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Jeff Masters is looking at the same information the rest of us are looking at. The 850mb chart at 96 hours shows this system in the SW Gulf of Mexico where it could be picked up by the latter shortwave associated with the surface cold front. The GFS loses it after 5 days and judging by the data I've looked at this afternoon this tropical system for the moment isn't projected to be that strong. It simply is unclear whether this system will take on a baroclinic low or a separate tropical identity. It's been somewhat dry of late over the SE USA as the region has been under NW flow aloft courtesy of the mid-continental ridge further west with troughing over the Eastern USA which has been commonplace throughout once again this tropical season making the upper level uninhabitable for tropical systems to its east. But as we roll towards autumn the westerlies begin to shift further southward and of course more major shortwaves and thus more cold fronts. Courtesy of WPC Extended Forecast Discussion - THE 17/00Z CYCLE DETERMINISTIC GFS/ECMWF AND CANADIAN WERE IN REASONABLE AGREEMENT AT THE SURFACE ACROSS NORTH AMERICA UNTIL DAY 5 WITH THIS 'PROCESSION' OF CYCLONES AND THEIR ATTENDANT COLD FRONTS TRACKING ACROSS SOUTHERN CANADA AND THE NORTHERN TIER STATES FROM OREGON TO MASSACHUSETTS (IN A GENERAL SENSE ALONG/NORTH OF 40N LATITUDE). THE DIFFERENCES CROP UP ALONG THE SOUTHERN EDGES OF THE FRONTAL BOUNDARIES SEEPING SOUTHWARD OVER THE SOUTH CENTRAL PLAINS AND SOUTHERN MID-ATLANTIC STATES...AND THE COMPLEX TIMING AND THERMAL INTERACTION OF MID-LEVEL ENERGY SHEARING EASTWARD OUT OF THE CENTRAL ROCKIES. CONVERSELY...THE EAST COAST FORECAST CHALLENGE IS--HOW FIRMLY THESE COLD FRONTS CAN DELINEATE THE 'CONTINENTAL' AIRMASS FROM THE MARITIME SUBTROPICAL AIRMASS IN THE SOUTHEAST? ALONG THIS BENT...WILL THE FRONTAL PROGRESSION BE SUFFICIENT TO 'AGITATE' A BROAD CYCLONIC LOW-LEVEL FLOW REGIME ANCHORED ACROSS MUCH OF THE CENTRAL GULF OF MEXICO AND NORTHWEST CARIBBEAN? THAT SAID... THE DETERMINISTIC GFS AND ECMWF WERE GENERALLY GOOD FORECAST 'AIDS' IN DETERMINING THE STRUCTURE OF WEAK DISTURBANCES IN THE TROPICAL GULF OF MEXICO AND CARIBBEAN. AM ANTICIPATING THAT SOME INTERACTION IS LIKELY THIS MEDIUM RANGE FORECAST WITH THE REMNANT/DECAYING FRONTAL BOUNDARY (DAY 5 THROUGH DAY 7) ALONG THE NORTHERN GULF. |