Thursday, July 10, 2014

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.

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.

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.


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.

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.