Tonight will bring another round of severe thunderstorms under a slight risk, with primary threats being large hail and damaging downburst winds. In Ohio, a moderate risk has been issued and contains a much greater chance for severe weather. The hourly weather graph from the Nashville National Weather Service office estimates thunderstorm activity to be anywhere from 7:00 P.M. to 3:00 A.M. in our area. The threat will mainly be over western and central portions of Tennessee, as seen in the image at left. Here is what the NWS said about tonight in this morning’s discussion.
A BROKEN BAND OF SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE AREA TONIGHT WITH PASSAGE OF A COLD FRONT. BRIEF DOWNPOURS ARE EXPECTED…WITH QPF AMOUNTS UNDER ONE QUARTER INCH. SOME OF THE STORMS COULD BE BRIEFLY SEVERE WITH STRONG WINDS BETWEEN 6 PM AND MIDNIGHT.
Some of the models have changed since then, but it is the same general idea. Before I get any further, some of you are probably wondering if this will affect any of the flooding. The answer is no. As said in the above statement, rainfall will be under 1/4 of an inch, and also very localized if more. This should not be a continuance of the flooding, so do not worry there. This cold front will pass fairly quickly and won’t linger like last weekend, which caused the flooding.
Now, it has been a VERY long time since I have done this, so I am rather excited. I will be pulling out the good ‘ol Skew-
T chart! For those who don’t know, a Skew-T chart is a product that shows different characteristics of the atmosphere for that hour. Weather balloons are sent up, and they collect data that is compiled onto the chart. Now, a strong reminder is that a Skew-T chart is only valid FOR THE HOUR IT WAS CREATED. However, we can use it to look at the characteristics of the atmosphere that may apply to the whole day.
Moving on, the Skew-T chart has picked up a nice little bit of instability, and a really strong cap. Instability is expected to increase throughout the day as daytime heating weakens ad eventually breaks the cap. That will happen around the same time the cold front pushes through, allowing thunderstorm development. Also, the nice little indent in the dewpoint part of the graph shows an ok potential for hail, one of the main threats.
(click on images to enlarge them) Now, here is the part that gets a little tricky… earlier models were showing not so great levels of wind shear, but as the day has progressed the models have increased the amount of helicity. Same goes for EHI . The EHI models were low, but now are pretty high. What does this mean? I have no idea… I am not too terribly experienced, but it is possible we will have a slightly larger tornado risk issued later. That is just speculation, I am still learning a lot but we will see how things pan out. Plus, with Lift Index at -6 I have no doubt there will be some form of severe weather, I just doubt how severe it will be. It will be interesting to see how it all pans out, so check back for updates!
