WDPN31 PGTW 082100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (LIONROCK) WARNING 
NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 19.5N 110.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 234 NM NORTH-NORTHEAST OF DA NANG, VIETNAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING LOW-LEVEL CIRCULATION (LLC) WITH IMPROVED CONVECTIVE
BANDING. A 081823Z ATMS 88.2GHZ IMAGE INDICATES THE CONVECTIVE
STRUCTURE MOVED TO THE NORTHWEST SIDE OF THE LLC POSITIONED OVER
CENTRAL HAINAN ISLAND. SURFACE OBSERVATIONS OVER HAINAN ISLAND ARE
WEAK WITH A MINIMUM SLP OF 994MB NEAR THE CENTER AT DANXIAN,
HAINAN. OVERALL, THERE IS HIGH CONFIDENCE IN THE INITIAL POSITION
BASED ON THE EIR AND RADAR IMAGERY. THERE IS HIGH CONFIDENCE IN THE
INITIAL INTENSITY BASED ON AN AVERAGE OF THE RJTD, RCTP DVORAK
INTENSITY ESTIMATES AND THE LATEST CIMSS SATCON ESTIMATE.
ENVIRONMENTAL CONDITIONS REMAIN FAVORABLE WITH STRONG POLEWARD AND
EQUATORWARD OUTFLOW, AND LOW TO MODERATE VERTICAL WIND SHEAR.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: TS 22W IS TRACKING ALONG THE SOUTHWEST
PERIPHERY OF A LOW- TO MID-LEVEL SUBTROPICAL RIDGE POSITIONED TO
THE NORTH AND NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.5 - 35 KTS
   RCTP: T2.5 - 35 KTS
   CIMSS SATCON: 48 KTS AT 081821Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: OVER LAND
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: INTERACTION WITH LAND

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 22W IS CONTINUING TO TRACK SLOWLY
WEST-NORTHWESTWARD THROUGH TAU 12 AS IT CONTINUES TO TRACK OVER
HAINAN ISLAND. AFTER TAU 12, THE SYSTEM WILL BEGIN TO INTENSIFY TO
40KTS AS IT MOVES OUT OVER THE WARM WATERS IN THE GULF OF TONKIN.
THE SYSTEM WILL CONTINUE TO TURN WEST-NORTHWESTWARD AND THEN
WEST-SOUTHWESTWARD THROUGH TAU 36. HOWEVER, INCREASING VERTICAL
WIND SHEAR OVER THE GULF OF TONKIN SHOULD HAMPER SIGNIFICANT
DEVELOPMENT AND THE LAND INTERACTION WILL BEGIN TO SLIGHTLY
DECREASE INTENSITY JUST BEFORE LANDFALL BETWEEN TAU 36 AND 48. TS
22W WILL CONTINUE TRACKING WEST-SOUTHWESTWARD THROUGH NORTHERN
VIETNAM AND LAOS WITH DISSIPATION EXPECTED NEAR OR BEFORE TAU 72.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE IS IN FAIR AGREEMENT 
AFTER LIONROCK ENTERS THE GULF OF TONKIN. THE MODEL GUIDANCE 
INDICATES A CROSS TRACK SPREAD AT 86NM ONCE IT MOVES OUT OVER WATER, 
WITH NAVGEM THE FAR LEFT OUTLIER AND UKMET AS THE FAR RIGHT. AFTER 
TAU 36 GFS AND NAVGEM BECOME THE FAR LEFT OUTLIERS WITH UKMET AND 
ECMWF REMAINING FAR RIGHT OF CONSENSUS LENDING TO MEDIUM CONFIDENCE 
TO THE JTWC FORECAST TRACK. THE JTWC FORECAST TRACK IS POSITIONED 
NEAR THE MULTI-MODEL CONSENSUS (CONW). INTENSITY GUIDANCE INDICATES 
A PEAK RANGING FROM 35 TO 40 KNOTS THROUGH THE REMAINDER OF THE 
FORECAST PERIOD.

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