MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... MESONET TICKER ... August 8, 2005 August 8, 2005 August 8, 2005 August 8, 2005
We're at a Loss to Explain This One
OCS's software engineers do more than engineer great software. They are also weather fans like the rest of us (most of them are, in fact, meteorologists). This morning, they noticed some bizarre goings-on using OCS's WeatherScope software.
Here are some WeatherScope screen captures from the, uh, event?
At 5:00 am, The Tulsa and Ft. Smith radars showed junky-looking clear-air returns near the radar sites (certainly not uncommon for a humid August morning):
http://ticker.mesonet.org/archive/20050808/0500.png
Notice, however, the subtle enhanced returns in eastern Oklahoma and western Arkansas. These are actually hilltops of the east-west mountain ranges bracketing the Arkansas River valley. These features typically don't show up so far from the radar site, which is important to later discussion.
By 5:47 am, the mountains hadn't moved (thankfully!), and the clear-air returns had started to clear up:
http://ticker.mesonet.org/archive/20050808/0547.png
By 5:56 am, both the Tulsa and Ft. Smith radars switched to clear-air mode. In clear-air mode, the radar is given much more time to rotate. Consequently, it is much more sensitive. To put it clumsily, the radar can "pick up subtle stuff" easier in clear air mode (this makes it valuable in a pre-storm environment, when subtle boundaries may be focal points for convection).
http://ticker.mesonet.org/archive/20050808/0556.png
The very "hot" whites and purples are the aforementioned hilltops. There is also a very curious feature over downtown Tulsa.
By 6:06 am, the downtown Tulsa feature was larger and showed stronger reflectivity:
http://ticker.mesonet.org/archive/20050808/0606.png
At 6:15, some bizarre circular features began to pop up all over northeastern Oklahoma and western Arkansas:
http://ticker.mesonet.org/archive/20050808/0615.png
Notice the circle over southeast Ottawa County, another in far northwestern Arkansas (near Bentonville), one just northwest of Hot Springs. and one directly over the Ft. Smith radar site (look closely!).
By 6:25 am, these features were obvious (the Hot Springs feature showed up particularly strongly):
http://ticker.mesonet.org/archive/20050808/0625.png
By 6:35 am, they were huge (and new ones started over Bartlesville and a few other places):
http://ticker.mesonet.org/archive/20050808/0635.png
For the 6:45 and 6:55 am snapshots, we turned off the Tulsa radar to reduce clutter:
http://ticker.mesonet.org/archive/20050808/0645.png http://ticker.mesonet.org/archive/20050808/0655.png
However, the four main features described earlier were quite visible on the Ft. Smith image.
By 7:14 am, the radars had switched back to precip mode, and the features dissipated (partly because of the switch, but mostly because they actually dissipated):
http://ticker.mesonet.org/archive/20050808/0714.png
So, here's the question: what were they?
And, here's the answer: we have no idea.
Some contributing factors that we ran through in our discussions:
1. The features showed up on at least two radars in the region. This eliminates the "one radar was acting screwy" explanation. These were actual atmospheric phenomona.
2. The radar beams were being refracted (bent back toward earth by the atmosphere) more strongly than usual. This is evidenced by the appearance of the hilltops of the Sans Bois and Lower Boston Mountains. So, these were near-surface features.
3. We toyed around with the idea of waves from collapsing convective clouds (aborted showers). However, the features were so synchronous that we ruled it out. Besides, no reflectivities were visible in preceding scans.
4. We toyed around with the idea of a sunrise burst of birds or bugs from each of the locales, but the features were so large and so symmetric that we leaned away from this. 5. A few of us nervously offered up extra-terrestrial explanations, but then we pretended we were just joking when folks looked at us strangely.
So, what's your take?
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