The highest part of the meteorological atmosphere is currently undergoing great changes. Researchers are finding that these changes occurring high up in the air eventually turn into a realignment of weather conditions here on the ground.
The second part of the Earth’s atmosphere is called the stratosphere. It sits at the top of the troposphere, where most of our weather occurs. Currently, Sudden Stratospheric Warming (SSW) is underway.
The stratosphere is about 100,000 feet above the ground. Usually in winter there is a swirling vortex centered on the north pole, with the vortex in the stratosphere. This is the vortex that most researchers call the polar vortex. On December 25, the average temperature in this vortex began to warm up. Since then, the temperature of around 100,000 feet has warmed by 54 degrees Fahrenheit. While this might be what you think defines an SSW, there is actually another weather feature that researchers are focusing on.
Michael ventrice, Ph.D, and IBM meteorologist, says the real key indicator is when the swirling winds from the stratospheric vortex slow down and reverse direction. Ventrice originally studied tropical meteorology and how atmospheric waves over other parts of the globe affect hurricanes in the Atlantic. Ventrice was in graduate school of meteorology in 2012 and says sudden stratospheric warmings were just discovered at that time. He believes that understanding the stratospheric polar vortex and sudden stratospheric warming will be key to making a more accurate sub-seasonal forecast. A sub-seasonal forecast would be a 30-day to 45-day forecast.
Ventrice explains how the domino effect works during and after an SSW. The swirling vortex slows down and the westerly wind normally swirling over the north pole becomes an easterly wind. The vortex, called the polar vortex, then slides out of being centered on the north pole. At this point, Ventrice is indicating where vortex changes are critical for weather in the eastern United States over the next few weeks. This SSW has the polar vortex initially moving to be centered over Siberia.
Now we turn to talking about the weather that accompanies it in the meteorological atmosphere, the troposphere and here on the ground. Once the stratospheric vortex moves towards Siberia, a powerful and deep storm system develops over the North Pacific. Powerful storm systems dominate and bend the jet stream across North America. The jet stream emerges from the Pacific storm and crosses Canada, bottling cold air in northern Canada. So Ventrice says that the first effect of this particular SSW is a heat wave in the eastern United States. This is the heat wave in which we are currently in Michigan and the Great Lakes. It’s not extremely hot, but we are running five to 15 degrees warmer than normal. After about a week, the strong storm in the North Pacific is replaced by a strong high pressure ridge. Cold air begins to form in western Canada. Then the domino effect bends the jet stream south across the eastern United States. Ventrice says that about two weeks after this SSW, the cooler air is expected to move to the eastern United States. United.
All of the weather models we look at, including Ventrice, show a slightly cooler trend around mid-January.
But will the cold be severe and last a long time? Ventrice’s research shows that when a sudden stratospheric warming begins to move toward Siberia, the subsequent effects on Michigan and the eastern United States are transient. He finds that the cold usually lasts for about a week and then can revert to a warmer-than-normal pattern. Ventrice says this up-and-coming cold-to-hot weather pattern could go through two or three cycles. This would give Michigan and the eastern United States an upward and downward trend in temperatures until mid-February.
Ventrice found a more severe and lasting cold pattern when the SSW begins over the North Atlantic.
One more thing Ventrice is monitoring to predict the severity and duration of the eastern US cold – an elevation block above Greenland. A strong upper-level boulder over Greenland accentuates the southerly fold in the jet stream over the eastern United States. Currently, a block of Greenland is expected, but not at a very high magnitude.
What does all of this mean for Michigan?
The main point here is that the upper atmosphere is undergoing significant changes now and in the coming weeks. This should bring Michigan and the eastern United States our first real winter cold. Does it bring snowstorms? It’s hard to say right now, but cold is needed for snowstorms. So the first piece of a winter puzzle will likely be in place around January 15 through January 18.
Ventrice suggests that the next avenue of research will be to learn how to quantify the amount of cold and the duration of the cold after these sudden stratospheric warmings. Ventrice reminds us that this is a relatively new forecasting technique for long-term forecasting.