What is the NOAA and CPC winter outlook really saying?

On October 17th 2019 the National Oceanic and Atmospheric Administration's Climate Prediction Center  (NOAA/CPC)  released their 2019-2020 Winter Outlook.  The Winter Outlook with temperature and precipitation predictions covers December  (2019), January and February (2020) . The agency is forecasting warmer-than-average temperatures over a large part of the United States. They are also increasing the odds for a wetter than average winter over the northern Plains into the Great Lakes, Midwest and western parts of the Northeast  and the Mid Atlantic Region.

In this post I will try to shed a little light on what the  NOAA/CPC  really indicate. I show some of the things they base their outlook on; then I will go over some key difference between their outlook and my outlook.

It is important to remember that the NOAA winter outlook is not a forecast Instead it's based on probabilities. My outlook is based on degrees and amounts above or below average.

When I was a Texas A&M I took the typical required math classes, like: linear Algebra, Calculus 1-4, Differential Equations...; I also took Finite Math, Discreet Math, and several different classes involving Statistics. Yes I'm a math geek....I love math!       

How does the NOAA/CPC seasonal outlook work?

One thing I want to make clear, the only probabilities that can be verified are 0% and 100%.

Here is a look at the temperature and precipitation outlooks for winter 2019-2020.  

 

 

The Outlook has labeled parts of the CONUS with EC; this means equal chances, which means there is no tilt in the odds toward any outcome. They also typically use the letters A,B, and N.

EC = Equal  chances  ( 33.3%) 

A= for above median

B= for below median

N = for near median

The above or below color shades work like this.  They are listed in lowest to highest probability

>33% chance

>40% chance

> 50% chance

>60% chance

And so on.

Here is a closer look at the color shading legion.

 

NOAA/CPC pretty much relies solely on the Madden-Julian Oscillation (MJO), El Nino Southern Oscillation (ENSO) region (Nino 3.4), and the Atlantic Oscillation (AO). This is compared to the 15 year mean and the 30 year climatology for that season (currently that is the 1981-2010 record). After the computers spit out the data. The NOAA/CPC forecasters, divide the data into three parts, the upper 1/3 median, the near 1/3 median, and the lower 1/3 median. All of this equals 100%. Each category has an equal chance of occurring. So the default probability is 33.3%.   So while the color shading indicates the probability of above or below temperature and precipitation. It doesn't indicate how much above average or below average those amounts will be.     

 

As for my outlook:

I look at dozens of things beyond that looked at by NOAA/CPC; some of these have a weak correlation while others have a strong correlation. But taken in their entirety I have found they do a decent job.  

With the ENSO looking to be a little negative of neutral. I think we will have a sort of hybrid La Nina. But ENSO neutral to weak La Nina is a cold signal for the Northeast into the Mid Atlantic.   When the ENSO is near neutral, it doesn't exert a lot of influence on the overall pattern. So, other teleconnections and short term climate patterns like the MJO, AO, and North Atlantic Oscillation (NAO), are able to wield more sway than when we're in a El Nino or a La Nina.    

The AO involves the upper level circulation around the North Pole. This is commonly called the Polar Vortex. The Polar Vortex is weaker than is typical for this time of year. This is a good sign, that polar air will have a good chance to work south at times during the upcoming winter.  A weak polar vertex has resulted in several cold outbreaks in similar years.   The MJO has a lot of influence on the jet stream pattern. This will have a big impact not only on how cold or warm we are, but also on the storm pattern. As we've seen the last few weeks, our current MJO pattern is helping Nor'easters and Coastal Storms to develop.  Most of the analog years I used, had a predominate negative NAO; when the NAO is negative we tend to see higher heights over eastern Canada, Greenland and Iceland. As a result of the higher latitude blocking we end up with a slower pattern, that favors locking colder in place for longer periods of time, it also helps ensure above average Clipper and Coastal Storm activity. Cool SST in Nino region 1+2 and that very warm blob in the Northeast Pacific is another cold signal.  The last couple of weeks has seen tremendous snowpack growth, Canada, and the Rockies and Northern Midwest have also see quite a bit of early season snow. While it's a weak correlation, it is still a signal for a colder than average winter in the Northeast.   Because the ENSO is looking to be sort of a hybrid La Nina, the pattern could be a bit erratic. As I said in my winter update a few days ago.  We're in the quietest solar minimum in around 100 years. The last time a solar cycle was this feeble was solar cycle 14 in the early 1900's.  there is a strong correlation to solar activity and winter in the Northeast. Quiet years see colder winters.  

 

While I will be making minor adjustments in my final outlook. I haven't seen anything going on that will drastically alter what I said in the preliminary winter outlook, nor the update I just posted the other day.

The reality is seasonal forecasting is extremely difficult to get right.  Every source you go to doesn't know what's exactly going to happen from December to February, especially this far in advance.   I don't know how things will actually workout on a day to day, or when we will see snowstorms and cold outbreaks, but all the things I look at, makes my guess, an educated guess.  Those things are telling me NOAA/CPC is showing too much warm possibilities for the Northeast and Mid Atlantic Region.  The pattern we've been in should continue into Winter 2019-2020. With a favorable pattern for Coastal Storms the Mid Atlantic. I-95, into southern and southeastern New England should see a few big storms.  With Interior sections of Pennsylvania, New York State, and the rest of New England seeing an active winter. With the pattern showing a decent chance for moisture moving north and east into our region, with the cold should come the snow. The Great Lakes are quite warm. So the clippers could bring an active lake effect snow season.  The Great Lakes, into western and northern New York State along with western Pennsylvania could end up being ground zero for winter mayhem.

Right now, I will continue to monitor and observe the overall pattern and teleconnections to see what else they can tell me......I will be coming out with my final 2019-2020 outlook in two to three weeks.

For anyone who didn't catch my preliminary 2019-2020 winter outlook, or the follow up post; here are the links.

Preliminary winter outlook.

Winter outlook follow up .