One potential track takes Sandy, or the so-called "post-tropical remnant low" of Sandy, on an east-northeastward bend soon after leaving the Bahamas.
This would essentially keep this cyclone separate from an approaching upper-level trough in the polar jet stream and its associated surface cold front.
In this scenario, the cyclone would head toward Bermuda, or the open waters of the Atlantic Ocean, with relatively little impact along the remainder of the Eastern seaboard.
Having said that, in this scenario, a new area of low pressure could form off the New England coast early next week, bringing at least some rain to that area. This would be separate from the wrapped-up "post-Sandy" extratropical cyclone.
Another track scenario is much more ominous for the East Coast.
In this case, a so-called "blocking pattern" in the upper levels of the atmosphere over the Atlantic is so strong that it would not allow the storm to turn east into the open Atlantic, but, rather, drive northward just off the East Coast.
Furthermore, the upper-level trough in the polar jet stream we referred to above would provide an additional turbo-charged boost to this low, producing an intense, East Coast storm!
High winds, heavy rain, coastal flooding and beach erosion would ride up the Northeast seaboard early next week, in this scenario. Of course, the high winds would extend inland, with the potential for downed trees and powerlines.
This scenario could even wrap in just enough cold air on its western edge to produce wet snow, possibly heavy, in some areas of the eastern Great Lakes and Appalachians! Eerily, this would take place around the one-year anniversary of the "Snowtober" snowstorm.
Quote:
Originally posted by Bryan Norcross' Official Blog
The forecast dilemma for Sandy continues as we look ahead to the weekend and beyond. For the next few days, the center of the strengthening tropical storm and likely hurricane will move north out of the Caribbean with direct, life-threatening impacts on Jamaica, eastern Cuba, Haiti, and the Dominican Republic tomorrow into Thursday. These islands all need to move to an alert status.
It also appears likely that much of the Bahamas will get flooding and high winds Friday into Saturday, similar to Hurricane Noel in 2007, with Florida feeling fringe effects, especially along the east coast.
Then things get murky, with the two groups of computer forecast models heading in different directions... two forks in the road. Both the American GFS and the European ECMWF show the jet stream dipping down from the north and beginning to affect the storm. The GFS affects it in the traditional sense of pushing it out to sea.
The European develops a jet-stream dip of VERY unusual shape and intensity, however, which wants to grab Sandy, inject significant energy into the system, and pull it north as a MEGA nor'easter.
This is an extremely unusual pattern which yields an extreme result, but it can't be totally discounted as a possibility. The European model has been the most accurate computer model for the last few years, though it has had some spectacular misses as well.
The upper-air disturbance that is forecast to turn into the jet-stream dip that grabs or doesn't grab Sandy is still developing off of western Canada... and there are a lot of pieces to fall into place. So for now our concern is for our friends in the northern Caribbean, but we watch for developments as the northern pattern develops over the next few days.
The fork comes around Saturday, so everybody from the Mid-Atlantic to the Northeast and well inland will need to pay close attention to developments.
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