FM Long Distance Transmissions during Thunderstorms

[Cairan]

The weirdest thing is happening today in my region. Me and my wife have been picking up distant FM stations, with varying quality but sometimes with enough signal quality to listen to in FM stereo...

We are located approximately at 48'30 N 67'30 W in Eastern Quebec, and so far, we've even been able to listen to an FM radio station in Champaign-Urbana, IL, as well as one in northern South Carolina.

Meanwhile, AM radio propagation is typical of daytime hours, that is, we can't pick up anything distant such as radio stations from New York, Montreal or Boston.

Here's the GOES satellite image at the time this phenomena is happening.

My theory is that the weather system is channeling the radio waves from the FM stations akin to a fiber optic is conducting light... that is, the air masses have sufficiently diverging electrical properties that the radio waves got refracted back and forth along the fronts...

 

[Zatnikitelman]

As a ham radio operator, I can guess that one (or more) of several things are happening. There could be tropospheric ducting where a temperature inversion acts like a duct bouncing the signal thousands of miles. This typically only happens between California and Hawaii's Volcano tops, but it could happen elsewhere. Sporadic E is a possibility where an area of the Ionosphere is super-ionized so that it bounces much higher frequency signals than it usually does. Other than that I'm not sure of special anomalies that could cause it. Thunderstorms don't seem that likely to me as except for brief moments when the lightning is flashing they really aren't ionized.

 

[Tommy]

Sounds like signal skipping. While this is far more common in the AM frequency range it can occur in the FM range as well. As I understand, the radio waves are reflected back and forth between the earth and the highly charged atmosphere (ionoshere?). This is quite common in some of the HAM radio frequencies, often enabling contacts from the opposite side of the planet. Perhaps there's a HAM enthusiast here who can give a more accurate and thorough explanation.

 

[Cairan]

As a ham radio operator, I can guess that one (or more) of several things are happening. There could be tropospheric ducting where a temperature inversion acts like a duct bouncing the signal thousands of miles.

Looks like it was ducting from an inversion. I drove from my home up to Quebec city tonight along the St Lawrence river and the cold water of this time of year was making the air several degrees below the air temperature aloft. I wonder if the same phenomena occurs every year, Ill have to check that out!!!