We are officially in spring, and I think many of us are more than happy to put winter in a ‘bad memory’ category. There were so many reasons why the winter of 2016 -2017 was remarkable that it’s hard to single out just a few. Here are the leading contenders.
Winter 2016-17 was the coldest on record for the Olympia area in over 30 years. Since October 1, 2016 we had 47 days below freezing (≤ 32°F) in the City of Olympia (several more days in outlying areas of Thurston County).
Putting that in perspective, when compared with the previous winters that is almost twice the freezing days that we have had in a long time. It was just the freezing days but also persistently low daytime high temperatures. Daytime highs in October through mid-March 2017 were on average fifteen degrees below normal.
The Table below summarizes the past two years of winter months with temperatures below freezing. There were twice as many freezing days during the winter of 2016-17 as there were during the previous winter and well above the average of 31 days.
The coldest temperature recorded near Olympia was 16 degrees F above zero on January 5, 2017. This temperature puts us right at the very lower limit of our USDA plant Zone 8a so some of our more delicate plants may be damaged or dead as a result.
There was a lot of it and it started early. October 2016 broke a record for rainfall with a little over 14 inches recorded in Olympia. That is 10 inches higher than average! That’s how we started our wet season and it didn’t get much better after that. We recorded above average rainfall in October, November, February and March. January 2017 was anomalously below average by four inches. As of March 22, 2017 we are currently at 56 inches of rain since October 1, 2016. That is more than the total average (52 inches) for the year in the first six months of the 2017 Water Year. Remember from earlier blogs that the water year runs from October 1- September 30. That is how precipitation is reported in order to account for the wet months without splitting them at January 1 in the middle of winter. Below is a table of where we stand for precipitation this winter vs the average we typically get.
Snow and Ice – Naturally the cold and the rain combine to make snow and sleet and we got more than our normal share of it. In fact, this past winter we had four minor snow events (4 inches or less) and one major snow event (greater than 8 inches). We typically get two minor snow events per season and one major event every four years.
Isn’t climate change supposed to make it warmer? Climate change is unpredictable in its effects and in its application to individual places and seasons across the world. Some areas will become much warmer very fast and other may get wetter or even colder.
The old phrase, “Global Warming” is misleading because the climate can become very unstable and change dramatically to become either warmer or cooler, or wetter, or drier. The average global temperature has risen steadily over the past forty years with dramatic increases in the past decade but some areas experience bizarre and unpredictable weather and seasonal fluctuations also.
If you are interested in the technical explanation, keep reading
The Jet Stream had a big impact. You could fundamentally explain the winter of 2016 -2017 by simply observing satellite images of the Jet Stream(s) over the northern hemisphere, including North America, the North Pacific Ocean and Europe throughout the winter months. The Jet Stream took extreme course changes and plunged huge amounts of tropical and temperate air deep into the arctic as far north as the North Pole. In fact, temperatures at the North Pole were twenty to forty degrees above normal. This strong push of massive amounts of temperate and subtropical air into the arctic did two things.
1. It warmed up the arctic substantially, and 2. Displaced huge plumes of arctic air southward in several locations around the northern hemisphere.
These plumes impacted the North Central Pacific Ocean, Northwest US, Northcentral Europe, and Siberia. Parts of Europe had the most severe winter in over 100 years. To make things worse, a strong circum-global jet (Southern Jet Stream) formed near latitudes 25 to 30 N which essentially confined the arctic plumes from driving far south as they normally do in typical winters when the Southern Jet is not as strong. The strong westerly jet stream airflow over the lower latitudes air kept the southern US above average (20 degrees above average in some places) by not allowing the cold air to travel south of about latitude 30N. The jet at this lower latitude also draws in more air from the tropics producing a strong westerly surface flow. That in turn warms the surface flow below 700 mb. This means anything south of the margin will be quite warm and anything north of it will be colder than normal.
The arctic air forms large ridges and domes of very high pressure which do not easily move once emplaced and so perpetuate the deformation and deflection in the normal jet patterns. In March 2017 the normal pattern emerged when a substantial arctic plume drove deep into North America on the path they typically take during winter. They generally form in northern Canada and migrate rapidly south through the Midwest. They are then deflected eastward by the normal northerly jet pattern over the northeast and mid-Atlantic region and all the way into Georgia and Florida. The typical pattern is beginning to emerge with the predominant jet returning to latitudes 40 to 50N thus limiting oscillations deep into the arctic. This should moderate temperatures but may not halt precipitation in the northern US.
2. One of the other results of climate change is the addition of more water vapor into the atmosphere, and with it, more heat energy. The atmosphere transports this water vapor into the cooler latitudes where it condenses (especially when it encounters mountain ranges) into rain and snow. California is a prime example of this happening. With the cold temperatures caused by the mechanisms described above and the southern Jet plowing into California bringing increased water vapor with it. These two forces met and delivered California from its worst drought in decades. It went beyond that and delivered three to four times what California typically receives in rain and snow in a normal season. Ten years of extreme drought was erased in three months because of the mechanisms described above. Similar things occurred in Northern Italy where four to six feet of snow fell in just days and temperatures in Moscow, Russia, experienced temperatures of -70 °F. Cold even by Russian standards.
There is evidence in the past two weeks that this pattern has abated and the polar jet Stream is returning to its normal pattern and the southern Jetstream is diminishing in it intensity as the Northern Hemisphere progresses into spring. This solves the winter weather dilemma but still leaves us with the undeniable realization that our climate is changing and that the types of disruptions we experienced this winter may well happens again. There may also be a warming pattern that develops next winter. It is very difficult to model and predict these patterns any more. Remember the climate models are a product of what happened in the past combined with future projection fluid dynamics supercomputer models. If the past can no longer be a guide in this equation then the results are anything but predictable and highly unlikely to be accurate. We shall see where this climate roads takes us.