Many of you have already seen this footage below, but I thought it would be interesting for WUWT readers to get a look at the cause behind it. Meteorologist Mike Smith, from WeatherData, sent an interesting picture and description of the incident vua email that I wanted to share. I’ve added some links and visuals also. – Anthony
Mike Smith writes: A “downburst” is a unique form of extreme winds unknown to meteorologists prior to 1977 when it was discovered by Drs. Ted Fujita and Horace Byers. While they can occur anywhere, the Dallas area has bitter experience with downbursts.
Delta Airlines’ flight 191 crashed in a downburst at DFW International Airport August 2, 1985, killing 135. In the quarter century since that horrible August day, meteorologists have made tremendous strides forecasting and warning of these small, but deadly, storms.
WeatherData Services, Inc., (an AccuWeather Company), applied that knowledge at 2:50pm May 2, 2009 when we issued a SkyGuard® warning of 65 mph winds for a client located in the Dallas suburb of Irving, TX. Based on radar, the winds struck between 3:10 and 3:15pm.
A post-storm survey by the National Weather Service determined winds were “nearly 70 mph.”
These winds collapsed the Dallas Cowboys’ practice facility where a “mini-camp” was in progress. According to NBC Sports, Cowboys’ owner Jerry Jones stated, “We did not get [a] good warning.” This may be because governmental sources did not issue a warning until 3:06pm, 16 minutes after WeatherData’s and just moments before the winds occurred.
Here is some background info on downbursts:
A downburst is created by an area of significantly rain-cooled air that, after hitting ground level, spreads out in all directions producing strong winds. Unlike winds in a tornado, winds in a downburst are directed outwards from the point where it hits land or water. Dry downbursts are associated with thunderstorms with very little rain, while wet downbursts are created by thunderstorms with high amounts of rainfall. Microbursts and macrobursts are downbursts at very small and larger scales respectively. Another variety, the heat burst, is created by vertical currents on the backside of old outflow boundaries and squall lines where rainfall is lacking. Heat bursts generate significantly higher temperatures due to the lack of rain-cooled air in their formation. Downbursts create vertical wind shear or microburst which is dangerous to aviation.
Definition:
A downburst is created by a column of sinking air that, after hitting ground level, spreads out in all directions and is capable of producing damaging straight-line winds of over 150 mph (240 km/h), often producing damage similar to, but distinguishable from, that caused by tornadoes. This is because the physical properties of a downburst are completely different from those of a tornado. Downburst damage will radiate from a central point as the descending column spreads out when impacting the surface, whereas tornado damage tends towards convergent damage consistent with rotating winds. To differentiate between tornado damage and damage from a downburst, the term straight-line winds is applied to damage from microbursts.
Downbursts are particularly strong downdrafts from thunderstorms. Downbursts in air that is precipitation free or contains virga are known as dry downbursts;[1] those accompanied with precipitation are known as wet downbursts. Most downbursts are less than 2.5 miles (4 km) in extent: these are called microbursts.[2] Downbursts larger than 2.5 miles (4 km) in extent are sometimes called macrobursts.[2] Downbursts can occur over large areas. In the extreme case, a derecho can cover a huge area more than 200 miles (320 km) wide and over 1000 miles (1600 km) long, lasting up to 12 hours or more, and is associated with some of the most intense straight-line winds,[3] but the generative process is somewhat different from that of most downbursts.
Here is why a downburst is so dangerous to aviation.
Source: NOAA
I wonder why it took so long for the government sources to issue a warning?What are they supposed to do in a downburst warning?Get out of buildings I suppose.I hope man never understands the full dynamics of world climate.If ever there came a time that man could damage another country with weather,without damaging their own,who would need nuclear weapons?Or is that too out there.
I love this thread. I love foul weather for some inexplicable reason. My storm story is a typical prairie thunderstorm (~65,000ft. tall anvil cloud) , middle of Lake Winnipeg. A google search will tell you it is a scary piece of water. Half the size of England and an average depth of only thirty feet. You can touch bottom in the middle of the lake during a storm. It started out as a hot summer day, didn’t end that way. Anyway, I lived to tell the tale, and I check the weather reports thoroughly now. Keep the storm stories coming. Love them.
Micro bursts and their effects close to ground level are quite well known to most of the world’s sail plane / glider pilots.
It is a fact of life for a glider pilot that he / she is made aware of the effects of strong downbursts.
We get a small taste of this nearly every day that we fly as we work the updrafts or lift and then have to fly through the often very strong downdrafts or sink to get to the next thermal or updraft.
Where air goes up, air also goes down.
Glider pilots, particularly when in competitions will often chance their arm and head for the strongest updraft cells even though they are developing into storm cells, to gain some advantage over their competitors.
These storm cells often turn into full blown thunderstorms in the right meteorological conditions with very strong updrafts as well as very strong downdrafts which the glider pilot obviously tries to avoid.
It can be at worst, an interesting ride and in glider pilot parlance, the buttons on the seat will get very severely nibbled and a firm hold on them is often established.
There have been a number of heavy landings and some crashes by gliders in Australia and in other parts of the world when the glider has got caught in downbursts from these storms and shear lines that can easily exceed three thousand feet a minute down and often at least twice this and that is right down to ground level.
The glider pilot may have been caught and may be unable to get out of the downburst before being dragged down to ground level at many thousands of feet per minute with the resultant very heavy landing or crash and possibly severe personal injury.
I have sat a few kilometres away and some 5000 feet up and watched the the down burst from a small storm cell, as it hit the ground.
The rapidly expanding circle of dust from the down burst, rising to only hundred or so feet above the ground and expanding at an astonishing rate was something to behold.
And this was just a very small downburst!
There are so many truly marvelous and amazing phenomena in our ever changing three dimensional atmosphere that only glider pilots and hang glider pilots and some power pilots ever experience.
Those mere mortals who have only ever seen the atmosphere in two dimensions from ground level and who ride along in the back of the geese trucks and think they are flying are just deluding themselves if they think they have got a serious taste as to what nature and it’s awe inspiring forces really has to offer.
IRT the down burst speeds, I was under the impression that they could be much faster than the 150 mph stated.
We experienced short powerful storms last summer here in Australia – one was a kilometer wide and travelled around 6 kilometers. In it’s path it sandblasted grey gum trees and a painted wall of a house with hail stones and stripped them back to natural timber. Totally weird.
My family and I were camping in the mountains of Pennsylvania some years back when our tent was flattened (and I do mean flattened…it looked like a giant had stepped on it) by a microburst. The campers immediately around us had their tent stakes pulled out but were otherwise unaffected. In our tent every single last tent pole was broken in a matter of seconds…luckily no one was in the tent when it happened. Darnedest thing I ever saw. Rain, big whoosh of wind and then flat tent.
Micro downbursts are a feature of every gust too. When all the trees were flattened in England’s 1987 ‘hurricane’, they all fanned out in a series of fan shapes, where a gust had hit the ground.
You can often see this effect over calm water too, where a small gust will hit the ground and spread out in a fan shape.
Trying to watch the video from the UK…
“This video is not available in your country or domain”.
a jones (19:22:16) : I heard the other day on a British quiz show (Eggheads) that Great Britain has the greatest number of tornadoes per unit area of any country in the world. I know my source is a quiz show but their researchers do seem very thorough. I haven’t checked this out anywhere but it was an interesting little fact to research later. 🙂
Not available in Spain either. Is this a new youtube ‘feature’?
I am writing youtube to complain about this. Is not a tv program or a explicit content video. I don’t know why it seems not to be available outside the USA/north america.
Reply: It looks like this particular video is from a commercial channel, ESPN, on youtube and there may be geographic restriction. ~ charles the moderator
Thanks Charles for your prompt reply. I am writing to complain, anyway. I know that ESPN is a sports commercial channel, I have lived in the USA for more than six years. And I can also watch ESPN overseas via satellite. That is why I don’t get why this particular video is not available outside the USA but you can watch it if you are in the USA. There is plenty of videos from a lot of USA tv channels uploaded on youtube and available to watch everywhere in the world. And I watch videos on youtube from other commercial tv channels all around the world without zone restrictions.
Sorry about the rant.
>> Great Britain has the greatest number of tornadoes
>> per unit area of any country in the world.
Yes, but ours are tiny in comparison to US monsters.
Regards this video not being available in the UK, Youtube is not available at all in many Eastern countries. Too subversive, you understand.
.
Imagine when NFL coaches start blaming climate change for an abysmal season 🙂
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In other news, Mike Hulme, founding director of the Tyndall Centre for Climate Change Research and Professor of Climate Change at the University of East Anglia, has come out as a sceptic! I’m not sure if Watts has spotted this one.
The most dangerous microbursts from a aviation standpoint are those that occur in clear air (dry micorbursts). Invisible to the pilots and the controllers since you can’t even see the effects until they strike the ground and start blowing things around. Doppler radars can’t see them because of the lack of something to reflect off of. Ground sensors can only detect them once they’re on the ground.
Nick (01:18:06) :
Trying to watch the video from the UK…
“This video is not available in your country or domain”.
Nick, the UK authorities have determined that this video is a hate video that fosters extremism and hatred and has been banned from viewing in the UK
“I think it’s important that people understand the sorts of values and sorts of standards that we have here, the fact that it’s a privilege to view certain videos and the sort of things that mean this video won’t be welcome in this country,” Home Secretary Jacqui Smith told GMTV.
savethesharks (19:59:55) :
You’re right, I meant Hurricane Ike. We lost power for about ten days last year because of it.
My bad.
http://www.insurancejournal.com/news/midwest/2008/09/29/94116.htm
Here is a link to it. I have read that it was Hurricane Ike related (not Hugo, oops), but I don’t know how it is related. I was hoping Anthony would know.
Moderators: We are talking about powerful puffs, but I think the powerpuff links a few comments above aren’t particularly informative.
Back in ’96 I was nearly slammed into the high desert of New Mexico by a downburst.
-Loaded DC-7 Airtanker. Barely got rid of our load in time, and we were into airframe stall warning as we escaped. That is one reason I sell real Estate now…
AEGeneral, as another Memphian, I, too, experienced Hurricane Elvis. I actually slept through it, as the main thrust of the storm was slightly north of where I lived at the time. My parents house, had some downed trees, however, and they were without power for a three days, and they only lived three miles from me.
There are pictures of the damage in Memphis available here:
http://www.mscema.org/index.php?name=coppermine&file=thumbnails&album=5
BTW, the video incorrectly calls the structure an “air-supported structure”. It’s not. The Houston Texans simply deflated their air-supported practice bubble as last year’s hurricane (I forget the name) approached, the one that ripped part of the roof of Reliant Stadium.
The Cowboy’s facility is supported by structural steel, i.e. it’s a glorified tent. Thus the injuries from falling support members, etc. A air-support bubble would deflate more slowly and while entrapping people in fabric wouldn’t cause them to be hit upside the head with steel beams etc (though falling lights and the like are still a danger, of course).
Mike McMillan (19:53:12) :
After the Delta crash and discovery of the microburst phenomenon, all the airlines began serious training in the simulators to counter the problem. The bottom diagram above needs a little explanation as to why it’s so dangerous.
NASA’s work showed that pilots required between 10 and 40 secs to be able to react appropriately to a microburst. Subsequently on-board detection systems were developed and mandated for air carriers in ’93 which is why the practice described by Mike can be put to good use.
What happened to my crop circle comment?