Weather Blog: New LRC Pattern Check
Thank you for stopping by the Weather Watch 12 Blog! Fall is a season of change, not only because our temperatures cool and the first hint of snow enters the forecast, but because a brand new weather pattern becomes established. A weather pattern theory called the LRC, or Lezak's Recurring Cycle uses the new pattern to help make long range weather forecasts. In today's blog we look at the early signs of what the new LRC may mean for southeast Wisconsin.
First, let's start with the basics of the LRC theory:
- A unique weather pattern becomes established every year between roughly 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 fall thru summer 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 around the Northern Hemisphere.
To aid in picking out the new LRC we look at 500mb maps. These maps show the middle of the atmosphere and the large scale flow where long term long-wave ridges and troughs reside. The 500mb map below is from Wednesday morning at 7am. Notice the large upper level low over the Great Lakes and Northeast, a ridge over the Plains and Rockies, and another trough digging into the Northwest north to Alaska.
Doing map comparisons to help find the new cycle duration is a challenge, but one that when accomplished can lead to accurate long range forecasts. One map comparison does not prove or disprove the theory. Other factors play into finding the cycle duration, but in today's blog I want to focus on a map comparison.
Remember the map above is from Wednesday, October 31. Going back to September 9, 2012 reveals a pattern very similar at the 500mb level. The archived 500mb map from September 9, 2012 is shown below. Notice the large trough in the Great Lakes and Northwest, ridge in the Plains and Rockies, and trough into the Northwest.
While the new LRC is still developing, it may be possible that these maps align and the new cycle duration is somewhere around 51 days this LRC season. The next two weeks will play a big role in gaining confidence in the new pattern and cycle duration. Taking the LRC and a handful of other factors into account, we will reveal our winter forecast in a few weeks!
Until then please follow along as the new pattern develops and ask questions along the way!
For the latest weather information watch WISN 12 News. Updates are available throughout the day, just follow me on Twitter @jnelsonweather
Have a great day!