Wednesday, October 19, 2016

Winter Outlook for the Mid-South (2016-2017)

By the end of March 2013, we were more than ready to put Winter behind us after bitterly cold temperatures hanging on and periods of snow blanketing the area. We were influenced by a weak La Nina episode and arctic air was readily available to the Eastern United States. Currently the Climate Prediction Center is in "La Nina Watch" mode with a 70% chance of development this Fall and continuing into Winter 2016-2017. A record El Nino episode came to an end early in the Summer and we have been in a neutral period for a couple of months now. Signs of continued cooling in the Pacific waters off the coast of South America points to the likely development of a weak La Nina episode for the cool season.

The reason we look at El Nino and La Nina episodes is because it has a direct impact on the overall weather pattern across North America. It gives us guidance. During La Nina, we tend to see colder winters and a higher likelihood of stormy (wintry) weather. Temperatures during past La Nina winters look like this:
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La Nina influenced winters have shown in the past:

  • Temperatures: The weakest episodes of La Nina have produced colder temperatures averaged from Dec-Feb. The stronger the episode the less likely it became 
  • Snowfall Totals: During the weaker La Nina episodes during winter months, higher snowfall totals were more common. The stronger the episode, the lower snow totals tended to be as a result. Some of our historically highest snowfall events have occurred during weak La Nina influenced winters. 
  • Precipitation Totals: Total precipitation (rain, sleet, snow, freezing rain) varied quite a bit for each La Nina winter but also trended toward being at or above average. 

Click to enlarge

NOAA will be posting new images on Thursday and I will update them when they are released. Here is what they currently forecast for the Oct-Nov-Dec period which finished up Fall and begins Winter. 
Folklore has been a fun and interesting way to "predict" upcoming winter seasons. In the Mid-South, many of us are familiar with two popular indicators, the persimmon seed and the woolly bear. I was driving through the campus of WKCTC last month and collected a few persimmon fruits to cut open a couple seeds. The result of the seeds opening are shown below. As for the woolly bear caterpillar, I "analyzed" one that a viewer sent me a picture of from South Fulton, TN. The segments/colors are also explained below.

One thing that can have a very large impact on the winter weather pattern is where the actual jet stream will set up for most of the season. It can make a big difference between cool & mild, snowy/icy/rainy across the Local 6 area alone. We've seen it time and time again. 

Here are some key points from the guidance that we've looked at and what folklore supports/suggests:

  • TEMPERATURE: Average or below average temperatures are most likely. A few warming periods are almost always expected during any winter in the Local 6 area.
  • PRECIPITATION: Average precipitation of including all forms is most likely. With average or below temperatures expected, a trend towards snow/sleet/freezing rain may be likely.
  • SNOWFALL: Average or above average snowfall is likely. Normal snowfall for the winter season is 8".

Tuesday, September 27, 2016

Is that really a Woolly Bear?

Many of you have been sharing with us your photos of the great Winter predictor....the Woolly Bear! You've probably noticed a wide variety showing up in your own backyard. Not all "woolly-looking" caterpillars are Woolly Bears. Even the all-black versions are actually a different type of caterpillar.
Below shows a good photo of what a TRUE Woolly Bear Caterpillar looks like. They have very full, thick bristles and have both orange and black segments.The other three caterpillars are often mistaken for the true Woolly Bear. Both the blond and tan colored caterpillar are the Yellow Bear Caterpillar.  The all black caterpillar with faint red stripes on the segments is the Giant Leopard Moth Caterpillar. They all have that bristled look but the one on the far right is the Woolly Bear.

Now let's get to specifics....The folklore says that the Woolly Bear Caterpillar is a predictor of the upcoming winters' harshness. Each Woolly Bear has orange and black segments (13 in all). Each segment is said to represent the 13 weeks of winter. The front or head of the caterpillar represents the start of winter and so forth to the tail-end of winter. The position of the longest dark bands indicate which parts of winter will be coldest/harshest. The more orange segments, the milder the winter will be.
So what have you found in your own backyard? I'd love to see your photos and we can "diagnose" winter by looking at what your Woolly Bear is wearing. :)

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