We are used to watching for severe weather in April and May as enter Spring severe weather season, but seeing severe weather in February is a fairly rare occurrence in North Carolina. While severe weather is possible at any point in the year, and North Carolina sees its fair share, getting February tornadoes is very rare. There have been less than 20 tornadoes in February in since 1950 in the National Weather Service Raleigh and Greenville-Spartanburg (they cover Charlotte) offices each.
How then, if they are so rare, did we see five of them to our west last week? Well, the ingredients needed for storms lined up perfectly. The first thing we need is fuel for storms, which comes from warm and humid air. We then needs winds to change with speed and direction with height, something we call wind shear. The final thing is forcing the air to rise to make a thunderstorm and allowing room for the storm to maintain itself and not instantly collapse, something we call divergence.
All of these ingredients can come into place when we have a large dip in the jet stream (the river of air at about 30,000 feet), as we did last week, that brings warm and northward and cold air southward. Lower than that, around 5,000 feet, air coming from the south and surface winds from the southeast provide that necessary turning of winds to allow storms to rotate.
Even with all of these things in place, a tornado is not a guarantee. As meteorologists, we don’t completely understand what gets the tornado to the ground (although we have some pretty good ideas, just nothing concrete). These ingredients make the likelihood of a tornado much greater, and are things we look for when forecasting for severe weather and the potential for tornadoes.
The CBS 17 Storm Team will keep you updated all year long regardless of what Mother Nature brings.