Here is an open thread to discuss the massive Oklahoma City tornado.
Here is an open thread to discuss the massive Oklahoma City tornado.
Good Morning, lets take a look at the phenomenon of Radar Blooms this morning for the Saturday Lecture Series:
Please Click the Below link for the entire article:
There are a lot of interesting anomalies that you may see on displays that show NEXRAD (or any kind of) weather radar data. Some are caused by software, some are caused by the radar misinterpreting what it sees. None are worth some of the conspiracy theories that non-scientists have come up with.
Last month, blog reader Mike asked what is responsible for the radar “bloom” (or “radar blobs”) that occurs nationwide, but especially in the Southeast U.S. in Spring and Fall. What he is referring to is the gradual growth of non-precipitation objects on radar after sunset (and the data fades after sunrise). During the night, this causes a large blob around each radar site. I have uploaded some examples from that night.
EXAMPLES OF RADAR BLOOM: In the Huge AccuWeather Raw U.S. Loop and the Huge NWS Raw U.S. Loop, you are seeing the raw data from each NEXRAD radar plotted on a U.S. map. But in the Small AccuWeather Processed Northeast Loop, AccuWeather’s computer algorithms and meteorologists have attempted to “clean up” the radar by taking out areas of data that they thought were invalid. This caused the “cookie cutter” hole around Indianapolis and the lack of clutter in the Southeast. The “C”-shaped object over the Great Lakes is rain from a low pressure system, though you can still see the “blooms” around and inside it. There are also a couple things of note in the Indianapolis Radar Site Raw Loop – the “spike” in the first frame is a “sunset spike” and is caused by the radar being temporarily “bllinded” by the setting sun. The blobs of blue and brown in the Northeast quadrant are areas of rain moving south from the aforementioned low pressure system.
I knew what Mike was referring to was a type of “Ground Clutter” – also known as false echoes – a wide-ranging problem with weather radars, I just didn’t know what specifically was causing it. So, I set out to do some research on Google, but I couldn’t come up with an explanation, and apparently neither could anyone else who writes blogs or web pages. In the late 1990′s, I wrote several articles on radar anomalies and Ground Clutter for AccuWeather.com properties — but I never was able to explain this one.
NOAA [JessePedia], who owns and operates the radars in the national network, has an excellent page explaining how radar beams work. It included the illustrations below about Superrefraction and Ducting (the radar beam is shown in comparison to a faded “normal” radar beam at the top of the illustrations). In both cases, the radar beam curves quicker than the curve of the Earth. I suspected this was to blame for the Radar Bloom.
In the case of “Ducting” the radar beam bends so much that it hits the earth, causing extremely dBZ returns (because the ground is much thicker than your average raindrop when the beam runs into it). dBZ, or “decibels of Z” is the way radar data (hopefully precipitation) is measured. The colors you see on radars correspond to dBZ levels, higher meaning more intense. When the radar beam hits the Earth, this phenomenon is called “high dBZ anomalous propagation” and is a real problem because, to the untrained eye, it looks just like thunderstorms.
EXAMPLES OF HIGH-DBZ AP: Notice on this example, a Northeast Still Image, how the high dBZ AP in Canada and New York looks a lot like the thunderstorms off the coast of the Carolinas. If you Download* This Northeast Loop then you can see that, while the thunderstorms move, the AP stays still. On the
Binghamton Radar Site Raw Loop, notice how the AP mimicks the mountain tops, because the beam won’t make it to the valleys once it hits the mountains. Notice also in the northwest part of the image how there are no echoes over the lake, because the surface is too flat to reflect back to the radar.
Other websites confirmed this explaination of Ducting, but while this is great, it doesn’t explain radar “bloom” which is much lower on the dBZ scale* (see below), nor does it explain why it grows and shrinks with time.
Since I couldn’t get an answer online, I wrote in to the NOAA radar experts. After a couple of returned emails due to a bad form on their site, I finally got in contact with Joe Chrisman from the ROC (Radar Operations Center) Engineering Branch, who explained:
When the sun goes down and the surface begins to cool, the change in refractive index in the lowest few (to several) hundred feet of the atmosphere tend to bend the radar beam toward the surface. This bending holds the radar beam near the surface for extended distances, where it encounters scatterers that would not normally be available above the boundary layer. These scatterers include insects, bats, aerosols, particulate matter, etc., and account for the increased radar return referred to as “radar bloom.”
To decode that answer a little, what he’s saying is that it is, in fact, superrefraction that causes radar bloom.
In the case of superrefraction, the beam bends low to the ground but, unlike Ducting, it doesn’t run into the ground (until it gets out of range anyway). With the beam so close to the ground, it keeps running into multiple insects/dust/other particulates as it moves outward from the radar. As the superrefraction becomes worse, the radar beam travels farther than it had previously, and encounters even more of these particles, causing the amount of clutter on the screen to “grow.” As the superrefraction decreases in the morning, it shrinks.
Why does refraction itself (be it Super, Sub or Ducting) occur? That’s a more complicated question and I’ll let you read the NOAA page for a lengthy explanation. Basically, where the beam travels with respect to the Earth’s curvature is determined by a complex equation of pressure, temperature and humidity that can vary greatly in small distances, and it’s possible you might have more than one type of refraction occurring at the same time.
P.S. “Trophospheric Ducting” is a similar phenomenon by which radio waves propagate thousands of miles further than they normally would due to atmospheric conditions, causing, in one documented case, an FM radio in Hawaii to pick up a radio station from Mexico (if you have an FM radio in your car and have trouble picking up FM stations in your own town then you understand why that would be quite unusual).
I drove through this on way home from work last night.
NOW I HAVE SUPER POWERS!!!!
Sometimes, you don’t need a lake to get lake-effect snow. A complex of power plants will do the job just as well.
Meteorologists at the National Weather Service’s office in Moon Township noticed something Tuesday night they apparently don’t see too often — a snow band, stretching for miles from western Beaver County across northern Allegheny County.
The band, which dropped a quick inch of snow in some places, didn’t originate at Lake Erie.
It came from the power plants at Shippingport.
OK, before you start with the jokes about nuclear winter, NWS meteorologist Lee Hendricks says there’s nothing sinister going on here. Rather, it’s just a matter of what happens when cold air meets steam.
“You had plumes of warm, moist air coming from the cooling towers of the power plants, and that was meeting the cold air we’ve had in place this week,” Hendricks said. “When the warm, moist air comes in contact with the cold air, it condenses and (Tuesday), it fell as snow.”
Actually, it fell as a lot of snow, in a very limited area. The screen cap shows the snow band stretching from a narrow ribbon at Shippingport and then spreading out as it stretched across Marshall, Pine and Richland townships. In those townships — and especially in the Wexford area, Hendricks said — the cooling tower-powered snow dumped an inch of snow or more very quickly.
“It’s the same process as lake-effect snow,” he said. “We just saw it on a very limited scale here.”
FirstEnergy, which operates both the Beaver Valley Nuclear Power Station and the coal-fired Bruce Mansfield Power Plant, pumps out a lot of warm, wet air from the cooling towers at both plants, spokeswoman Jennifer Young said. The 90-degree water from a single Beaver Valley stack evaporates at a rate of about 10,000 gallons a minute, and output from the Bruce Mansfield plant is about the same.
And when the two Beaver Valley towers and the three Bruce Mansfield towers are all running at the same time — as they were on Tuesday — that’s more then enough steam to power a mini lake-effect event.
Or, perhaps, a more apt comparison would be the snow guns that coat ski areas with man-made snow when Mother Nature isn’t feeling cooperative. Anna Weltz, spokeswoman for Seven Springs Mountain Resort, said the principle is the same.
“We pump very cold water from our storage lakes down to the guns and that water is met with compressed air,” Weltz said. “When that spray meets the cold air — the colder, the better — it turns into snow.”
Weltz said Seven Springs can make snow when the temperatures reach 28 degrees, but colder and drier is better.
“Twenty-six seems to be the magic number for light, dry snow,” she said. “Anything warmer than that can mean you get something wet and sloppy, something closer to rain.”
Hendricks, who lives in Hookstown, said that happens around Shippingport as well, especially in the spring and fall.
“Those plants can actually generate a drizzle when the conditions are right,” he said. “Shippingport has its own micro-climate, thanks to the power plants.”
I pledge to use my new powers only for good!
The 1990′s was probably the best time of my life. I made good money, travel and had fun in life. One thing I don’t miss is Bill Clinton and Al Gore, not that I liked what came after also. Unlike the 1990′s Bill Clinton and Al Gore never went away. Clinton is campaigning for Obama. Gore is like a diseases that refuses to go away. He made a movie based on the AG hysteria and made millions in speeches. He is held up by the media as some prophet who must be heeded. Both of these clowns have weighed in on Hurricane Sandy.
Bill Clinton while campaigning for Obama, blamed Global Warming for Hurricane Sandy and attacks Mitt Romney.
Bill Clinton should ask his new buddy Obama why he hasn’t stopped sea rise. Not to be undone, Al Gore joins his old boss in blaming Global Warming for Hurricane Sandy.
While it did not take long it was expected. Former vice president Al Gore put out a statement on his blog on Tuesday and blamed the intensity of Hurricane Sandy on “global warming pollution.”
The images of Sandy’s flooding brought back memories of a similar–albeit smaller scale– event in Nashville just two years ago. There, unprecedented rainfall caused widespread flooding, wreaking havoc and submerging sections of my hometown. For me, the Nashville flood was a milestone. For many, Hurricane Sandy may prove to be a similar event: a time when the climate crisis—which is often sequestered to the far reaches of our everyday awareness became a reality.
Gore concluded at the end of his blog that “dirty energy makes dirty weather.”:
Hurricane Sandy is a disturbing sign of things to come. We must heed this warning and act quickly to solve the climate crisis. Dirty energy makes dirty weather.
Bill Clinton and Al Gore should have stayed in the 90′s. These 2 clowns need to go away and just disappear.
Many on the Left are blaming global warming for Hurricane Sandy. They act as if Hurricanes have never hit the Northeast. Yes it is rare, but it has nothing to do with Global Warming. Following in the footsteps of her senile and Islamic terrorist loving father, Meghan McCain agrees with the Progressive narrative. She blames Sandy on Global Warming and chides Republicans for not agreeing with this lie.
Meghan is known more for her boobs than her brain. She’s really an idiot but then again apples don’t fall far from the tree! Expect her to run for her father’s Senate seat in 2016!
Here is the reason it is so damned hot. These are essentially jet stream maps. South of the jet stream its hot, north, not so much. This is caused by back to back la Nina years.
And here are the maps
No new cloud type has been officially classified since 1951 but Gavin Pretor-Pinney who runs the Cloud Appreciation Society believes that there is a new cloud that deserves international recognition. He calls it asperatus, which means rough in Latin. Hanmer Springs, South Island, New Zealand, 2009. [via]
If I saw a sky like this, I’d tell the missus and the kids to pack a bag and get in the car as quietly as possible. Then we’d back out slowly, idle to the freeway on-ramp, and floor it for a couple of days.
Or not. Apparently this unusual cloud formation is benign, not related to precipitation, violent weather or mass extinctions, but merely a harbinger of
The Overnight Open Thread.
The Dallas Fort Worth was struct by multiple tornadoes, hail and thunder storms this afternoon. Many of the twisters that remained on the ground for up to half an hour. There was a report that one touched down in Cleburne and then tracked north through Burleson and ended up causing considerable damage in Arlington. That would be about 35 miles. There will be widespread devastation and power outages throughout 5 or 6 counties. I have not heard of any fatalities, yet.
We have an interesting meteorology for today. What are Microbursts?
Microbursts downburst less than 2.5 miles in diameterA downburst is a strong downdraft which includes an outburst of potentially damaging winds on or near the ground. If the diameter of the downburst is less than 2.5 miles, it is called a microburst. The diagrams below depict the evolution of a microburst.
A microburst initially develops as the downdraft begins its descent from cloud base. The downdraft accelerates and within minutes, reaches the ground (contact stage). It is during the contact stage that the highest winds are observed. During the outburst stage (above), the wind “curls” as the cold air of the microburst moves away from the point of impact with the ground. During the cushion stage, winds about the curl continue to accelerate, posing a great threat to nearby aircraft. These are very weak, high based showers without thunder, but with microbursts. Studies have shown that they predominantly occur in the High Plains and western U.S.: particularly in unstable, very dry low level environments with surface temperature-dew point spreads of 30 to 50 degrees and an area of mid-level moisture as a source for the weak showers.
The cloud on the left is developing, whereas the fuzzy anvil on the right has matured and is producing a trail of virga. Microbursts would be most likely to occur beneath the virga, when the downdraft reaches the ground. Several of these virga showers did produce microbursts in the Lubbock, Texas area.
Photograph by: Moller
The same day, near the Lubbock Airport, we see several of the small microbursts which emanated from the virga patch in the upper right corner of the photograph. Wind shifts of 35 to 40 MPH were noted shortly after this time, with a rapid onset and cessation of the wind gusts.
Photograph by: Moller
Microburst in aviation:
This is what happened to Delta 191 in Dallas:
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