Amateur radio operators are very familiar with atmospheric ducting or “skip” as we call it, which (with the help of the ionosphere when the sun is cooperative) enables some very long distance radio communications well beyond line of sight. The same sometimes holds true for loud audio, such as thunder or sonic booms. See my descriptive graphic below the “continue reading” line.
TheTempestSpark writes in Tips and Notes:
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Is this “ducting”?? the Tallahassee National Weather Service office addressed it in a special statement.
“We had a lot of calls early Wednesday evening, primarily from the area from Woodville to Crawfordville, about rumbling sounds that sounded like a freight train, with residents fearing it was a tornado. But, it was NOT. The leading edge of thunderstorms was well to the south by that time, and while there were still rumbles of thunder, the severe weather was over.
It was certainly unusual, and for those residents – a bit scary, but it was not a funnel cloud or tornado. It was likely a phenomena called “ducting”, and the Tallahassee National Weather Service office addressed it in the special statement below. (Thanks Tallahassee NWS!)
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WWUS82 KTAE 100018
SPSTAE
SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TALLAHASSEE FL
718 PM EST WED MAR 9 2011
FLZ011-013>018-026-027-114-115-118-127-GAZ155>158-100230-
JACKSON-CALHOUN-INLAND GULF-INLAND FRANKLIN-GADSDEN-LEON- INLAND JEFFERSON-LIBERTY-INLAND WAKULLA-COASTAL GULF-COASTAL FRANKLIN-COASTAL JEFFERSON-COASTAL WAKULLA-SEMINOLE-DECATUR-GRADY-THOMAS
718 PM EST WED MAR 9 2011 /618 PM CST WED MAR 9 2011/
…STRANGE SOUNDS BEING REPORTED ACROSS THE FLORIDA BIG BEND…
THERE HAVE BEEN SEVERAL REPORTS OF VERY STRANGE SOUNDS FROM THE WOODVILLE AREA SINCE ABOUT 645 PM EST. THE NATIONAL WEATHER SERVICE BELIEVES THIS PHENOMENON IS BEING CAUSED BY THUNDER FROM DISTANT LIGHTNING STROKES… BOUNCING OFF A VERY STABLE LAYER ABOVE THE GROUND. THIS IS CALLED DUCTING…AND CAN ALLOW SOUND TO TRAVEL UNUSUALLY LONG DISTANCES. THIS SOUND HAS BEEN MISTAKENLY ATTRIBUTED TO POSSIBLE TORNADOES…BUT WE AT THE NATIONAL WEATHER SERVICE WANT TO BE VERY CLEAR THAT THERE ARE NO TORNADOES … AND NONE ARE EXPECTED.“
SOURCE: http://www.wctv.tv/home/headlines/Tornado-like_Sounds_Worried_A_Few_Residents_Wednesday_Evening_117711483.html?storySection=story
I’d like to know Before someone attributes this phenomena to man made climate change.
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Here’s the basic idea:
When I was at NAS Fallon NV in the mid `80’s we’d have to check the upper air sounding for conditions which would cause “audio ducting” as you called it. If the conditions were ‘right’ some of the bombing ranges around the area were closed because the sound of the bombs would be refracted right at the town of Fallon, which wasn’t appreciated by the residents.
“Jeff Carlson says:
April 18, 2011 at 8:29 am
Same thing occurs in the ocean with sonar and sounds waves … it allows for some long range tracking but also short range dead zones …”
When I started doing acoustic predictions in the `80 while on the USS Midway I was shocked to discover how limited the ranges were most of the time. Sure you could get a nice duct occasionally and catch a sub out at 60nm but most of the time a sub could be in periscope (and torpedo) range but sonar would not pick it up. We spotted a periscope once between us and another ship (about 200yards) but the sub wasn’t on sonar.
A possible source for this noise could engine testing at Eglin AFB, home of the 96th Air Base Wing. This air base is located 150 miles upwind from Talahassee. I expect that a lot of engine testing occurs there. Smooth water on Choctawhatchee Bay could also act as a proximal reflector for eastbound sound.
This differential refractive index thing is what allows light to be transmitted through fiber optic cables. Microwatt light pulses can be reliably received over 2400 miles from the source using this technique.
I get this all the time. The closest train track is 20 miles away on the other side of the river but every once in a while, I hear a train horn and engine noise that sounds like it is just out in the front pasture.
I live near the approach pattern of a naval air station. We get a similar (although shorter) type of phenomenon almost every time it is cloudy. On a clear day, the noise from a passing F-18 might only be heard for 5 seconds, about the same time it would be easily visible as it passes over. However on very cloudy days, the volume of the noise is greatly amplified and it can last for up to 2 or 3 minutes.
@BrianP
Are you suggesting this is a once in at least 26 year event? I’m not saying that’s impossible but I would think it highly improbable that the AFB could cause that and not have done it in the 26 years I’ve been living here. It doesn’t really explain that whole flash of light and suddenly stop thing either. I realize anecdotal evidence is not exactly proof of anything, but I don’t believe this lines up with an engine test at all.
Do we have any idea what the probability is for sound ducting to occur between here and the AFB while they were testing an engine at night just after a thunderstorm?
http://www.miamiherald.com/2011/04/19/2176185/military-style-helicopters-over.html
listen closely.
apparently homeland security is conducting unreported exercises around florida.