WDPN31 PGTW 092100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (LIONROCK) WARNING 
NR 011//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.2N 108.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 164 NM EAST-SOUTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 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 OFFSET WESTWARD OF THE LOW LEVEL
CIRCULATION (LLC). THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON AN LLC FEATURE IN A COMPOSITE RADAR LOOP FROM
CMA AND AN OBSERVATION FROM BACH LONG VI ISLAND, VIETNAM. 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, STRONG
POLEWARD OUTFLOW, AND VERY WARM (28-30C) 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: 34 KTS AT 091900Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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 CONTINUE TURNING TOWARDS THE WEST
AS THE STEERING STR BUILDS AND EXTENDS WESTWARD, THE STORM WILL
TRACK MORE SOUTHWESTWARD BY TAU 24. THE FAVORABLE ENVIRONMENT WILL
FUEL INTENSIFICATION TO A PEAK OF 40KTS AT TAU 12. AS THE SYSTEM
MOVES SOUTHWEST IT WILL BEGIN TO EXPERIENCE A SLIGHT INCREASE IN
VWS DECREASE IN INTENSITY JUST BEFORE LANDFALL SHORTLY AFTER TAU
24. THEREAFTER, LIONROCK WILL MOVE OVER LAND AND INTERACT WITH THE
RUGGED TERRAIN AND DISSIPATE BY BETWEEN TAU 36 AND 48 AS IT CROSSES
THROUGH LAOS AND CAMBODIA.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GENERAL AGREEMENT WITH
THE FORECAST TRACK. NAVGEM REMAINS THE FAR LEFT OUTLIER, WHILE GFS
IS THE FAR RIGHT. THE CROSS TRACK ONLY GAINS TO A MAXIMUM SPREAD OF
68NM 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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