Tornado or someting else? Breaking down the Virginia Beach storm

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by Jeff Lawson, 13News Now Weather Authority

WVEC.com

Posted on July 10, 2014 at 6:55 PM

Updated Thursday, Jul 10 at 11:20 PM

Tornado vs Downburst differences: We have had a lot of questions about whether the damage in VB was from a tornado or not. Also a lot of questions about why there was no tornado warning. So, let me explain.

If we did have a tornado it was a weak EF-0 twister (on a scale of 0 to 5) with winds up to 85 mph. Severe thunderstorm winds (or microbust or downburst winds) can themselves be up to 100 mph.

That means the type of damage is identical between the two types of systems when you talk about a weak tornado versus a strong thunderstorm downburst.

So what is the difference? It is simply the damage pattern and not the type of damage. Thunderstorm winds are all in the same direction and all the snapped trees, fences, roofs, etc blow in the same direction.



With a weak tornado you would have the same wind speeds but from different directions. Your fence might be blown down to the north while your neighbors tree a few houses away might be blown down to the south. If you don't have damage in all different directions you don't have a tornado. That is what the National Weather Service will look for when the survey the scene to determine if it was a tornado or not.

Now, let's talk about why there was no tornado warning. As the storm was moving through the region the NWS was watching the radar for signs of rotation and for hours there was no indication of that. Because there were reports of damage from straight-line winds a severe thunderstorm warning was issued. That means that damaging winds are likely to occur (at least 60 mph and higher!).

This dangerous situation is why we stayed on the air from approximately 1:45 pm on because we knew that thunderstorm winds this strong could do similar damage to a weak tornado.

Looking back at the radar data the NWS says that a northward moving storm near the Va. Beach shoreline collided with the main eastward moving line of storms and that for a few minutes there was a very brief rotation on radar. As soon as they saw it they got ready to issue a tornado warning but as soon as they did the rotation was gone again.

So was it a tornado? Very possibly! We have video of a funnel cloud spinning up for a few seconds just south of the Oceanfront that doesn't look like it touched down, but as it moved north it is certainly possible.

Kimberly Bonanno posted  the following video of a funnel cloud at Strawbridge Marketplace.

Again, if doesn't really matter if it was severe thunderstorm winds or a tornado. The bottom line is that damaging winds can come from either situation and the people who had their lives upended are seeing damage from very strong winds. Within a day or so we should have an official determination on what exactly it was that hit Va. Beach.

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