WDPN33 PGTW 292100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 11W (CO-MAY) WARNING NR 
028//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 29.3N 122.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 135 NM SOUTH-SOUTHEAST OF SHANGHAI, CHINA
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED SATELLITE IMAGERY (EIR) DEPICTS A SOMEWHAT
ELONGATED LLCC WITH MULTIPLE EDDIES ROTATING AROUND A COMMON
CENTROID. DEEP CONVECTION REMAINS CONFINED WEST AND NORTH OF THE
LLCC DUE TO CONTINUING LIGHT TO MODERATE SOUTHEASTERLY VERTICAL
SHEAR, COUPLED WITH A DEEPLY DRY AIR MASS TO THE SOUTH. CONVECTION
HAS BEEN BUILDING CYCLONICALLY INTO THE SOUTHWESTERN QUADRANT BUT
HAS NOT YET ROTATED SIGNIFICANTLY UPSHEAR. SLIGHT VORTEX TILT
WESTWARD WITH HEIGHT IS EVIDENT IN ANIMATED SHORTWAVE INFRARED
IMAGERY. THE INITIAL INTENSITY IS SET AT 40 KT BASED ON 291318Z
ASCAT DATA, SUPPORTED BY A BLEND OF OBJECTIVE SATELLITE-DERIVED
INTENSITY ESTIMATES.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: DEEP-LAYER RIDGE OVER JAPAN

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RCTP: T2.0 - 30 KTS
   CIMSS SATCON: 44 KTS AT 291259Z
   CIMSS ADT: 37 KTS AT 291740Z
   CIMSS AIDT: 42 KTS AT 291740Z
   CIMSS D-PRINT: 49 KTS AT 291740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY AIR MASS IN SOUTHERN SEMICIRCLE

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

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, MAKING LANDFALL IN THE ISLANDS
SOUTHEAST OF SHANGHAI, CHINA WITHIN THE NEXT 12 HOURS, THEN
CROSSING HANGZHOU BAY AND MOVING INTO SHANGHAI THEREAFTER. LITTLE
OR NO CHANGE IN INTENSITY IS EXPECTED IN THE REMAINING HOURS PRIOR
TO LANDFALL DUE TO A STILL ASYMMETRIC AND ELONGATED STRUCTURE,
CAUSED BY PERSISTENT SOUTHEASTERLY VERTICAL SHEAR AND DRY AIR IN
PROXIMITY TO THE SOUTH SIDE. A COMPLETE INNER CONVECTIVE CORE HAS
NOT YET DEVELOPED, WHICH SUGGESTS THE CYCLONE WILL STRUGGLE TO
INTENSIFY IN ITS REMAINING TIME OVER WATER. STEADY WEAKENING WILL
OCCUR ONCE CO-MAY MOVES INLAND. DYNAMICAL TRACK MODELS ARE IN
AGREEMENT ON THE INITIAL NORTHWESTWARD TRACK INLAND OVER THE NEXT
36 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. SOME MODELS
SUGGEST A SMALL CHANCE OF THE REMNANTS RE-EMERGING OFFSHORE IN THE
YELLOW SEA BEYOND 72 HOURS, BUT FOR NOW, THE JTWC FORECAST
TERMINATES AT 48 HOURS WHEN 11W IS EXPECTED TO WEAKEN BELOW WARNING
CRITERIA.

MODEL DISCUSSION: THE JTWC TRACK FORECAST IS CLOSE TO THE
MULTI-MODEL CONSENSUS FOR THE FIRST 24 HOURS, THEN SLIGHTLY NORTH
OF THE CONSENSUS THEREAFTER. THE JTWC INTENSITY FORECAST IS CLOSE
TO THE MULTI-MODEL CONSENSUS.

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