Thursday, April 03, 2014

A SPC High or KAIT High?

When it snows, we make a forecast map showing the accumulation that we think will occur. We adjust it between shifts and make changes based on the latest data. We look at the National Weather Service's forecast to get their thinking and may or may not incorporate their thoughts into our forecast. We do not simply take their forecast and broadcast it to the viewers. We are fortunate to have some great people at the NWS offices that cover Region 8 and it's great to get their opinions on winter storms and severe storms.

As I mentioned in a previous blog post, we are going to try to become more intentional on making forecasts that make sense to the viewers. I want maps that my kids can understand. If my kids can understand them, then most of our viewers will be able to understand them.

I say all of this to address the thunderstorm outlook for today. The Storm Prediction Center, a branch of the National Weather Service, issues thunderstorm outlooks. They issue 1, 2, 3, and 4-7 day outlooks. They use the terminology "see text", "slight", "moderate", and "high" to communicate the threats. The probabilities of severe weather dictate whether it is a slight, moderate, or high risk. The confusing part to the viewer is that these corresponding probablities differ from Day 1, 2, and 3. To add to the confusion, they are soon breaking the terms into more categories including marginal, slight, enhanced, moderate, and high. Here are some charts explaining the changes. Click to enlarge:
Now, let's have some real talk. If I asked most of our viewers if an enhanced risk of thunderstorms or moderate risk of thunderstorms was worse, most would not know. Heck, I'm not sure I would remember! Do you know what you and most of our viewers will understand, including kids? Low, medium, and high (and occasionally extreme):
So, in an effort to make a forecast that people understand, we are doing this and our forecast will not always match the Storm Prediction Center. I will ALWAYS look at the Storm Prediction Center for guidance. The people that work at the SPC are some of the best severe weather meteorologists in the country. But, my job is to make a forecast and communicate it to the viewers in a way that they understand and can use to prepare their family.

This is nothing new. Television stations in Oklahoma City are also trying to make a thunderstorm risk map easier for the public. Thanks to Jason Prentice and Nate Johnson for this pic:

I say all of this to tell you that OUR forecast has a high risk of severe weather today, even though the terminology from the SPC is a "moderate" risk. Here's our latest severe weather threat map for today:

This SPC map looks like this:

But, if you break down the probabilities of the SPC, they also feel the threat is significant. I feel that a 15% chance of a tornado, with a 10% chance of EF2-EF5 damage within a 25 mile radius is a "high" risk, even though it does not meet their threshold to use that terminology:

When you look at their probabilities of hail and wind, the threat is also quite high:

So, our forecasts are not that different, we are just trying to communicate the threats better. 

Lastly, ALL watches and warnings come from the National Weather Service. Warnings come from the local offices in Memphis, Little Rock, Paducah, and Springfield. All watches come from the SPC. That will not change.

I hope this helps! Be safe today.


Rhonda said...

Thanks Ryan!!! We appreciate you so much!

Lauren P said...

Having a fear of storms I always look at the SPC to see what they say. However, like you mentioned once I try to read the text all the terms they use don't make sense to me! (Maybe I need a meteorology dictionary ) I wish they would try to be more user friendly like you are doing. Thank you for being so diligent at forecasting.

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