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.