June 17, 2012

Across the country, May was quietest month for tornadoes in 60 years

Although it’s been an active tornado season in Kansas, the rest of Tornado Alley has been remarkably quiet.

Although it’s been an active tornado season in Kansas, the rest of Tornado Alley has been remarkably quiet.

In fact, preliminary numbers indicate the tornado tally nationwide in May was the lowest in 60 years.

The tentative national total for tornadoes in May is 110, well below the 10-year average of 300.

For just the 15th time since records began being kept in 1875, there were no deaths caused by tornadoes in May anywhere in the U.S.

The unusually quiet May can be blamed on temperatures that were much warmer than normal throughout spring in Tornado Alley, said Harold Brooks, a research meteorologist with the National Oceanic and Atmospheric Administration’s National Severe Storms Laboratory in Norman, Okla.

Thunderstorms capable of producing tornadoes rely on the instability created when warm, moist air collides with cold, dry air. With the temperature contrast between the air masses reduced, the atmosphere was more stable.

The differences in wind speeds at different levels of the atmosphere — known in meteorological parlance as “deep shear” — was also reduced.

The jet stream shifted north earlier than normal this spring, Brooks said, meaning strong storms typically tracked through the northern Great Plains in May rather than Kansas and Oklahoma.

April was more placid than normal as well, statistics show.

Confirmed totals for April are not yet available, but the preliminary total of 233 is well below the three-year average for April of 371. Since preliminary reports commonly include the same tornado reported multiple times, the actual total will likely drop substantially.

But don’t try to tell meteorologists in Kansas it’s been a quiet spring for tornadoes.

In May, Kansas saw 46 tornadoes — more than 40 percent of the tornadoes that touched down in the nation that month — state climatologist Mary Knapp said.

“We’ve had several,” said Chance Hayes, warning coordination meteorologist for the National Weather Service in Wichita.

There have been 45 tornadoes in the 26 counties of southeast Kansas covered by the Wichita branch this year, including an EF-3 that slammed into Oaklawn and portions of southeast Wichita on April 14.

“We’re well above average” for the year, Hayes said.

There has been an average of 33 tornadoes a year in the Wichita coverage area over the past five years, excluding 2012, he said.

Thirteen of this year’s tornadoes in the Wichita area touched down in May, Hayes said.

Southwest Kansas has also been hit hard, logging more than two dozen tornadoes so far this year.

The preliminary tornado count for Kansas is 142 through June 13, Knapp said. That number may include tornadoes counted more than once — either because they were reported from multiple vantage points or their paths spanned multiple counties.

Last year saw 67 tornadoes touch down in Kansas, Knapp said, and there were 94 in 2010.

The state has averaged 104 tornadoes a year since 2000, she said.

The absence of tornado deaths last month across the U.S. stands in stark contrast to last May, when 178 people died in tornadoes. Most of those people died in Joplin, which was struck by an EF-5 tornado on May 22.

The May death toll in 2011 was the largest since 211 people died in 1933, Brooks said.

Related content



Editor's Choice Videos