STORM TRACK: March 31, 1982 (Volume 5 Issue 3)

The conventional wisdom on what to do in open country when confronted with a twister is to "move away from the tornado's path at right angles" (Tornado, NOAA, Dept. of Commerce, 1970). Unlike that other spin-off of the "old time religion" that told you to go to the southwest corner of the basement, I am not aware of anyone who has challenged this advice on "moving ... at right angles." Here is my effort to amend this potentially dangerous advice. If most tornadoes occur in the midwest and plains states, where and descriptive information on these slides, it is incumbent on us to be as accurate as possible. Perhaps NWS should develop a set of training/tornado slides of known distances to train spotters and/or develop a technique for use "in the field" to immediately approximate distance. For example, a spotter looking across a town at a tornado on the other side should be able to report whether it is 5 or 15 miles away (how much time does the town have to seek shelter?). I concede that different mesoscale parameters (humidity, pressure, etc.) may affect the cloud base in different parts of the country. Perhaps an average cloud base could be stated on a regional/climatic basis by month. Anything that would give spotters a standard to go by would aid in estimating tornadic distance.

Print #1

Print #2

Let's test your sense of distance. The following prints were copied almost border to border from the original slide. Each tornado was taken with a 50 mm lens and had a known or close-to-known distance from the photographer at the time of the picture. Examine and guess these distances, then look at the answers on the last page. You will also find there a proposed scale card for use with similar 50mm slides/prints of yours.

This was developed based on close analysis of 9 of 12 tornado slides. Four of the twelve vortices were from what appeared to be high based storms (three in the western third of Kansas), and 3 of these gave widely different data from other comparable slides. All four were excluded from development of the card scale. Also shown is the simple chart which I used to develop the card, including comparative accuracy of my distance estimates. Such a rudimentary guide could be used by a spotter with a camera or could be modified to a single marked-ruler-scale held at arm's length toward --a tornado (e.g. 6" = 1 1/2 miles, 4" = 3 miles, etc. ) or to a simple hand spread at arm's length (e.g. tip of thumb to forefinger = 1 to 2 miles, etc.). A clear plastic sheet could also be used with a pre- printed scale across the the sides and top to measure vortex width as well as distance. For example, a spotter looking north with a town to the northeast could quickly assess the immediate peril to that, town. Although such reports could not be taken as conclusive on their own, they might still provide useful information.