advertisement

Federal scientists study wild weather during April

Tuesday, May 10, 2011 | 12:20 p.m. CDT

WASHINGTON — April was a historic month for wild weather in the United States, and it wasn't just the killer tornado outbreak that set records, according to scientists with the National Oceanic and Atmospheric Administration.

April included an odd mix of downpours, droughts and wildfires. Six states — Illinois, Indiana, Ohio, Kentucky, Pennsylvania, and West Virginia — set records for the wettest April since 1895. Kentucky, for example, got nearly a foot of rain, which was more than three times its normal for the month, NOAA reported.

Yet the U.S. also had the most acres burned by wildfire for April since 2000. Nearly 95 percent of Texas has a drought categorized as severe or worse, exacerbated by the fifth driest April on record for the Lone Star state.

Add to a record 305 tornadoes from April 25-28, which killed at least 309 people and the most tornadoes ever for all of April: 875. The death toll and total tornado figures are still being finalized.

Much of the southern and eastern United States were near record hot for April, while northwestern states were cooler than normal. Overall, the month was warmer than normal for the nation, but not record-setting.

The odd mix of massive April showers and bone-dry drought can be blamed on the cooling of the central Pacific Ocean, which causes storm tracks to lock in along certain paths, said Mike Halpert, deputy director of NOAA's Climate Prediction Center.

"It's very consistent with La Nina; maybe we've had more extremes," Halpert said. "It's a shift of the jet stream, providing all that moisture and shifting it away from the south, so you've seen a lot of drought in Texas."

U.S. scientists also looked for the fingerprints of global warming and La Nina on last month's deadly tornadoes, but couldn't find evidence to blame those oft-cited weather phenomena.

NOAA research meteorologist Martin Hoerling tracked three major factors that go into tornadoes — air instability, wind shear and water vapor — and found no long-term trends that point to either climate change or La Nina. That doesn't mean those factors aren't to blame, but Hoerling couldn't show it, he said.

Climate models say that because of changes in instability and water vapor, severe thunderstorms and maybe tornadoes should increase in the future. But it may take another 30 years for the predicted slow increase to be statistically noticeable, said NOAA research meteorologist and tornado expert Harold Brooks.

But Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research in Boulder, said the preliminary study that Hoerling conducted was flawed and too simplified. He said there is evidence of an increase in instability in the atmosphere happening now.

 


Like what you see here? Become a member.


Show Me the Errors (What's this?)

Report corrections or additions here. Leave comments below here.

You must be logged in to participate in the Show Me the Errors contest.


Comments

Leave a comment

Speak up and join the conversation! Make sure to follow the guidelines outlined below and register with our site. You must be logged in to comment. (Our full comment policy is here.)

  • Don't use obscene, profane or vulgar language.
  • Don't use language that makes personal attacks on fellow commenters or discriminates based on race, religion, gender or ethnicity.
  • Use your real first and last name when registering on the website. It will be published with every comment. (Read why we ask for that here.)
  • Don’t solicit or promote businesses.

We are not able to monitor every comment that comes through. If you see something objectionable, please click the "Report comment" link.

You must be logged in to comment.

Forget your password?

Don't have an account? Register here.

advertisements