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Posted at 10:00 AM ET, 04/29/2008

Inside the Suffolk, Va. Tornado

By Jason Samenow

[Update, 10:15 p.m.: The National Weather Service (NWS) rated the Suffolk tornado a "3" on the Enhanced Fujita Scale. It has put together an excellent page with imagery, video, photos and its storm assessment.]

We preempt the Weekly Top Five to provide an inside look at yesterday's tornado that flattened areas around Suffolk, Va. and caused nearly 200 injuries.

While rain-cooled air created an atmosphere too stable for severe thunderstorms in the D.C. metro area, a bit of morning sunshine helped raise temperatures above 70 in Norfolk, Va. And it wasn't just warm, but it was also humid with dewpoints in the sticky upper 60s. The warm, sticky air and its interaction with the strong approaching cold front fueled the development of storms in southeast Virginia.

But the clash of the warm and cool air alone didn't cause the tornadoes.

Keep reading for more on the Suffolk tornado. See our full forecast for the outlook through the weekend, and NatCast for tonight's game at Nationals Park.

The other key ingredient was wind shear; that is, winds changing in direction as you go up in the atmosphere. A lot of wind shear was present yesterday due to fast winds 15,000 feet up blowing in a different direction than winds closer to the surface. And this wind shear served to turn the winds inside developing thunderstorms. National Weather Service meteorologist Bryan Jackson, on-duty in southeast Va. during yesterday's storms, told me "the Suffolk tornado was from a classic supercell -- a thunderstorm with a rotating updraft [upward movement of air]."

sevavelocity.jpg
Velocity radar image from ~4:20 p.m. yesterday near Suffolk, Va. Courtesy Brandon Orr.

The rotation within the tornado-producing thunderstorm is evident from radar. Radar can measure the velocity of wind blowing towards and away from it. When wind blowing away from the radar is adjacent to wind blowing towards the radar, that's an indicator of spin and, in many instances, a funnel cloud or tornado. The image to the right shows such a velocity couplet. The tornado, denoted by the "x," is located at the intersection of green and red shading, which shows wind blowing towards and away from the radar, respectively. (Note: the green triangle is where the radar algorithm detected the tornado, but I suspect it was slightly south of that based on the radar presentation; hence where I drew in the "x").

sevahook.jpg
Reflectivity radar image from ~4:20 p.m. yesterday near Suffolk, Va. Courtesy Brandon Orr.

The tornado-producing storm also produced what's called a "hook echo" on radar, which is the classic indicator of a rotating supercell thunderstorm. On the right, you can see the radar image (this time displaying precipitation, as opposed to wind velocity in the above example) of the thunderstorm and its hook-like signature. I've noted where the tornado was likely located with an 'x' at the tip or point of the hook.

In addition to its definitive representation on radar, the Suffolk tornado was notable for its size. Initial indications from video suggest it was at least several hundred yards wide. It may have been wide enough to be considered a "wedge" tornado -- or one which appears wider than it is tall. NWS's Jackson suspects there may have been multiple vortices (columns of whirling air) within this large tornado:

Tornadoes this large typically have vortices an order of magnitude smaller that rotate about the main funnel. The nature of these multi-vortices as they revolve and move with the storm leads to the sporadic nature of tornado damage. I cannot confirm for sure that there were multi-vortices, but it did appear [there were]...

The intensity of the Suffolk tornado has not been confirmed. But judging from some of the video of the tornado and its damage, I'd guess it was an EF-3 or EF-4. EF stands for "Enhanced Fujita Scale," and the scale spans from 0 (least intense, 65-85 mph) to 5 (most intense, over 200 mph). Tornadoes of this intensity (EF-3 or EF-4) are pretty rare in Virginia.

The Suffolk tornado and the others that impacted southeast Virginia occurred on the six-year anniversary of the devastating La Plata, Md. tornado. Like the La Plata tornado, the Suffolk tornado will be remembered for years to come.

By Jason Samenow  | April 29, 2008; 10:00 AM ET
Categories:  Thunderstorms  
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Comments

The dot of pink next to (left of) the "x" in the reflectivity radar image-- is a very high reflectivity radar return and may be indicator of the tornado's debris!

Posted by: Capital Weather Gang | April 29, 2008 10:35 AM | Report abuse

The footage I saw on Channels 5 and 9 last night definitely looked like a good sized "wedge" tornado. I bet the final NWS analysis may well upgrade its strength to EF-4. This tornado and the LaPlata tornado looked like classic "Midwestern" tornadoes. Too often around here fog and humidity tend to obscure the view of Eastern tornadoes, as compared with their counterparts in the Middle West.

As to how the Suffolk and LaPlata tornadoes compare in strength with others in the east...I bet the one stronger tornado cited in historical records for the East Coast area is the one which struck Worcester MA back some time in the 1950's. When that tornado struck with considerable loss of life, it was regarded as "unprecedented" in magnitude for a New England tornado. The September College Park tornado the fall before the LaPlata storm was probably around EF-3. There was apparently no immediate loss of life in yesterday's Suffolk tornado but the 100+ injuries constituted a respectable figure. By comparison the June 4, 1958 Colfax tornado in Western Wisconsin nearly fifty years ago claimed 29 lives with over 200 injuries. That tornado was actually a series of supercell vortices, most of which were EF-4 with one possible EF-5 vortex.

Posted by: El Bombo | April 29, 2008 11:07 AM | Report abuse

Update: News Channel 8 now gives the injury figure for the Suffolk tornado as 200+, making it comparable to the 1958 Colfax tornado (cited above) in that respect. Fortunately the loss of life is far lower than that of the 1958 Wisconsin tornado.

Posted by: El Bombo | April 29, 2008 11:17 AM | Report abuse

Quoting from above:
[NWS's Jackson suspects there may have been multiple vortices within this large tornado:

Tornadoes this large typically have vortices an order of magnitude smaller that rotate about the main funnel. The nature of these multi-vortices as they revolve and move with the storm leads to the sporadic nature of tornado damage. I cannot confirm for sure that there were multi-vortices, but it did appear [there were]...]

Monday night, one of the Norfolk TV stations aired more footage that clearly showed smaller, thinner vortices rotating around the main funnel. The destruction in Suffolk is of a magnitude no one remembers in this area.

Posted by: tperry1 | April 29, 2008 11:36 AM | Report abuse

Some of the photos I saw from, I believe, a WTOP news gallery suggested a multi-vortex structure also. What is peculiar about this event, at least to me, is that the NWS put SE Va and NE NC in a marginal slight risk early Monday with less than 2% probability for tornadoes. It wasn't until about 1PM that the magnitude of the event was coming into focus. I checked the Wakefield radar around then and I could see discrete cells forming ahead of a developing squall line--I believe the squall line was responsible for the weaker tornadoes in Colonial Heights and Brunswick county but a lone supercell appears to have caused the Suffolk tornado.

As I recall, the DC forecast area was in a moderate risk zone prior to the LaPlata tornado and in a slight risk zone before the College Park tornado, but the slight risk included an enhanced tornado threat.

Posted by: Steve Wasko | April 29, 2008 11:58 AM | Report abuse

This video has some good footage of the cell that produced the tornado. Looks like the guy filming had to bail at the last minute because he had his daughter with him. But still good footage of the cloud and rotation.

http://youtube.com/watch?v=WqNCU5H6P6s

Posted by: Laura in NWDC | April 29, 2008 12:28 PM | Report abuse

holly crap!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Posted by: erin | April 29, 2008 12:56 PM | Report abuse

I feel so sorry for the ingered in the Suffolk Va aree. They are in our preres.

Posted by: Sarah | April 29, 2008 2:34 PM | Report abuse

I was within 1 mile of this tornado. I had come out of the closet to grab a flashlight and was able to see the back end of this tornado out of my back sliding glass door. What happened next is what is interesting. I knew we were safe from this tornado due to distance, but then we "Whited Out"...I was unable to see the tornado any longer due to strong winds and all the moisture/showers in the air basically atomizing...probably not that, but we went to 0 visibility in hardcore BLSHRA. What is perplexing to me is that the tornado was 1/2-1 mile to the east. Usually you have the white out within close distance of the tornado. Makes me wonder if we didn't have something through our area...if even a Tuba. No damage to our house or to any in our subdivision, but I find this very interesting. Any ideas?

Posted by: Mark | April 29, 2008 4:39 PM | Report abuse

The Suffolk, VA tornado has been rated an EF-3 (pending further assessment). More info.

Posted by: Ian, Capital Weather Gang | April 29, 2008 7:40 PM | Report abuse

Mark: Not sure what was happening where you were. It's not out of the question there was another funnel. It does look like there was a small velocity couplet west of the main one. Did you see any debris or have limbs down?

Ian-- Great link. Thanks.

Posted by: Jason, Capital Weather Gang | April 29, 2008 10:33 PM | Report abuse

Jason...

There isn't any debris or trees down in my area but we are a new subdivision without any trees. I've also looked at the top of all the houses and don't see any shingles off the houses...but then most of the houses are under two years old. It was odd...pure white blowing rain. Misted out to total ground based obscuration. I'm including a link to some video I shot within 10 minutes of the tornado rolling through. I was looking downstream as they had just issued another warning from Franklin through Suffolk. Not great video, but interesting none-the-less:

http://www.youtube.com/watch?v=WZGiDsuXznw

Posted by: Mark | April 30, 2008 12:41 PM | Report abuse

hi thanks

Posted by: joshua | May 1, 2008 11:52 AM | Report abuse

wow that was cool I want to be a Meteroligest when I grow up like chaseing tornadoes. I saw a tornado on 5/1/08 that is the date. I saw the tornado in Kanses City Missouri. It was exsiteing and scarey all at the same time I wonder your exspretion was when you saw yuor frist tornado. you might think that I am prity enoughing I am 12 yrs. old and I like to do exstream thing. So have a nice day and I was pity inpress!!!

Posted by: maggie | May 2, 2008 5:55 PM | Report abuse

If the tornado is an EF3 but they say possibly an EF4.I have seen less damage than this in Suffolk.But I mean why would they say its an EF4 possibly?Would it because of the damage that it left Suffolk in.I hate to see Suffolk,VA in this much disaster.

Posted by: Samantha | May 3, 2008 3:39 PM | Report abuse

Mark-

What you were experiencing is another feature of the classic supercell called the Rear Flank Downdraft or RFD for short. Strong winds are associated with this feature and sometimes heavy precip, which could have combined and produced the white out you reference.

http://en.wikipedia.org/wiki/Rear_flank_downdraft

Posted by: Andrew | May 5, 2008 3:23 PM | Report abuse

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