As I write this on Thursday morning, a severe thunderstorm outbreak seems likely for parts of the Great Plains, Mid-South, and lower Mississippi Valley today. As a reminder, severe thunderstorms are capable of producing large hail, strong wind gusts, and tornadoes. With this particular event, all of those hazards are actually expected. As of March 1st, we entered meteorological Spring. This part of the year is the ramp up to the particularly active part of the year-round tornado season. Geographically, what region of the U.S. is most likely to experience a tornado in the month of March?
To answer that question, I turn to the National Oceanic and Atmospheric Administration (NOAA)’s Storm Prediction Center. They are a part of the National Weather Service that issues storm outlooks, discussions, and climatological analysis related to hail, wind gusts, tornadoes, fires, and more. I reviewed their 30-year climatology (map above) over the period 1982-2011. As you see, the most likely region for tornadoes in the early part of March is Alabama and Mississippi with elevated chances extending eastward into Southeast, westward into the Great Plains, and northward into the Mid-South.
According to the Storm Prediction Center outlook issued on Thursday morning, “Multiple episodes of severe thunderstorms are possible across the area, mainly this afternoon and tonight, with both discrete supercells and ultimate QLCS development offering a tornado threat.” Supercells are dangerous thunderstorms with rotating updrafts that can produce tornadoes. QLCS stands for Quasi-Linear Convective Systems, which is a class of storms that have a linear shape but are not quite straight. According to the National Weather Service, these can include squall lines and bow echoes.
Severe weather can happen at any time. In March we start to see a dangerous brew coming together. The large-scale atmospheric processes associated with the jet stream and strong fronts are still quite potent. They provide lift and wind shear often associated with severe weather outbreaks. Additionally, warm, moist air starts to stream in more abundantly from the Gulf of Mexico region. For the current threat, you can clearly see the moisture (shades of green in the map above depicting high dew points) available to the region at risk.
By late March, the tornado threat for the U.S. expands to include much of the South, Mid-South, and Great Plains. A combination of moisture, atmospheric forcing, and even dry air from the Mexican plateau leads to optimized conditions for severe as we progress further into Spring. Even so, tornadoes, in the grand scheme of things are still relatively rare. Of all the storms in the U.S. each year, there are only a little over a 1000 tornadoes, but they certainly can be quite impactful and deadly.
#Experience #Tornado #March