Featured Research

from universities, journals, and other organizations

Dry Autumns And Winters May Lead To Fewer Tornadoes In The Spring

Date:
June 24, 2009
Source:
University of Georgia
Summary:
Global warming will likely mean more unpredictable weather, scientists say, and a new study pins down, possibly for the first time, how drought conditions in an area's fall and winter may effect tornado activity the following spring.

Global warming will likely mean more unpredictable weather, scientists say, and a new study by researchers at the University of Georgia pins down, possibly for the first time, how drought conditions in an area's fall and winter may effect tornado activity the following spring.

The study, published today in the journal Environmental Research Letters, is specific to Georgia and the Southeast, but further study could reveal patterns that might make this more general—including the already tornado-prone Great Plains.

"Our results suggest that there is a statistically significant reduction in tornado activity during a tornado season following drought the preceding fall and winter," said Marshall Shepherd, a meteorologist and lead author of the study. On the other hand, wet autumns and winters examined in the study had nearly twice as many spring tornado days as drought years did.

The research gives hope that one day meteorologists and climatologists may be able to predict the severity of a spring tornado season the way they now do for hurricanes. Other authors of the paper were Thomas Mote, also of the University of Georgia, and Dev Niyogi of Purdue University. Shepherd and Mote are in department of geography in UGA's Franklin College of Arts and Sciences.

The genesis for the research was the severe Atlanta tornado in March 2008, and Shepherd's interest in how tornadoes form during severe drought years.

While such tools as Doppler radar have increased our ability to "see" tornadoes as they form, predicting a tornado season's potential severity has remained elusive. The Intergovernmental Panel on Climate Change projected in 2007 that the frequency and severity of droughts may increase over time, but very little is known about drought conditions affect the frequency or intensity of severe weather hazards such as tornadoes.

To help understand how fall and winter weather might affect spring tornado seasons, the research team acquired the historical database of severe thunderstorms and tornado occurrences from 1951-2006 from the Storm Prediction Center of the National Oceanic and Atmospheric Administration. They also analyzed storm data reports from the National Climactic Data Center and meteorological drought conditions using historical rain gauge and Tropical Rainfall Measuring Mission (TRMM) satellite data from the National Aeronautics and Space Administration (NASA).

Using a number of tools of scientific analysis, the team primarily focused on tornado activity from March-June in Georgia and the Southeast. What they found was shocking, Shepherd said, yet plausible.

On average, wet autumns and winters presaged nearly twice as many spring tornado days in the study area as prior drought seasons. Springs following wet winters and falls were also five to six times more likely to have multiple tornado days than antecedent drought years.

"We do not suggest that soil moisture or precipitation the previous fall and winter exert a direct control on which individual storms will spawn tornadoes," said Shepherd. "But these long-term seasonal relationships in the study area are striking."

Correlating historical records and tornado activity has been difficult at best for scientists over the years. For one thing, the National Weather Service did not implement its watch and warning system until the mid-1950s, and only with advent of advanced radar techniques and ground examination of storm sites have researchers been able to say categorically that a certain storm even was a tornado. Also, studies linking tornadic activity with the El Niño cycle have been contradictory.

While it clearly seems that wet falls and winters lead to more severe spring tornado seasons, antecedent seasonal drought scenarios in north Georgia were almost never associated with above-normal tornadic activity the following spring over the 50-years period of the study.

The results for north Georgia were essentially replicated for the larger region encompassing Tennessee, Georgia, Alabama and Mississippi. For this entire region, a stunning 75 percent of years characterized by meteorological drought in falls and winters had below-normal tornado seasons in the spring.

While the new study, which was supported by grants from NASA, offers strong clues about how spring tornado seasons form, the authors urge caution in interpreting the findings until the analysis is repeated for other locations.

Just how the connection works between fall-winter rainfall and spring tornado seasons remains unclear. One possibility is that the atmosphere uses soil moisture "memory" from the fall and winter to modify conditions suitable for severe weather. A related hypothesis is related to "soil moisture" pockets and storm initiation.


Story Source:

The above story is based on materials provided by University of Georgia. Note: Materials may be edited for content and length.


Cite This Page:

University of Georgia. "Dry Autumns And Winters May Lead To Fewer Tornadoes In The Spring." ScienceDaily. ScienceDaily, 24 June 2009. <www.sciencedaily.com/releases/2009/06/090624093311.htm>.
University of Georgia. (2009, June 24). Dry Autumns And Winters May Lead To Fewer Tornadoes In The Spring. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2009/06/090624093311.htm
University of Georgia. "Dry Autumns And Winters May Lead To Fewer Tornadoes In The Spring." ScienceDaily. www.sciencedaily.com/releases/2009/06/090624093311.htm (accessed July 31, 2014).

Share This




More Earth & Climate News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Visitors Feel Part of the Pack at Wolf Preserve

Visitors Feel Part of the Pack at Wolf Preserve

AP (July 31, 2014) — Seacrest Wolf Preserve on the northern Florida panhandle allows more than 10,000 visitors each year to get up close and personal with Arctic and British Columbian Wolves. (July 31) Video provided by AP
Powered by NewsLook.com
Big Waves In Arctic Ocean Threaten Polar Ice

Big Waves In Arctic Ocean Threaten Polar Ice

Newsy (July 30, 2014) — Big waves in parts of the Arctic Ocean are unprecedented, mainly because they used to be covered in ice. Video provided by Newsy
Powered by NewsLook.com
Raw: Thousands Flocking to German Crop Circle

Raw: Thousands Flocking to German Crop Circle

AP (July 30, 2014) — Thousands of people are trekking to a Bavarian farmer's field to check out a mysterious set of crop circles. (July 30) Video provided by AP
Powered by NewsLook.com
Weather Kills 2K A Year, But Storms Aren't The Main Offender

Weather Kills 2K A Year, But Storms Aren't The Main Offender

Newsy (July 30, 2014) — Health officials say 2,000 deaths occur each year in the U.S. due to weather, but it's excessive heat and cold that claim the most lives. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:  

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile iPhone Android Web
      Follow Facebook Twitter Google+
      Subscribe RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins