After two weeks of every-day-there-is-a-tornado-somewhere weather, the big subtropical ridge in the southeast is shifting to the west. This will shove the jet stream further north and re-position a lot of the moving pieces needed to create severe weather – ending the barrage.
RECAP
These numbers are preliminary, and are likely going to change. Plus, this data does not include most of the severe weather reports on May 28th, May 29th and May 30th. But, even still, take a look at all the severe weather reports from the last two weeks:
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And a map of where all of the reported tornadoes have occured:
There has been a tornado reported every day – somewhere in the United States – for the last two weeks.
This has been one of the most prolonged active setups since 2011. For reference, here is a look at the 2011 statistics:
This has been a pretty incredible, and long-lasting, synoptic setup. One that the country hasn’t had to endure in about eight years.
Breaking Down the Setup
In general, the setup has looked like this:
The Big ridge in the southeast kept pumping Gulf of Mexico – and at times Caribbean – air into the Southern Plains, Midwest and eventually all the way around the ridge and into the Northeast.
This ‘pulling of moisture’ is shown pretty well on the PWAT Anomaly map.
PWAT is short for Precipitable Water, and it is a measure of just how much water is in a column of air. You can think of it like putting all the moisture in the air in a particular area – from the ground all the way up as high as you can go in the atmosphere – into a sponge, and then ringing that sponge out into a bowl. And how much water you have in that bowl, is the PWAT value.
PWAT values were between 0.5″ and 1.5″ around the periphery of the ridge. That is ample moisture (fuel) for thunderstorms to use.
What ended up happening is little storm systems would ride out from the Rocky Mountains and toward the Great Lakes and the Northeast, around the big ridge of higher pressure. When these storm systems did that, they would offer the spark in the atmosphere needed to create thunderstorms and severe weahter. And because a few of these storm systems were sufficiently potent, the atmosphere was oriented in a way to produce – at times – significant severe weather.
Results
Today’s Severe Risk
Today’s Tornado Risk
