Is Winter Over?

So, the predicted cold outbreak that was supposed to happen around February 14th didn’t happen. Actually we are seeing just the opposite with above normal temperatures not seen since late November.

The sun angle is getting higher and I am hearing a lot of folks saying winter is over. But not so fast. Beyond next week, or in about 10 days around the 24th or 25th of February, there is the potential for cold air to return based on recent events occurring high in the atmosphere over the North Pole. A recent major sudden stratospheric warming event occurred near the North Pole last week.

To make this as simple as possible, a sudden stratospheric warming (SSW) is an event where the polar vortex of westerly winds in the winter hemisphere slows down or even reverses direction over the course of a few days. The change is accompanied by a rise of stratospheric temperature by several tens of degrees. This disrupts the jet stream and even reverses the winds from a westerly direction to an easterly direction. The winds of the jet stream is what usually helps hold the polar vortex in place. When this happens, it usually translates to a discharge of frigid air over the mid-latitudes of one to two continents of North America, Europe or Asia beginning 10-14 days later.

While a major event only occurs every so many years, there is a problem when they do occur with either the collapse of the entire polar vortex or a split. This time, it looks like a split. Either way we know its effects often lead to extreme cold winter weather for a prolonged period within the mid-latitudes. At least that is what is supposed to happen. The stratospheric Polar Vortex split is now in full swing and it seems to be a fairly extreme event. The poleward heat flux into the polar stratosphere is at an all-time record. An important question is will the extreme event in the stratosphere translate into an extreme event in the weather such as a huge storm or extreme cold?

In Polar Vortex disruptions, including those most similar to the current event we are seeing, cold temperatures arrive in the Northeastern US in about two weeks’ time. But something is not right here. The model forecasts are saying warmer than normal to end the month. Though on average it takes about two weeks’ time for the transition from mild to cold, it can vary. Following the Polar Vortex split of early January 2013 the cold was delayed well beyond two weeks, with the core of the cold not arriving until March. A similar lengthy delay cannot be ruled out this year. This pattern favors cold temperatures in the Eastern US, Southeastern Canada, Europe, Siberia and East Asia with mild temperatures in western North America and Eastern Siberia going into March.

In the near future, as more and more warmth and instability comes into play, chances for thunderstorms, even severe weather, will expand from Texas and the Gulf Coast into the Tennessee Valley. The weather down south looks mainly warm for the next week or more. Sure, some cold fronts will move in and cool some folks down for a day or two and the colder intrusions might lead to bouts of ice or snow in a few places.

Over the next few weeks Kentucky will be sandwiched between mild air in the south and cold air to our north and northwest. This means we are smack dab in the middle of the battle zone between the two air masses. The result will be heavy rains and potential severe storms. Some models are showing anywhere from 6 to 8 inches of rain between now and Feb. 24th. So, is winter over? I think not. Will there be more snow chances in the future? Yes, at least through much of March. If the Polar Vortex arrives as expected by a few others and myself it could be a while before true spring sets in. Feel free to leave comments and be sure to hit the “Like” button at the bottom of this post.