If you look closely at the nao ensemble forecast and you discount the single most positive ensemble member, you'll see all the others are steeply inclining or dropping from the 13th on. This movement of the nao from a much more neutral area, to either negative territory or back up is a sign that this is a time period that has to be watched.
What John said, models are guidance! When I see the models pumping up up a ridge out west with blocking near Greenland(especially a little west of there) I pay attention. You have to look at the entire pattern, not just just model run to model run verbatim.
This current pattern will cycle thru much like the mild wet cycles
were doing most of this season.
The big difference now is the systems are cold snow events, this is a sign a transition has already taken place, so anything goes with the clippers cycling in and out.
The Nao abruptly plateau's and is declining during a particularly busy pattern. This is when we can get the big one out of nowhere, winter is gonna happen, the models have to figure it out, we have not been here with this pattern this year, yet.
What I'm trying to say is you have to use your skills as a meteorologist or as a forecaster, in tandem with the guidance you get from the models, guidance being the operative word. Anyone who relies of the models will be wrong, just as anyone who does not know the fundamentals of meteorology will not do very well, no matter the performance of the models.
John, tell me im wrong, have the models been correct on any storm past 7 days for us this year. Hell no, not even close, they either over amp it, turn it to rain or loose it completely, not one storm has been nailed this year that far out.
Tim; with technology and computer guidance that was significantly inferior to what we have now the blizzard of '93 was seen coming 10-15 days out, how do you suppose that happened if they were of no use past a few days?
phillywhiteout, the models were picking up on something on several occasions back in early Jan and it never happened. You cant look at long range models anymore, none of them are reliable. Look at models 2 days out then we will find out what's happening until then, I don't care what the models show.
I hear you John, but I couldn't even begin to count the number of times I have seen a big time snowstorm for us near philly on the long range of the GFS and then it just never comes. I would only be excited if it was showing a bomb a couple days out.
Tim; first to answer a question you had asked, "Isn't the 540 line over us meaning any precip would be rain." Yes the 540 line is over us and no it would not be rain, a system of this magnitude in this position would be manufacturing it's own cold air via strong vertical motion mixing it down from the upper levels and keeping it all snow. Also, we all know that this is a 312 hr forecast, it's more for conversation then planning a wedding around. The key here Tim, is that several of us have been mentioning the pattern becoming conducive for something like this for weeks, at the 300 and beyond marker (present tense-future forecast) and to see it show up on operational guidance, even if it is for one run then gone then back (which will likely be the case) is a good sign that we were on the right track.
Tim it was too early to get excited and its too early to say it won't happen either. We shouldn't really look at it for at least a week if not more. The models are so crazy right now because of all the clippers and shots of light snow we have been getting.