It sounds more like cosmology than weather. Jr & I actually left the house, fearing one of the nearby tall pines would squash us. It was craazee. We went over to PDK airport to watch them try to land their planes. Even the bizjets were using using one of the shorter runways that was better aligned to the howling SE wind.
What seemed really weird was the huge, long, low cloud that was downwind– but it steadily moved upwind toward us. It extended as far as you could see and was perpendicular to the wind direction. When it got over the airport, the wind went from 30-45 to dead calm in about 1 minute.
From what I read, this isn't so much like waves that glider pilots know all about, but it's associated with the passing front and is sort of like a small scale gradient wind on steroids... I really don't completely understand it but NWS had it nailed, down to the time it would start. We were pretty much unscathed. Hope ya'll were the same.
I'm finally back online. Our neighbor's house was slammed by a 5 ft diameter oak. It was big enough to snap a 4 ft pine in half on the way down. Fortunately, the neighbor was in another part of the house and escaped any harm. Their car is totalled and house will need a major rebuild. While it was blowing, you could hear trees going down all around the neighborhood. The gust that took down the oak was probably 45-50 mph. btw, the oak didn't uproot like a lot of trees but actually broke. Part of it is still sticking up like an enormous splinter.
The calm afterward was about as weird as the wind. Like cv said, dropped quickly to nothing.
That oak tree had to have other issues going on. Seem improbable to the point of impossibility that in a heavily wooded neighborhood like yours, webguy, that a 50mph gust could sustain the uumph to break in half a 5' diameter healthy, growing oak tree. I mean, we measure over 50 and even 60 on occasion at the lake and the pine trees and other hard woods don't snap. But, it can surely kill a person flying a kite at the time. Have y'all heard about the kiter in Hatteras who was killed this past Saturday?
Chuck Hardin
Whitecap Windsurfing, Inc.
c:706-833-WIND (9463)
http://forums.ikitesurf.com/viewtopic.php?t=12924
Bill Herderich
Hey Chuck -- I happened to be in Atlanta on Monday, and they got a windstorm like I have NEVER seen before (at least inland). I forgot what the guy on the Weather Channel called it, but is was a rare phenomena where a curved warm front was being pushed by a cold front, and Altanta was in just the right spot to get hammered. The winds were violent and lasted about 45 minutes. My parents place (a heavily wooded 8 acre lot) saw several trees snap if half.
Well DUH. When you put it this way it seems so obvious:
"This small scale temperature/pressure/wind oscillation is called a wake depression or a wake low gravity wave, and was first researched in the 1970s and 80s by Dr. Ted Fujita of the University of Chicago.The thunderstorms and widespread rain that came through Monday morning was an MCC/QLCS mesoscale convective complex quasi-linear convective system. Stumpf el. al. (1991) concluded that the trailing stratiform rain shield of mesoscale convective systems can be dynamically significant by generating rapidly descending inflow jets at their back edges producing pronounced lower-tropospheric warming, intense surface pressure gradients and strong low-level winds. These MCC/MCS are like an inland hurricane without an eye and less round in shape. They are often the size of Missouri. This represents a huge amount of energy in the atmosphere and is enough to disturb even the large-scale atmosphere and jet stream. They typically develop a mesoscale rise-fall pressure couplet or mesohigh/mesolow coupling resulting in a mass momentum energy transfer flux equilibrium adjustment, which we simply notice as high winds. This is why the NWS had a wind advisory in effect for the entire metro Atlanta area starting at 5 am Monday morning and we warned of potential problems with trees and power lines. But it was worse than expected. I would speculate this is because of the drought followed by all the rain making trees weaker and root zones soggy, and the fact that the strong winds came from the Southeast, an unusual direction for strong winds in this area, and thus one to which the trees are not acclimated. Gravity waves do not usually cause winds this high 40-60 mph. They can also cause sudden heat waves, initiate tornadoes, cause flight level air turbulence and various cloud formations. Many gravity waves are benign and most go bye unnoticed."
(Kirk Mellish weather blog)
btw: If you ever get a complex mesoscale quasi-linear convective system, just slob a little salt water on your inflow jets– clears it right up.
you're not making this up, are you?
Chuck Hardin
Whitecap Windsurfing, Inc.
c:706-833-WIND (9463)
I couldn't make up that stuff! He was so showing off. I do like my new favorite word for "wind":
Energy-transfer-flux-equilibrium-adjustment
As in, "I really need an energy-transfer-flux-equilibrium-adjustment fix".
Very interesting about Wake Depression - cause of high winds in ATL. Thanks to Chris V. for posting this.
The death of the kiter in Avon is disturbing. (See the the above link posted by Windlord.) I'm especially concerned because my son plans to take kiting lessons in Guam so he can go out in low winds. Even the kiting instructor recently suffered a concussion and all the kiters seem to have had injuries that they shrug off.
Barrett