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 attended a talk by Dr Fujita a number of years ago and he described how he came to the realization about microbursts. It was based on a survey that he did during WWII of the results of the atomic bomb (I forget which one he was at). He noticed that all of the lamp posts were bent in a circular pattern radiating out from the site of the bomb blast which was an airburst to give maximum effect. He later went up in small planes and took pictures of the microbursts destruction (which no one knew exsisted) and noticed the similarity of the pattern. There as a great deal of resistance to his theory at the time.
Check out this link for information on a microburst in Brisbane, Australia last year. The look at the NW quadrant of the radar sequence.
http://www.bom.gov.au/weather/qld/cyclone/thunderstorms/16Nov2008/qldth20081116.shtml#radar
There are a few videos on youtube – search Brisbane storms the Gap
http://www.youtube.com/results?search_type=&search_query=brisbane+storms+the+gap&aq=1&oq=brisbane+storms
Current estimate is over $80 million damage.
So when is this going to be attributed to AGW?
Hello Anthony, since you have this subject up, I was wondering if you knew how we got the winds from Hugo all the way up here in Ohio back in August. It was really strange, like a dry hurricane, there was no rain attached to it.
Yes is is amazing what we learn from new technology that allows us to observe and record events which were a matter of speculation until recently.
For instance when i was young, a long time ago, there was great debate on whether miniature cyclonic storms as they were then called, twisters in US parlance, occurred in England. There was evidence from minor damage to buildings and the like that they possibly did: others thought the notion ridiculous.
The rise or prevalence of the personal video cameras has shown us that indeed they not only exist but are commonplace: to the point that some authorities now claim that the UK is a hotbed of the things.
Fortunately they are usually either too small or too short lived or both to do much damage even in this densely populated Island.
But the fact that the idea, even though there were what now seem to be very accurate eyewitness accounts going back some hundreds of years, was ridiculed by the then modern science as being an old wives tale is, or should be, instructive.
But I fear it won’t be.
So much more comfortable in the office or the lab than out in the field don’tcha know: and anyway who wants to spoil elegant speculation over dinner with observations from the real world.
Kindest Regards
The Dallas Morning News today had an amazing picture of the actual downburst that wrecked the Cowboys’ facility, taken from a phone camera. I’m not sure if it’s on their web site or not- haven’t been able to find it. It looks just like an inverted funnel.
We must had one of these here (20 or so miles west of Omaha) several years ago, although I have never seen anything official.
We had a hell of a wind headed pretty much due east from here–some damage to trees nearby it seems like.
A couple of blocks farther west there were several topped trees (I wish I could remember which way they pointed.
A couple of blocks east there were topped trees (pointing east I think, but my memory is hazy).
When the power went off, I drove out to the road (about 3 blocks) and found that the power line was down right there–ten or twelve spans of a north-south line had the tops of the poles removed, almost as of cut with a saw.
The crossbars and all the attachment hardware was intact on the wires, but all drapped down toward or on the ground.
Dallas news has had several photos of the downburst taken by folks with camera phones. Here’s one.
http://www.cnn.com/2009/US/05/02/cowboys.practice.field.collapse/index.html?eref=ib_topstories
pretty incredible.
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.
When entering a microburst area (1) the landing aircraft experiences both an uplift and a headwind-induced airspeed increase (2). The normal response would be to reduce power to slow to approach airspeed, and lower the nose to get back down on the glide path. Reaching point (3), the aircraft hits the downdraft with the nose pointed down and the power that it would need to fight the downdraft, reduced. The pilot pulls the nose up to stop the sudden sink rate, which immediately drops airspeed, while the engines take a few seconds to come back up to full power. The aircraft then moves to point (4), where the sudden tailwind sucks out what’s left of the already reduced airspeed. No airspeed, no fly. Kerthunk.
Training now to counter this is when landing in a thunderstorm area, if you get the uplift and airspeed increase, don’t reduce power too much or dive for the glide path. If you can’t get back to proper position and airspeed, give up the approach. Go around and come back to try again.
Newer aircraft radars have processing that detects downbursts and highlights the area on the radar screen and issues a voice alert. Airport radars also spot microbursts, and wind monitors scattered around the airport raise an alarm when wind direction differs greatly.
I’ve been through many simulator rides with the microburst program, and it can be a really wild ride, but proper procedures will beat it.
Ohioholic (19:15:42) :Hello Anthony, since you have this subject up, I was wondering if you knew how we got the winds from Hugo all the way up here in Ohio back in August. It was really strange, like a dry hurricane, there was no rain attached to it.
You can’t mean Hugo. That was in 1989.
Also….downbursts….derechos….squall lines…..they really have nothing to do with hurricanes whatsoever.
Sorry….i know this question was to Anthony but I thought I would go ahead and address anyway.
To what exact event are you referring?
Chris
Norfolk, VA
When I was storm chasing actively in the period around 1993, I got the chance to see several of them from various angles and experience them as well.
We had an event at Hillrose Colorado that killed one man and injured his wife when a down burst picked up their mobile home (not tied down properly), lifting it over a swing set and then slam dunked it on the driveway and rolled it a couple times.
In addition to the radiating wind pattern there is one other visual clue to differentiate tornado damage from down burst damage. A tornado touch down and damage has a signature of damage that is easy to recognize once you have seen it several times.
For one thing, trees has a characteristic “shredded” appearance from a tornado with trash wrapped in the limbs and random breakage through out the crown of the tree. Down bursts being straight line winds (locally) tend to blow down the trees in a common direction and break tree limbs in a more uniform pattern that indicates wind direction, with the down wind limbs being little effected, and upwind and cross wind tree branches being broken back in a common direction.
The winds at Hillrose were in the 100+ mph range as it stripped a couple of empty grain bins off their bolted down foundations and rolled them for several hundred yards. Looking at the hold down bolts you could see how the upwind bolts were pulled out of the bottom of the grain bin mounting flange due to uplift forces on the windward side of the bin, and the grain bin was “peeled back” by the wind with the down wind bolts laid over pointing down wind. A couple of traffic signs were also “wind flagged” and bent over or buckled in that same direction. One a sound 4×4 post was broken off clean at the ground by the wind load on a small sign about 1 foot square.
Looking at the mobile home and analysing the debris you could see that the initial wind gust blew in the skirting on the windward side of the mobile home which pressurized the area under it as the down wind skirting held slightly longer. That uplift from the under floor pressure and aerodynamic lift over the roof picked the mobile home (about 12×50 as I recall) up high enough that a small porch on the down wind side was not even moved. The home rolled over a picnic table partially crushing it, vaulted high enough to almost completely clear a child’s swing set, and rolling landed on its side or roof on top of some parked cars in the driveway, then it disintegrated as it rolled one more time coming to rest about 100 ft down wind on its top with the floor decking crushing most of the contents of the home.
The damage was highly localized. Just a few hundred yards away you could find very little if any evidence that any high winds had occurred.
Someplace around here I have some storm damage photos of that event.
Larry
When I wrote that I knew “crossbar” was wrong–that is telephonish.
“Crossarm” is what I ment.
Craigo (19:12:11) :Check out this link for information on a microburst in Brisbane, Australia last year.
WOW. Thanks for those links, Craigo.
Chris
Norfolk, VA, USA
I’ve not access to the video posted here or to the same video at U-Tube. If someone is experiencing the same problem, here is another video of a downburst:
BarryW (19:03:24) :
I attended a talk by Dr Fujita …He noticed that all of the lamp posts were bent in a circular pattern radiating out from the site of the bomb blast which was an airburst to give maximum effect.
This is so interesting and makes the pieces fit. In January 2007 a violent storm moved through our area in KS, ripping off our roof and damaging neighbors’ barns. The weather service reported that there were microbursts in the area, yet people just KNEW there had been tornadoes because they observed twisted trees and debris on their properties. It seems that is characteristic of downbursts. I was in our garage when the storm passed over and it was as if the building was breathing as the pressure changed – the walls and roof seemed to rapidly expand and contract.
Collapse of a manmade structure during a natural disaster, with survivors headed toward a football stadium? I think that’s traditionally FEMA’s fault.
I had heard of microbursts bursts at DIA, once or twice I thought. Googling ‘microburst, Denver’, came up with events in 1977, 82, 84, 88 and 89 on the first page. Not as uncommon as I remembered.
“The weather service reported that there were microbursts in the area, yet people just KNEW there had been tornadoes because they observed twisted trees and debris on their properties. It seems that is characteristic of downbursts. I was in our garage when the storm passed over and it was as if the building was breathing as the pressure changed – the walls and roof seemed to rapidly expand and contract.”
Perhaps the twisted trees and the twisted “twister” signature of the debris may have indicated that you were on the edge of the bow echo where sometimes more vorticity [rather than clear straight line winds] are present.
Chris
Norfolk, VA
Thank you, this is fascinating. In the early ’70’s I was crewing in a sailboat race on upper Galveston Bay when the fleet was overtaken by the sort of very fast and nasty storm that can pop up there in the heat of the summer. Now that I see this I realize the boats at the windward mark must have been hit by a microburst. Many sails shredded, some spars broke and more than half the boats were completely knocked over. I don’t recall an injury worse than a broken arm. This was in the era of heavy-keeled racer-cruisers with thick, over-engineered fiberglass and lots of flotation, hard to knock over and unlikely to sink. I believe contemporary purpose-built, lightweight, stripped-down racers would be at much greater risk of sinking.
We sail, and my husband races, on the other side of Dallas from Irving, on a lake with four marinas. In the 70’s only one or two commonly-sailed classes were trailered “on the hard.” Now, racing boats up to 35′ are routinely strapped to trailers and bolted to the parking lot. They withstand 75mph straight-line winds, but will they withstand a microburst? It’s only a matter of time before we find out. My old fat, heavy, tubby and very comfortable cruiser is looking better and better!
Since at least Berry Switzer’s time, anything bad that happens to the Cowboys is either Jerry’s or DPD’s fault. Jerry was in Kentucky. Therefore, it must be DPD’s fault.
Question: If you have more than two Cowboys in a car, who’s driving?
Answer: DPD
*rimshot*
I have seen the results of two of these events. One was in Huntsville Alabama in the early 90’s when a microburst blew every single shingle off of a single house and blew all of the windows and the doors out. A house next door had the aluminum siding pulled off the wall and no other damage in the area. This happened right in the middle of a 70 year old neighborhood with houses on all sides of the one affected.
The other was in Farragut Tennessee in the early 2000’s when a microburst literally snapped every tree within about a fifty foot radius and blew them down. A house about 100 feet away was completely untouched. However, my buddy that was watching this happen from his front porch required several beers to calm him down along with a trip to the bathroom.
“AnonyMoose (20:33:50) :
Pat (19:14:10) :
So when is this going to be attributed to AGW?
Collapse of a manmade structure during a natural disaster, with survivors headed toward a football stadium? I think that’s traditionally FEMA’s fault.”
The point I was trying to make is that pro-AGW suporters believe more CO2 in the atmosphere leads to more warming, leading to more “extream weather” events. As an example, in the AGW camp, Katrina *is* firmly blamed on AGW.
Common theme of the comments (mostly personal experience):
Hey, striking up a conversation by talking about the weather still works:-)
Man, until relatively recently, did not understand the dynamics of many aspects of weather. I would submit that Man still does not understand many of the dynamical processes of weather (slowly, but surely, Man’s understanding is increasing).
If Man does not understand the dynamics of localized weather phenomena, it makes it that much harder to believe Man understands the full dynamics of world climate.
Therefore, rushing headlong into legislation to attempt to control world climate is the height of folly.
Let’s focus on observation & measurement, and, while applying reasonable sceptism, keep an open-mind. There are possible weather dynamics and climate dynamics afoot that few have actively considered.
About 15 years ago I had an excellent view of two microbursts occurring similtaneously about 3 miles (5km) apart. I was on a commercial jet on climb outbound from DIA. We were about 3,000ft (900m) AGL with broken cumulus congestsus based at about 5-6kft (1500-1800m) AGL. There was plenty of room between the two bursts and the climbout was in clear air and smooth as glass!
The microburst on my (starboard) side of the plane showed a truncated column of precip (virga) descending from the base of a cloud. The air below was obviously quite dry below as the moisture evaporated before descending much more than 1,000ft (300m). Evaporative cooling increased the density of the air and accelerated it downward. The most interesting thing was that along the circular outflow front from where the burst hit the ground that was about a half mile ().8km) in diameter, there were about half a dozen small whirlwinds resembling powerful dust devils that had formed along the leading edge of the outflow moving outward with the gust front. The terrain was flat open pastureland. As for the companion burst farther north on the port side of the aircraft, from what I could see as I looked across the aisle looked to be an almost identical feature.
When the plane landed in Chicago I went up to the pilot to report what I’d seen and he said; “Oh, you saw them too! Weren’t they great!?.”
In my youthful years I was always a little frustrated by the lack of interest given to unusual observed phenomena expressed by scientists whose field of knowledge would have included the phenomena. One of the first “official” examinations of tornadoes by a weather officer was by John Finley who was a sergeant in the US Signal Corps (a military unit which later evolved into the US Weather Bureau). Finley was investigating a severe tornado outbreak in the Great Plains, May 29-30, 1879 just a few days after the event.
His study consisted of field observations of the tornadoes’ effects and included diagrams of the various tornadoes’ paths and numerous interviews of anyone he could find that was in or near the path. The published report included numerous hand-drawn depictions of what the interviewees saw. The pictures included some with multiple funnels, funnels emanating from a wall cloud and cyclonic rotation in the parent clouds. Many scientists of the era scoffed at these depictions claiming it was impossible for more than one funnel to coexist in the same space. Of course we now know a lot better now.
The point is that I have little respect for so-called scientists who know better than the people who actually observed the phenomena. I’m reminded of the tag line of a popular radio comedian in the ’30s who called himself Baron Munchausen, which was; “Vas you there, Charlie?”
The best current example (among many) that I know of involving meterological phenomena that has yet to be adequately explained and that has frustrated a handful of researchers most of whom ultimately gave up on the subject, is the kugelblitz; or literally, ball lightning. I suspect that a true understanding of the kugelblitz would reveal some hidden information about plasma behavior and possibly quantum physics.
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.
Having lived through one of these (it’s referred to as “Hurricane Elvis” around here), I have to admit that scared the ever-living **** out of me when it happened. I thought I was going to be roadkill on I-40. How my car didn’t flip over, I’ll never know.
I never knew there was a term for that event, other than hurricane-force winds in a region nowhere near where such events are known to occur.
Here’s a link to it, if anyone’s interested. It never got much press for some reason:
http://en.wikipedia.org/wiki/Memphis_Summer_Storm_of_2003
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?
ohioholic (06:32:27) …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.
Oh Ike. You bet it was related to Ike.
What I was saying is that derechos and downbursts often originate from thunderstorms or thunderstorm complexes…not from hurricanes turning extratropical.
But you were right about this unusually widespread wind event…and I see why you would call it a “dry hurricane”.
Here is a GREAT explanation from Dr. Greg Forbes [severe weather expert] from his blog.
Definitely check it out.
http://www.weather.com/blog/weather/8_17237.html
Also, and interestingly this June in Atlanta there is the AMS Conference on the Inland Impacts of Tropical Cyclones.
I see a couple of Ike presentations are on the schedule.
http://74.125.93.132/search?q=cache:SpCzO-T7gaUJ:www.ametsoc.org/chapters/atlanta/IITCagenda.pdf+inland+effect+on+hurricanes&cd=3&hl=en&ct=clnk&gl=us&client=safari
Chris
Norfolk, VA, USA
About 25 years ago I experienced a Number 10 Typhoon in Hong Kong, that’s one with very destructive wind speeds. I was involved in the clear-up operations and noticed that a fairly large number of trees in certain limited locations had been blown down in directions describing a circle. Typhoon winds come from one direction and then, after the eye has passed, from the opposite direction. Some of these downed trees were at right angles to either wind direction.
My Chinese co-workers told me that this was the work of the ‘Dai Fung’, the phenomenon which gives the storm its English name. The Chinese name is reserved for the incredibly strong bursts of wind which wreak so much localised damage. I wonder if the circular damage patterns I saw could have been the result of some sort of localised downburst within a typhoon event?
Here is an account about observations of “crop circles” and a weatherman’s view. Could microdownbursts also occur in straight line patterns?
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Crop Circles in Hyde Park
by Ben Hogwood
HYDE PARK Sean Hill was driving to his friend’s house, with his
girlfriend, Kaitrin Arnot, and sister in the car, when Arnot saw
something a little strange. “Did you guys see that?” She said to the
others in the car.
When they pulled over to look, they saw a whole hayfield covered with
what looked like crop circles. A huge portion of the field was
completely flattened, with the hay laid flat across the floor with the
stems all bent approximately six inches up from the ground. The
direction which the hay laid, often changed directions and some areas
had what Arnot described as ‘cowlicks’ with the wheat pushed out in
every direction in a circular pattern. Separate from this main
flattened portion were smaller circles, or almost circles, completely
unconnected from the rest. Hill didn’t know what it was, but it didn’t
look man-made.
But if it were aliens, they clearly didn’t use a meter stick or
protractor. The patterns were disorderly and didn’t seem to make any
specific shapes. A few weeds, with stronger stems than the wheat,
remained standing in areas where everything else was completely
flattened. It didn’t make sense: why would aliens, possessing the
technology to fly thousands of light years, come to Vermont to leave the
equivalent of a two year old’s drawing on a field?
The answer, obviously, is a little closer to home. Vermont Public
Radio’s Steve Maleski, a well known meteorologist, gave a number of
possibilities as to what it could be. One possibility, he said, is a
small tornado, another being a downburst, which is a blast of wind which
comes down and leaves a starburst pattern. However, given the night on
which it probably occurred (Monday, July 21) Maleski said it was most
likely a microburst. “This is a rapidly accelerating downdraft which
smacks into the ground and spreads out,” he said. “That would be the
most probable,” he said. This explanation would account for the large
flattened area, the smaller circles and why the weeds with thicker stems
remained standing.
aurbo (21:58:46) :
Ball lightning has been proposed as a means of long-term plasma confinement for fusion power plants. Paul Koloc has done a lot of work, but not recently. See http://www.prometheus2.net/ for lots of fascinating stuff.
Stephen Brown (14:49:09) :
Check out http://findarticles.com/p/articles/mi_m1200/is_n6_v143/ai_13434075/ which says in part:
Fujita proposes that the eye wall of the hurricane-the region of strongest winds surrounding the calm “eye”-spawns small, swirling eddies that measure only 500 feet in diameter. If these eddies drift into the eye, they are harmless. But if they pass under the fast-growing clouds outside the eye, the cloud convection pulls air upward, stretching the vortex skyward and causing it to tighten. Like spinning skaters who pull their arms inward, the tightening vortex swirls faster, reaching speeds of up to 80 miles per hour during Hurricane Andrew. Because these spinning features were carried along by the 120-mile-per-hour winds of the hurricane, they produced combined winds of 200 miles per hour, Fujita says.
Here’s an account of a downburst near Spokane last night, that
caused severe damage to exactly one farm.
http://www.spokesman.com/stories/2009/may/07/wind-tears-through-north-spokane-property/