Violent Weather / DX

[Steve Green NEPA]

While certainly not the most prudently-timed muse of the
morning, considering that huge OKC tornado, I inquire
completely from a clinical/physics perspective.

How does weather such as tornados and hurricanes affect
regional DXing throughout, say, a 300-mile radius at the center?

Would it affect FM far more than AM ?
If weather like that alters things at all?

I know fog usually = tropo. But that's about it. (I barely graduated
with a 66 in Physics II on the last regents score I checked :- )

Another reason I ask is the gut feeling that this country is going
to see a lot more of these warped meterological instances this
summer -- uncharacteristic ones even for people used to having
'seen it all'.

 

[rbrucecarter5]

While certainly not the most prudently-timed muse of the
morning, considering that huge OKC tornado, I inquire
completely from a clinical/physics perspective.

How does weather such as tornados and hurricanes affect
regional DXing throughout, say, a 300-mile radius at the center?

Would it affect FM far more than AM ?
If weather like that alters things at all?

I know fog usually = tropo. But that's about it. (I barely graduated
with a 66 in Physics II on the last regents score I checked :- )

Another reason I ask is the gut feeling that this country is going
to see a lot more of these warped meterological instances this
summer -- uncharacteristic ones even for people used to having
'seen it all'.

I would put this in the same category as my Columbia breakup scatter DX ten years ago. Not the primary concern. With that said ---

Dry lines that form these storms can make for spectacular DX. I remember following a dry line several years ago - parking in a gas station in little towns west of Lubbock on highway 114. Absolutely incredible skip from the Los Angeles area. It lasted for half an hour, then the dry line started moving again. I drove ten miles to the next gas station under the dry line as it approached, and the DX resumed as strong as before. I did that all afternoon until it finally started moving more rapidly, and I was needing to get back to Lubbock before getting any farther west. I was able to do this on several occasions.

While not the same as tornado DX, I imagine the debris vortex inside the tornado would have a sizable metal content, and DX would be similar to meteor scatter. It would probably be a very localized phenomenon - because the tornados don't go up that far to the wall cloud that spawned them. I would certainly not expect a 300 mile radius. More like a few miles under the reflective path of the debris. But if one of those tornados is on the ground, you probably need to be in a shelter and not fooling with DX.

I can't think of any physical reason why a supercell itself would lend reflection to radio signals. But the outflow boundary associated with one might create a reflective layer. Thermal inversions after the ocean front thunderstorm lines in Florida open up the whole FM band to incredible late night DX until the atmosphere stabilizes in the wee hours of the morning. The same thing happens, but less often, along the Gulf coast when a seabreeze front sets up.

 

[Geographer]

As far as AM DXing is concerned near a tornado, I suspect that any changes for the good would be muted by the continuous lightning in the vicinity of a storm system that produces a tornado. I recall being in a severe thunderstorm near the Cincinnati area, and the audio of WLW was nearly obliterated within 10 miles of their tower from the continuous static. I remember sitting in my car within about 500' of their tower and watching it getting hit by lightning. Ironically, one direct hit caused only a small splash in the audio. I guess the signal was almost as strong as the field generated by the lightning. Occasionally, the station would go silent just before a strike, but I am not sure why. On one occasion, a bolt struck a guy wire about 50' from my car. It was like a stick of dynamite and scared the daylights out of me. Next time I will take a camcorder and post the video.

 

[Cincinnati Kid]

I recall being in a severe thunderstorm near the Cincinnati area, and the audio of WLW was nearly obliterated within 10 miles of their tower from the continuous static. I remember sitting in my car within about 500' of their tower and watching it getting hit by lightning. Ironically, one direct hit caused only a small splash in the audio. I guess the signal was almost as strong as the field generated by the lightning. Occasionally, the station would go silent just before a strike, but I am not sure why.

According to the late Jack Gray, a former WLW engineer, a development of Crosley Broadcasting in its early years was a device which functioned much like a "seeing eye". It sensed the lightning charge just as it was about to strike the tower and took the station off the air before it hit.

 

[1L6E6VHF]

It's by no means unique to WLW. I'm a regular listener to WWJ, which has six relatively tall towers. I know their is a thunderstorm near Newport whenever WWJ keeps popping off the air briefly, It sounds like a pattern change, and I assume works like one. Too strong a static charge on a tower, and a voltage-activated system cuts off the transmitter, disconnects the transmitter from the array, grounds the array (immediately causing the lightning to strike it and get shorted out), then breaks the ground connection to the array, reconnects the transmitter, and turns the transmitter back on - all in less than a second.

 

[tomservo]

The debris ball ahead of a tornado can extend to several miles away from the vortex, so some near field reflection could certainly be possible. After all, the debris is showing up in reflectivity scans of weather radar and is one of the best indicators meteorologists can use to confirm a tornado touch down without eyewitness accounts.

But as has been said… If you're that close, checking the dial is not a high priority thing.

As for hurry-canes, I've never had the displeasure of living through one (but, at 14 miles from the Gulf of Mexico, it's an inevitability.) I've dealt with the aftermath as they track inland and don't recall any unusual DX when Ivan and Charlie (?) came through the Birmingham area.

I suppose a consequence of the damage was enhanced DX opportunities here, as Ivan felled a tower or two here and a majority of our 100 kW FMs were off the air for some time. On an unrelated note, I'd hate to be anywhere near a 2000' tower when it comes down in a windstorm!

 

[nd2023]

I've noticed that if there's strong tropo in the morning and a line of severe thunderstorms approaching from the west, the storms will usually die down, and sometimes not even produce rain by the coast, and the tropo would continue.