There is no doubt about the fact that the models are being driven crazy by the North Atlantic Oscillation or blocking. Every run deals with the magnitude and position of the rising pressures and a possible blocking high in the North Atlantic differently This creates ridiculous volatility in the weather models beyond day 7 in the long range. This of course creates chaos on the pattern and how it evolves. The last 24 hours continues to show this back and forth trend and has made coming to grips with the long term outlook extremely difficult.
The index that measures the magnitude of the North Atlantic Oscillation is off the wall negative. When the index is negative it means that pressure across the North Atlantic are higher than normal and in this case much higher than normal. Usually the N.A.O. means colder than average temperatures in the Eastern US but not always. At the moment the "block" is "east based" which favors cold air into Western Europe. There are also other factors which are favoring average temperatures in the East with quick shots of chilly air and short warm ups of a day or so with very little precipitation. This will continue through this coming weekend. We have a cold front coming with some showers Thursday night into Friday morning which won't amount to much. We also have a weak system that will develop just offshore on Sunday which could bring clouds and maybe a little rain for coastal areas. Other than that we wait until the middle of next week when the N.A.O. index begins to rise toward neutral. This could be an indication of an important change and when combined with other changes across North America, could be indicating a storm signal of some kind in the Eastern US. All of this at this point is speculative. It doesn't guarantee anything of consequence but it is something to watch...READ MORE AT http://www.meteorologistjoecioffi.com/index.php/2017/11/28/north-atlantic-oscillation-driving-models-crazy/