Tuesday, October 14, 2014


Welcome to my official 2014-2015 winter forecast! I want to start off by saying that, although scientific advances in long term weather prediction have come a long way, the weather will always continue to do what it wants to do. In fact every year that passes is a new opportunity for members of the scientific community (I am not a scientist) to study potential new drivers to the weather pattern. Why am I saying this? Quite simply, because I think its important to be humble and not think you have it all figured out when it comes to the weather. With that being said, my forecast below is the result of  studying many factors I have watched evolve over the last 6 months. It is my best educated guess and hopefully its a damn good one. If not the comment section is always open for everybody's choice words.

This outlook is broken down into two sections:

  • The Consolidated Forecast:
    • Graphics showing the prediction for temperature and snowfall compared to averages for the overall season. 
    • Let's admit, not everyone cares how I made the forecast. They just want the bottom line.
    • I will give specific parameters. No general statements.
  • The details behind the forecast:
    • This will be an explanation on the factors I analyzed to come up with this forecast and how each one of them could influence our winter pattern.
    • I will give month to month predictions.
    • This for the the people who are actually interested in the data behind my predictions.

The Consolidated Forecast:

Buckle up, a cold and snowy winter is in store for the Central and Eastern United States with some similarities and differences to last winter. Winter will start off strong in December and hold firm through the end of February. I think we see our first snow by the first week in December. By March the pattern breaks earlier than last year and spring arrives quickly. 

 Temperature Predictions (departure from averages):

Most areas of the country will see a big chill that will develop in December and last into late February with only occasional relief at times. But again, good news is the early arrival of spring in March.

Snowfall Predictions:

I expect the core of above average snows to be focused on the Mid-Atlantic and Southern New England. On average, I think this means 1.2-1.5 times normal snowfall in the above average region. Majority of this snow will come from two major coastal storms (10+ inches per storm). The Great Lakes region and central states can expect to see normal snowfall. Out west, reaching to Utah, it looks to be a below normal season. 

Since most viewers are from the NJ area, here is normal snowfall for the state:

Expect 25-35% more snow than average this year. Most of this should come from the predicted two major storms I mentioned above.

Storm Tracks: These are the types of low pressure systems I expect to develop this winter.

For the most part, coastal storms or Nor'easters should be more frequent than we saw last winter. 

Now for the details behind the forecast:

I look at many large scale factors when I organize a winter forecast. Some of these factors have a big influence on the weather pattern and others enhance an existing pattern in place. Lets start off by listing the factors that influence a winter in North America.

1. El Nino Southern Oscillation:

This is basically a water pattern in the Tropical Pacific off the coast of South America. When the water in this region is above normal in temperature we have an El Nino and when it is below normal we have a La Nina. Both have large effects on the overall placement of the sub-tropical jet stream in the winter. This year I am expecting a weak west-based El Nino. This means the sub-tropical jet stream will be enhanced at times and bring moisture into the United States that could potentially merge with the northern jet stream. The graphics below help explain. It is important to note, jet streams strengthen in the winter months due to the sharper contrast between cold air to the north and warm air from the tropical regions.

El Nino Region:

Typical effects of a weak El Nino:

2. Rate of snow over Eurasia:

A lot of research has been done on the rate of snow in Eurasia during October and its affect on the Arctic Oscillation in the winter. What is the Arctic Oscillation (AO)? In quite simple terms, it is the pressure pattern over the Arctic. During it's negative phase, high pressure develops over the Arctic which allows cold air to funnel south. In it's positive phase, low pressure prevails over the arctic and the cold stays locked up. Here is a diagram to explain.

The next image averages out all the years that had a negative AO during the winter and the corresponding temperature pattern in the USA. Notice the warm colors over the poles. These represent high pressure. Just as the diagram above shows, this weakens the polar vortex and pushes the jet stream south which bleeds in the cold arctic air.

On the flip side, here is what the positive AO years looked like: The complete opposite. The polar vortex over the pole is strengthened and the cold air stays locked to the north. As you can see this is a very important piece of the puzzle for this winter. 

Now back to snow cover. When snow advances at a high rate in October, research suggests this results in high pressure strengthening over the arctic thus creating a negative AO. Below is the current snow cover in Eurasia month to date. Blue is above normal, red is below normal. I boxed out the area that is most important.

At this rate, things look very good for this index to lead to a negative AO. You can see a lot of above average snow growth in the yellow box. In fact, September saw the 3rd most snow cover on record for the Northern Hemisphere! Based on model forecasts, the snow growth should maintain through the end of October.

3. Water temperatures in the North Pacific and Atlantic:

This is a very important piece of the puzzle. It is the reason we had such a cold winter last year. In general, when looking at water temps in the northern latitudes, warm water favors high pressure and cold water favors low pressure. This naturally steers the jet stream. When temperatures are above normal off the West Coast and in the Gulf of Alaska, a ridge of high pressure develops downstream over the West Coast. This leads to a cold air trough over the East. In addition, when we see warm water in the North Atlantic near Greenland, high pressure forms due to warm air expanding and creating higher pressure areas. Here is a particular climate model's projected water temps for this winter (this is common among many models).

I circled important areas including the El Nino I spoke about earlier. The black line basically shows how the jet stream should react to very warm water in the Pacific. Also note, the cold water in the Central Pacific. This is something called the Pacific Decadal Oscillation in its positive phase. This difference in water temperatures should cause a nice trough to develop south of the Aleutian Islands due to the contrast in ocean and air temps with the warm water off the coast and the colder water south of the Aleutians. This is a big driver of cold along the east coast. 

Turning our attention to the Atlantic, I marked something called the Atlantic Tri-Pole. This basically is a pattern of warm water in the Central Atlantic, cold water in the North/Central Atlantic, then finally warm water in the North Atlantic. This pattern favors the negative phase of the North Atlantic Oscillation (NAO) which I will discuss in a little.

To illustrate my point further, here is what happens when water is cold off the Pacific Coast and Gulf of Alaska. Image below shows some of the warmest snowless winters on record. Take a look at the difference in water temps compared to the above model.

Very cold water off of the West Coast. This is the kiss of death for snow lovers along the East Coast as it usually results in a trough over Alaska which locks the cold air to the north resulting in very warm winters. You can see below what those ocean temps in particular off the West Coast caused for temps those winters (technically 500mb heights).

This should not be the case this year, however, as seen by the model projected ocean temps.

To conclude, I expect a deep low pressure area to form south of the Aleutian Islands (the chain of islands off of Alaska) which in turn will pump up a ridge over the West Coast and trough over the east due to the water temperature profile this winter.

4. The Sun and Solar Impacts

When the sun is active, it breaks down the ozone in the stratosphere which leads to the positive phase of the Arctic Oscillation I spoke about above. We are currently in a very quiet sun cycle as measured by a low number of sun spots. This means the sun is not active at all. This causes the build up of ozone in the upper atmosphere which leads to a negative phase of the Arctic Oscillation due to something called stratospheric warming. Sun cycles last around 11 years roughly and the sun has been extremely quiet lately compared to other solar cycles. The image below shows the current cycle 24 compared to the last two.

As you can see, cycle 24 is very low in sun spots which favors more high pressure forming over the poles. In fact, the current solar cycle is the quietest we have seen in nearly 100 years! Real quick - here is the upper air pattern for low solar winters notice the impact on the AO.

5. Stratospheric Winds (QBO) and the North Atlantic Oscillation (NAO):

Along with the Arctic Oscillation, another big component of a cold snowy winter in the east is the North Atlantic Oscillation that some of you may have had me talk about before. In its negative phase high pressure develops over Greenland which blocks the jet stream south over the East Coast. In its positive phase, lower pressure is over Greenland and high pressure offshore takes over causing warmer than normal conditions due to a flatter jet stream. Here is an image to help show the negative NAO. This is a big component to big East Coast storms.

Winds help transport heat to the upper levels of the atmosphere over the poles. This heat transport can lead to the AO and NAO going into their negative phases due to something called stratospheric warming. This transport is called the Quasi-biennial Oscillation (QBO) and in simple terms favors heat transport in its easterly phase. In its easterly phase, winds from high above in the stratosphere are moving down in an easterly fashion. This favors the negative AO and NAO. A westerly QBO in simple terms (solar has an impact on their effect too) does not favor the negative NAO and AO. This year the QBO will be in its easterly phase which means combined with the other factors, the diagrams showing the effects of a negative NAO and AO above could tell the tale for this winter. 

Here are all the years the QBO has been in its easterly phase and the corresponding pressure pattern over the northern hemisphere:

Again, another factor predicted for this winter that should support those high pressure areas to our north which will bring the cold air south. 

6. Model Projections:

Always a wildcard in long term forecasting. Climate models are very volatile and need to be taken with a grain of salt. With that being said here are an example of a few of them and what they show:

 The American CFSv2 model shows a very warm winter..

However, this model over the last few years has been way off and its projections for sea surface temperatures do not match the output in temps it is showing here. In addition, it is bringing on the El Nino too strong which floods the USA with pacific air. 

Here is a model out of Japan which has a little bit of a better track record that has a cold look. However, it too has been known to swing rapidly. In fact, last winter it flopped to warm around this time which was way off.

The next model is what I think the most accurate assessment compared to my winter thoughts are. It uses sea surface temperatures to make its forecast.

There are many other models I can show (the very accurate European model shows a cold winter but I don't have access to its seasonal forecast) but to restrict the length of this post I will cut it off here. We will see how these models trend by December. From my experience they never do a great job and instead it is important to look at what factors are driving the atmosphere such as the ones I listed above. But who knows maybe I am way off that is always a possibility. 

If you take a look at all of those factors above and then say when in history did things look similar and what were those winter like, then you can get some hints on what this year will bring. From what I am observing the past winters that are the closest matches in order of relevance are:

1977,2003,1959,1994 and 2010. 

If you average these winters out, you end up with a weak west based El Nino, high snow cover over Eurasia, warm water in the north east pacific, the Atlantic Tri-Pole, low sun activity and finally a easterly QBO. Below shows what the water temps looked like if you average out those years and double weight the top two.

The historical years sea surface temperatures:

An average of the climate models projections for sea surface temperatures:

Not a perfect match but close enough for my liking and to give me the confidence to make my winter forecast. 

Now finally if you take a look at this winter using the historical years shown above, which  have all the factors I am expecting this winter(El Nino,low solar,east QBO,high snow cover,ocean temps) you end up with what we have below for each months temperatures. These are departure from normal in degrees C. 

December: Cold works its way into the East Coast as the western ridge develops

January: Very cold central and east

February: A continuation of the colder than normal temperatures

March:A snap into spring with warmer than normal temps over the east

The winter as a whole: Which naturally looks like the graphic I drew.

And of course taking a look above at the pressure pattern for those winters: There it is the negative AO and NAO

So there you have it my 2015 winter outlook. I hope all of you enjoyed reading (if you made it this far down the page) and I encourage you all to spread the word. The comment section is open from those who have additional questions along with those who are far more certified than I in this field to insert your commentary. 

I look forward to updating everyone as the months go on leading into winter. As you can see the forecast I made is bold so the pressure is on!

1 comment:

  1. Thanks, WIlly. Always informative. Always instructive. Always appreciated.