Saturday, October 11, 2014

Alaska 2014-2015 Winter Forecast

This is a regional winter forecast for the Alaska region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

* Uncertainty for this regional forecast is high. Use caution.

The Weather Centre
Temperatures across Alaska will likely end up average to slightly above average, thanks in large part to the swath of warmer than normal waters in the Gulf of Alaska. This feature may allow for persistent high pressure to position itself along the western coast of North America, extending into Alaska. The far northern reaches of the state may also see warmer than normal weather, as analog years from the Official winter forecast are calling for widespread upper latitude blocking (high pressure).

Precipitation is a big question mark this winter, but if any area is to see above-normal precipitation, I'm expecting it to be the southern half of the state.

Snowfall is the other big question mark this winter, such a wild card that the only guess I'm willing to make is that the coastal region of southern Alaska sees either average or slightly above-average snowfall.


Southwest 2014-2015 Winter Forecast

This is a regional winter forecast for the Southwest region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
Temperatures in the Southwest are listed as warm, but I might be more comfortable describing it as slightly above average. The expectation this winter is that we will see high pressure affecting the west coast of North America for prolonged periods, and this should keep most of the region warm. However, if the El Nino-enhanced subtropical jet stream can hold its ground, the region might come out of this winter with around average temperatures.

Precipitation will likely be more average than anything else, despite the image describing it as slightly dry. It is listed as slightly dry due to the uncertainty with how wet the El Nino situation will make the Southwest this winter, but uncertainty is slowly lessening in favor of a slightly wetter outlook than the one posted above.

Snowfall should be around average, maybe even a bit above average. Uncertainty is quite high here, so a more in-depth forecast cannot be given just yet.


Northwest 2014-2015 Winter Forecast

This is a regional winter forecast for the Northwest region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
The snapshot above pretty much defines this regional forecast. Temperatures are expected to be above normal this winter, with occasional shots of cooler air if strong storm systems from the Gulf of Alaska can push over the area. However, with the alignment of sea surface temperature anomalies over the Gulf of Alaska right now, as well as the incoming El Nino, I'm favoring a warm winter.

Precipitation is likely to end up below average, as typical El Nino conditions shift precipitation away from the Pacific Northwest. Expected ridging along the west coast of North America ought to limit precipitation as well.

Snowfall is expected to be below normal, as you could probably derive from the temperature and precipitation outlooks above. The reasons behind this outlook are the same: West Coast ridging and the El Nino.


South Plains 2014-2015 Winter Forecast

This is a regional winter forecast for the South Plains region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
In the temperature department, I'm expecting the Southern Plains to end up around average, as warmth in the Western US glides east into the Plains at times, and the cold weather in the Midwest and East pushes south at times as well. More prolonged periods of colder weather are possible, so long as the jet stream is suppressed south, as usually happens in El Nino periods.

Precipitation should end up around average, if not slightly above normal. An enhanced subtropical jet stream due to the incoming El Nino should help to boost precipitation trends in the Southern Plains, particularly along the Gulf Coast.

Snowfall is the wild card here, since it really takes just one storm to define the winter as below or above normal in the snowfall category. For that reason, and the consequential high level of uncertainty, I'll keep my snowfall estimate around average.


North Plains 2014-2015 Winter Forecast

This is a regional winter forecast for the North Plains region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
Temperatures should be between two dominant air masses. I expect the eastern part of this region (i.e. eastern Dakotas into Minnesota, part of Nebraska) to see below normal temperatures, while the western portion (Montana into Wyoming and Colorado) should expect warmer than normal conditions. Between these two outlooks, relatively normal temperature anomalies should prevail.

Precipitation should be average to below-normal, with the below-normal anomalies confined to the western part of this region. Around normal precipitation values can be anticipated elsewhere.

Snowfall is a big question mark. Right now, above normal snowfall is favored in the Nebraska/South Dakota corridor into Minnesota, with below-normal snowfall in the Rockies around the Front Range. Depending on how this fall unfolds, this snowy corridor may shift.


Midwest & Great Lakes 2014-2015 Winter Forecast

This is a regional winter forecast for the Midwest and Great Lakes regions. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
The phrase was accidentally cut off, but says "Snowy, Chilly Winter"
For temperatures in the Midwest and Great Lakes, below-normal should be the big story. Potentially well-below normal temperature anomalies may be positioned in the Central and eastern Great Lakes, as upper latitude blocking may try to force the polar vortex more into North America, and closer to the northern US.

Precipitation is the wild card here. As of now, I'm expecting average to slightly below average precipitation in the Midwest area. Below normal precipitation should be the story in the southern Midwest, such as southern Indiana and much of Kentucky. Precipitation may then be average further to the north, in the Upper Midwest.

Snowfall projections include a snowy winter for the Upper Midwest, though keep in mind this may change in the future. The heaviest snow is currently favored to fall from the Upper Midwest regions (i.e. Minnesota and Wisconsin) into northern Illinois and most of Michigan. Lake effect snowfall is expected to hover around normal to below normal.


Ohio Valley 2014-2015 Winter Forecast

This is a regional winter forecast for the Ohio Valley region. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
In this (very poor resolution) graphic, we'll review temperature, precipitation and snowfall outlooks for the Ohio Valley.

For temperatures, the entire area is expected to see below normal temperatures, as analogs suggest the emergence of persistent upper-latitude blocking, which could then lead to multiple Arctic air intrusions in the United States. More pronounced below-normal anomalies may be found in the northern portion of the Ohio Valley.

Precipitation is favored to be below-normal, as typically is seen in weak El Nino scenarios. Our analog package confirms that this is the expected prognosis.

Due to the below-normal precipitation outlook, snowfall is expected to be less than normal as well. I would watch for a few strong storm systems to bring the area a good bout of snow, as typically happens each winter, but the overall outlook is grim for above-normal snowfall.


Southeast & Gulf Coast 2014-2015 Winter Forecast

This is a regional winter forecast for the Southeast and Gulf Coast regions. For more winter forecasts, please visit the 2014-2015 Winter Forecast Directory.

The Weather Centre
In terms of temperatures, a generally below-normal outlook is favored. This comes as analog years suggest much of the Central and East US to be under negative 500mb height anomalies, resulting in cold weather thanks to a favorable global weather pattern. The cold may not be as intense in Florida, as the jet stream is suppressed south from time to time, allowing warmer weather to surge north on intervals. However, areas north may find themselves in for a chilly winter.

With respect to precipitation, I'm expecting most of the Gulf Coast to emerge in March 2015 with a wetter than normal winter having just finished up. In typical El Nino set-ups, the jet stream is pushed south due to upper-latitude blocking, something that may unfold again this winter. The Southeast region - that is, to the north of Florida and the Gulf Coast - may see relatively average to slightly below-average anomalies, particularly in the northern parts of Mississippi, Alabama, and into Tennessee.

Snowfall is expected to be average to slightly below average, but a lengthy discussion is not needed, since snow is pretty much nonexistent for the Gulf Coast and most of the Southeast.


Northeast & Mid-Atlantic 2014-2015 Winter Forecast

This is the regional forecast for the Northeast and Mid-Atlantic regions. For other forecasts, please go to the 2014-2015 Winter Forecast Directory.

The Weather Centre
For temperatures, I'm expecting most of the region to experience below normal to well-below normal temperatures this winter. This outlook comes from the expectation of upper-latitude blocking to prevail during the cold season, which may then force the polar vortex (or at least cold air masses) down south into North America, likely near the Northeast. The Mid-Atlantic may expect cold weather, though likely not as intensive as the Northeast and New England areas.

In the precipitation department, I'm expecting the coastline to see a few big-time storms this winter season. The emergence of a weak El Nino this winter should enable the jet stream to buckle south at times, likely resulting in threats for potentially significant snowstorms. I'd place the regions under average precipitation, as the degree to how often this jet stream buckling occurs is not yet known.

Lastly, with respect to snowfall, as stated above, I am expecting a handful of substantial storms, known as "Nor'easters" to many. Regardless of if they are true Nor'easters when they occur, or are just strong coastal storms, I do think the region has a decent shot at at least average snowfall, if not above average.


Official 2014-2015 Winter Forecast

"Second Consecutive Frigid Winter Expected..."

Hello everyone, and welcome to The Weather Centre's Official 2014-2015 Winter Forecast. This forecast will detail an examination of current atmospheric conditions, from the surface to the stratosphere, all around the world. Following the analysis, and discussion of analog years, the forecast will be discussed, which will include graphics and quick break-downs by region.

Please note that more in-depth regional outlooks are being issued from 12:00 PM Central Time to 1:40 PM Central Time today, October 11th. You can find all regional outlooks on the 'Winter Forecast Directory' tab at the top of this page.

Let’s jump right in and begin with an analysis of sea surface temperature anomalies across the world.

There are a few areas of interest in the image above, so let's break it all down.

1. Below Normal SST Anomalies in the Sea of Japan
In the Sea of Japan, located to the west of Japan, we see a swath of below-normal to well below-normal sea surface temperature anomalies (henceforth abbreviated as SSTAs). These below-normal water temperatures were recently stirred up by the passage of a Typhoon Halong in early August, making quick work of what had previously been a rather prominent basin of well above-normal water temperature anomalies. If these below-normal anomalies persist into the winter, we would likely see two important consequences, which would have an impact on our winter.

First of all, the presence of negative SST anomalies tends to allow stormy weather and general low pressure to form over the region. A similar situation occurs with high pressure tendencies over warm SST anomalies. In our case, these negative SSTAs in the Sea of Japan would likely allow for predominantly stormy weather. This would, consequently, allow for the jet stream to be forced more to the south, allowing cold weather to hit Japan.

This leads into the second consequence, which focuses on a neat tool I've used for the past few years on this blog, with impressive accuracy. The tool is known as the Typhoon Rule, which you may have also seen referred to as something along the lines of an East Asian correlation or something similar. The gist of the Typhoon Rule, henceforth abbreviated as the TR, is that weather in Japan can be reciprocated in the United States 6-10 days after it happens in Japan. For example, a strong storm crossing Japan on a hypothetical date of January 12th would then lead to a chance for a storm system in the US 6-10 days later, around January 18th to 22nd.
If we do see the jet stream forced south due to these below-normal waters in the Sea of Japan, it may provide the opportunity for cold weather and storm systems to frequent the region. When you bring the Typhoon Rule into play after accounting for such storminess and cold in Japan, the risk of a cold and snowy winter suddenly becomes much higher. It remains to be seen if this sort of thing will work out, but there certainly is the risk for it to happen.

2. Well Above-Normal Water Temperatures in the Gulf of Alaska
This next SST feature is something I've been discussing here for the last few months. Since last winter, we've seen a swath of well above-normal SSTAs dominating the Gulf of Alaska and general Northeast Pacific region.

In the two-panel image above, we see observed 500mb height anomalies from the December-January-February period of 2013-2014 on the left, with SSTAs from the same timeframe on the right. If you were to compare the two images, you might notice something interesting: the well above-normal SST anomalies are in the same place as the big ridge of high pressure in the Northeast Pacific. That's a correlation at work there- as we discussed with the Sea of Japan, cooler than normal water temperatures tend to bring about stormy and cold weather, while above-normal water temperatures permit the formation of high pressure. As the example above shows, the warm pool in the Northeast Pacific last winter certainly allowed strong ridging to form, and it was that ridge which became a significant piece to the puzzle of the historic cold weather to kick off January 2014.

If we now compare the latest sea surface temperature anomaly image from UNISYS at the top of this post to the SSTA graphic on the right in the image directly above, it becomes clear that the warm pool really hasn't weakened all that much. That could spell big trouble for the United States; if this warm pool continues to persist into this winter, it could very well create another semi-permanent body of ridging/high pressure over the Gulf of Alaska this winter. For an example of what that would look like, just take a look at what happened with respect to temperature anomalies when that very thing happened last winter...

December-January-February temperature anomalies from this past winter

3. Well-Above Normal SST Anomalies in the Bering Sea
This last factor could act as either a saving grace for the winter, from the eyes of a cold winter fan, but also from the eyes of a warm winter fan. Let me explain.

In my mind, there are two things that could happen, *IF* the Bering Sea becomes a major influence on the pattern this winter (which is a possibility, though you can thoroughly sense my uncertainty at all of this).

The first possibility I believe might happen is instead of persistent ridging forming in the Gulf of Alaska, it forms in the Bering Sea. This could happen, because like the Gulf of Alaska, the Bering also has a swath of well-above normal SST anomalies. If this does happen, I would expect that the Gulf of Alaska would suddenly become a very cold, stormy place, as the jet stream buckles south. What this would then do, is the stormy weather in the Gulf of Alaska (also abbreviated as GOA) would provoke high pressure to form in the West US.

This is where it gets dicey. The first possibility, one of the two things that could happen, is that the ridge of high pressure could then either stick around in the Rockies, where the pattern would then favor a cold winter for the Central & East US, or the ridge could shift east, and flood the Central US with warmth. The former option would favor a positive PNA-like pattern, while the latter option would support more of a negative PNA option. You can view both phases of the PNA to see what they look like in our Weather Glossary entry here.

It's a little early to be discussing which option might be more viable. As I make this forecast in mid-September, I'm seeing a very stormy period coming up for both the Bering Sea and Gulf of Alaska in the near future, which could complicate the situation even further.
To summarize, just keep an eye out to see what the Bering Sea does this cold season.

4. Above-Normal SST Anomalies Near Greenland
The last factor in this sea surface temperature anomaly chart we'll examine is the presence of warmer than normal waters near Greenland.

The presence of above-normal water temperatures near Greenland isn't just some random occurrence; it's a legitimate pattern in its own right. In the winter, warmer than normal SSTAs near Greenland and eastern Canada can allow for persistent ridging/high pressure to form over the land mass. You Northeastern weather junkies may know this phenomenon to be the negative phase of the North Atlantic Oscillation (NAO); the Weather Glossary definition for the NAO can be accessed here.

Considering we're likely heading into a weak El Nino (which we'll discuss next), and warm waters are indeed surrounding Greenland, high pressure/ridging over Greenland might be something to watch carefully for. We could even see some upper-latitude 'blocking' scenarios*.

*Blocking is defined as when strong ridges or upper level lows become entrenched in the atmosphere, literally "blocking" the atmospheric flow from continuing to move west-to-east. This has been known to enhance droughts in areas where blocking high pressure remains for days (or even weeks), as well as flooding in areas where blocking low pressure is found.

Sea Surface Temperature Anomaly Summarization

Even if you just skimmed over all of those words, you can probably get the gist that the ocean temperature patterns are supportive of a colder than normal winter right now. As was stated, though, watch for some surprises, especially with respect to the Bering Sea.

Up next, we'll branch off from the SST anomaly discussion, into a similar-yet-different talk about the El Nino-Southern Oscillation (ENSO) phenomenon.

Refresh page if animation stops looping.
The animation above shows a depth-by-longitude "cross-section" of the Equatorial Pacific. In other words, these are the water temperature anomalies you would see if you took a look at the subsurface Equatorial Pacific waters, from the coast of Ecuador (right side of animation) to around 140E. In this animation, we can see a few things happening from the start of this animation in July/August, to the present day.

First and foremost, we saw a Kelvin Wave push through in the last few weeks, which resulted in the formation of above-normal water temperature anomalies a couple hundred meters below the surface. As time went on, the Kelvin Wave pushed east, as did the warm waters. In the last few weeks, we've begun to see these warm waters push up to the surface, a natural phenomenon for a Kelvin Wave. We saw a similar event happen this past spring, but we never got the El Nino to form.

Many people asked 'Why?'
The answer's more simple than you might expect.

The graphic above shows us anomalies for the Southern Oscillation Index (SOI) from January 2012 to present day. The Southern Oscillation Index is calculated by examining the pressure differences between Tahiti and Darwin, Australia. When values drop below -8, conditions are considered optimal for El Nino formation. Values above +8 are considered optimal for La Nina conditions.

This past April, when the record-breaking Kelvin Wave traversed the Pacific, the SOI was definitely below that negative-8 threshold. In fact, we almost saw it reach negative-15. However, in the following first days of April, the SOI spiked back to neutral, then to positive for another few months. This resulted in Equatorial trade winds essentially shutting down the whole operation, making all that excitement go to waste.

Now, however, we have the Kelvin Wave-induced waters pushing to the surface at a time when the SOI has been negative since the first days of July. Put two and two together, and the ingredients are coming together for our highly-anticipated El Nino to show itself in the next several weeks.

We can use long range model guidance to our advantage here. The image above shows a number of global forecasting systems (called a 'plume' projection, in this case), projecting the anomaly of the ENSO phenomenon from now until next spring. As this projection shows, the model guidance doesn't exactly have a consensus nailed down, though that's to be expected with the massive uncertainty that comes with long-range forecasting.

What we take away from this forecast plume is that the average of all of these models predicts a respectable weak El Nino to form this fall and continue into the winter, as that yellow line shows. This jives well with all other indications we've been receiving, and I see no reason to disagree with it at this time.

Let's quickly review what a typical weak to moderate El Nino, the sort of thing we're expecting this winter, brings to the United States in terms of precipitation and temperature anomalies.

For temperature, weak El Nino's tend to bring about warmer than normal winters in the Western United States, all the way into the Upper Midwest. The Southern Plains and western Great Lakes regions are caught in average temperatures. It is the Ohio Valley that receives the brunt of the cold weather normally seen in weak El Nino's, even though the entire Eastern US is affected (save for Maine).

On the precipitation front, weak El Nino's will normally bring very dry conditions to the Pacific Northwest, with wetter than normal conditions to the state of California (something badly needed right now for that area). Most of the Plains tend to observe neutral anomalies (a paradoxical phrase, but bear with me), while the Midwest, Gulf Coast, and Ohio Valley regions tend to see drier than normal winters. Only slightly above-normal precipitation anomalies are observed in Florida.

Now, here's the thing about the lack of an anomaly like we see in the Plains above- it's rubbish. Trash. False. However you prefer to say it, there's no way every weak El Nino brings normal precipitation to the Plains every time. That's why I caution people when looking at composites like these, because they aren't set in stone... at all. It would be a poor decision on my end to base my forecast off of these composites, because 99.999% of the time, other factors in the atmosphere will make the winter different than these composites say. Somewhere along the line, yes, the Ohio Valley will probably get more dry winter seasons than wet ones in El Nino, but for those neutral-shaded areas (again, another paradoxical phrase), I wouldn't put much stock into it.

El Nino-Southern Oscillation (ENSO) Summarization

The theme this winter is expected to be a weak to possibly moderate El Nino, though if I had to make a decision this moment I'd go more for a weak El Nino as opposed to moderate. Regardless, this should add some more support for a chilly winter in parts of the Central and East US, while making prospects in the West even warmer.

Next up, we'll take a look at the state of the sun.

The chart above shows observed monthly sunspot values on the individual points, with a smoothed monthly values line shown by the blue demarcation. The red curve illustrates the expected smoothed monthly values over the next 5 or so years. Taking a close look at sunspot values over the past few months, we can see how weak the current solar cycle is, compared to the previous solar cycle, which ended around the 2008-2009 timeframe. Last cycle, sunspots averaged around 100 to 125 per month. These past few years, the maximum smoothed values has only just surpassed 75, meaning we are in a very quiet cycle.

From here, conditions only get quieter. The red forecast curve has us on the downward trend in coming years, meaning we have now passed the peak of this solar cycle. In a decade or two, this may have profound effects on the weather as we know it, but let's stick to the next several months for now.

The sun influences our weather more than most people realize. In a general nutshell, when the sun is in/around its peak of the solar cycle, sunspot numbers are enhanced, and winters tend to feature warmer weather at the mid-latitudes. This comes as a result of ozone being depleted en masse, as the active sun sends harmful rays into the stratosphere, dissolving that ozone, and cooling the atmosphere. This results in fewer opportunities for upper-latitude blocking, which leads to fewer opportunities for cold weather, and so forth. In a winter with a low number of sunspots, ozone is able to build up more freely, which warms the stratosphere. This warmth prohibits the polar vortex from strengthening too much (since it is also located in the stratosphere), which then leads to upper latitude blocking, and then additional opportunities for colder than normal winters.

A glance at the 30-day sunspot numbers over the past year or so shows how we've been experiencing a gradual decline in sunspot numbers over the past several months. Some activity has been picking up in recent days, but in due time, likely in the next several weeks, activity is expected to once again quiet down.

Solar Summary

The sun is expected to remain anomalously weak as we head into this winter, setting the stage for another exciting time in the stratosphere. The door is open for events such as sudden stratospheric warming (SSW) events, which could lead to outbreaks of cold air this winter.

Something I want to briefly touch on before we proceed is the Quasi-Biennial Oscillation (QBO).

The chart above shows positive and negative zonal wind values from the 1950s to present day. All gray shadings indicate the presence of positive zonal wind anomalies, while white contours depict negative zonal wind anomalies. As a quick refresher, positive zonal wind anomalies are winds that go from west to east, also known as westerlies. These westerlies enhance the strength of upper level lows (namely, the polar vortex) in the stratosphere. In turn, this limits the opportunities for polar vortex disruption and cold air outbreaks in North America. On the other hand, negative zonal winds, nicknamed 'easterlies' for their east-to-west movement, help weaken the polar vortex and open it up to potential intrusions from upper-latitude blocking and/or other methods of vortex disruption. Winters with these easterlies in place generally tend to be colder.

The Quasi-Biennial Oscillation (QBO) is what makes these positive and negative anomalies flip on a regular basis. In the last few weeks, we've just made the transition from a positive QBO to a negative QBO, as the elimination of positive zonal wind anomalies in the bottom panel shows. As we enter the upcoming winter, a negative QBO is expected to be in place. In essence, this will likely strengthen the risk for another cold winter this year.

Now, it's time for our final portion of the analysis section for the Official 2014-2015 Winter Forecast: the Analogs.

I created this year's analogs out of a four chosen long range predictors, before using personal judgement and individual examinations to narrow it down to my four analog years.

The image above shows 500mb height anomalies from my four analog winters of 1958-1959, 1960-1961, 1977-1978, as well as 2003-2004. In an earlier post, I mentioned how the winter of 1958-1959 was a "perfect scoring" analog, thanks to its remarkable similarities to expected conditions this winter. Since that time, the outlook has changed, and three other analog years have been introduced, all with relatively equal degrees of similarity to what I'm expecting this winter.

In this 500mb height anomaly image, we see quite a few interesting features. First and foremost, we see the Arctic Circle inundated with blocking high pressure, with the polar vortex virtually nonexistent in the upper latitudes. Three areas of significant ridging exist, as shown by the yellows and reds- one is located north of the Bering Sea, another juxtaposed over Greenland, and a third displaced in the middle of Eurasia. This leaves us with a very important question... Where did the polar vortex go?

It looks like the analogs are seeing the polar vortex positioned right over the Northeastern United States.

A very strong area of troughing is visible over the Northeast into the Canadian Maritimes, and a glance around the world shows no other body of troughing that is comparable to the one in North America. With that in mind, I do believe the analog years are pushing the polar vortex into the Eastern US.

This is something that can be predicted, as the analogs show sustained blocking high pressure over Greenland, as well as ridging over the Western US. These two factors, combined with overwhelming blocking in the entire Arctic Circle and general upper latitudes, easily permit the polar vortex and associated bone-chilling air to push into North America, specifically the eastern section.

The four analog years' temperature reanalysis shows that the four years were intensely cold for millions. We saw temperature anomalies below -4.0 degrees Fahrenheit in the Northeast, with below-normal anomalies hitting cities such as Chicago, Milwaukee, St. Louis, Little Rock, Houston, and New Orleans.

The Western US averaged above normal for these four years, with the West Coast and Rockies experiencing temperature anomalies anywhere from +1.0 degrees to +3.0 degrees or so above normal. This doesn't exactly spell good news for those hoping for drought relief in the West, as the ridging and warm temperatures shown in these two images typically result in dry conditions as well.

Unfortunately, that's just what these four years show. We saw precipitation anomalies nearing -6.0 inches below normal in the average of these four analog winers along the West Coast, with more-sporadic negative precipitation anomalies in the Rockies. Below-normal precipitation then engulfed the Midwest and Ohio Valley, extending all the way into the Northeast. Only eastern Texas and a small portion of southwest Louisiana saw above-normal precipitation for these four years.

The above image shows a pretty daunting image of the stratosphere, so let's decipher it. The red line shows observed temperatures at the 70 millibar level of the stratosphere, between the 65N and 90N latitude lines. The dashed green line illustrates average temperatures for any given time, while the gray outlines give an indication of the record high and low stratospheric temperatures for any given time period over the past few decades of records.

Gazing over the image above, specifically around the most recent records of temperatures, we find ourselves on the above-normal side, with that red line bursting up into above-normal territory more than once in the last few weeks. This year's warmth at the 70mb level looks to be a bit more prevalent than that of last year, as you can see just to the left of the center of this image.

Why is this important to the coming winter? Above-normal temperatures in the stratosphere allow for a higher threat for persistent high pressure to form over the Arctic Circle, and general upper-latitude area. The polar vortex, a strong low pressure system of cold air located across the troposphere and stratosphere, can be strengthened during times when the stratosphere is colder than normal, and weakened when warmth prevails.

When this warmth prevails, strong bodies of high pressure can punch north from the lower latitudes into the Arctic, disrupting the polar vortex. When this happens, fragments of the vortex can break off and be sent to the lower latitudes (as was seen last winter), or the whole vortex can be shunted down south. If the high pressure sticks around in the Arctic for long periods of time, it can be referred to as "blocking" high pressure, for the way it "blocks" the pattern from flowing east to west around the globe, since the high pressure remains stagnant and backs everything up.

If the stratosphere is to remain warmer than normal this winter, the polar vortex may fragment, leading to increased risks for cold air outbreaks in North America.

To sum everything up, here are the main points I'm looking at.

• Warmer than normal stratosphere may create blocking high pressure
• Positive PNA pattern expected this winter
• Negative NAO pattern possible, duration unknown.

After discussing everything above, here is the Official 2014-2015 Winter Forecast.

The Weather Centre
For temperatures this winter, I expect below normal anomalies to extend from the Northern Plains into the Deep South, and all points east. The Great Lakes, Northeast and New England areas may expect to experience well-below normal temperatures at times, as the ingredients are there for frigidly cold air to enter the North US in a similar fashion as last year.

In the Western US, warmer than normal temperatures are expected to prevail, in light of ridging shown in my analog years above, and the current positive-PDO state. These warmer than normal anomalies should extend into the central Rockies, before variable/average temperatures are anticipated.

The Weather Centre
For precipitation, a rather dry winter is expected. Below-normal precipitation anomalies are projected for the Ohio Valley and Northeast, a typical feature of El Nino winters. Around average to slightly below normal anomalies are expected to show themselves in the Midwest and Great Lakes, though not as pronounced as their Ohio Valley counterparts. Above normal precipitation is then expected in the Southeast.

In the West, another dry winter looks to be in store. The dry anomalies should focus in on the Pacific Northwest, as that region is typically drier than normal in an El Nino. However, dry anomalies may work their way south into the Southwest area, but I'm anticipating average to slightly below average anomalies there. The Plains are shown as average now, but may require a boost to slightly above average in the future.

The Weather Centre
Lastly, but definitely not least, the snowfall forecast. This forecast was the toughest to make, so bear with me as we navigate the uncertainty. I'm expecting below-normal snowfall for the Ohio Valley area, into the southern Midwest. This comes as a result of the weak to moderate El Nino expectation, which usually limits snowfall in this area. I'm watching closely for above-average snowfall in the Plains and Midwest, depending on how the Northeast Pacific and Western US regions evolve this fall and into the early winter. Around average snowfall is expected in the East US, with caution placed on the risk for big storms.

Without further ado, here is the overall graphic.

The Weather Centre
If you have any questions, comments or concerns about the forecast, don't hesitate to comment below. Please do not ask for your individual location's winter outlook- take a look at the 2014-2015 Winter Forecast Directory for a more localized view.

Thanks for viewing!

For regional, international, and personalized winter forecasts: CLICK HERE