WDPN33 PGTW 300300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY) WARNING NR 
029//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.0N 122.3E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 83 NM SOUTH-SOUTHEAST OF SHANGHAI, CHINA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND RADAR IMAGERY
DEPICT A MORE SYMMETRIC CIRCULATION STRUCTURE THAN SIX HOURS AGO,
THOUGH DEEP CONVECTION REMAINS LIMITED IN THE EASTERN SEMICIRCLE
DUE TO A DRY AIR MASS WRAPPING INTO THE CIRCULATION. 11W IS NOW
MAKING LANDFALL NEAR ZHOUSHAN, CHINA. SURFACE OBSERVATIONS ALONG
THE COASTLINE AND OFFSHORE INDICATE THAT MAXIMUM SUSTAINED WINDS
REMAIN AROUND 40 KT.

INITIAL WIND RADII BASIS: SURFACE OBSERVATIONS AND PERSISTENCE

CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS ADT: 34 KTS AT 292030Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: TROPICAL STORM 11W (CO-MAY) IS EXPECTED TO
CONTINUE MOVING NORTHWESTWARD IN RESPONSE TO AN ENTRENCHED
DEEP-LAYER RIDGE OVER JAPAN, MOVING INLAND OVER CHINA IN THE
VICINITY OF SHANGHAI. STEADY WEAKENING WILL COMMENCE ONCE CO-MAY
MOVES FULLY INLAND. DYNAMICAL TRACK MODELS ARE IN AGREEMENT ON THE
INITIAL NORTHWESTWARD TRACK INLAND OVER THE NEXT 36 TO 48 HOURS,
BUT SPREAD SIGNIFICANTLY THEREAFTER AS THE STORM SLOWS DUE TO A
LONGWAVE TROUGH PASSING BY TO ITS NORTH. THE TROUGH WILL NOT DIG
SOUTHWARD ENOUGH TO CLEANLY PICK UP THE CYCLONE'S REMNANTS,
INCREASING UNCERTAINTY IN THE TRACK BEYOND 48 HOURS. MODELS SHOW AN
INCREASING CHANCE OF THE REMNANTS RE-EMERGING OFFSHORE IN THE
YELLOW SEA BEYOND 72 HOURS, BUT THE MAJORITY FAIL TO REGENERATE
INTO A SIGNIFICANT TROPICAL CYCLONE. THE JTWC FORECAST TERMINATES
AT 48 HOURS WHEN 11W IS EXPECTED TO WEAKEN BELOW WARNING CRITERIA.

MODEL DISCUSSION: THE JTWC TRACK AND INTENSITY FORECASTS ARE BOTH
CLOSE TO THE MULTI-MODEL CONSENSUS. MODEL SPREAD HAS TIGHTENED
DURING THE FORECAST PERIOD RELATIVE TO THE PREVIOUS FORECAST.

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