WDPN31 PGTW 090900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (LIONROCK) WARNING 
NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 20.0N 109.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 206 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). A BROAD RAIN BAND ALSO EXTENDS EASTWARD AND
SOUTHEASTWARD OF THE LLC. THE INITIAL POSITION IS PLACED WITH
MEDIUM CONFIDENCE BASED ON AN LLC FEATURE IN A COMPOSITE RADAR LOOP
FROM CMA THAT HAS TRACKED ACROSS NORTHERN HAINAN AND HAS EXITED
INTO THE GULF OF TONKIN. THE INITIAL INTENSITY OF 35KTS IS ASSESSED
WITH MEDIUM CONFIDENCE FROM THE MAJORITY OF AGENCY AND AUTOMATED
DVORAK ESTIMATES. ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH
LOW VWS, STRONG POLEWARD OUTFLOW, AND VERY WARM 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: T2.5 - 35 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 090540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS LIONROCK WILL CONTINUE ON ITS CURRENT TRACK
UP TO TAU 12. AFTERWARD, AS THE STR BUILDS AND EXTENDS WESTWARD,
THE STORM WILL TRACK MORE WESTWARD THEN SOUTHWESTWARD, MAKING
LANDFALL OVER NORTHERN VIETNAM SOUTHEAST OF HANOI JUST AFTER TAU
24. THE FAVORABLE ENVIRONMENT WILL FUEL INTENSIFICATION TO A PEAK
OF 40KTS AT TAU 12. AFTERWARD, INTERACTION WITH VIETNAM AND ITS
RUGGED TERRAIN WILL GRADUALLY THEN RAPIDLY ERODE THE SYSTEM TO
DISSIPATION BY TAU 48 AS IT CROSSES INTO CAMBODIA.  

MODEL DISCUSSION: NUMERICAL MODELS ARE IN GENERAL AGREEMENT WITH
THE FORECAST TRACK WITH SIGNIFICANT SPREADING AFTER LANDFALL,
LEADING 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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