An Odd Winter Leads To A Quick Start To Spring
by Angela Schilling, Meteorologist
March 03, 2012 9:22 PM
The first day of spring is just around the corner, and as a matter of fact it’s going to start feeling like spring in the next couple of days. Along with springtime comes severe weather and tornado season for many areas to our south, such as the gulf coast. This past Friday proved to be a widespread severe weather event stretching from the southeastern United States into the Ohio Valley. Strong tornadoes rolled through sections of Alabama, Georgia, Kentucky, Indiana, and Ohio. This same system brought snow to eastern Iowa, as well as Wisconsin and Minnesota yesterday afternoon. In our neck of the woods we saw strong winds on Friday, and some light snow late Friday night, looks like we’ll get a second shot of light snow later Saturday night into Sunday morning, before a huge warm up on Monday and Tuesday. The image to the left is from around 1:30pm Saturday and shows preliminary storm reports from the past 24 hours, so keep in mind severe weather was ongoing well before then. The red dots represent tornadoes, with several reports in southern Indiana and northern Kentucky around Louisville.
Along with spring comes a battle of the air masses with warm humid air colliding with cold dry air. It is the collision of both cold and warm air which causes severe weather. In the northern plains we typically see severe weather in the summer time, around June and July, while in the Southern Plains severe weather season typically peaks around April and May. In the southeast or Dixie Alley, tornado season is a little bit earlier, towards the beginning of spring. What’s uncommon is to have such a widespread event, stretching as far north as the Great Lakes this early in the season, for example Indiana and Ohio. Out ahead of the front we had more than enough fuel to produce severe weather with plenty of warm air and moisture in place. The jet stream is found in the upper levels of the atmosphere and is what drives our weather. Yesterday the jet stream was rather strong over the southeast and Tennessee Valley, acting as a forcing mechanism for the majority of the storms. The low was strong enough to have temperatures in the 80's ahead of the low and snow behind it. The images below are from Friday afternoon.
Notice the high in Nashville, 81 degrees...compare that to Chicago with 40 degrees, a huge difference in a relatively short distance. The hot spot on Friday was Miami with 84 degrees...In Sioux Falls we made it up to 36.
Southern Indiana and Kentucky got hit the worst on Friday with several deadly tornadoes, primarily the one that touched down in Henryville,Indiana comes to mind which is several miles north of Louisville, Kentucky. The image below shows the low over Illinois late Friday morning, with a warm front draped acrossed Indiana and Tennessee, as well as a cold front stretching as far south as Texas.
The radar image below is from Friday afternoon around 12:30pm and shows a tornado rolling through Posey County, Indiana. Preliminary reports suggest this was an EF-2 tornado with a path length of 6 miles and peak wind of 125 miles per hour. In the image below you can get a feel for the structure of the tornado in the top left, which shows basic reflectivity. Notice how the storm has a tail like structure or pendant coming down from the core of the storm, it was around there where the tornado would be found. The boxes to the right show the rotation of the storm, with the reds going away from the radar and the greens going towards the radar. When you get reds up next to greens it is typically indicative of some kind of rotation. Keep in mind where the radar is, in this case Evansville, or where the black dot is located.
In south Dakota we have seen our fair share of severe weather in March, but it is not very common, and has only happened a couple of times. In 2009 on March 23rd, we saw some wind damage in the southeast and a couple tornadoes in Nebraska one of which was on the South Dakota/Nebraska border.
Last week Nebraska had their first ever confirmed tornado during the month of February, and it happened about 20 miles northeast of North Platte with a rating of an EF 0.
Before we get a taste of spring come Monday and Tuesday we do have one more round of snow to get through Saturday night into Sunday morning, with around 1 to 2 inches expected north of Highway 14 in the northeast, and less than an inch in the southeast. Strong winds will funnel in behind the storm by Sunday afternoon, lowering visibilities due to blowing and drifting.
Once we get through Sunday much warmer air will be knocking on our door by Monday and Tuesday, allowing temperatures to be well above average, with 50's and 60's expected.