WNP: TD 06W, Up-dated position at 21/09utc, forecast to track south of Guam within 12hours

21/09UTC. UP-DATED POSITION NEAR 11.9N 145.8E APPRX 190KM SOUTHEAST OF GUAM.

WARNING 2 ISSUED AT 21/09UTC. THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS WARNING. FORECAST DISCUSSION: TD 06W IS FORECAST TO TRACK AROUND THE SOUTHWESTERN PERIPHERY OF THE DEEP STR CENTERED FAR TO THE NORTHEAST THROUGH 36H, THEN SLOW SLIGHTLY AS IT APPROACHES THE RIDGE AXIS BY TAU 48. THE SYSTEM IS EXPECTED TO ROUND THE RIDGE AXIS BY AROUND 96H, THEN BEGIN TO ACCELERATE NORTH-NORTHEASTWARD THROUGH 120H. BY 120H, AS THE SYSTEM BEGINS TO MOVE NORTHEASTWARD, IT WILL BEGIN TO INTERACT BOTH WITH THE MEIYU BOUNDARY AND A MID-LATITUDE MAJOR SHORTWAVE TROUGH MOVING SOUTH OVER HONSHU, AND BEGIN TO TRANSITION TO AN EXTRATROPICAL SYSTEM. IN LIGHT OF THE POOR UPPER-LEVEL ENVIRONMENT AND THE SLOW DEVELOPMENT OF THE CONVECTIVE CORE, THE SYSTEM IS EXPECTED TO ONLY SLOWLY INTENSIFY OVER THE NEXT 24 HOURS. A PERIOD OF SLIGHTLY FASTER INTENSIFICATION IS EXPECTED BETWEEN 36H AND 48H AS THE SYSTEM TRACKS OVER VERY WARM, HIGH OHC WATERS WITH A SIMULTANEOUS IMPROVEMENT IN THE UPPER-LEVEL OUTFLOW PATTERN. AFTER 96H, THE COMBINATION OF DECREASING SSTS, INCREASING NORTHERLY VERTICAL WIND SHEAR AND CONVERGENT FLOW ALOFT WILL CONSPIRE TO INDUCE STEADY WEAKENING THROUGH THE REMAINDER OF THE FORECAST PERIOD// ANALYSIS CONFIDENCE: INITIAL POSITION: HIGH INITIAL INTENSITY: MEDIUM

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE VERTICAL WIND SHEAR: 5-10 KTS SST: 29-30 CELSIUS OUTFLOW: WEAK POLEWARD OTHER FACTORS: WHILE OVERALL VERTICAL WIND SHEAR VALUES ARE LOW, THE PRESENCE OF A MESOSCALE UPPER-LEVEL TROUGH IN THE VICINITY IS INDUCING SUBSIDENT FLOW ON THE SOUTHWESTERN SIDE OF THE SYSTEM WHICH IS SERVING TO ENHANCE THE IMPACT OF THE SOUTHERLY SHEAR AND INHIBIT CONVECTIVE CONSOLIDATION NEAR THE CORE OF THE SYSTEM.

MODEL DISCUSSION: OVERALL, DYNAMIC MODEL GUIDANCE SUPPORTS THE OFFICIAL FORECAST TRACK, WITH THE CENTER OF TD 06W PASSING SOUTH OF GUAM WITH A SPREAD OF 120KM AT 24H, INCREASING TO 230KM BY 48H. THE JTWC TRACK LIES ON THE POLEWARD SIDE OF THE GUIDANCE ENVELOPE THROUGH 36H, CONSISTENT WITH THE PREVIOUS SIX HOUR TRACK MOTION. FOR THE REMAINDER OF THE FORECAST PERIOD, THE JTWC TRACK LIES CLOSE TO THE ECMWF SOLUTION, WHICH ITSELF CLOSELY FOLLOWS THE MULTI-MODEL CONSENSUS MEAN. GUIDANCE SPREAD INCREASING TO 1195KM BY 120H, PRIMARILY DUE TO INCREASED ALONG TRACK ERRORS, AS THE ECMWF FAR OUTPACES THE REMAINDER OF THE GUIDANCE AFTER 96H. THE GFS REMAINS A SLOW AND EASTWARD OUTLIER FOR THE DURATION OF THE FORECAST.

ANIMATED MULTISPECTRAL SATELLITE IMAGERY ILLUSTRATES A SOMEWHAT SHEARED DEPICTION, WITH THE OUTER BANDS OF THE LOW LEVEL CIRCULATION CENTER EVIDENT IN THE SOUTHWESTERN QUADRANT AND DEEP PERSISTENT CONVECTION ISOLATED TO THEN NORTHEASTERN QUADRANT.

210335Z AMSR2 89GHZ MICROWAVE IMAGE SHOWED THE CURVED CONVECTIVE BANDS EXTENDING FURTHER AROUND THE WESTERN SIDE OF THE LOW LEVEL CIRCULATION CENTER, PRIOR TO THE ONSET OF SOME ADDITIONAL SOUTHERLY WIND SHEAR, WHICH HAS SINCE MOVED THE CONVECTION OFF THE CENTER TO THE NORTHEAST.

THE JTWC IS ISSUING 6HOURLY WARNINGS AND 3HOURLY SATELLITE BULLETINS ON 06W.