SPRINGFIELD, Mo. —
This is Severe Weather Awareness Week in the Ozarks. All week long the Springfield National Weather Service and the KY3 StormTeam will share tips to help keep you out of danger during the 2008 Severe Weather Season.
Plan and prepare now to keep you and your family safe.
If current patterns remain the same, 2008 could be an active and dangerous storm season. What follows below explains why the KY3 StormTeam expects to see a continuation of the active weather pattern thus far.
STRONGEST LA NIÑA SINCE 1988-1989
The United Kingdom's Meteorological Office and the Climate Prediction Center (NOAA) both concluded this is the strongest La Niña since the La Niña of 1988-1989. And this winter's La Niña bears a similar pattern to the patterns noticed during that period.
La Niña is the opposite of El Niño, a warming of Pacific Ocean waters.
COLD, PACIFIC WATERS CHANGE THE STORM TRACK OVER THE UNITED STATES
La Niña , an expansive area of unusually cold water temperatures in the Pacific, leads to a change in global wind currents. In the United States, we notice that the Polar Jet is greatly affected by both El Niño and La Niña. This year, and during other La Niña events, the Pacific Northwest experiences many more storms, while the California coast is usually drier.
This year, however, there's been a strong connection to moisture moving off the Pacific Ocean. As such, the active Polar Jet has coupled numerous times with the moisture field coming from the ocean to create frequent winter storms since December 2007.
And when the air has been warm and wet enough, we've had massive thunderstorm and tornado outbreaks in the Ozarks. As spring heating returns to the region, this pattern could linger over the Ohio Valley, the Midwest and parts of the Ozarks.
COOL WATERS LEAD TO COOLER AIR TEMPERATURES, DIFFERENT STORM PATTERN
Close to home, the southward-dipping polar jet stream allows colder-than-normal air to drain into the Midwest, the Ohio Valley and the Ozarks. This continues, even as spring heating is forcing warm, wet air northward from the tropics.
During storm season, this process is usually occurring anyhow but, during a La Niña event, the warm wet air is forced even farther northward, changing the average storm track and increasing the number of severe weather and tornado days around the heart of the United States.
THE OZARKS SEE AN INCREASE IN TORNADO DAYS DURING LA NIÑA
With more intrusions of cold air plowing into warm, wet air under an active storm pattern, La Niña can create more frequent occurrences of severe weather and tornado days. Shown below are the total days between February and April during which at least one tornado occurs. These figures are taken from a paper written by Marc Bove at Florida State University's Center for Ocean-Atmospheric Prediction Studies (COAPS), entitled Impacts Of ENSO On United States Tornadic Activity.
2008 TORNADO TRENDS ARE WELL AHEAD OF AVERAGE
In just two months, the trend for tornadoes is well ahead of the 10-year average and even the very-active 2005 season, which totaled 1,264 tornadoes before the end of the year.
The Climate Prediction Center is forecasting a continued strong La Niña through spring and the Ozarks' main severe weather season.
Here are links to national severe weather climatology and severe storm climatology in the Ozarks.