WDPN32 PGTW 021500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (SAOLA) WARNING NR 
040//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.9N 110.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 262 NM EAST-NORTHEAST OF HANOI, VIETNAM
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: XX FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 09W (SAOLA) CONTINUES TO TRACK INLAND OVER SOUTHERN
CHINA, WHILE STEADILY AND RAPIDLY WEAKENING. ANIMATED ENHANCED
INFRARED (EIR) SATELLITE IMAGERY CONTINUES TO SHOW THE UPPER-LEVEL
CIRCULATION CENTER ASSOCIATED WITH TS 09W MOVING WESTWARD.
MEANWHILE, A 021010Z SSMIS MICROWAVE IMAGER PASS SHOWS A REMNANT
EYE FEATURE ON THE SOUTHERN SIDE OF A LARGE MASS OF DEEP
CONVECTION. THIS DEPICTION MATCHES UP WITH THE ANIMATED RADAR DATA
WHICH DEPICTS THE LOW-LEVEL CIRCULATION CENTER JUST A SHADE FURTHER
SOUTH. A MELD OF THE MICROWAVE AND RADAR DATA PROVIDES MEDIUM
CONFIDENCE TO THE INITIAL POSITION. THE INITIAL INTENSITY IS
ASSESSED WITH LOW CONFIDENCE. DUE TO A DEARTH OF INTENSITY
ESTIMATES FOR A SYSTEM OVER LAND. THE ONLY INTENSITY ESTIMATES
AVAILABLE INCLUDE THE DPRINT AND DMINT, BOTH OF WHICH WERE 40 KNOTS
AT 1200Z. SOUTHEASTERLY SHEAR REMAINS RELATIVELY HIGH, WHICH
COMBINED WITH THE NEGATIVE IMPACT OF TERRAIN INTERACTION, MORE THAN
OFFSETS ANY POSITIVE SUPPORT PROVIDED BY THE ROBUST POLEWARD
OUTFLOW CHANNEL.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHEASTERN PERIPHERY OF A LOW TO
MID-LEVEL RIDGE OVER CENTRAL CHINA. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RCTP: T4.0 - 65 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 15-20 KTS
   SST: OVER LAND
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: DESPITE A RECENT JOG A BIT FURTHER NORTH THAN
ANTICIPATED, TS 09W IS STILL EXPECTED TO TURN MORE WEST AND
ULTIMATELY SOUTHWEST OVER THE NEXT 12 TO 24 HOURS, EMERGING INTO
THE GULF OF TONKIN AROUND TAU 12. THE SYSTEM WILL SLOWLY DRIFT
SOUTHWESTWARD BEFORE ROUNDING THE WESTERN SIDE OF HAINAN ISLAND BY
THE END OF THE FORECAST PERIOD. THE SYSTEM IS WEAKENING AT A FASTER
PACE THAN ORIGINALLY ANTICIPATED BUT IS STILL LIKELY TO EMERGE INTO
THE GULF OF TONKIN AS A WEAK TROPICAL STORM. HOWEVER, WHILE SSTS
ARE VERY WARM IN THE GULF, THE LACK OF MUCH, OR ANY, UPPER-LEVEL
OUTFLOW AND THE ENVELOPMENT OF THE CIRCULATION IN DRY AIR MEANS
THAT IT WILL NOT BE LONG FOR THIS WORLD. THE SYSTEM STEADILY
WEAKENS THROUGH THE FORECAST PERIOD, BEFORE DISSIPATING AS A
TROPICAL CYCLONE OFF THE SOUTHWEST COAST OF HAINAN BY TAU 72. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS STILL SOMEWHAT
SPLIT BETWEEN THE EUROPEAN MODELS AND THE US MODELS PLUS THE
ENSEMBLE MEANS. THE ECMWF AND EGRR TRACKERS INSIST ON TAKING THE
SYSTEM STRAIT SOUTHWEST TO A VIETNAM LANDFALL AROUND TAU 72, AND
QUICK DISSIPATION THEREAFTER. THE REMAINDER OF THE CONSENSUS
MEMBERS INCLUDING THE GFS AND THE GEFS AND ECENS ENSEMBLE MEANS,
TRACK THE SYSTEM CLOSER TO HAINAN ON A BROADLY CURVING TRACK BEFORE
SHIFTING TO A QUASI-STATIONARY MOTION AROUND TAU 72 AS THE SYSTEM
DISSIPATES. THE JTWC FORECAST IS CONSISTENT WITH THE BULK OF THE
MODEL GUIDANCE WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN
GOOD AGREEMENT THAT THE SYSTEM WILL WEAKEN TO TAU 24, THEN HOLD
STEADY FOR A BRIEF PERIOD, BEFORE DISSIPATING BY TAU 72. HOWEVER,
UNCERTAINTY IN THE INTENSITY OF THE SYSTEM AS IT MOVES BACK OVER
WATER GENERATES MEDIUM CONFIDENCE IN THE JTWC FORECAST. 

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