SOUTHWESTERN PERIPHERY OF THE LOW TO
MID-LEVEL REFLECTION OF THE STR TO THE NORTHEAST.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 100040Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 27-29 CELSIUS
   OUTFLOW: WEAK RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 22W WILL BEGIN MOVING IN A MORE
WEST-SOUTHWEST TRACK AS THE STEERING STR BUILDS AND EXTENDS
WESTWARD OVER THE NEXT 12 HOURS. LIONROCK WILL CONTINUE ON THIS
TRACK AND IS NO LONGER FAVORED TO INTENSIFY AS THE WATERS NEAR THE
COAST HAVE COOLED SLIGHTLY DUE TO UPWELLING IN THE SHALLOWER
WATERS. THE INTERACTION WITH LAND HAS ALSO INHIBITED THE GROWTH
POTENTIAL AS THIS SYSTEM CONTINUES MOVING ALONG THE COAST,
EXPECTING TO MAKE LANDFALL WITHIN THE NEXT 12 HOURS. DURING THIS
TIME, THE SYSTEM WILL BEGIN THE DISSIPATION PROCESS AS IT MOVES
OVER THE RUGGED TERRAIN OF VIETNAM AND WILL COMPLETE DISSIPATION
NEAR THE LAOS BORDER BETWEEN TAUS 24 AND 36.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GENERAL AGREEMENT WITH
THE FORECAST TRACK. NAVGEM CONTINUES TO BE THE FAR LEFT OUTLIER,
WHILE GFS REMAINS ON THE FAR RIGHT OF CONSENSUS. THE CROSS-TRACK
ONLY GAINS TO A MAXIMUM SPREAD OF 41NM JUST BEFORE LANDFALL,
LENDING TO MEDIUM CONFIDENCE IN BOTH THE TRACK AND INTENSITY
FORECASTS. 

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