TL;DR: a cold front is moving through the midwest, some thunderstorms this afternoon/evening but limited severity. Unfortunately the front doesn’t look to bring rain to the southeast and the drought looks to deepen. And what is CAPE and what does it have to do with thunderstorms and cool new animations? Read on to find out …
There is a nicely defined front on radar this morning draped across the central US …
A few thunderstorms embedded, but the Storm Prediction Center only has one area in the north central states tagged and that only as “slight” risk …
Why is that? One of the parameters we look at in forecasting thunderstorms is called CAPE: Convective Available Potential Energy. CAPE is a measure of the instability of the atmosphere, and is basically an indicator of the amount of energy available to fuel a thunderstorm. It is measured in Joules per kilogram (J/kg) and can range from zero to over 5000. In general, CAPE values of less than 1000 J/kg represent weak instability, 1000 to 2500 J/kg moderate instability, 2500-4000 J/kg strong instability, and greater than 4000 J/kg extreme instability. As you might expect, the thresholds depend on the time of year, location, and other factors, so like most parameters in meteorology you don’t want to look at it in isolation, but that’s a good rule of thumb.
Here is an animation of the CAPE values over the next 72 hours. As you can see, it doesn’t really getup into the higher values, so that’s an indication that any thunderstorms should be limited. Of course it is spring, and isolated flareups can happen. You can also see how the CAPE values fade as the system approaches the coast using the new QGIS based automated map generator:
So now you can shock and impress your friends by slowly chewing on a leaf, look up at the sky, and say in your best Missouri hillbilly accent “Yep, shore enough tain’t gonna be no thunderstorms t’day, CAPE’s ain’t gonna break 1000.”
So this isn’t likely to do much to improve the drought, only 20% chance of rain tomorrow in Savannah. The numbers are pretty grim here on the coast in the latest drought monitor report. Here are their numbers along with the data from the Enki station in Midtown Savannah:
The soil moisture sensor is still setting after I had to replace it in early March. It was fully saturated as part of the installation/calibration process – look at how the curve has collapsed as the soil is literally sucking the moisture out of it. The soil here is super dry at this point. Parts of Liberty and Bulloch are now in the 1 in 50 year drought category. Combined with the high fuel costs, expect food prices to increase this year since this is starting to hit the growing season …
If you appreciate the blog, the best way to get it is to subscribe to the emails. Many thanks to those who responded to the gentle hint yesterday (and those who had contributed to the blog previously, including a large well timed contribution that immediately went to replace a blown out NFS server). You can subscribe and also donate to keep it going at this link.
You can also follow us on X/Twitter (@EnkiResearch), Telegram, BlueSky, or even Facebook if that is your preferred social media mayhem.