U.S. tornado deaths already nearing national annual average

April 7 (UPI) -- U.S. deaths related to tornadoes in 2023 have nearly reached the yearly national average just a third of the way into the year, according to the National Weather Service.

To date, there have been more than 60 deaths tied to tornado activity in the United States so far, despite the national yearly average of 71.

A wave of tornado-producing storms over the past two weeks that stretched from Michigan to Tennessee and the south killed at least 32 people. And another five deaths were confirmed as a tornado tore through Missouri on Wednesday.

Data from the NES's Storm Prediction Center show that Alabama, Missouri, Tennessee, Oklahoma and Georgia hold the highest average death tolls in the nation but some of those states have already individually come near their annual averages this year.

"The death toll is up for a couple of reasons," Weather Channel meteorologist Jacqui Jeras told CBS News. "Obviously the more tornadoes you have, the greater the risk of deaths. But the number of deaths is higher when the tornadoes are stronger. We have also had a lot of nighttime, or nocturnal tornadoes, which are twice as likely to be deadly."

While tornadoes can happen at any time in the United States, the time that is usually considered "tornado season" typically peaks late spring or summer, which could vary by region.

The NWS reported 422 tornadoes already in 2023, which Harold Brooks, a senior research scientist at the National Oceanic and Atmospheric Administration's National Severe Storms Laboratory, told NBC News were likely sparked by the warmer-than-usual winter this past season.

"If you don't get the cold fronts across the Gulf, all you need is a little bit of wind to bring in a lot of warm, moist air," Brooks said.

"And this has been a year where cold fronts really haven't gotten that far south. The southern part of the U.S. was not particularly cold this winter."

Jeras said the wave may be caused by a persistent upper-level weather pattern, possibly from an uptick of a La Nina, climate conditions connected to cooler temperatures in the Pacific Ocean that affect global weather patterns.

"It has been unusually busy with tornadoes since the beginning of the year," Jeras said. "Our busiest tornado seasons are typical during La Nina."