Western North Pacific: TD 06W is still forecast to intensify next 72hours, 23/03utc update

WARNING 9 ISSUED AT 23/03UTC.FORECAST DISCUSSION: TROPICAL DEPRESSION (TD) 06W CONTINUES TO TRACK NORTHWESTWARD AROUND THE PERIPHERY OF THE SUBTROPICAL RIDGE TO THE NORTHEAST. A TURN TOWARD THE NORTH BY 48 HOURS AND THEN NORTHEAST BY 72 HOURS AND MODERATE ACCELERATION IS EXPECTED AS THE CYCLONE ROUNDS THE RIDGE NEAR THE BAIU FRONTAL BOUNDARY SOUTHEAST OF JAPAN. THE JTWC INTENSITY FORECAST ASSUMES THAT THE VORTEX WILL BE ABLE TO MIX OUT THE DRY AIR IN A LOW SHEAR ENVIRONMENT DURING THE NEXT 36-48 HOURS, AS SUGGESTED BY THE HWRF AND GFS MODELS, ALLOWING MODEST INTENSIFICATION DURING THE 36-72 HOUR PERIOD TO A PEAK OF AROUND 60 KNOTS. MODERATE NORTHERLY SHEAR AFTER 36 HOURS IS EXPECTED TO BE A LIMITING FACTOR, ESPECIALLY GIVEN THE CYCLONE'S SMALL SIZE, WHICH MAKES IT MORE SUSCEPTIBLE TO SHEAR. THE TIMING ULTIMATELY WILL BE THE HARDEST TO ASCERTAIN WITH ANY CLARITY UNTIL THE SYSTEM IS INFLUENCED BY THE BOUNDARY. THE CYCLONE'S FORWARD SPEED WILL VARY LARGELY IN PART DUE TO THE SENSITIVITY OF TIMING AND POSITION OF THE DEEP-LAYER STEERING FLOW BETWEEN THE SUBTROPICAL RIDGE AND THE BAIU FRONT. THE INTENSITY FORECAST ALSO DEPENDS ON THIS EVOLUTION. EVENTUAL ABSORPTION INTO THE BAIU BOUNDARY REMAINS MOST PLAUSIBLE ALONG WITH THE ASSOCIATED TRANSITION DUE TO COOLER SEA SURFACE TEMPERATURES (SSTS) AND INCREASED SHEAR, LEADING TO A RAPID EXTRATROPICAL TRANSITION BEGINNING AROUND 96H THROUGH 120H.

MODEL DISCUSSION: THE SYSTEM'S ALONG-TRACK FORWARD SPEED DURING THE 72-120 HOUR VARIES EXTREMELY IN THE MODEL GUIDANCE DURING THE EXTENDED FORECAST, WITH THE VARIANCE BETWEEN NAVGEM AND GFS AT WELL OVER 1575 KM BY 120H. THE JTWC TRACK FORECAST LIES CLOSE TO THE MULTI-MODEL CONSENSUS, BETWEEN THE LEFTWARD, SLOW ECMWF ENSEMBLE AND THE RIGHTWARD, FAST GFS. THE JTWC INTENSITY FORECAST IS SLIGHTLY BELOW THE MULTI-MODEL CONSENSUS THROUGH 48 HOURS, THEN CLOSE TO CONSENSUS THEREAFTER.

22/18UTC. HWRF INTENSITY GUIDANCE: 69KNOTS AT +84H.

23/0247UTC. SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION: ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES A CENTRAL COLD COVER (CCC) HAS COMPLETELY OBSCURED THE LOW-LEVEL CENTER (LLC) UNDER A MASS OF CONVECTION. A 222055Z SSMIS 91GHZ MICROWAVE IMAGE SHOWS NO ORGANIZED STRUCTURE TO THE MID-LEVEL VORTEX REMAINS SLIGHTLY DISPLACED FROM THE LLC WITH A SW TO NE TILT. THE EMBEDDED LLC UNDER THE CCC IS INDICATIVE OF SLOW GROWTH FOR THE SYSTEM. THE ENVIRONMENT REMAINS MARGINALLY FAVORABLE WITH DRIER AIR TO THE WEST, ALONG WITH WEAK RADIAL OUTFLOW ALOFT. THE CONVECTIVE STRUCTURE HAS IMPROVED SLIGHTLY OVER THE NORTHWEST AND NORTHEAST SECTOR OF THE LLC AS SEEN ON THE LATEST MSI. HOWEVER, THE DRY AIR TO THE WEST WILL CONTINUE TO ALLOW ONLY SLOW DEVELOPMENT.

23/0048UTC. ASCAT READ 30KNOT WINDS.

23/00UTC.24H SHEAR TENDENCY.UW-CIMSS Experimental Vertical Shear and TC Intensity Trend Estimates: CIMSS Vertical Shear Magnitude : 1.0 m/s (1.9 kts)Direction : 343.8deg Outlook for TC Intensification Based on Current Env. Shear Values and MPI Differential: VERY FAVOURABLE OVER 24H.

SLIGHTLY IMPROVED RADIAL OUTFLOW.

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

23/00UTC.

23/00UTC.