WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 09W (IN-FA) WARNING NR 
038//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.1N 122.0E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 71 NM SOUTH-SOUTHEAST OF SHANGHAI, CHINA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 25 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY SHOWS THE CORE
OF TROPICAL STORM 09W (IN-FA) MOVING ASHORE SOUTH OF SHANGHAI,
CHINA. THE WIND DIRECTION AT DINGHAI RECENTLY SHIFTED FROM NORTH TO
SOUTH-SOUTHEAST AS THE EYE PASSED OVER, INDICATING THAT IN-FA IS
NOW CENTERED JUST WEST OF THERE. THE CYCLONE'S CORE CONVECTIVE
STRUCTURE HAS CONTINUED TO BECOME MORE COMPACT DURING THE PAST SIX
HOURS, BUT SURFACE OBSERVATIONS INDICATE THAT THE GALE-FORCE WIND
FIELD REMAINS EXPANSIVE. THE INITIAL INTENSITY IS HELD AT 55 KT IN
GENERAL AGREEMENT WITH A BLEND OF AGENCY DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: BLEND OF PERSISTENCE AND AVAILABLE
SURFACE OBSERVATIONS

CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER THE SEA OF JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RCTP: T4.0 - 65 KTS
   CIMSS ADT: 39 KTS AT 250840Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 09W (IN-FA) WILL SLOWLY TRACK
INLAND OVER EASTERN CHINA DURING THE NEXT 72 HOURS AS STEERING
CURRENTS WEAKEN. BROAD UPPER-LEVEL TROUGHING OVER MONGOLIA IS
EXPECTED TO INDUCE A GRADUAL TURN TOWARD THE NORTH OR NORTHEAST
AFTER 72 HOURS, POTENTIALLY BRINGING THE CIRCULATION OUT OVER THE
WESTERN SIDE OF THE YELLOW SEA. THE JTWC FORECAST REMAINS JUST
INLAND THROUGH 120 HOURS, CLOSE TO THE MULTI-MODEL CONSENSUS. THE
CYCLONE WILL BE MOVING OVER MOSTLY FLAT TERRAIN, AND WITHOUT
SIGNIFICANT BAROCLINIC INTERACTION DURING THE FORECAST PERIOD, A
COHERENT CIRCULATION IS FORECAST TO PERSIST FOR SEVERAL DAYS OVER
EASTERN CHINA BY MOST DYNAMICAL MODEL GUIDANCE. THE JTWC FORECAST
THUS MAINTAINS IN-FA AS A TROPICAL CYCLONE FOR THE FULL 120-HOUR
FORECAST PERIOD. IF THE CIRCULATION MOVES OUT OVER THE YELLOW SEA,
SOME RESTRENGTHENING WOULD BE POSSIBLE. THE CURRENT JTWC INTENSITY
FORECAST ASSUMES THAT THE CIRCULATION WILL REMAIN OVER LAND
THROUGH
120 HOURS.

MODEL DISCUSSION: THE MULTI-MODEL CONSENSUS SHIFTED SLIGHTLY
SOUTHWARD FOR THE FIRST 48 HOURS COMPARED TO SIX HOURS AGO. THE
JTWC FORECAST REMAINS CLOSE TO THE TRACK CONSENSUS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
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