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In Various Parts of the World Are Not Given by the Weather Bureau, Nor As Far As I Know by Any European Government

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In Various Parts of the World Are Not Given by the Weather Bureau, Nor As Far As I Know by Any European Government in various parts of the world are not given by the Weather Bureau, nor as far as I know by any European government. They cannot be deduced from the records of the ordinary anemometer, and anemometers especially devised to give these data are expensive and not wholly reliable. The only information regarding the velocities of the wind in tornadoes are mere guesses. It was thought that a simple and inexpensive device which would give at least an approximate idea of them would be of value. I sent a description of such a plan to the editor of the Scientific Amer- ican of which he wrote an account, 1924, 288. It consists merely of a set of hollow metallic cylinders either of lead or iron, all of exactly the same size, but with walls of different thickness. Small cylinders could consist merely of tin boxes laden with different materials ranging in specific gravity from feathers to alternate layers of wood and lead. At present I am merely partly filling the boxes with bird shot. The cyl- inders are arranged on a base which will trip them if they are blown over by the wind, and are tied by cords to prevent their rolling away. The pressure of the overturn is measured later by a horizontal spring balance. I sent the suggestion to the Weather Bureau, but the Washington authorities thought it was not practicable, so I made a model out of tin boxes such as were formerly used by the Kodak Co. in sending their films to the tropics, and it worked very well for the winds up to thirty miles an hour, which was the highest velocity measured. From 1924, when the apparatus was constructed, until the present day we have not had a single hurricane in Jamaica. November hurricanes are scarce, and the last one occurred just twenty years ago, but at the present time we are recovering from a rather severe one. I started to set up my apparatus, but found in the meantime it had all gone to pieces, and by the time I had got it properly in order the hurricane was over. However, I set it up, and it recorded a velocity of one gust of 17 miles. The formula for the reduction of the results is given in Mark's Engineer's Handbook, 1248, and doubtless in other similar publications. My idea for tornado measurements would be to use hollow iron cylinders 12 inches high and 5 inches in diameter, or 25 cm. by 10 for a universal standard. In case a dozen such sets could be set up in some of our middle western states I have no doubt but that in a few years we might really get some idea of the actual velocity of the wind in an active tornado. It would cer- tainly be of interest.—William H. Pickering, Mandeville, Jamaica, B. W. I., November 9, 1932. TORNADO CLOUDS IV^uch attention has been given to tornado clouds the past few years and many photographs have been published, including photos in series, showing the development of these storms and the accompanying cloud formations. Published literature on tornadoes enumerates many shapes, the fun- nel-shape being the general type. Other forms reported are sheaf- shaped, rope-like, serpent-like, cone-shaped, elephant trunk shaped, hour glass, truncated cone, inverted cone, basket-shaped and wine glass. Dense rolling, boiling effects and clouds converging from opposite direc- Unauthenticated | Downloaded 09/28/21 11:59 AM UTC tions are often reported preceding a tornado. Occasionally tornadoes are reported without a distinct funnel cloud, but only a lowering of the main ceiling as a violent storm passes. Nothing is offered in most in- stances explaining the cause of the cloud forms except that they accom- pany a violent whirl. The same processes form tornado clouds that form other clouds, the condensation of atmospheric moisture due to lowering the temperature below the dew point. Their shape and action are largely determined by the movements and locations of a supercooled mass of air through an- other mass of air with high humidities and tem'peratures. The tornado cloud forms around the core of the whirl or spin. The air in the core of the whirl has been supercooled by attenuation, or rarefaction, pro- duced by mechanically diminished pressure, since the air is drawn away from the center of the whirl by centrifugal force. The diminished pressure in the whirl is proved by barometer readings and explosive effects observed on buildings located near or in the path of tornadoes. The vortex of an approaching tornado observed before the formation of the funnel cloud is quite interesting. It shows clouds rushing and converging towards a central point and disappearing as if being drawn up into the heavens. If the vortex continues and increases its angular velocity, the sky opens at the center and the observer reports "A hole in the sky," with the clouds revolving around an open space. This hap- pens before the core of the whirl below has been cooled enough to pro- duce a cloud sheath, and the observer sees through the transparent walls of the whirl into the space above. This phenomenon is rarely reported because the funnel cloud usually forms promptly and observers are too alarmed to give it attention. This feature is similar to the one reported by an observer in Kansas reporting conditions inside of a tornado funnel cloud from a cyclone cellar seeing clouds and debris whirling around the inner walls of the cloud sheath. This incident is reported on pages 205- 206, M. W. R. Vol. 58, 1930. The first funnel cloud forms are usually inverted cones not reaching the earth. The cloud formations extend lower as the storm proceeds. Whirls may extend to the earth without the cloud sheath following, since whirls with revolving debris have been reported without the cloud sheath. Greater cooling in the upper sections than in the lower sections of the whirl would explain this feature. The earlier funnel clouds extending to the earth are usually slender forms like a rope, serpent or the stem of a wine glass. The cloud sheet is thin and clean looking, appearing sometimes like a fog or vapor. This indicates that condensation has just started. As the cooling process pro- ceeds, the cloud sheet becomes denser and blacker and is often fouled by ascending debris. The larger, broader, blacker, and denser tornado clouds are characteristic of the later history of an individual tornado. Funnel clouds are sometimes obscured by rain. Absence of funnel clouds during the history of a tornado is explained in various ways. Opposing parallel currents contribute largely to the maintenance of a whirl, and anything which disturbs their position or velocity would tend to interrupt it and the cloud forming processes. The Unauthenticated | Downloaded 09/28/21 11:59 AM UTC whirl may also be broken up by topography. The progressive movement of a tornado contributes to breaking up of the funnel clouds; slow forward movement of the storm would favor formation of the whirls. This process is similar to the formation of fracto-cumulus on a windy day. An interesting example of this process is shown in the Tri-state tornado of March, 1925. The progressive velocity of this storm was 57 miles per hour in Missouri, 59 in Illinois, and 68 in Indiana. The few observations reported of a funnel cloud in the early history of storm and its almost total absence in the latter part was a subject of comment by officials discussing the storm.—T. G. Shipmctn, U. S. Weather Bureau, Daven- port, Iowa. DAILY AIRPLANE WEATHER OBSERVATION OF OCTOBER 31, 1932, DALLAS, TEXAS The pilot takes off at the usual time—3.30 a. m. A windshift is due shortly, Can he make the hour and a half flight before it arrives? The plane climbs for an hour, only two thousand feet more to go. Lightning is closing in from all directions. Suddenly the ship falls out of the climb. It is in a violent down draft. The wind-shift has struck. The pilot dives the plane to the southeast to try to get out of the grip of the elements. The rate of climb meter registers fourteen hundred feet per minute descent. The motor is roaring out twenty-six hundred revo- lutions per minute. Very suddenly the rate of climb meter changes to zero although the plane is still in the diving attitude. Out of the corners of his eyes the pilot notes that the wings are still with him—hardly expected. The pilot now takes a terrific beating. Even though he is holding the joy stick with both hands it pounds his legs until they are painfully sore. The blind flying instruments are jumping so much that it is guess-work to read them. It is impossible to hear the radio beam signals with the radio. The pilot thinks he is somewhere east of Dallas. He is now close to the ground and looking for a light. There is a very heavy rain in progress. It looks as if buckets of water were being poured against the windshield. The pilot turns on his landing lights trying to see the ground. The lights run out a few feet and are cut off sharp. The pilot comes down every few minutes until the altimeter reads zero. (The pressure trace on the Weather Bureau Meteorograph bears this out. He couldn't have been more than a very few feet from the ground several times.) However, the pilot can't see a thing.
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