First High Risk of 2013

The first High Risk for 2013 was issued today, and it stretched from eastern Iowa to northwestern Ohio.  That puts a total of 12 million people in the risk area for severe weather such as straigh-line wind damage and tornadoes.

The bullseye of this high risk is right over Chicago. In fact, this is the first high risk tat has been issued for Chicago since May 30, 2004, and only the third since 2000. The Storm Prediction Center issues these categories on a daily basis based off of the current/forecasted weather, and they have three categories: Slight, Moderate,and High. High risks are extremely rare, and are only issued prior to large outbreaks of severe weather.

So what do the different risk levels mean? Below is what the SPC uses to define their outlook categories:

 

Slight, moderate, and high risks represent progressively larger threat for organized severe storm episodes. These risks and their graphical labels (Slight, Moderate, High) are based directly on the numerical probabilities of severe weather that we provide with every outlook. The probability values represent the chance of severe weather within about 25 miles of a point, which is about the size of a major metropolitan area. Though severe storms tend to receive a large amount of media coverage, severe weather is uncommon at any one location. Your chance of getting a tornado on any random day are very small, climatologically speaking. Put in that context, even a 10% chance of a tornado within 25 miles of a point means a much bigger threat than usual, and should be taken seriously. Think of how often tornadoes normally happen close to you on any given day, and those small-looking probabilities start to seem large by comparison!

For a complete list of all the Risk Outlooks, Tornado Watches (formerly called “tornado forecasts”), you can use this link here.

This is a link to all of the times the SPC has issued a High Risk Day, use this link here. Notice that the only month that has never had a High Risk issued was September. Also, the last time a High Risk was never issued once during the year was back in 2000.

Sources: SPC, NOAA, NWS-Chicago