I believe all of this is germaine, including the "Weller Method..." It is excerpted from
www.usatoday.com/weather/wtwistqa.htm .
Q: I've heard about a guy who was able to predict a tornado by using a bunch of garden hoses all connected at a central spot. Evidently, he could hear sound changes, much as varying levels of water in a thin-necked bottle will produce different sounds if you blow across the top of it. Have you heard anything about this? If so, Where can I find more information?
Answered by: Alfred Bedard, Jr., aerospace engineer, NOAA Environmental Teachnology Laboratory, Boulder, Colo.
A: The system detects very low frequency sound waves well below the range of human hearing (near 1 Hertz) and uses an array of 4 sensors located on an area about the size of a football field.
Because the sounds are weak we need to remove wind noise and hence the use of lengths of porous irrigation garden hose at each of the 4 sensors. Sound appears over the area covered by the "octopus" of hose essentially simultaneously while wind eddies do not and are averaged out. We have detected sounds using this system at ranges greater than 1,000 miles. Low frequency sounds travel in a detectable form for long distances. (more below)
Q: About a month ago on ABC news Al Bedard from NOAA demonstrated a devise for detecting tornadoes. The devise consisted of an array of common garden hoses connected to a central sensor. It was able to give 30 minutes warning of a approaching tornado. I am trying to find out what he is using for a sensor.
Answered by: Alfred Bedard, Jr., aerospace engineer, NOAA Environmental Technology Laboratory, Boulder, Colo.
A: Our goal is to detect sounds at low frequencies near 1 Hertz in the presence of wind noise. The pressure amplitudes are quite small (about 1 microbar or the equivalent in pressure altitude of about 1 centimeter).
Conventional microphones do not respond at such low frequencies and conventional microbarographs do not have enough sensitivity.
We use a differential pressure sensor with a high pass pneumatic filter to get the sensitivity we need, but the filter insures that we do not let lower frequency, large amplitude pressure changes exceed the dynamic range of the sensor and yet respond to the frequencies we are interested in.
Q: When I was a young person, I recall a rumor that the close proximity of a tornado could be "seen" by tuning your television (black and white in those days) to channel 13, darkening the screen, then turning to channel 2 to see if the screen was dark or bright (or something like this). Is there any method to use a television for such a purpose?
Answered by: John Snow, dean of the College of Geosciences at the University of Oklahoma, Norman, Okla.
A: You are referring to what was (or is called) the "Weller Method" of tornado detection (named after its proponent). This was a popular technique a decade or so ago, when people still had individual TV antenna's. The idea was to use the TV set as a lightning detector (a detector of the radio waves emitted by a lightning flash), and under some conditions it would work. The idea was that tornadic thunderstorms were very active lightning producers. However, the method had (has) several shortcomings. Not all tornadic storms produce large amounts of lightning. TV's are not all equally sensitive, and in fact some are made to filter out lightning signals. If you are connected to cable, it won't work. The bottom line is that the method provide completely unreliable in actual field tests. Did it work sometimes? Yes, but most of the time it did not -- it either indicated a tornadic storm when none occurred, or it did not indicate the presence of such a storm when in fact one was nearby. In meteorological terms, its success score was too low and its false alarm rate too high to be of use.
