336 MONTHLY WEATHER REVIEW AUGUST,1929 mailing, require a total of slightly over four and one-half vening gradients and all the information derived from hours time. these factors form the basis for accurnte conclusions in Due to tlie successful and extensive development of the forecasting. Without vessel-weather observations fore- vessel weather service comprehensive studies are made casters would be confronted with a very puzzling situa- of meteorolopical coiiditions over the Pacific Ocean. tion. The knowledge of ocerinic pressure clistrihution, the most The value of tlie forecasting md wariiings can not be vital factor in forecasting for the far Western Statcs, estimated. Every industry, enterprise, organization, becomes available to forecasters. The isobaric reprcdnc- or the individual, whose n-eifare is affected by weather tion on the synoptic charts of pressure systems as indi- conditions receives invaluable benefits from this service. cated by vessel reports pictures the nioveiiients ol cyclonic Ever increasing deniands for a more extensive weather and anticyclonic. areas. The cuntinuous enstwnrd march service are taxing tl:e Weather Fureau to capacity. of “HIGHS ” and “LO% s ” niny he closely followed. ‘I’hr Feirly r:tpid strides liave been macle in recent years in constant changing conciitions; the rapidity of iim\-rnient ; the extension of the services of the Weather Bureau and the relative positions of c.yclonic rLnd tintic?-clonic arcbns : vessel weather reporting has p!ayed nn important part the intensity of a depression; the steepness of iiiter- in the advance. METEOROLOGICAL NEEDS OF A CLASS A 1 A AIRPORT1 .j-h-/. 5 : 72c 3 9 By D. R.1. LITTLE The Secretary of Commerce is empowered by law to stations is progrwsing at, a fast pace. Izsperience has rate airports as to thcir suitability upon epplication of the sIiown t1i:tt close contact betn eeii tlie meteorologist and owner. After conforming to certain ljrrsic requirements, the pilot is absolutely necessary, and this mutual ex- airports mag be given ratings indicated by :i letter, IL change of ineieorclogical information and flying problems figure, and another letter, the first’ letter indicating the is conducive to s:tfe and econoniical air transportation. general facilities aiid equipment at the airport, the 3. Uunicipr7 serrice at (iirporis.--hlany large and in- figure indicating the available landing area, and the Inst port.int municipal airports orer the coiintry, located on letter indicating the night flying equiplent . Thus the ~ndadjnc-ent to established :tirways, will not be needed rating A 1 A is the highest rnting given airports. AS Weather Bnreaii airway control stntions, ancl therefore Under general facilities and equqiiiient, tin airport, in will be n-ithout Government meteorologists. However, order to obtain a rating of “A” or “B,” inlist have Government airway weather anrl communication service nietcorological inst,ruments including nii , is available at small cost to such airports, but it is , and a , in addition to a bulletin 1ieccss:ir-y for the ni,unicipalities to employ their own board and facilities for giving pilots the most recent metcorologists. This has already been done in several weather information. Ratings of “C” or “D” do not, instances, ancl the airports are rendering as efficient require meteorological facilities. Under night-flying service as at the Weather Bureau airport stations. equipment an airport must have a ceiling projector, nn 3. Serrrice tit priwitely ownet7 rrirpor.ts.-The need for alidade for measuring the height of ceiling, and sufficient meteorological service at a privately owned airport personnel for giving weather service at all times in order where air-transport operations are carried on is just as to receive a rating of “A.” A ratins of “B” will be great as at H. municipal aiqiort. Here, again, it will be given when an airport is without a ceiling projector, and necessary for the airports or air-transport companies to ratings of “C” or “D” may be given when the airport employ their own meteorologists. In some cases it will is without night nietcorological facilities or personnel. he necessary for an air-transport company to employ one The meteorological needs of a class A 1 ,4 airport is or more meteorologists, plncing then1 at strategic points much greater than the bare recluirciiientq lor the rating. along their I:artictiIar flying route when such route does In this paper the needs are classified under threc head- not follow tlie established commercial airway. One ings-Personnel anrl service, Comiiiunication facilities, company has alread~7set aside $100,000 for its own corn- and Meteorological instrumenbs and facilities. plete nieteorological service along such a route. PERSONhTEL AND SERVICE Private and inmiicipal airport meteorologists, of course, should be experienced and thoroughly faiiiiliar with the I. Gowrnitrent sewice (it uiryort,e.-At airports clesig- nerologicnl, marine, and weather codes of the United nated as control stations on established commercial air- States Weather Bureau. With the wealth of inforniation ways in use more or less 24 hours per day there are available, as esplained later under L‘Communicat,ions,’’ ordinarily not less than four JVeather Bureau officials on the meteorologist can prepare synoptic maps of 12-hour the meteorological stafy-i. e., two nietrorologists and weather conditions, tabulale and map hourly airway two observers. At similar stations on established coni- weather reports supplemented with 3-hour summariza- iiiercinl airways where froin 1.5 to 30 lioilrs’ service per tions ancl short-range forecasts based on of?’ airway re- day is suficient for the present flying one meteorologist ports, prepare niultilevel niaps of upper air winds, and and two observers are usually assigned. At all other furnish all pilots with current weather reports in tabular airport stations and aerological stations 12-hour sen-ice Iorm. In addition he v;ould advise the pilot of the best is maintained by the assigiirnent of one meteorolog.ist, weather route, how high to fly in order to take advantage and one observer. Employees below the rank of junior of “tail winds,” and the weather changes to be espected observer should not be assigned to airport stations, as during a flight along an off airway route. In short, he the responsibility is too great to be placed with men of would render for the municip:il and privately owned lesser capacity. Service at \Teather l3ureau airport airport all of the service available at a Government ~~~~~~ station and devote a portion of his time to research on 1 Presented before the Borlicley meeting of the American hIcteorologica1 Swiety in lune. 1929, nieteorological problems particularly affecting his area.

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COMMUNICATION FACILITIES close t’o a We,at,her Bureau aerological station, frequently an observation can not be obtained at the Weather At airports where Wenther Bureau airport stations are Bure,au station because of local low clouds or fog, while established the Goveriinien t provides all necessary coni- fin airport meteorological station several miles away could munication facilities, such as long-clistnnce telephone, make t,he observation in a clear sky or vice versa. In telegraph, teletype circuits. eiic! radio stations. hlunici- one case this is carried on successfully through the Gov- pal and private airports without such a stat‘?on can ernment st.ation advising t,he municipal st>ationat times easily avail themselves of all meteorological information. when low clouds interfere wit,h the observation at the An airport located near a Government airway station Government stat.ion. The ce.iling projector and alidade where long-line teletype facilities are avaiiable can arrange for nieasuring the ceiling or altitude of the clouds at for a drop on the circuit whereby the airport pays for its night is required for a c.lass A rating. Height of ceiling, own drop. Also the instn!!ntion of an inexpensive short a clifficult observation at best, is made extremely simple and long wave radio receivinc set is essential. Reports with t,his e,quipinent,. All airport’s should have this transmitted. by the Weather Bureau to the Department equipment, regardless of whet,her or not a meteorological of Conimerce radio station me transmitted on the long- statmionis planned. An airplane iiieteorograph has been line teletype ns well as broadcast by voice. For the included wit,h the list of meteorological instruments for preparation of 13-hour synoptic mnps arid niultilevel airports employing rneteorolo~ist~sfor t’he re.ason that upper air maps, it will be necessary for tlie airports to iipper air records are badly needed. The airport meteor- arrange to hare an operator copy tlie Weather Bureau ologist would have litt.le difficulty in securing the pilot’s broadcast froin the naval radio. An ai1 port complying cooperation iii t,liis work. with the A 1 A requirenients needs this tie in uith the Subst,itut,ionsarid omissions in t’he above list of instru- Government coiiimunication system before it cnn hope menbs iiiay be made, of course, to meet the requirements to give its pilots the best service obtcinnble. and budget of each individual airport. The rule to fol- low in select,ing met,eorological instruments is to begin METEOROLOGICAL INSTRUMENTS AND PACII ITIEd with t,he basic requirements of an “A” rating ancl sub- st,itute or supplement) witdl self-recording instrumenbs as For t,lie larger iniport,ant airports an ideal instruinental far as possible. layout is as follows : Pressure, tube anemograph, mercu- Under “Facilities” an airport should provide space rial barometer, high-grade aneroid barometaex-,, and office equipment for a met,eorological office in the hygrotherniograph, psyclironiet~e.r,maximum ininimum administ,ration building. The office should contain a and exposed t,hermomet8ers,rain gage, , bullet,in board showing current upper-air wind data from pilot-balloon e.cluipment8,ceiling proj &or with alidade, surrounding aerologic,al stations, United States Weather and an airplane meteorogrnph. In this list the pressure- Bureau airway forecasts, current airway weather reports, tube anemograph was select,ecl in prefe.rence to t,he wind and a daily went81iermap. Wall maps, topographic maps, vane, anemometer, and recorc1e.r because a record of wind and airway strip maps are desirable in the meteorological fluctua,tions and gust,iness is ne.eded at important air- office. ports. A mercurial barometer is needed for ac,curate It is interest.ing t,o note that one after another of the measurement>sof barometric pre.ssure. A record of tem- problems affecting comniercial aviation have been over- perature and humiditmyas obt,ained wit,h a hygrothermo- c.ome; motors have be,en developed to the point where graph and psychroniete,r is important. All airport,s have wit.h proper ewe. seldom is there a cornplebe failure; in- more or less fog t,o cont,end with during cert’nin periods struments have been developed and irnproved ; pilots are of the year, and n c.ont,inuoiis record of relative humiclity becoming more and more experienced : planes have been and temperature will be useful in research worli on his improved for speed and safety; ancl now one of the vital problem. In acldit.ion, the dew point, of the air is required problems affe.ct,ingc.onimercia1 aviation-i. e., the weather when giving airway weat,her reports. ,4 sunshine re- problem-is being investigated and minimized by the corder is of value for records of beginnings and endings inst,allation of niet,eorologic,aJ instrument’s, by fast com- of cloudiness or fog at the airport’. Pilot-balloon equip- munication service, by the tie in of airport,s with the ment is recommended for airports employing meteorolo- Government airway meteorological and communication gists, especially where the airport’ is far removed from a syst,eni, and by the employment, of meteorologists at Weather Bureau aerological station. Even if located airports.

ss/.515 (73) WHAT A TORNADO LOOKS LIKE By S. D. FLORA A well-developed tornado is the most amazing and from the sky that spreads destruction where ever it terrifying atmospheric phenomenon ever seen in inland touches the ground. America. The first sight of one at n distance-and a One of the most spectacular tornadoes on record hundred or more occur each yenr in the country-gives struck the edge of Hnrdtner, Kans., about 5:15 p. m. the impression of a contradiction of nature’s laws that of June 2, 1929. The sky was only partly overcast at permits such a storm to forin at all. As it approaches the time and the sun shone full on the pendant cloud, with its peculiar whistling sound that rapidly changes making it a striking sight for 30 miles across the almost to a terrific roar and buildings arc blnwn to pieces as level country adjoining. Instead of moving at espress- though they were made of cards, the eflect is enough to train speed, as tornadoes generally do, this one seemed strike terror in the stoutest of hearts. to loiter ancl remain almost stationary for the greater Contrary to the popular idea, a tornado seldom gives part of half an hour. the impression of a huge inverted funnel. It has been In describing it an eye witness said, “If you can more commonly clescrihed by eyewitnesses as a gigantic imagine a big, gray elephant trunk or sausage balloon elephant trunk writhing about or a long rope dangling strung across the town with the upper end in the clouds

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