I’ve had this post brewing awhile, but I was inspired today by a friend’s photos on Facebook. I want to show you a couple cool radar images from the last couple weeks, from the Weather Underground weather website. Radar is obviously primarily used to track precipitation and thunderstorms. But, it can also be used to find hail cores in thunderstorms, areas of rotation in thunderstorms that may be producing tornadoes, rain/snow lines, areas of gusty winds, birds, and more!
Well, a couple recent examples of cool stuff you can see on radar.
If you click the map to the left, it will open up a radar loop from the San Francisco Bay Area that I caught a couple weeks ago. It was generally a quiet day, with just some showers offshore. But, if you look at the image, you’ll see a couple stationary areas, which, if you didn’t know better, you might assume are thunderstorms. Those areas are west of Modesto and south of Sacramento. Well, we know that it was a quiet morning, so it wasn’t a thunderstorm. So what’s going on?
Well, if you know about that area, there’s a gigantic wind farm in Altamont Pass. It’s the largest concentration of wind turbines in the world, with a capacity of 576 MW…through 4,900 turbines! So it’s huge. The other large wind farm there is north of that little lake: Shiloh Wind Power Plant. Smaller, with 300 MW of capacity and about 175 turbines. So what happens with radar in simple terms: The radar emits an electromagnetic beam, which will reflect off of objects and bounce bank to the radar, producing a pixel at the location where the beam bounced from. The radar almost always aims upward (so it doesn’t bounce off of ground level objects and can “look” into the clouds, where the rain/snow falls), so if there are any objects in the line of sight, they will reflect back a pixel. Given the location of the radar, just south of Sacramento, and assuming the line of sight is higher up…but not too terribly high (the radar beam was probably aimed low to look for patchy drizzle this morning), it’s obvious that the radar is picking up the turbines at those wind farms. The radar beam is hitting the rotating turbine, and firing back to the computer that “something” is there. That something is the wind turbine.
A lot of good, easy to understand information is here from the NWS Milwaukee, in a case study on their Butler Ridge wind farm.
More technical details are here…a website from the NWS explaining the issues with wind turbines and radar.
Example II
This afternoon, there’s a fairly large brush fire burning near Edison, NJ. Well, in addition to picking up a lot of the other cool things I talked about above, radar can also detect smoke from large fires. If you look the image at right, you’ll see a great example of this happening…as the fire grows and the smoke plume rises, you can see it on radar. Essentially, the same process is at work. The radar beam is looking up into the clouds and instead of seeing a wind turbine, now it’s seeing (the many) particles contained within the smoke. We see this a lot.
Occasionally these fire plumes can put off enough heat to help clouds actually form above the fire, often in the smoke plume, called pyrocumulus clouds. These essentially are formed by the same process that forms thunderstorms, and like those, they can occasionally have lightning too. I do have a few photos from last year’s massive Station Fire near LA on Flickr here. More on that another time though.
Here’s a link with more ways radar can be interfered with…from the NWS Milwaukee, which seems to be a treasure trove of cool links.
So there’s some of the “fun” we can have with radar.
Hitting the Links
Here are some links I’ve encountered the last few days.
Ahead of the impending disaster likely from Tomas, Haiti is trying to get refugees from the earthquake as far out of harm’s way as is humanly possible. Tomas does not appear to be as big of a threat in terms of wind potential. However, it is equally as disheartening to watch as I warned you over the weekend from a rain potential. Tomas nearly fell apart this morning, as it was downgraded to a tropical depression. It has since restrengthened into a 45 mph tropical storm. The good news is that, as previously mentioned, everything got to this storm and it will likely NOT reintensify into a major storm. The bad news is that it’s still going for Haiti, and they should expect 5-10″ of rain, with upwards of 15″ possible in favorable upslope areas. Just a terrible situation. Stay tuned on this.
A trio of links for folks in the Mid Atlantic…
Part II of Wes Junker’s detailed analysis of last winter’s record snow in Baltimore/DC and surrounding areas from the Capital Weather Gang.
An article that claims last winter could have been far colder, possibly prevented by global warming!
Visualizing just how much snow fell last winter in the Mid Atlantic.
And lastly, Minnesota set a record for most tornadoes in a year in 2010.
Go Rutgers tonight…beat USF!
State of Occlusion 