Just two weeks ago the United States was struck by a tornado outbreak which was named the deadliest tornado outbreak since the Super Tuesday outbreak in 2008. Now the United States has been struck by another system that is currently ongoing, and has surpassed the previous April 14 -17 tornado outbreak as the deadliest since the Super Tuesday outbreak. It is also the worst the United States has had since the Super Outbreak in 1974. Currently there have been 273 deaths from the storm and many of those deaths occurred in Alabama, where and tornado struck Tuscaloosa. Footage from witnesses have captured the intensity of storm. This amazing footage of the tornado was recorded by Christoper England of Crimson Tide Productions at the University of Alabama:
The magnitude of the storm is incredible. Many experts are calling this tornado outbreak "historic" as the average amount of tornadoes in April is 133 and this storm along produced more than 260. Some are even saying that "Tornado Alley" may have shifted south. So what could be causing these tornado outbreaks? Well many experts are looking at the current La Nina oscillation which may play a role in the weather we have been receiving. Normally during a La Nina "the jet stream tends to move north through the Pacific Northwest and Great Lakes, keeping cold air on the northern side while the southern side tends to have warm, humid air. Cold fronts that would dry out the atmosphere on the south side are blocked, which means wet storms there." source
The result can develop tornadoes. As with the current outbreak, a cold front was met with warm, moist air in the south and a strong upper level jet, and lead in the development of the tornadoes.
The 1974 outbreak occurred during a La Nina year. Another La Nina year was 1999 when the Oklahoma tornado outbreak occurred. The duration of the event was May 3-6 and 140 tornadoes were confirmed. La Nina pattern we are in is currently weakening, so does this mean the intensity and the frequency of the tornadoes will subside? Looking at a chart by NOAA, on the number of tornadoes in April from 1950 to 2010, we can see an increase in the frequency of tornadoes in the past four years. This chart also provides a big picture of the events and looking at the decadal averages we can see an increase in the number of tornadoes in the pass decade. Not every year included in the chart was a La Nina year however and though the number of tornadoes may be increasing, the effect by a La Nina pattern is not as clear.
Below is a map of the storm reports for April 27, 2011. It is has since been updated.
This is the activity chart for yesterday.
Here is the radar:
All images are from NOAA.
The magnitude of the storm is incredible. Many experts are calling this tornado outbreak "historic" as the average amount of tornadoes in April is 133 and this storm along produced more than 260. Some are even saying that "Tornado Alley" may have shifted south. So what could be causing these tornado outbreaks? Well many experts are looking at the current La Nina oscillation which may play a role in the weather we have been receiving. Normally during a La Nina "the jet stream tends to move north through the Pacific Northwest and Great Lakes, keeping cold air on the northern side while the southern side tends to have warm, humid air. Cold fronts that would dry out the atmosphere on the south side are blocked, which means wet storms there." source
The result can develop tornadoes. As with the current outbreak, a cold front was met with warm, moist air in the south and a strong upper level jet, and lead in the development of the tornadoes.The 1974 outbreak occurred during a La Nina year. Another La Nina year was 1999 when the Oklahoma tornado outbreak occurred. The duration of the event was May 3-6 and 140 tornadoes were confirmed. La Nina pattern we are in is currently weakening, so does this mean the intensity and the frequency of the tornadoes will subside? Looking at a chart by NOAA, on the number of tornadoes in April from 1950 to 2010, we can see an increase in the frequency of tornadoes in the past four years. This chart also provides a big picture of the events and looking at the decadal averages we can see an increase in the number of tornadoes in the pass decade. Not every year included in the chart was a La Nina year however and though the number of tornadoes may be increasing, the effect by a La Nina pattern is not as clear.
Below is a map of the storm reports for April 27, 2011. It is has since been updated.
This is the activity chart for yesterday.
Here is the radar:
All images are from NOAA.
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