Blog: Weekend/Tornado Recap; Cooler/More Stable Today

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I want to recap the weekend a little bit, before we go into the forecast for the next few days.

On Friday, we predicted the heavy rain that would come in on Saturday evening for a large portion of the area. That did happen as predicted. Some locations had about 3 or more inches of rain in a short amount of time.  However, the threat for severe weather was not high. We did have some ingredients for a tornado though that were not obvious at the time.

On Saturday evening, a torndado formed and touched down near downtown Suffolk, VA. Then it moved east and dissipated near the Great Dismal Swamp.

Tornado Information

The rating was an EF-1 on the Enhanced Fujita scale.  The tornado was on the ground for approximately 2 miles, according to the National Weather Service in Wakefield. Luckily, there were no injuries nor any fatalities.  Howevere, there were over a dozen reports of damage.

While the signs for a tornado weren’t obvious, I did go back and analyze some things.

There was a cool front that came in and stalled out as expected. It also bumped back north a little bit, and that was also expected. Sometimes, as these fronts move back north as a warm front, you have to watch them for thunderstorm or heavy shower formation. Especially when the air is warm and saturated. You need a lot more ingredients, though, to get a tornado.

I found a mesoscale discussion from the Storm Prediction Center that talked about a Mescoscale Convective Vortex (MCV) that was moving out of the Tennessee River Valley towards the east. That is a spinning mass of organized thunderstorms that is bigger than the thunderstorms themselves, but smaller than a big synpoptic (large scale) area of low pressure. It is generally found in the mid levels of the troposphere, but it can help to focus rotation down to lower levels under the right condtions.

So this feature ran into a zone of high humidity. Temps were pretty warm ahead of the storms. They had reached the upper 70s to near 80. Plus, dew points were in the mid-upper 60s. LCL’s were very low. That is the Lowest Condensation Level, and it is bascially the base of where clouds form. They were only a couple hundred feet off the ground.

I personally witnessed this as I was driving through part of the storm as I came home from dinner.  Clouds were almost to the level of the West Norfolk Bridge.  That’s low…I don’t know the CAPE (instability) at the time, but the mesoscale discussion from the Storm Prediction Center mentioned about 500 J/KgK. While that is not very high, it could have locally been a little higher. Their discussion was focused a little more to our west.

I think basically that the MCV hit a slightly unstable, but also very saturated airmass. There were some surface winds out of the southeast. Which is a hint of some low level helicty, but I don’t have that actual number. So its seems that these features together created a local environment for tornado formation.  The velocity was impressive on the radar at the time.

So anyway, the area was lucky that there were no deaths nor injuries. 

On Sunday, there were supposed to be more rain showers on and off through the day. However, the front stayed a little more north than expected. The models kept pushing the rain back further and further in time. So we did have some more scattered showers, but there weren’t as many as forecast. Even the late evening showers fell apart as they moved east. This morning we had another round of showers moving through the area. We even had a couple of downpours. A cool front was slowly dropping to our south. An area of low pressure was moving offshore. There was also a smaller wind-shift line that was moving across central Virginia toward Hampton Roads. 

We’ll definitely be cooler today. So we’ll be more stable. However, there is some upper level energy in the region. So there will still be scattered rain showers. There may be some more isolated heavy downpours. An isolated thundestorm is possible over North Carolina. High temps will only be in the upper 60s to near 70.  Winds will be northeasterly then northwesterly at 8-12mph. Skies will be mostly cloudy or cloudy.

By tomorrow, high pressure will edge closer to the region. We’ll have a little more sunshine. However, an upper level low will still bring a few isolated-scattered rain showers. High temps will mainly be in the 60s tomorrorw.

Warmer temps will build to our west. They will move east through the week. We’ll be near 80 by Thursday. 

Meteorologist: Jeremy Wheeler

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