Anatomy of a Microburst

From Mike Smith @ Meteorological Musings

A microburst descends from the parent cloud to the ground

A central Oklahoma microburst descends from the parent cloud to the ground. Photo from National Severe Storms Lab

At 6:46pm yesterday (Sunday) evening, a strong microburst (likely strong enough to bring down a commercial airliner, had it been at the end of a runway) occurred in northwest Wichita a few miles northeast of Mid-Continent Airport. Since these are fairly rare, I thought it might be of interest to view the microburst in several different ways:

First, here it is in the radar reflectivity data (the type you usually see on TV weathercasts). The center of the microburst is near the deepest red pixel. The time is 6:45pm.

A second view of the microburst comes from the Wichita Terminal Doppler Weather Radar (TDWR), an instrument designed specifically to detect microbursts, installed in the wake of Delta 191 and the series of downburst-related crashes in the 70’s and 80’s. Compare the location of “Wichita” on the two radar images and the freeway (Interstate 235, not labeled, but wraps around the west side of the city) on both maps to orient yourself.

This radar senses the wind in great detail. The radar at 6:46pm is showing a 46 knot (53 mph, deep brown pixel) wind blowing toward the north on the north side of the microburst and a winds blowing toward the south at 39 mph (light green) on the south side of the microburst. This represents 92 mph of wind shear, likely enough to bring down an aircraft!

more here at Meteorological Musings

=====================================

Also, for anyone wanting to track storms on radar in near real time, inexpensively on your PC, with no data fees, I have an app for that, StormPredator.  – Anthony

Advertisements

33 thoughts on “Anatomy of a Microburst

  1. Isn’t a mircroburst the same as the collapse of a thunderhead, which creates the same wind shear as all that energy moves down from the top of the cloud?

  2. It was an impressive little cell. I watched it from the baseball game at Lawrence-Dumont Stadium. It dropped the temp from 90 to around 78. Several cells on Saturday and Sunday were surprisingly strong for non-supercell thunderstorms.

  3. I find microbursts facinating as it is a very quick encompasing of water vapour to come together into a change of density and then released.
    You change the density of water vapour to water, gravity tends to want to pull it down. While wind shears and centrifugal force try to keep them up.

  4. Being an old Airline jockey on Boeings in Australia some thirty odd years ago, some uncontrolled ups and downs were rather nerve shattering. When the wind beneath your wings ceases to work in your favour, it can spoil your day. When it happens in clear air with no storms, it is even more alarming. I do understand that science is the art of this site, but I came to the conclusion that in Oz we have holes in the sky. Something like potholes in the road only big. Sudden loss of 15 thousand feet and pull out 3 thousand above ground with climb power on, could only be a pothole.

  5. An offering of better images for the top of the page:
    http://www.free-online-private-pilot-ground-school.com/images/microburst.gif
    which is about 40% down on
    http://www.free-online-private-pilot-ground-school.com/Aviation-Weather-Principles.html
    which looks like a rather informative page in it’s own right.
    The image shows a plane heading in to a microburst and cutting throttle to compensate for the extra lift, and then entering the tailwind and losing the lift it needs for a safe landing.
    Another good one is http://www-frd.fsl.noaa.gov/~caracena/micro/DFWxsec.gif
    from http://www-frd.fsl.noaa.gov/~caracena/micro/MBVoring.htm
    That image shows the derived cross section of the microburst that brought down Delta 191.

  6. It wasn’t that long ago that scientists did not believe in them. Fujita finally produced evidence by flying over areas of wind damage and photographing the pattern created by the microburst.

  7. We’ve had those in Wallowa County. The darned things can flatten an old barn if it happens to be underneath.
    Because of the isolation, we get little to no warning about these fast moving cells, especially if they pop over the Wallowa Mountains south of the valley. We had a major thunderstorm yesterday that did just that. It hit our blind side and we didn’t see it coming. The electricity blew out as soon as the storm hit, leaving us without power for hours, even for most of our phones. These days, people have multiple unit or specialty phones that must be plugged into an electrical circuit in order for them to work. I was reminded that every home needs to have one phone that does not require electricity to work. With the radio signal and internet off as well, we were at the mercy of a system that was big enough to cover nearly the entire populated part of the county almost at the same time. It moved incredibly fast and its path was not very predictable. Dangerous times.

  8. What advantage does a StormPredator offer over already available radar imaging we can get at almost every weather page in the internet? Just wondering.
    REPLY: The ability to run a tracker analyser which gives cell direction and ETA. Alerts to cell/pager/email. The ability to export radar image to a web page automatically – Anthony

  9. I’ve driven through a couple of those here in Texas – astounding when you get to the point where the wind suddenly appears to stop and then changes directions violently!
    Rain was quite heavy – ok, my wife was begging me to get off the road at the time, but what the heck, I could almost see so I didn’t see no reason to stop.

  10. Anthony
    I almost got caught in one of these in1989 on a flight to Knoxville, to negotiate to finance to acquire part of the Beecham Massengil business and of course to see the Volunteers play Duke! One of these things must have followed use down the runway as we landed – very scary we we stuck on the plane for a least a hour at the end of the runway not being able to reach the terminal building for wind very heavy rain and hail the size of golf balls. Wouldn’t like to be involved with that again… the Vols won by the way!
    Tony

  11. And the microbursts are cooling events. The cold air is much heavier and goes down rapidly.

  12. Doppler Radar, even the more advanced versions, still cannot see over the tops of mountains into a valley. In Wallowa County we have Pendleton’s radar scanning up the Blue Moutains (which forms the West boarder) and to the South we have Boise’s radar scanning up the South side of the Wallowa Mountains. No other radar system gets any closer to the county. Consequently, we do not have complete radar images of storm cells in the valley. When you see one that seems to cover the entire populated valley, it is likely a fill-in guesstimate. This is what happened yesterday. The storm cell was tracked up the South side of the Wallowa Mountains. However, it deepened tremendously once it fell into the valley and layed us low. There was no indication early on that something this dangerous was coming our way.
    There are other areas in our still very rural US that have the same problem. It leaves us vulnerable. We are hit with storm cells without warning. Livestock, agricultural products, and humans have been destroyed due to this lack of warning. Maybe this time we got lucky. The last time this happened, cows were killed, and horses impaled themselves on fencing trying to escape the terrible demon.

  13. Monday evening we went from relatively clear and warm to a few drops of gentle rain to one of the most intense raging (brief) storms I’ve seen in years. I could barely even see my car 20 feet away from the window and the lake I live on might as well have vanished. Unfortunately I had just taken my camera out to the car, and there was no way I could get out there to get it, so no pics.
    I only had pebble sized hail, but apparently just a mile away they had some 1lb monsters go crashing down.
    Thunderstorms can be both awesome and terrifying. I got some beautiful shots on the weekend of a gigantic storm in the distance that I later found out had hurled baseball sized hail across a large area of farmland.
    This has also fascinated me since Delta 191, which I remember. It’s common knowledge amongst old-school PC people that the guy who originally designed the IBM PC was killed in that crash, too.

  14. brad says:
    July 28, 2010 at 5:27 am
    In other storm news – what oil? Did we get very lucky that the spill happened so far from shore that it broke up (mostly) before hitting land?

    I wouldn’t bet on it, escpecially after noting the look on Lisa Jackson’s face, as she ladled out her excuse for allowing millions of gallons of dispersants to be dumped.

  15. How is this year’s tornado season shaping up? I think it was predicted to be heavy, but it hasn’t been so far, IIRC.

  16. Pamela, just an FYI but they are not any better over here in western Oregon at predicting these events then in eastern Oregon. Would’nt be suprised it has more to do with the forecasters not looking for wind events then anything else since microburst/tornadoes are fairly rare for us.
    As a side note, my parents live in Albany, OR. Quite a few years ago (10 or so) they and the neighbors swear up an down that a tornado touched down. The weathermen said no, it was a microburst because we don’t get tornadoes in these parts. Since then we’ve had a couple confirmed tornadoes. Just goes to show (sorry Anthony) weathermen don’t know everything about weather.

  17. What ever happened to the vertical wind profiler the NWS was developing about the sane time as Nexrad?

  18. In the early ’80s I was ‘drafted in’ to sit in the RH seat whilst several training captains tested out some new software for our DC10 simulator. The ability to recognise the early onset of windshear was one of the most important things I think I ever learnt in a sim.
    Fortunately, I was never called upon to use my newly aquired skills.
    Modern day aircraft have loads of kit to warn you of impending doom of course:-)
    Ahh the good old days!

  19. wayne Job – I been there done that in a DC7-loaded Airtanker and dang near got
    whacked by a Downburst in New Mexico out near Holbrook it hit us as we were about to drop our load of fire Retardant. Came as close to Crashing as I ever want.
    Pamela Gray- Try Boise Radar- as they can get to the South side of the Blues and Wallowas- better than nothing -things are forecast to be interesting today….

  20. Wonderful pics and graphics here and on the source site. Takes me back to my flight weather forecasting days in the late 70s, when downbursts, as we called them, were a hot topic. The big problem was the slow response-time of big jet engines compared to the rapid changes of windspeed and direction that could be encountered.

  21. Ric Werme: July 28, 2010 at 5:36 am
    The image shows a plane heading in to a microburst and cutting throttle to compensate for the extra lift, and then entering the tailwind and losing the lift it needs for a safe landing.
    Figure 17 is a gross oversimplification, Ric. A microburst is an intense, highly-localized, highly-transient downdraft, and long before that Cessna in the illustration reached midpoint, it would have crashed. I saw the results of a microburst in the Pygmy Pines area of southern New Jersey. All the trees within a 50-meter circle had been snapped in half two feet above ground level, and the broken portions were all oriented directly outward from the center of the circle — it looked like a mini Tunguska event…

  22. You’re probably inadvertantly comparing oranges and apples: I’m not sure where the Doppler radar is for Wichita, but it is probably surprisingly distant from Wichita and the storm. Because the earth curves more than the radar beam, even if this is the bottom reflectively slice, the strong echo is probably centered quite far above the ground. If this is a composite reflectivity, a sum of all the slices pertaining to that storm, that strong return is probably quite high in altitude. Storms are not only 8 km deep or more, but they are not vertical, especially violent thunderstorms, because they thrive on wind shear through the entire troposphere. Your TDWR image, of strongest velocity, is probably quite distant from the WS Doppler radar and quite close to the storm outflow. So that peak velocity could be close to the ground.
    There is another point about downbursts: If a relatively low slice is being used, the darkest reflectivity may be close to where the strongest downdraft is; this is because the weight of hail and the rapid cooling of that area by heavy and evaporating rain is bringing the air down the fastest. When the downburt approaches the ground, it spreads out. There might be very little wind directly under the core of the downdraft, with a vaguely doughnut shaped zone of high winds pushing out in every direction. If the thunderstorm is moving, possibly as fast or faster than a car travelling on an interstate, the strongest winds would be away from the downdraft, and located beyond the downdraft in the direction toward where the storm is moving.
    Much literature by Fujita and others clearly explain common downburst dynamics.

  23. Roger Knights says:
    July 28, 2010 at 8:55 am
    “How is this year’s tornado season shaping up? I think it was predicted to be heavy, but it hasn’t been so far, IIRC.”
    Just wait till August. Things could warm up a bit on the tornado front then.

  24. I know I have shared this before, but for those of you who have not seen it (I have watched it again and again)….check out this powerful wet microburst outside of Brisbane, Australia in Nov. 2008.
    Ignore the “cyclone” title. It was not, but it sure looked like one.
    Amazing….the maximum winds here were calculated to have hit 111 MPH.

    Does anyone know of a paper or abstract analyzing this event? I would love to read it.
    Chris
    Norfolk, VA, USA

  25. In the last “cold phase” of the ’60s and ’70s there were a lot of microbursts and a lot of crashes. The PDO shifted to warm. .. Then in the ’80s the crashes faded and in the ’90s we even had a year or two with NO airline fatalities. Then the PDO shifted to cold…
    And we promptly had something like 3 airline crashes with fatalities (one or two with the loss of all on board. I think it was an Airbus near Mautius? Mauritania? with ‘weather related’ complications.).
    So any one keep records of weather related airline crashes and / or micrburst activity such that a correlation coefficient could be calculated? Yeah, lots of confounders (like technology change…), but if it’s a strong signal…
    If we’re getting a lot more and a lot more violent downdrafts of very cold air, and that’s not ‘expected’, well, it would point to a very interesting question or three about how well we understand climate dynamics…

  26. Darrin, it was a tornado. I was there, or at least about 1 mile as the crow flies from that tornado. Took out the entire inside of a warehouse and broke the windows, but left the outer walls standing. It lifted the debris and spread it around, instead of smashing it to the ground underfoot. Tornado. But relatively speaking, not a strong one and didn’t last but a few seconds on the ground.
    FYI, I was born and raised in NE Oregon, then moved to Corvallis and Albany for 30 years to attend college, get married, raise kids, and attend more college. VERY glad to be back in NE Oregon.

  27. Thanks Ric Werme for those helpful links (see top of this thread). Everyone who is just like me (not a climeatoligist/scientist) – but obsessed and passionate about this whole CO2 warming hoax – should save them on their favourites as a simple, but general weather reference.
    As you know, here in the UK, we rarely see the intense variety of weather events that you guys frequently experience in North America. As I look out of my window, the sun’s up now, it’s 7.40am, it might be overcast and it might rain again and I’ll probably say the obligatory British “Good morning, bit overcast” to the newsagent later on. But just for a change, I’d love to capture the occasional ‘twister’ or severe microburst. As you’ve all just gone to bed, when you guys wake up tomorrow, could you please send us some of your wonderful dramatic weather – then we would really have something exiting to complain about. “Morning, looks like the whole sky actually fell on Tom’s house last night”.
    Keep up the good work Anthony.

  28. Here’s the link to the NWS Full-Resolution Radar mosaic, folks.
    http://radar.weather.gov/Conus/full_loop.php
    It’s interactive. Find your local area and double-click — it’ll send you to the nearest radar site. It’s real time, but you can loop it to see trends.
    Sorry, Mizz Pamela, but it can’t reach down into the valleys — however, a violent T-storm building in your area will show up on the scope as the core updrafts carry water vapor above the condensation level.

  29. That “central Oklahoma microburst” actually happened in KANSAS. Even Toto knows Wichita ain’t in Oklahoma. The highway layout in the screen shots confirms, Wichita, KS.

Comments are closed.