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Thank you for stopping by the Weather Watch 12 blog! If you are new to our interactive blog…welcome! Each day we discuss a wide range of weather topics from the current days weather, to the big weather story across the U.S., or look ahead at the weather pattern.
A couple days ago one of our bloggers asked if I could discuss the weather pattern and what lies ahead. So in today’s blog I will look back and ahead to let you know exactly what to expect coming up.
Making long range forecasts is risky business and never perfect, but a weather pattern theory known as the LRC allows for accurate long range weather forecasts to be made. LRC stands for Lezak’s Recurring Cycle. I have been very excited to introduce this theory to viewers and bloggers here in Southeast Wisconsin. I first learned about the theory 4 years ago while working in Kansas City. Here is what the theory states:
- 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. Determining the cycle length each Fall really holds the key in using the LRC to forecast into the future. A very good idea of the cycle length is usually determined anywhere from late November thru December. Once the pattern goes thru its second cycle a period of days can be placed on the cycle length. As I have mentioned in previous blog entries, the cycle length this year is about 60-62 days.
When doing a map comparison to show a previous part of the cycle to the current weather I will use 500mb maps. A 500mb map is basically the middle of the atmosphere. This part of the atmosphere is a good areas to pick up on the long wave pattern across the U.S. It also eliminates surfaces effects such as friction and microclimates. In other words this helps to focus on the overall pattern.
Let’s start by looking back to November 21 and the pattern on that date. Below is an archived 500mb map showing many features(click on the map to enlarge). I labeled parts of the map 1-4 to highlight areas to compare on the next map. #1 is a compact upper low around Nova Scotia in Canada…while #2 is an upper low over the southern Plains. #3 is a weaker trough over Canada, and #4 is a trough digging into the Western U.S.
Now according to the theory, the overall weather pattern and same general flow should exist roughly 120 days or so later…or two cycle periods.
Let’s look at the latest 500mb forecast map for March 25. I again labeled 1-4 on the map below to correspond with what I am comparing the feature to on the map above from November 21.
Numbers 1 and 2 are almost spot on matches to the features from November 21. For number 3 and 4 the troughs exist, but slight position and strength differences are present, but the overall pattern is the same. The trough near the Pacific Northwest Coast for March 25 is a little farther west than the one in November. This slight shift and the presence of a ridge just to its east near the northern Rockies is allowing the upper low/trough over Canada to dive farthern south.
This is just one example of the LRC, and an example of where the pattern is currently at. Remember, the more ‘active’ months for Milwaukee and Southeast Wisconsin in terms of precipitation and temperature swings have occurred in October, December, and February. With a roughly 60ish day cycle present…this means April will be more active and present more rain and maybe snow chances for the area compared to March. Coming up soon I will issue a forecast for April & May!
In the meantime, please take our poll question. The LRC is a theory(not proven yet) that states the weather pattern repeats. What to you think?
Have a great day and make sure to post your thoughts or questions to the comments section!