It was a picturesque overnight snowfall, coating the trees and lawns and rooftops without causing much disruption to the morning commute. Alas, the East Coast won’t be so lucky. That same trough, coupled with Sandy, is going to be very disruptive. Take it away, Angela Fritz, filling in for Dr. Jeff Masters:
Sandy’s appearance on satellite is a bit ragged this afternoon as it approaches very high wind shear (40-50 knots). The hurricane is obviously already undergoing structural changes this afternoon, caused in part by an upper level low over western Cuba. This low is prohibiting Sandy’s outflow on the west side, and as a result, the storm appears asymmetrical with a large area of outflow and circulation to the north, and only a tail of circulation on the southeast of the hurricane. Visually, Sandy is a huge storm. Based on clouds alone, Sandy stretches from Jacksonville, Florida, east to Bermuda, and south to the southern Caribbean Sea. Sandy’s radius of outer closed isobar is 350 miles, though tropical storm-force winds only extend around 200 miles from the center. …
As Sandy moves north, it will grow larger and the hurricane’s energy will spread out even more, which will lead to a slight decrease in maximum wind speed. Models agree on this steady decrease in intensity over the next few days, though beyond that, the intensity forecast is still in question since Sandy could begin to gain non-tropical energy as it transitions into a non-tropical storm. The track through Saturday evening remains well understood by the models: Sandy will move north with a slight turn to the west before being yanked north-northeast again by the approaching mid-latitude trough. It’s at this point in the forecast that the models diverge, though all but the HWRF are forecasting the unfortunate turn back to the west and into the Northeast U.S. Furthest south along the East Coast is the ECMWF, which forecasts a turn into Maryland/North Carolina on Monday. The GFS forecast is a bit further north than the ECMWF, pushing Sandy onshore near Long Island late Tuesday night. However, this represents a large shift south from earlier GFS runs, and puts the Mid-Atlantic into play more than it was in earlier forecasts. [NOTE: The GFS has now shifted further, to a northern New Jersey landfall, as shown at the top of this post.] The forecast from the National Hurricane Center appears to be a compromise between the ECMWF and the GFS. The Center is forecasting Sandy to approach the New Jersey coast on Tuesday afternoon.
There are many questions surrounding this hurricane and its forecast, but I find it important to convey that Sandy’s impacts will be widespread, no matter the location of “landfall.” Risk to the Mid-Atlantic seems higher this afternoon, and as Jeff noted in his morning blog, Sandy will be a very large and possibly non-tropical storm as it approaches the coast, with gale-force winds extending up to 300 miles from its center. This increases the probability of storm surge extending far from the center of the storm, which, combined with the timing of a full moon tide, is a big concern, along with freshwater and river flooding from heavy, extended periods of rain.
I’d again urge you to read the whole Capital Weather Gang post, which in turn contains links to many other sources that are also worth reading.