Looking Back At Yesterday’s Storms, And What’s Next?July 11th, 2014 at 9:09 am by Jeremy Wheeler under Weather
(Update on the Virginia Beach Damage. See bold line below:)
Things got rough yesterday. An isolated area of storms fired up over Emporia. As they moved east they grew in size and strength. We were tracking the storms as they showed a high indication of hail over Franklin, Courtland, and Capron, VA. So we had reports of golf ball to baseball sized hail. Here was one of the reports from Robin Eason:
The storms grew into a wide area of heavy rain and strong winds. It moved east causing wind damage, flooding streets, and more large hail. Here are some of the official reports:
The hail reached 1.75″ over western Virginia Beach. That’s huge for this area. Then there was wind damage near the Oceanfront. It is possible that it was a tornado, but so far I’ve seen more evidence for straight-lined winds. While I have seen video of a brief funnel cloud over part of Virginia Beach, it wasn’t big enough or large enough to cause the wide area of damage that has been reported. We’ll have an update on that later today.
Here is what the storms looked like on radar yesterday afternoon.
Along with the damage we also had flooding rain. It got pretty bad over many cities on the Southside. Here is one photo of the flooding sent in by Cristina Davis in Downtown Norfolk:
The rain totals were very impressive.
Notice that Chesapeake had 1.23″ yesterday. The day before they had almost 3″. So we are talking about 2-5″ over the Southside within 48 hours. It’s great that we got the rain in the region, but it was too much-too soon for some cities.
Now I’ve looked back at some of the data from this storm system. So here is some deeper details of what happened. I’ll warn you that it will be a little technical for this paragraph. So there was a stationary front in place just to our north. Moisture was pretty deep in our region to the south of the front. Dew points were in the low/mid 70s. Precipitable waters were around 2″. That is how much water is in the total column of air in the atmosphere over a certain area. We did have a lot of clouds through the region which typically works against the chance for severe weather. However, the clouds did thin out by midday. So the temperatures rose to the low/mid 80s in the region. CAPE or (Convective Available Potential Energy) aka. “the instability” was decent, but not super high. It was between 1,000 and 2,000 with one spot up to 2,500. 500-100 is about the minimum for strong storms. The wind shear was about 30 knots. That is about the minimum for severe weather. So there wasn’t a smoking gun there between the instability and the upper level winds. However, I did notice that there was a 700 mb (level of pressure) jetstreak. Basically that is a stronger area of winds in the mid-upper levels that rolled on through the region. It can promote rising air, and severe weather. Especially if there is a cold pool along with it. I noticed it yesterday as the storms were forming over Emporia. I’ve seen these features create severe weather events if they are potent enough. Even when there is a lot of cloud cover. The Suffolk tornado of 2008 comes to mind. It was a different setup, but those were two things in common (cloud cover and the jetstreak). I also noticed that there was a high amount of surface convergence yesterday. That is where a lot of surface winds push towards each other. When the air meets at the surface there is forcing upward since the extra air has to go somewhere. We were not in a a slight risk for severe weather yesterday until around the midday. Then the Storm Prediction Center upgraded us. Things ramped up quickly. So those are my latest thoughts on yesterday’s storms.
(update: The National Weather Service has done a survey of the damage in Virginia Beach. They claimed that most of the damage was caused by straight-lined winds, however there was one section that appears to have been hit by an EF – 0 tornado. We’ll have more info as it is put out).
Today we still have the stationary front in place, but it is trying to drift south. Also the mid-level energy over us yesterday is pushing out to sea. So we will have less of a chance for storms today. However, it’s not zero either. I put it up to a 30-40% chance for scattered showers and storms later this morning through the early afternoon. These storms are expected to push south and west of Hampton Roads through the late afternoon into the evening. So by the evening commute we should be looking good.
Highs will be in the low/mid 80s today. The good news is that we are looking at nice/quiet weather for the weekend. We’ll have partly cloudy skies and highs in the 80s on Saturday. It will be near 90 on Sunday. The chance for rain will resume on Monday. Then on Tuesday a very strong system (large trough) will drop down out of the Midwest. As this sinks south it will help to push a cold front through the the Mid Atlantic and Southeast. That will be at the surface. So we could see some strong storms next Tuesday as that comes through. Then we will get a nice cool down later in the week. It’s possible that low temperatures will drop down to the 40s over parts of the Midwest. Very unusual for this time of year. Some are calling it the Polar Vortex of the Summer. Me? Pfffft. And that’s not a typo.
Meteorologist: Jeremy Wheeler