The Birmingham age-herald., 1917-09-30
INTERESTING DATA
 ABOUT TORNADOES Disturbances Described and People Intructed How to
 Forecast Them

present season is particularly favor able to the development of tornadoes, according to the weather experts of the department of agriculture, which has issued a bulletin giving warnings and descriptions of storm conditions.
 It says that tornadoes are usually preceded by high temperature and hu- midty-a weather condition generally said to be "sultry," Sticky" or "op- pressive." Rain may come before, with or after a tornado. or, very rarely there may be no rain at all. The ba- rometer does not foretell a tornado, though 1t indicates low pressures and tornadoes always occur in a How" area
 The season in which tornadoes may be expected varies according to the region They may vist the gulf states in winter and as the season advances the region of greatest frequency is in the plains states and the Mississippi valley, from April to September, in- elusive. Tn this region May Is the worst month. with April next. East of the Appalachian mountains however, tornadoes rarely occur until after July. Generally they come between 30 and p. n1.. but they may even come at night.
 Persons may somewhat avoid tor nado danger by watching the local signs and reading the weather maps, which at least show the conditions which favor tornado formation. The local signs are heavy. dark clouds
 first in the southwest. almost imme- diately followed by clouds in the northwest and north. A funnel-shaped cloud is sure sign. though there may be tornado when such a cloud is not readily seen. If funnel cloud cannot be seen the whirlling motion of the air may be known by a peculiar roar ipg noise. somewhat like the rumble of distant thunder or the approach of heavy train of cars
 If one can see the cloud and get an idea of the direction in which it Is moving, the zone of safety is at right angles to the direction of motion. The southern margin is usually more dan gerous than the northern and this should be remembered Ia seeking a place of safety. The width of the path of greatest destruction is ordinarily not more than few hundred yards, though this destructive diameter may be from some rods wide to half HlIic, CT SOIHetlmeS WlQef.
 In some of the plain states there are so-called "cyclone" cellars. and where these are not available the southwest corner of the cellar of d frame building is the next best place Brick buildings are not so safe but the cellar Is probably the safest placs in them.
 Weather men define a tornado as a violent windstorm with rain or hail. rarxt> masses whilr with great velocity around central core while the whole storm travels across the country in a narrow path at high speed
 cyclone. in the definition of the weather bureau. Is not necessarily a windstorm of great velocity. but rather a widespread storm that moves with no great speed. Its width may cover several states. This cyclone, or area or low pressure-indicated as low on the weather map-gives conditions essential to tornadoes. Many cyclones never develop tornado, but a torna- do never develops without the cyclone and almost invariably the tornadoes occur in the southeast quarter of the low area. About 120 cyclones pass across the United States each year, moving in general way from west to east They are of great benefit be- cause they induce a movement of sur face air from the south and south east, and the rainfall that makes the great interior valleys rich agricul- tural region is dependent upon these southerly. moisture bearing winds
 Tornadoes almost invariably move in an easterly direction and generally from southwest to northeast The average length of the path of destruc- tion is about 25 miles. and this path may not be continuous. if the funnel cloud is not in contact with the earth during it's whole course. Sometimes it rises and goes for a considerable distance before descending again.