***Watch WISN 12 News for the latest weather information!***
Thank you for stopping by the Weather Watch 12 blog! After a relatively quiet first week of January in the books, signs of a much more active pattern are beginning to show.
The more active pattern should lead to several chances for precipitation, including some ‘wetter’ storms and also shots of frigid arctic air! If you are new to the blog or just need a quick refresher, I base my long range forecasts and trends off a weather pattern theory called the LRC, or Lezak’s Recurring Cycle.
Here are the basics of the theory:
- A unique weather pattern sets up every year between October 1st and November 10th
- The weather pattern cycles, repeats, and continues through winter, spring and into summer. Identifying the cycle length helps tremendously when making long range weather predictions.
- Long term long-wave troughs and ridges become established and also repeat at regular times within the cycle. These dominant repeating features are a clue to where storm systems will reach peak strength, and where they will be their weakest.
- The LRC is a winter-long pattern! There is a pattern! It isn’t just one long-wave trough, storm system, or ridge. It is a sequence of troughs and ridges that are cycling across the Northern Hemisphere.
To put this in very simple terms, the weather pattern that occurs in October and November repeats thru the Winter, Spring, and into the Summer. The cycle length will vary each year. I’ve seen cycles of 42-46 days, 60-62 days, etc. This year’s cycle is around 46-52 days, but as of this writing the cycle duration has been hanging around 50 days for the past few weeks.
The quick moving clipper systems and shots of light snow that we have experienced this week were a highlight of this year’s pattern identified in the winter forecast. Below is the map that I showed back on November 23. The trough in the Great Lakes to the Ohio Valley is one of the main long term longwaves in this year’s cycling pattern.
To some, this may be the ‘boring’ part of the pattern. A northwest flow generally brings lighter snows and doses of cold air. But a pattern shift is ahead, and that should lead to more active weather.
As the pattern shifts, a transition to more of a southwest flow will occur. This will allow more moisture to work into the systems as they move into the central U.S. As the storms move by, the flood gates may open up allowing very cold air to spill into the Midwest.
Below is the map that I showed in the winter forecast highlighting the long term longwave that will likely bring us a majority of our precipitation this winter. Remember Minneapolis had a record setting snowy December? This year’s LRC has Minneapolis in a prime location for snow.
While southeastern Wisconsin is not in the bullseye this winter, I do expect to see more good snow opportunities as the active part of the pattern returns beginning this week.
Another indicator that a more active pattern may be right around the corner is looking at the arctic oscillation. Here is a quick explainer of the ‘AO’.
The Arctic Oscillation
The Arctic Oscillation refers to opposing atmospheric pressure patterns in northern middle and high latitudes.
The oscillation exhibits a “negative phase” with relatively high pressure over the polar region and low pressure at midlatitudes (about 45 degrees North), and a “positive phase” in which the pattern is reversed. In the positive phase, higher pressure at midlatitudes drives ocean storms farther north, and changes in the circulation pattern bring wetter weather to Alaska, Scotland and Scandinavia, as well as drier conditions to the western United States and the Mediterranean. In the positive phase, frigid winter air does not extend as far into the middle of North America as it would during the negative phase of the oscillation. This keeps much of the United States east of the Rocky Mountains warmer than normal, but leaves Greenland and Newfoundland colder than usual.
Now that you know what the AO is, let’s look at whether we are in a positive or negative phase. Since December 16 the AO has been negative, but around Christmas it became a little less negative. But heading into next week, the AO is forecast is become more negative again.
Many of the dips in the AO observed data below were accompanied by ‘wettter’ periods. Including November 21-25, which moving that forward 50 days(current cycle duration) leads us to this coming week!
So by using the LRC and the arctic oscillation, I am confident that we are heading into a more active part of the pattern. If you have questions about the pattern or this blog, just post your question to the comments section.
Make sure to watch WISN 12 News for the latest on the weekend.
Have a great day!