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Thank you for stopping by the Weather Watch 12 blog! Over the past couple of weeks I have been getting a lot of questions surrounding the weather pattern and what it will mean for this summer. In this entry we will discuss what to expect for the remainder of May, and touch on what to expect for June.
It seems like just yesterday that I started working at WISN, but it has already been 6 months! In this short amount of time I have been providing long range forecasts exclusively in the Weather Watch 12 blog. If you are new to the blog, or just need a quick refresher, I use a weather pattern theory called the LRC to make long range forecasts.
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/spring/early summer-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.
As I have mentioned many times in the past 6 months, this year’s cycling weather pattern is on roughly a 60-62 day cycle. The best place to view the theory is in the middle of the atmosphere, or at the 500mb level. This eliminates surface features such as moisture, friction, and microscale influences(such as a lake breeze or lake effect snow). Remember, we are looking at the long term, long wave ridges and troughs.
Let’s check out a couple of examples. The maps I’m about to show are ARCHIVED 500mb maps. Since we are on roughly a 60-62 day cycle, let’s look back to November and January and then compare the pattern to where we are at in May.
To help everyone see the features that I am discussing, I will put numbers on the items that I am highlighting. Also, you can click on the image to enlarge. The map below is from November 22, or 3 cycles ago. 3 main features are shown on this map. Let’s focus on numbers 2 and 3. #2 is an upper level low that is somewhat cut-off from the main flow. #3 is a large trough across the West.
The overall pattern repeated again roughly 60 days later. On January 22 the same features were present. The upper low labeled #2 and a large trough in the West, #3.
Now let’s fast forward 120 days and look ahead to this coming Friday/Saturday. Below is a forecast map from the 6Z GFS(Global Forecast System). This may seem amazing…but the pattern is about to repeat again! Below you notice the upper low labeled #2 and the large trough in the West #3.
The maps for November and May match up much better because the jet stream position/strength is closer during this timeframe. The jet stream in January is much stronger and typically farther to the south.
With the large trough in the West, this should allow warm air to pur into the nation’s mid-section and give us highs in the 70s this weekend! If you are wondering, I used the LRC to make long range forecasts all winter and spring. The most recent long range forecast that I made was posted to the blog on March 31. This was a forecast for April and May.
Outside of the heavy rain we had last week, the forecast has worked out well. Below is the exact forecast that was made for southeast Wisconsin for May back on March 31.
Precipitation: Below Average
Tempeatures: Above Average
Notes: If the trends continue this should be a warm month with below average precipitation. A warmer period may occur around the 17-24 of the month, and then a bigger warm-up the last day or two of the month that will extend into early June. This would be great news because Memorial Day is th 31st! I think a day of 85 degrees or warmer is likely sometime in May.
This forecast took into account the pattern in November, January, and March…the months that correspond to May. Again, translating the upper level features to the surface is tricky. The only part of the above forecast that will be off is the below average amount of rain. While I think the last half of May will be pretty dry, last week’s 2″+ rainfall brought the month to average, even if May ended now.
The warm-up in the 17-24th time window is spot on, and a reading of 85 or higher is still a possibility, along with a warm Memorial Day!
I will issue a June forecast next week, but right now I would say more active weather occurs in southeast Wisconsin. That means very likely several severe weather chances, and at least 1 severe weather outbreak. Temperatures should continue to trend above average. This is just a quick glimpse of June, but we will get into more of the specifics next week!
If you have questions about the pattern, or anything weather related, please post them to the comments section of the blog!
Have a great day!