BULLETIN OF THE AMERICAN METEOROLOGICAL SOCIETY Published Monthly by the American Meteorological Society at Worcester, Mass. Address All Communications and Exchanges to "Secretary, Am. Meteorological Society, Clark University, Worcester, Mass.” Vol. 6 NOVEMBER, 1925 No. 11 KANSAS CITY MEETING The list of papers for the Kansas City meeting is rapidly being completed, with subjects of a wide range of interest: rainfall periods, winds and the Air Mail, upper air winds, solar radiation and weather forecasting, tornadoes of the Middle West, exposure of rain gages, and others. Four sessions are planned: Monday, December 28, 3.30 to 12, and 2 to 4.30; Tuesday, December 29, 9-12, and 2-4. The annual business meeting is tentatively set for 11 A. M., December 29. There will be no presidential address this year. The program will be published in the December BULLETIN, to be issued about December 12. Those who will offer papers should communicate at once with the Secretary, at Clark University, Worcester, Mass., giving title, time required for presentation, and whether or not lantern will be needed. An abstract suitable for publication in the BULLETIN in connection with any discussion the paper may occasion should be sent to the Secretary. Two copies of the abstract and also, if possible, of the paper itself should be prepared and sent, one to Science Service, B and 21st Streets, Washington, D. C., and the other to Mr. Lyle Stephenson, care Mr. W. M. Symon, Chamber of Commerce, Kansas City, Mo., for their use in press releases appropriately timed. There will be an exhibition of scientific research. Our meeting will plan to visit it in a group. An excursion to the University of Kansas, under the leadership of Dr. Dinsmore Alter, may be made by those interested, at some time to be arranged. Persons going to the meeting should purchase one-way tickets, securing a certificate for the American Association for the Advancement of Science and Associated Societies. (A receipt is not what is needed). After validation (50c) at the Muehlebach Hotel, Kansas City, the certificate will entitle the bearer to purchase a return ticket at half the regular fare. Our meeting place will be Room 38, Junior College, and our hotel headquarters, Hotel Kupper, 11th and McGee Streets, two blocks away. Mr. P. Connor, Official-in-charge, local office of the Weather Bureau, recommends the following hotels near his office, but all six blocks or more from Junior College: Savoy, $2-$2.50, with bath; Westgate, $1.50 $3.50, with bath; Stats, $2.50-$3.50, with bath. The K. C. A. C. (no ladies), and the Baltimore are higher priced hotels. The Kupper asks $1.50-$3 for single rooms without bath, and $3-$5 with. Reservations should be made direct with the hotel chosen. SOUTH AFRICAN WEATHER (Notes based on three sojourns one of them for five years) The winter rains at Cape Town and in the area of winter rains along the south coast are caused by a succession of ocean depressions coming from a westerly direction-apparently not always from exactly the same direction. These depressions are first seen from Cape Town, coming from the western ocean, and their cloud indications are generally sufficiently marked to give ample warning of their approach. The center of the worst depression always passes entirely south of the land, but after the disturbance has left Cape Town there is nearly always a progressive fall of the barometer at Port Elizabeth, East London and Durban (the fall at Durban being usually small), showing the eastward motion of the depression-though their centers probably pass farther and farther from the land-it would be interesting to determine their exact tracks. Sometimes the depressions curve to the south, even before they should arrive off Port Elizabeth, and pass away into the southern ocean. One year when the writer noticed (by cloud, wind and barometer observations made about 100 miles from the coast between Cape Town and Port Elizabeth) that an unusually large number of these winter, ocean depressions were passing, the procession continuing almost into the southern summer, he read that Mauritius reported "an extraordinary number of winter atmospheric depressions" as the outstanding meteorological feature of that year-so perhaps they were the same line of depressions, though Mauritius seems rather far north for the track. A meteorologist at Cape Town told the writer that he thought some of these passing ocean depressions were a succession of secondaries (sometimes three), as they were so close together. The writer noticed that when the S.W. wind at the back of a depression was to back within 12, or so, hours to the N.W., for a new depression, with rain, not more than 24 hours or so after the preceding depression, at least one small wisp of cirrus appears during the S.W. wind-sometimes it was only a single twisted thread-otherwise there would be no cirrus or other very high cloud anywhere in sight. It was such depressions that the meteorologist thought were probably secondaries. The fall of the barometer at Cape Town even for the worst of these depressions seemed small compared with the fall in winter depressions on the west coast of Europe, the strength of the N.W. and S.W. gales being apparently out of proportion to the change in the barometer. Perhaps some of the worst depressions have deep centers far to the south. Cape Town gets most of its rain with the N.W. (generally N.N.W.) wind in front of the depression. When the wind veers to the S.W. the weather generally clears up quickly, but with the worst (deepest, chiefly) depressions a succession of heavy showers occurs with the S.W. wind, some of them contain winter hail with rather large stones, and the writer heard winter thunder in some of the worst showers. These S.W. showers seem to correspond to the N.W. showers at the back of most important winter depressions on the west coast of the British Isles but the cloud forms are a little different at Cape Town, in part due to the influence of the Table Mountain range. The rain with these winter depressions has been aptly described as "English rain," meaning that it is of the small drop variety and different from the hard, large drop thunder rain which prevails in the interior of South Africa. The eastern suburbs of Cape Town under the lee of Table Mountain and its outlyer, the Devil's Peak, receive much more rain than the city or other suburbs. The N.W. (damp) current in front of the depressions is raised by Table Mountain and the Devil's Peak and their windward slopes are too abrupt and not high enough to deposit the moisture on the wind side, and the range is not wide enough to use it up, so a great deal falls on the lee slope, the nearer the mountain the heavier the fall. Table Mountain is used as a weather forecast by the inhabitants, for it is heavily cloud capped on the approach of a depression, and, as stated, has a very great effect on the distribution of rain during the passage of the depression. * The writer observed, before some of the very worst gales only, lenticular cumulus over the Cape Flats to the lee of Table Mountain-the summit of the mountain was generally quite clear at the time and the cloud-capped stage before a depression had not begun yet. These lenticular cumuli were of striking appearance, very like a large wellbaked reddish-yellow smooth biscuit, or the top of a large spread-out mushroom. They were the only clouds in that part of the sky, and the writer saw none except before a few of the most severe gales. On pp. 392-393 of "The Climate of the Continent of Africa" (Cambridge, England, 1911), Knox writes, "A pretty little controversy is raging as to the connection between the winds and the rains of Southern Africa." He adds, "The old and long-accepted theory is receiving violent shocks." He goes on to imply that the old theory is that with the exception of Cape Town and vicinity, most places receive their rain with Southeast "Trades" and that lately coast stations have reported that it is the S.W. wind, not the S.E., that brings their rain, and inland stations have also turned heretic in most reports. As regards the coast stations, the real explanation appears to the writer to be that the S.W. wind which brings the rain is merely the temporary S.W. wind at the backs of the passing depressions and the rain is therefore caused by these depressions and would certainly not occur without them. At * See "The "Tablecloth' of Table Mountain," by C. F. Talman, Mo. Weather Rev., Apr., 1921, vol. 49, p. 192, plate with 2 photos and 1 woodcut. A fourth picture shows a corresponding cloud on Mt. Shasta. Cape Town the N.W. wind in front of the depression comes off the ocean and brings most of the rain there, as stated above; but further east, along the coast, the N.W. wind is an off-shore wind blowing down from a dry tableland and over coast ranges, so it could naturally not be expected to bring rain, so the coast has to rely on the, so to speak, clearing shower coming from the S.W., as the wind veers, and to the S.W. showers which sometimes follow (just as at Cape Town) and perhaps, occasionally, to a short piece of set-in rain from the S.W. at the back of the depression—just as occurs elsewhere occasionally after the passage of the center of a depression. The writer felt sure such was the case from his cloud and barometer observations, made about 100 miles from the coast during the passage of these ocean depressions, but he had a few weeks of actual experience on the coast near Knysna, to the east of Port Elizabeth. There is a considerable rainfall at Knysna (the Knysna Forest is apparently the result) and there are a rather large number of rainy days, with comparatively light daily rainfalls. During these few weeks several ocean depressions passed and the rain began with a sort of line “clearing shower" coming from the S.W., as the center of the depression passed somewhere to the south over the ocean and the glass began to rise. Mr. Knox states that Port Elizabeth reported "no rain" with a S.E. wind. The writer would be surprised if any place in most of South Africa reported any rain of consequence with a S.E. wind, except under exceptional circumstances due to unusual causes. Inland, the S.E. wind is often anathematized as the wind which sets in and spoils the chance for rain or causes the rain to cease. For example, the writer's "up-country" landlady (in the area of summer rain) said to him, "here comes that wretched S.E. wind and spoils everything." There had been a little thunder rain with prospect of more, but after the incidence of the S.E. wind there was no hope whatever of more rain that day, and the thunder area passed rapidly eastward and the clouds were absorbed overhead. The S.E. wind behaves just as a N.W. wind often does in a large part of the United States, in putting an end to hope of rain. The writer's reply to his landlady, however, is given, for it states what is probably the very useful function of the S.E. wind. He said, "It is filling the tanks" and he looked up to show which tanks he meant. Later, after apparently carefully noticing, the results of successive S.E. winds the same woman said she now saw that the writer was "certainly" right and how she had all her life maligned the S.E. wind. The S.E. wind which is both common and strong in South Africa, especially in the summer, appears to bring up moisture from the Indian Ocean (Mozambique Current) and thus allow shallow disturbances or other causes to form rain which the dryness of the air would otherwise nearly or quite prevent. This refers to the area of summer rains, chiefly, which includes most of South Africa and overlaps the winter rain area. The rain clouds, however, very rarely come from the S.E. or with a S.E. wind at the surface. When the S.E. wind has brought moisture (after blowing some while) clouds associated with thunder showers often appear in the N.W. or N. moving from N.W., N., or even N.E. sometimes-they are apparently due to shallow depressions. As soon as the showers have passed, the S.E. wind is apt to set in violently. During, and before the showers, the wind is usually N.W. or N.E. (hardly ever S.E.) or sometimes due east, and it is obviously not the ordinary S.E. wind even when it blows from S.E. When the shower clouds move from the N. (not N.W.) in many inland parts of the summer rain area, the showers are frequent and severemany farmers asked if the writer had noticed this obvious fact, but they do not often move from the north. I also noticed that on the rare occasions when the cumulo-nimbus moved from the N.E. or a point east of north they were exceptionally severe and appeared to penerate further into the arid parts. In the Transvaal the writer believes the N.E. and E. wind also bring up much of the moisture from the coast, the S.E. wind being the bearer especially for the inland portions further south. On the coast of Cape Colony the summer thunderstorms, therefore, always come from off the land, though their moisture has been brought in by S.E. winds the S.E. wind on the coast being practically a dry wind. The usual direction from which thunder or heavy rain showers come in summer varies in different parts of the interior. As stated above, in most places the rain clouds move from the N.W., and over a considerable area they are exceptionally widespread and severe when they move from the N., as, for example, in the Dordrecht district. In many places when the showers move (rarely) from the N.E., they are very heavy indeed. The writer saw what was apparently a rather large real tornado, with a smaller, pointed, slightly spiral black funnel at either side, the small funnels not reaching the ground. All were from a cumulo-nimbus which had formed with great rapidity, apparently near the center of a shallow depression. Very large hail stones were reported as falling from the tornado shower. The tornado appeared to move very slowly, but the whole cloud was also moving very slowly. The Johannesburg-Pretoria neighborhood is so important that one should add that at Pretoria the storms generally come from the S.W. and sometimes from the S. or S.S.E. even, though they also form locally. When they come from the S.W. or S. they are usually in the form of a line squall often with a strong wind in them. This usually comes late in the day (in the late afternoon or evening). This squall usually also passes over the Johannesburg ridge (the Rand) a little earlier, and is then usually not so well developed as regards rain, so that, so far as the writer could see by cloud observation from both Pretoria and Johannesburg, Pretoria gets more rain from these showers. On the other hand, Johannesburg in the summer gets a number of local showers at about noon, while Pretoria gets none (not even clouds). It is the reg |