Long Range Climate Models Show Snowy Eurasia in October

Long range models are giving indications that the coming October may feature above normal precipitation in the Eurasia area, something that could then favor a colder than normal winter for the United States.

NOAA

The image above shows a global probability of above, below, and neutral precipitation anomalies. We can focus in on many areas of the world and try to decipher what they mean for the coming winter, but today, we’re going to keep our attention on the forecast over Russia and the general north Asia area.

This forecast, a probability forecast using a combination of roughly six or seven different climate models from various global meteorological agencies, shows a swath of above normal precipitation probabilities across a good portion of central Russia. In the forecast, we see the precipitation anomalies extending north of the 60N longitude line, an important line in our situation.

A few years ago, Dr. Judah Cohen created the Snow Advance Index, abbreviated as the SAI. Dr. Cohen claimed that by measuring snow cover anomalies in Eurasia, namely north of the 60N parallel, one could decipher temperature anomalies for the upcoming winter. For example, an October with sustained below-normal snow cover anomalies would favor a warmer than normal winter. Similarly, above-normal snow cover in Eurasia for the month of October would then tell us to anticipate a colder than normal winter. In past winters, I have seen the SAI perform quite well, the only exception being this past winter. Thus, I hold this index in fairly high regard in terms of accuracy.

As of now, guidance does favor a wetter than normal October over Eurasia, with some of that likely putting down snow cover in the process. While this is expected to change in the future, this could be an indication that we may expect a snowy October in Russia, which may lead to a colder winter here in the United States.

Andrew

2014-2015 Winter Forecast Update; Colder Outlook Now Favored

This post will examine the factors being analyzed for the upcoming winter, their impacts on the cold season, and anything that may have changed from the issuance of the Preliminary 2014-2015 Winter Forecast to today.

After going over the factors presented in our Preliminary winter forecast, and examining new data presented to me, I’m electing to favor a colder outlook to this winter, over the original warmer projection earlier this summer.

ESRL

The above image shows observed sea surface temperature anomalies across the globe from July 1, 2014, to July 8, 2014. In this image, we notice three particularly interesting features. One of these features is the pool of well above normal water temperatures in the Northeast Pacific into the Gulf of Alaska. This particular mechanism is one of substantial importance, given it also played a significant role in our last winter.

In the winter of 2013-2014, we had this warm pool present throughout the entire season, and it was quite possibly the most influential factor in making that winter as cold as it was. The warm water enabled strong high pressure to form over the Northeast Pacific, something that is continuing even to this day. See the examples below.

ESRL

The image above shows mid-level geopotential height anomalies in early January 2014. Cold colors indicate the presence of strong low pressure, hence below normal temperatures. The yellows and reds indicate high pressure, and warmer than normal weather. This image was recorded in the middle of the extreme cold spell that kicked off the new year, also spawning the ‘polar vortex’ hype. In this graphic, we can see the polar vortex located somewhere in south-central Canada, bringing that extreme cold to much of the United States. We also saw strong high pressure centered over Nova Scotia, and quite extensive high pressure from the Southwest United States to Alaska. It was this second body of high pressure that formed as a result of those aforementioned warm waters in the northeast Pacific, and we saw this ridge stay in place consistently throughout the winter. Now, with the warm waters in the Gulf of Alaska still in place a good year later, I am significantly concerned with the idea that we could see this extensive ridge forming yet again this coming winter.

Building off of this idea, in addition to the water temperature pattern in the Pacific going relatively unchanged since last winter, the upper air flow has remained relatively unchanged as a result.

Tropical Tidbits

This forecast image, valid on Monday, July 14, shows the same 500mb geopotential height concept that we saw earlier in this post, with blues indicating low pressure and reds indicating high pressure. In this forecast image, once again, we see strong high pressure stretching along the western coast of North America, with another body of high pressure being observed over Nova Scotia and far eastern Canada. And in a situation just like the polar vortex plunge last winter, we see anomalous low pressure crashing into the United States. This upper air pattern is almost (keyword almost) exactly like the one we saw last winter, bringing into question if we could see this pattern persist into next winter as well. In my opinion, if the sea surface temperature anomalies remain the same into next winter as they are now, I see no reason to discount the idea that the coming winter could be like last winter; a cold, potentially brutal one.

ESRL

Adding to the pieces of this puzzle is the body of significantly above normal temperature anomalies near Greenland. This is a change in what we saw from last winter. This past cold season, we observed primarily below-normal water temperatures near Greenland, resulting in some very stormy periods in the northern Atlantic. However, now that we’ve entered July, we now find ourselves with a formidable body of positive water temperature anomalies, something likely to change the game for the coming winter.

When warmer than normal water temperatures exist near Greenland, it provides a similar opportunity to that in the northeast Pacific, where high pressure can form. In this instance, high pressure can form over Greenland, and actually force the jet stream to buckle in the East US, resulting in an influx of colder than normal air to that area, as the image below shows.


NWS

 We didn’t have that warm water in place last year, meaning such a sequence of events couldn’t happen often, if at all. However, now that the anomalies have reversed, we’re in a much better position to see the jet stream buckle more frequently over the East US, resulting in another cold winter.

On a side note, we also see persistent above normal water temperatures near Nova Scotia, which could provide the mechanism needed to create high pressure in that area. This could then combine with the warm SSTs in the northeast Pacific to create an environment very similar to the one observed with the polar vortex incident.


DMI

We now continue on with a look at temperatures in the Arctic Circle. The graph above shows observed temperatures in Kelvin over the Arctic Circle (colored red), from the first day of 2014 to present day. We also see a green line, indicating the average Arctic Circle temperature for that given day, allowing us to compare with the observed temperatures to detect any anomalies. The consistent blue line highlights the freezing temperature mark. On this image, we see Arctic temperatures have been steadily below normal this summer, something that does not bode well for us in North America.

In order for winter to even be cold to begin with, one needs cold air. It seems simple to understand, but now we need to understand where this cold air will come from. By using this graph above, we can get an early glimpse at how much cold air the upper latitudes may be storing up for this winter. In this instance, below-normal Arctic temperatures in the summer might tell us to prepare for a cooler than normal winter ahead, while a warm Arctic summer could indicate a warmer winter ahead. Going by this guideline, we might be best off preparing for a chilly winter.

Now, last but definitely not least, we will go over the evolving situation in the Equatorial Pacific.

CPC

The image above shows equatorial upper-ocean heat anomalies, in Celsius. This means that the temperature anomaly for the upper portion of the Equatorial Pacific is calculated, giving a helpful indicator to the state of the El Nino-Southern Oscillation (ENSO) phenomenon. In this case, positive anomalies indicate the presence of warmer than normal waters, and potentially an El Nino. Similarly, below normal upper ocean heat anomalies highlight below normal water temperatures, potentially also the presence of a La Nina.

Looking at this graph over the past year, particularly since February 2014, we see that the upper ocean heat anomalies have skyrocketed, up to abut 2.0º Celsius above normal in late March 2014. It was at this time that we were expecting a strong El Nino to evolve for the coming winter. Things have certainly changed since then. The warm waters began to hit the surface this past spring, but couldn’t hold their ground, per se. As a result, we have seen the positive anomalies drop off to neutral territory, indicating that any possible El Nino no longer theoretically exists. Time will tell if we see another body of warmer than normal water temperatures pushing to the surface, possibly creating an El Nino. If that does not happen, we can expect the winter pattern to be dominated by more mesoscale (smaller-scale) features, such as the bodies of warm water temperatures in the northeast Pacific and around Greenland. This could then lead us into - you guessed it - a cold winter.

All of this is expected to change as we progress through summer and into fall; this is merely an update to the situation, since many things have changed since the initial issuance of our Preliminary 2014-2015 Winter Forecast.

Andrew

Upcoming Winter Shaping Up Similar to Last Winter; 2014-2015 Could Be More Severe

Note: The idea of this winter being more severe than last is a preliminary finding based on the work presented in this post. It is by no means set in stone, and is subject to revision.

After a look back at July 2013, I'm finding that July 2014 sea surface temperature anomalies are not only similar to last July, but could be foreshadowing a more severe winter than last.

ESRL

Shown above is a reanalysis image of sea surface temperature anomalies from July 1, 2013 to July 8, 2013. During that timeframe, we saw a large body of warmer than normal waters controlling the northeast Pacific into the Gulf of Alaska, even stretching down towards the coastal waters near southern California. We also saw a pocket of well above normal water temperatures west of Japan, with opposing cooler than normal waters to the east. We also saw the La Nina-like water pattern along the Equatorial Pacific, which helped keep us in a Neutral-ENSO winter for this past cold season. Transitioning to the Atlantic, we saw a snaking line of below normal SST anomalies, occasionally interrupted by small bodies of positive water temperature anomalies, which were mainly confined to the northwestern Atlantic.

Now, let's compare all of that to what we've seen so far this year.

ESRL

The image above now shows sea surface temperature anomalies, still on the same intervals, but now valid from July 1, 2014 to July 8, 2014. Looking to the northeast Pacific, we see that the large body of above normal-temperature waters has not only persisted, but has now intensified and expanded its influence. This was a major factor in last winter's atmospheric flow, and I don't expect things to be any different this winter. We now see the Bering Sea flooded in warmer than normal waters, though just what impact this particular feature may have is unclear right now. We see a similar opposing water temperature pattern to the west and east of Japan, though a substantial change in the Equatorial Pacific is the presence of warmer than normal water temperatures as opposed to the below normal temperatures last year at this time. This would typically indicate the presence of an El Nino, but with uncertainties as to if it will sustain itself, and if the atmosphere will actually "recognize" the presence of an El Nino, some things still need to be sorted out.

Now that we've gone over the similarities, why am I thinking that this winter could be more severe than last?

1. Above Normal Water Temperatures in the Northeast Pacific
Last winter, we experienced extreme bouts of cold, many of which were due to the proximity of the United States to the polar vortex, a massive, semi-permanent low pressure system stationed over the Arctic Circle. The polar vortex was persuaded to dip south into North America, thanks in large part to a massive ridge that constantly formed and re-formed along the west coast of the continent. Because the jet stream went up with the ridge pushing northward, it had to also dip down somewhere, and that somewhere became the United States. The big ridge originated from the body of warm waters in the northeast Pacific last winter, which is why I'm so concerned seeing that mechanism still in place today. If those warm waters stay in place in the northeast Pacific into the winter, they could make that big ridge re-appear, possibly stronger than last winter, leading to an even colder winter this year.

2. Above Normal Water Temperatures near Greenland
Something we didn't have last winter was a swath of above normal water temperatures near Greenland. This prevented high pressure from forming over that area, something that would have raised the chances of an even colder winter than what we ended up seeing. This year, as the July 2014 SST image shows, we do now have a large body of above normal SST anomalies near Greenland. This significantly raises the potential of high pressure forming in that area, buckling the jet stream to the west and resulting in an even colder winter possible. This is just another mechanism I'm watching this winter that could cool down the temperature forecasts even further.

Whether all of this ends up happening, or doesn't happen at all, is yet to be seen. The point is, based on sea surface temperature anomalies, this year is looking a lot like last year at this time. And according to preliminary looks at some key SST anomaly features, things could be more rough than last winter.

Andrew

Midwest, Ohio Valley Threatened by Significant Cold Blast Next Week

The upcoming cold blast is expected to drop temperatures into levels more akin to those observed in the fall season.

CPC

The Climate Prediction Center's 6-10 day temperature anomaly outlook shows significant warm temperature anomalies, centered over Washington, Oregon, Idaho and Nevada. These warm anomalies look to be produced by strong high pressure building up across the West Coast into Canada. As a result of this strong ridge, a strong low pressure system looks to drop south into the United States. This system looks to be the summer version of the infamous polar vortex, and even though the harsh cold is reduced due to the summer season, anomalous cold is still expected. For this reason, we see below normal temperature anomalies stretching from Montana to the Atlantic Ocean, maximized over Minnesota, Wisconsin, Michigan, New York, Pennsylvania, Ohio, Indiana, Illinois and Iowa. These aforementioned states could see temperatures drop into the low-40s, or even an isolated upper-30 degree reading.

Drag me to storm models

On the morning of July 16th, we see the cold blast taking hold over much of the country. Lows below 60 degrees extend from Montana to North Dakota, down to Kansas and West Virginia. We then see the core of the cold slamming the Plains and Midwest, where lows in the 40s can be expected in many spots. Towards the Great Lakes in the Upper Peninsula of Michigan, lower-40s may be possible.

Drag me to storm models

By the morning of July 17th, the cold is beginning to recede from the western Plains, but is only intensifying in the Ohio Valley. We still see lows around the mid-40s around Iowa, Minnesota, Wisconsin and Michigan, with lows flirting with 50 degrees closer to Missouri, Nebraska and Kansas. The coldest weather now stretches into the Northeast, with states like Pennsylvania, New York, Vermont and New Hampshire experiencing lows deep into the 40s. The mountainous regions of West Virginia could actually see lows nearing 40 degrees, or even into the upper 30s.

Make sure any sensitive outdoor plants are prepared for this cold blast, as damage could be done due to the longevity and pure anomaly of this cold weather event.

Andrew

Unseasonable Cold Blast Looming; Pattern Similar to Last Winter

An unseasonably cold airmass looks to wash over the northern United States, in a pattern eerily similar to the one seen this past winter.

CPC

The Climate Prediction Center's 6-10 day temperature outlook shows significantly above normal temperatures across the West US, most severe over Washington, Oregon, Nevada, Idaho and California. In response to this warmth, we see a deep airmass of unseasonably cool temperatures pushing south across the Midwest, with states like Minnesota, Wisconsin, Illinois, Iowa, South Dakota, Nebraska, Kansas and Missouri all affected on the highest level. Warmer than normal weather looks to retreat to the Gulf Coast and coastal regions along the Eastern Seaboard, but the main story here is indeed the colder than normal weather.

Drag me to storm models

Shown above is a long range forecast of temperatures on the morning of July 15th, in the middle of this unusually cold spell. We see temperatures on this morning plummeting to as low as the mid-40s in the Midwest, where the heavy blankets might need to make a surprise appearance. Temperatures in the far northern Plains into the upper Midwest might even flirt with the low-40s, possibly even into the upper-30s if there will be clear skies. Those finer details will need to be ironed out in days to come, but the general idea is that things are looking pretty cold for a wide swath of the country in the next week or two.

PSU

Oddly enough, the atmospheric pattern behind this expected cold blast is quite similar to the pattern we observed this past winter. On the top-left image, we see the mid-level atmospheric flow valid on July 14th. Here, we can see a strong vortex dropping anomalously south from Canada, nearly pushing into the United States. If you recall, we had the polar vortex take a very similar path down south more than once last winter, which is how the weather got so cold so often. So what's provoking this to happen again, only this time in mid-July? The same thing that made it happen six months ago. We see a very strong ridge pushing north across the northeast Pacific and into the Gulf of Alaska, which is how the West US should end up with those much warmer than normal temperatures. And, bringing things back full-circle, that ridge is likely being caused/enhanced by the body of above-normal water temperatures in the Gulf of Alaska that we targeted as the mechanism responsible for the brutality of last year's winter. The latest water temperature anomaly image is shown below, which identifies the body of much warmer than normal water in the northeast Pacific.

ESRL

Andrew