Difference Between a NAO Positive and a NAO Negative

Definition of NAO

The North Atlantic oscillation (NAO) is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level between the Icelandic low and the Azores high

~from Wikipedia: read more about NAO at http://en.wikipedia.org/wiki/North_Atlantic_oscillation

What is a Positive NAO?

 
This is when much of the east coast gets warmer than normal temperatures. The west coast gets below normal temperatures. If you didn't notice, this is what has been giving the east coast hardly any winter. Except the rare snowstrom in October, the Northeast hasn't seen any big snow events. Some areas in the Southwest have seen more snow than areas in the Northeast. Weirdly enough, areas like northern Texas have been hammered with snow. You can also say that the west has had a pretty cold winter so far this year. Only 25.7% of the United States is covered in snow right now, while this time last year, while 48.0% of the United States was covered in snow last year, what the negative NAO was persistent.

Current Snow Depth

Snow Depth This Time Last Year

A Positive NAO

What is a Negative NAO?

A negative NAO is when much of the east coast gets below normal temperatures. The west coast usually gets milder than normal temperatures. This pretty much could cancel out the effects of the La Nina pattern (just as it did last year). Last year was a year of records being set. Areas like NYC got feet of snowfall, starting the end of December (from the same snowstorm that gave many areas in the Southeast a very rare white Christmas). Schools in NYC were closed two days, while schools are rarly closed there. The negative NAO would pretty much switch our weather with the west coast.

  

A Negative NAO

Is The NAO Expected to Go Down?

Yes, the NAO is expected to go down, possibily going negative as early as ealry January. This is why I am sticking with my forecast that the Southeast will be cold this year. As you can see, a good 4+ models have the NAO going negative by the 2nd of January. This will switch around our weather, giving the east coast, including the Southeast some persistent cold air. Many areas in the Southeast will there first snow. Many people are already giving up on winter, but you don't have to. What must come up, must go down. It is an uncertainty how long the NAO will stay negative.

   

 

Scenario #1

Scenario #1 is that the NAO stays negative persistently. This might cause a similar winter as last year, giving the Midwest, Northeast, and Southeast several chances for snow, since we would be in a cold air just sticking around for a while.

Scenario #2

Scenario #2 is that the NAO goes up and down. This will cause periods of cold air and warm air. This will lower the amount of snowstorms for the east coast, since some of the times the storm will run into warm air, when the NAO goes positive. This will also possibly increase the chances for anything in between rain and snow, like sleet, freezing rain, and wintery mixes. 

Scenario #3

Scenario #3 is that the NAO never goes negative, giving the east coast hardly any winter. I think there is only a low chance of happening, so don't worry. This will cause most of the storms to produce only rain. Most of the time, big cities like New York City, Washington,DC, and even Boston will get all rain, while areas inland could get snow.

Mid-December Snowstorm "Possibility" Is Becoming A Reality!

A lot of things are pointing to a possible snowstorm in mid-December. First of all if you missed it this is what The Old Farmer's Alamac said. (you can find the 2 month forecast for the Southeast in the link)  http://www.almanac.com/weather/longrange/region/us/4
"Dec 16-20: Rain and snow north, rain south, then sunny, cold"

Second of all, here are hours 216-240 of the GFS showing a pretty good snowstorm next weekend, and pleanty of cold air for it too! (the blue line is the rain/snow line, were temperatures will be at or below freezing)

Third of all, the NAO (North Atlantic Oscillation) for around mid-December looks possibly negative, which usually means a lot of cold air deep south. This is what caused all the cold air and snow last year, even though it was a La Nina year which is usually warm and dry.

What The........SNOW!

A lot of people are wondering "when are we going to get our first snowfall?" Some areas in the Tennessee Valley have seen there first snowfall. Even areas that rarly see snow this early in the year, such as Memphis,TN have seen there first snowfall. Other areas like Charlotte and Atlanta have seen a few flakes. No a big deal, right? Ok.......... back to the topic: when is the first snowfall going to happen in the areas that have not seen there fair share of snow yet? Well, I expect there to be a storm (maybe a snowstorm or BLIZZARD) to effect many areas in the Southeast in mid-December or maybe even the end of December. Any exact dates? Yes, anywhere from the 15-31 of December. My best BOLD guess for now is December 16th-20th. Old Farmers Alamac (which is a really great and accurate long-ranged forecaster) says that there will be rain and snow north and rain south for the Southeast. Something else that is intresting is that intellicast.com is saying a pretty good chance for snow on December 7th BUT according to all the other forecasts it looks to be only a chance for the mountains, especailly the mountains of North Carolina. Weirdly and intrestingly enough, they said a 36% chance of snow for the major city of Charlotte (which is actually a pretty good chance if you think about it). The least I could say is that I will have to keep a close eye on it, but it doesn't look like anything major as of now. There looks to be too much warm air.

Snow?

I will tell you where and when in an upcoming blog (HINT)- sometime next week

Dec 16-20 Possible Winter Storm For The Southeast?

Dec 16-20 Possible Winter Storm? 

If you read the words "winter storm", and "southeast", yes you are reading this right. According to Old Farmer's Alamac they say:

"Dec 16-20: Rain and snow north, rain south, then sunny, cold"

I believe there is a chance that it could really snow in some areas, because Old Farmer's Alamac is usually very accurate. A clue that it could actually snow in December is that we are in a very pattern as last year, when a lot of areas in the southeast got a record white Christmas. I believe that it will be what you can call an "early winter", most of the snow and cold will be in the beginning of the season, while a warm pattern can start as early as Febuary.

Bold Guess On What The Accumulations Could Be?

I know that there is no proof that this storm is even going to exist, but I am going to make a bold guess on accumulations, based on storms the southeast had in the past and geography of the land.

NC Mountains:5-8 inches

Southeastern NC (Including Charlotte):2-4 inches

SC Moutains:4-7 inches
Peidmont of SC:3-5 inches

Western SC/NC (Closer to the Rain/Snow Line):1-2 inches

Northern/Central NC (Including Raleigh):3-5 inches

TN Mountains:6-9 inches

Eastern TN:4-8 inches

GA Moutains:4-7 inches

Northern Ga(NOT INCLUDING MOUTAINS), Northern AL, Northern MS:1-2 inches ( Possibly 3 inches in some areas) 

Other Chances For Snow(Including This Month)?

I still have not given up on thinking there is a chace of snow this month. I think that after all this warm weather is done (by the end of next week) we will start to see a pattern of cold weather setting up. I think the brunt of it will start the week of the 13th. I think this cold pattern might last a while, maybe even a few weeks. I think by the end of month, some areas will see a light snow, but nothing major until December.

11/8/11 Update: Now I am thinking the brunt of the cold air will start at the end of November, with MAYBE a chance of SNOW? "WHAT? SNOW!" is probably what you are saying now, I will better explain this in a new blog coming out soon. The situation will become clearer also in a couple of weeks, when we get closer to the possible upcoming pattern of cold air

11/14/11 Update: Now I am thinking there is still a chance of snow at the end of the month, but very low. My best guess of the first snowfall would probably be around the beginning to middle of December, maybe even a couple of snow events, depending on how long the cold air lasts.

New Updated Winter Forecast, Blog also coming Soon

Southeast Winter Forecast 2011-2012

Southeast Winter Forecast 2011-2012

Temperature
The coldest temperatures will be in Tennessee, North Carolina, and South Carolina. Mississippi, Alabama, and Georgia will have temperatures slighty below average. Florida will have near normal temperatures, and will likely some blasts of cold air from time to time. Also, just like last year, I am expecting there to be periods of warmth between all the cold blasts of air. I think this because just like last year, we have a La Nina pattern.

Precipitation
(Note that by precipitation I mean in the liquid form, so for example, lets say your area gets an average of 5 inches of snow a year and 2 inches of rain, and you get 10 inches of snow the whole season, that would be below normal precipitation((think about the snow to liquid equivalent)) and it would be above normal snowfall) Northern Tennessee will have slightly above average precipitation. Also, the mountains of South Carolina, North Carolina, and Tennessee will have slightly above average precipitation. There will also be drier than average conditions in southern Mississippi, Albama, Georgia, and also eastern North Carolina and South Carolina. Northern Florida will also fit in this category, while southern Florida will have the driest conditions out of the whole southeast.

 Snowfall
Snowfall will be much above average in the moutains of North Carolina, South Carolina, Tennessee, and Georgia. Much of the southeast will also be in the "above average" category, as you can see in the map above. Southern Mississippi, Alabama, Georgia, and also the coast of South Carolina and North Carolina will see slightly above average snowfall. Also, as you can see, Florida in colored in pink because it means if there is any rare snow events (yes, it happens) they will be late in the season. I also have a gut feeling that a lot of areas will get there first snowfall in November, most likely late in the month. I had this same "gut feeling" last year a few months before Christmas, that it would actually snow on Christmas, and it did! I nailed it. I was thinking a pretty heavy snow was going to start on Christmas Eve and end on christmas day, and amazingly I was straight on(I live in SC). I will have a blog more on my "gut feeling" that it was going to snow and also more on possible November snow withen the next couple of weeks.

Southeast 2011-2012 Winter Forecast Video
Also, below is the video that pretty much sums up the 2011-2012 forecast. Anyway, expect my next and final winter forecast to be in early December.