Clues from a decade of Storm Prediction Center tornado outlooks during peak season

Despite some breaks in the action, it’s an above average spring for tornado numbers, and we’re now getting into the heart of when tornadoes are likely across the country.

The top months for touchdowns are April, May and June. And much like tornadoes themselves, the highest tornado risk days — as forecast by the Storm Prediction Center — are somewhat weighted toward the first half of peak tornado season. Day-to-day consistency in tornado threats peaks in the second half of the three-month period.

The weight of big tornadoes and big tornado events early-season is often due to the fact the jet stream is at its most intense of spring at that point. Later on, more of the nation is in play, but events tend to become smaller and more nuanced.

Since this is research that is still close its infancy, I’ll let the graphics below do most of the talking.

The idea of higher risk weighted in the first half of the period and more consistent risks later is shown well above. It’s a plot of category levels accomplished by date. Multiply by 10 percent to get the overall frequency through the decade.

A whopping 96 percent of days in June have at least a low level tornado threat somewhere in the country. Looking for the enhanced (10%) or greater tornado risks? April is your best bet.

No major trends present themselves in this short period, but we do see that April-June days with no or minimal tornado threat have been on the high side of average in recent years.

P.S., if you got this far and are still wondering what the Storm Prediction Center is, check out this nice NY Times article about it.