If you are not hardcore weather you may be asking yourself what the heck is the NAO and why is this weather signal so important to winter storms east of the Mississippi?
It's like a traffic cop of weather and when this traffic cop in Greenland slows down the weather pattern it allows for storms to develop along the east coast and it allows allows the cold air to hang around a bit longer to feed into these nor'easter beasts.
So now you may be asking does that mean less snow and cold for the winter ahead ? Well it all depends on where you live. We talked about this in our winter outlook and told you it's not one factor that decides how cold or snowy a winter will get...it's the combo and teleconnections of all of them that brings snowstorms & cold weather.
It could not resist...just kiddin on this but a funny cartoon on El Nino. So with El nino not a MAJOR factor what are we left with for the next few months ?
Well the one thing that will set this winter is the big dip in the NAO or North American Oscillation. This is known as the Greenland Block.
This is how we see the block now and at the end of DECEMBER. So what does that means for snowstorms ? Simply put...higher risk for snow along the east and maybe even the south under the right conditions.
The Arctic Oscillation is a pool of Arctic Air that comes down south when there is not a lock on the Arctic air stating north.
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@Weatherman71, I'm going to respectfully disagree. I would like to take a bet that Philly will only get 6.2 inches this year. I agree that things seem eerily similar to last year(hurricanes,earthquakes and early season snowstorm), but the pattern is much different!
Last year, we had a weak to moderate La Nina while this year there is a neutral ENSO! Last fall the NAO was positive for most of the fall season(it was only negative for the freak snowstorm at the end of October). The NAO has been predominantly negative this fall. I know the NAO is going positive now, but there are already signs of the next nagative phase. My worry for winter is in the Pacific! It seems that the PNA has been negative for much of the fall and is forecasted to be negative for the next couple of weeks. That could be a problem for snowlovers!
I think we are looking at a pretty normal winter this year. Temps will probably average out to about normal. November has a good chance of ending up below normal because we are so far below normal for the month so far. I think average temps will be the rule and slightly above average snowfall forecast makes sense at this point. As others have said, it depends how negative the NAO wants to be this winter, but early indications suggest that it will be much more negative than last winter(not saying much there).
It is all about timing here with this past storm. The unfortunate thing for those on the West Side of The Delaware River in PA was that the NAO block broke down just enough to allow this most recent Winter Storm Athena to escape to our NE.
Rob I totally agree with you with El Nino and LA Nina out we turn most of our attention to the NAO for blocking.
This will be the year that the NAO controls our winter and we will find out over the next two to three weeks in my opinion exactly what kind of a winter it will be.
I am betting on an average to above average snowfall this year. I do believe 30" of snow is not a stretch especially is our NAO goes to negative 1.50 and 2.00 again.
Cold air is really start to fill into western Canada and that blizzard is making for some nice low Canadian latitude snow cover. Last years snow cover was pretty awful. Lows are already going negative out west in Montana. Cold air shouldn't be a problem this year. It was trapped in Europe last year.
What effect do people think the solar max (albeit a weak one) will have? Usually a solar max increases the zonal index. Also, lots of cold air will build in central Canada over the next couple of weeks and there will be a good snowcover there thanks to the storm over the next few days.
I agree, Weatherman. I am hoping we can break some records this winter with the warm temps ( maybe 80 in December or January). It might be that Sandy and the last storm sets up the pattern similar to last year when the Halloween storm blew through and it basically blew out the remainder of our winter weather ( no major snow and above normal temps). El Nino will play a much less significant role as described above. So basically, blocking and the NAO will be bigger players and unfortunately you cannot predict those indicators any further out than 2 weeks. It will make long range predictions virtually impossible this year. So let the guessing begin!!!!
I'm calling for 6.2 inches of snow at the airport this year. We are in an almost exact pattern as this time last year, and when you look long range, it blowtorch city, with occasional cool spells. Luckily, yesterdays total of a trace at the airport won't affect my seasonal total.
Well said Rob.. and I think we are going to have the key blocking to get the major winter weather events as we head into winter. You can clearly see based on the AO and NAO charts that they trend back to the negative later in November. It will be interesting if we match what happend in 2009-2010. Still, have to wait and see how this all plays out.
Gfs shows the -NAO setting up out around the 17th as well as a storm system coming up from from southern Cali across the southern states and GoM then up the east coast. Something to keep an eye on could be another nor'easter in the making. Granted 10 days away, well see.