Weather question

[jagr707]

Something strange happend during the thunderstorms two days ago. I was scanning the Detroit simulcast in my room where I have never had my s-meter go over 3 bars (with the stock duck) then when the storms went through I suddenly had 5 bars. I went from hearing some conversations to what seemed like ALL the users in the city with full clarity. This persisted for about 3 hours after the storms and went back to normal. How the heck did this happen?


J

[wesm1957]

Lightning does strange things to how radio waves travel

[Thunderbolt]

I noticed the same reception characteristics as you did, and I have to believe this was an acute case of "Tropo Ducting" as a result of the thunderstorms. In the past this has happened quite often, but not since the installation of the new Detroit TRS. Moreover, when there is a squall line of storms, this can also affect propagation along the entire front from end of the state to the other, on the VHF and UHF bands.

I can remember back on July 16, 1980, when a line of severe storms went through the town I was living in, and I was able to monitor NOAA Weather Radio Stations and police departments on 155.370 MHz into northern Tennessee. However, two hours later the conditions finally faded away. Nonetheless, I was unable to receive the local weather warnings from the Detroit NWS office as the line approached, since the NWR transmitter in Columbus, Ohio was completely covering up the Detroit station. Thankfully, the local police and fire departments were good about broadcasting warnings on their frequencies, or else I would have been caught off guard.

73’s


Ron

[MacombMonitor]

Lightning ionizes the air, and this could have an affect on radio signals.

[RevGary]

Originally Posted by MacombMonitor

Lightning ionizes the air, and this could have an affect on radio signals.

In addition, the cooler slightly less humid air and wind shift just behind a storm front, increases atmospheric RF conductivity. It is associated with the proverbial 'dryline' portion of the storm* - the fairly narrow band of warm, humid air from the south that overruns the cool dry air mass from the northwest. It is similar to lakeshore humidity ducting, but doesn't last as long.

[* Info recapped from a NWS Meteorologist TV interview about the weather front from southern Wisconsin.]

Two Wednesdays ago, I was monitoring 155.340 - hospital network - from my Wisconsin Rectory Office just before and just after a front moved through, while in the "dryline". I was able to hear a hospital base station in Kankakee, Illinois - 296 miles away using a 3db gain omni.

[Hoofy]

We refer to it around here as thermal ducting. I see a lot of it up here when a warm front rolls over Lake Superior or one of the Great Lakes. The warm air tends to act like a wave guide. If you watch the weather fronts moving across the country you can sometimes see when this can happen. I worked a guy on 2 meters in Oklahoma City one nite on 25 watts from here in the U.P. It's more prevalent in the spring and fall.

Have fun.

[rdale]

"It is associated with the proverbial 'dryline' portion of the storm"

That would be a cold front or outflow boundary - not a dryline. The dryline is only found in our area once every 5 years or so, that's usually in the southern Plains and has nothing to do with cold temperatures or inversions.

[jagr707]

Thanks for all the info! I kinda wish it was like that all the time. My roomate actually had a similar thing happen at the same time. He started picking up channel 54 from somewhere in Ontario. It was in French but interesting none the less..

J