,,wind ,,and ,,weather ,illustration3 ,logo ,,the ,,macmillan ,,company ,,new ,,york 4 ,,boston 4 ,,chicago 4 ,,dallas ,,atlanta 4 ,,san ,,francisco ,,macmillan ,,co41 ,,limited ,,london 4 ,,bombay 4 ,,calcutta ,,melbourne ,,the ,,macmillan ,,co4 ,,of ,,canada1 ,,ltd4 ,,toronto ,illustration3 ,,how ,,the ,,wind ,,ruffles ,,the ,,top ,,of ,a ,,fog ,,bank ,frontispiece ,,wind ,,and ,,weather ,,by ,,alexander ,mc,a,d,i,e ,a4 ,lawrence ,rotch ,professor of ,meteorology1 ,harvard ,university and ,director of the ,blue ,hill ,observatory ,new ,york ,,the ,,macmillan ,,company #aibb ,all rights reserved ,copyright1 #aibb1 ,by ,,alexander ,mc,a,d,i,e4 ,set up and electrotyped4 ,published ,november1 #aibb4 ,,list ,,of ,,illustrations ,,how ,,the ,,wind ,,ruffles ,,the ,,top ,,of ,a ,,fog ,,bank ,frontispiece ,,page ,,fig4 #a4 ,,the ,,tower ,,of ,,the ,,winds #ac #b4 ,,boreas--,,the ,,north ,,wind #ai #c4 ,,kaikias--,,the ,,northeast ,,wind #bc #d4 ,,apheliotes--,,the ,,east ,,wind #bi #e4 ,,euros--,,the ,,southeast ,,wind #cc #f4 ,,notos--,,the ,,south ,,wind #cg #g4 ,,lips--,,the ,,southwest ,,wind #da #h4 ,,all ,,storms ,,lead ,,to ,,new ,,england #de #i4 ,,zephyros--,,the ,,west ,,wind #di #aj4 ,,paths ,,of ,,high ,,and ,,low1 ,,january1 #aibb #ee #aa4 ,,skiron--,,the ,,northwest ,,wind #ei #ab4 ,,the ,,idealized ,,storm #fc #ac4 ,,turning ,,of ,,wind ,,with ,,altitude #fg #ad4 ,,velocity ,,of ,,summer ,,and ,,winter ,,winds #gc #ae4 ,,blue ,,hill ,,observatory ,,in ,,an ,,ice ,,storm #gi ,,wind ,,and ,,weather ,,the ,,tower ,,of ,,the ,,winds ,in ,athens on the north side and near the base of the hill on which the upper city--the ,acropolis--is built1 there is a small temple still standing1 altho its walls were completed twenty-two centuries ago4 ,it is known as the ,tower of the ,winds2 but as a matter of fact1 the citizens of ,athens used it to tell the hour of the day and the seasonal position of the sun4 ,it was a public timepiece4 ,it served as a huge sun dial4 ,water from a spring on the hillside filled the basins of a water clock in the basement of the ,tower4 ,and so1 whether the day was clear or cloudy the measure of the outflow of water indicated the time elapsed4 ,also there were markings or dials on each of the eight walls of the temple1 and the position of the shadow of a marker indicated the seasonal advance or retreat of the sun as it moved north from the time of the winter solstice and then south after the summer solstice4 ,the sun is not an accurate time keeper and no one to-day runs his business or keeps engagements on sun time4 ,but the old ,athenians were quite content to do so2 and their ,tower served excellently for their needs4 ,and they did what we moderns fail to do1 namely1 give distinctive names to the winds4 ,they represented figuratively the characteristics of the weather as the wind blew from each of the eight cardinal directions4 ,illustration3 ,,fig4 #a4 ,,the ,,tower ,,of ,,the ,,winds ,erected in ,athens1 on the north side of the ,acropolis1 ,b4 ,c4 #aej ,the allegorical figures of the winds used in this little book are reproductions of the eight bas-reliefs in the library of the ,blue ,hill ,observatory1 placed there by the late ,professor ,a4 ,lawrence ,rotch4 ,they are copied from the frieze of the ,tower of the ,winds at ,athens4 ,,the ,,names ,,of ,,the ,,winds ,boreas1 the north wind1 is perhaps the most important of all winds4 ,at ,athens this a cold1 boisterous wind from the mountains of ,thrace4 ,the noise of the gusts is so loud that the ,greek sculptor symbolized the tumult by placing a conch shell in the mouth of ,boreas4 ,his modern namesake1 the ,bora of the ,adriatic1 is the same noisy1 blustering1 cold wind-rush from the north4 ,the northeast wind ,kaikias is a trifle more pleasant looking than ,boreas1 but still not much to brag about4 ,master of the squall and thunderstorm1 he carries in his shield an ample supply of hailstones1 ready to spill them on defenseless humanity4 ,he might well serve as the patron saint of air raiders dropping their bombs on helpless humans below4 ,apheliotes1 the east wind1 is a graceful youth1 with arms full of flowers1 fruit and wheat4 ,naturally this was a favorite wind1 blowing in from the sea1 with frequent light showers4 ,some of us who dwell on the ,atlantic ,coast1 in more northern latitudes than ,athens1 do not always regard with favor the east wind1 associating it with chilly1 damp and sombre weather4 ,yet it is the harbinger of good--tempering the cold of winter and the heat of summer4 ,it is an angel of mercy in mid-summer when the temperature is above the nineties and there is no air stirring4 ,then it is1 that we all welcome the refreshing wind from the sea4 ,euros1 the southeast wind1 and neighbor to ,apheliotes1 is a cross old fellow1 intent on the business of cloud making4 ,he alone of all the winds carries nothing in his hands4 ,in the ,new ,testament he becomes ,euroclydon1 wind of the waves4 ,he is no friend of the sailor2 and the seasick traveler prays to be rid of his company4 ,the figure on the south face of the tower1 ,notos1 is the master of the warm rain4 ,he carries with him a water jar which has just been emptied4 ,compare his light flowing robes and half-clad neck and arms with the close fitting jacket of old ,boreas4 ,at his shrine1 hydraulic engineers well might worship4 ,next1 the ,mariner's wind1 ,lips1 the southwest favoring breeze bringing the ships speedily into harbor2 yes1 into that ,piraeus1 famed in classic history4 ,incidentally it is the southwest wind which differentiates the climate of ,great ,britain from that of ,labrador4 ,this wind makes ,northwest ,europe habitable2 while on the other side of the ,atlantic1 in similar latitudes1 but under the influence of prevailing northwest winds1 we find ,labrador--a section certainly misnamed1 for it is not the abode of farmers1 as the name implies--but barren and bleak4 ,what a difference it would make thruout this region if the ,gulf ,stream continued north1 close to the shore1 and the prevailing winds were from the east4 ,our ,north ,atlantic ,coast would then be the land of zephyrs1 using the word in the sense of pleasant1 gentle winds4 ,illustration3 ,,fig4 #b4 ,,boreas--,,the ,,north ,,wind ,zephyros1 the west wind1 is represented as a graceful youth1 scantily clad1 with his arms filled with flowers4 ,in ,greece this wind traversed the ,ionian ,sea and the ,gulf of ,corinth before reaching ,athens4 ,it is quite unlike our west wind which blows across a continent1 and is continuously robbed of its water vapor on the long passage4 ,the ,ionian wind is pleasantly moist and refreshing4 ,last of all1 but by no means least important1 is ,skiron1 lord of gusty northwest gales4 ,freezing in winter1 parching in summer1 he carries with him a brazen fire basket and spills a generous stream of hot air on all below4 ,his husky ,highness might not inappropriately adorn legislative halls and editorial sanctums4 ,he would displace the blindfolded lady holding scales very much out of balance4 ,think of the deep significance of his presence4 ,in our country the northwest is of all winds1 except the west1 most persistent4 ,for #afjj hours in a year1 this wind is with us4 ,joining forces with the west wind1 these directions prevail one third of the time4 ,these northwest-west winds also have the greatest speed and gustiness4 ,the climate of the ,united ,states is essentially determined by the prevalence of the north1 northwest and west winds4 ,,forecasting ,,the ,,weather ,in old days1 the haruspices 7for this is what the ,romans called weather men in the days of ,caesar7 proclaimed the will of the gods by consulting the entrails of some freshly killed animal4 ,evidently these haruspices did not always make correct forecasts2 for there were some ,romans who openly questioned their worth4 ,cato1 the ,censor1 is on record as saying that he wondered how one haruspex could look another in the face without laughing6 ,illustration3 ,,fig4 #c4 ,,kaikias--,,the ,,northeast ,,wind ,the modern professional forecaster would scorn to consult the entrails4 ,there are however many amateur forecasters who foretell weather by their aches and rheumatic pains4 ,probably there is a high correlation factor between body sensations and dampness2 and some individuals are quite sensitive to changes in both relative and absolute humidity4 ,this1 however1 does not always mean that a storm is approaching4 ,humidity or dampness is only one factor and may be quite local1 whereas most storms are wide-spread4 ,,the ,,weather ,,map ,the official forecaster consults a daily weather map and certain auxiliary maps which show changes in pressure and temperature for twelve hours or more4 ,he examines closely the contours of pressure as shown on the map4 ,the synoptic map1 as it is called1 because it is a glance at weather conditions over a large area at one and the same moment1 is a map on which are plotted pressure1 temperature1 wind direction1 velocity and rainfall4 ,the lines of equal pressure or isobars generally curve and inclose what is known as a cyclonic centre1 or depression or ,,low4 ,the arrows point in1 but not exactly toward the centre of the depression4 ,on the map there will probably appear also an area of high pressure where the surface air flows leisurely outward and away from the place of highest pressure4 ,such an area is called an anticyclone1 a word first used by ,sir ,francis ,galton in #ahfc to designate not only high pressure1 but general flow of the air in a reversed or opposite direction to that of the low area or cyclone4 ,the word cyclone was first used by ,piddington in #ahdc in describing the flow of the air in the typhoons of the ,east ,indian ,seas4 ,it is from the ,greek and literally means the coils of a serpent4 ,the word cyclone must possess some special merit in the minds of journalists for it is quite commonly misused for tornado in descriptions of the smaller and more destructive storm4 ,,the ,,low ,cyclone is simply the generic name for a large rotating air mass4 ,it is a barometric depression or ,,low and is characterized by a flow of air inward and around a moving centre4 ,the air circulation is counter-clockwise in the northern hemisphere and clockwise in the south4 ,perhaps if the earth stopped rotating and there was no planetary circulation1 with the great west-moving trades and east-moving westerlies1 the arrows on the weather map would all point directly toward the centre of the ,,low2 but1 as things are1 there are some very good reasons why air can not move directly into a ,,low1 that is at right angles to the isobars4 ,moreover1 the weather map does not indicate the true flow of the air1 for observations of the wind made at the ground tell only a part of the story of the balance which the flowing air must maintain under the action of various forces1 such as gravitation1 rotational deflection1 centrifugal tendency1 and the various expansion and compression forces4 ,the winds near the ground are modified both in velocity and direction by friction4 ,the free flow is often interfered with by topography4 ,,the ,,true ,,air ,,flow ,one must rise above the ground some distance to get the true air flow1 or what is known as the gradient wind1 the flow which balances the gradient1 i4e4 a flow along the isobars4 ,the gradient velocity is found about #cjj metres above the ground1 and the gradient direction a little higher4 ,the lower clouds as a rule indicate true wind values very well2 and so1 it is desirable in studying winds to use cloud directions and velocities rather than surface values4 ,in cloud work a nephoscope is essential4 ,the unaided eye1 unless properly shielded1 suffers from the glare of a sunlit sky2 and moreover1 there are no fixed points or references4 ,a black mirror1 with suitable sighting rods and measuring devices1 enables an observer to follow the cloud1 estimate its height and determine with accuracy the direction from which it is moving4 ,there is an average difference of #cj degrees between the cloud direction and the surface wind2 the upper direction being more to the right4 ,at times the directions may be opposite4 ,illustration3 ,,fig4 #d4 ,,apheliotes--,,the ,,east ,,wind ,it may seem surprising but few of us1 except at sunrise and sunset1 really see what is going on in cloud land4 ,some meteorologists hold that the circulation of air #cjjj to #ejjj metres above the ground controls the path and perhaps the intensity of storms4 ,it is therefore important to know something of the flow at high levels if we would improve the forecasts4 ,,limitations ,,of ,,map ,the weather map fails to indicate what shifts of direction and changes in velocity are likely to occur4 ,the forecaster tries to anticipate these1 but he bases his conclusions chiefly upon an expected movement of the low area2 using the accumulated records of the paths of past storms4 ,but each storm is in reality a law unto itself2 and while we know something of the relations between pressure and flow of the air2 as yet we know very little about the relations of wind and weather4 ,the problem is complicated by the behavior of the load of water vapor4 ,illustration3 ,,fig4 #e4 ,,euros--,,the ,,southeast ,,wind ,the ,chief ,forecaster of one of the great national weather services recently wrote3 ,despite the fact that maps have now been drawn day by day for over half a century1 we may safely say that no two maps have been identical4 ,it is perhaps unfortunate that so much attention has been given to the cyclone or depression or ,,low1 and comparatively little to the ,,high or anticyclone4 ,for we are now beginning to understand that while there may seem at first to be nothing specially noteworthy about a mass of air where the pressure varies from #ajbj to #ajdj kilobars1 that is1 #b to #d per cent above a standard atmosphere1 with isobars irregularly curved and feeble surface winds1 yet the anticyclone is more important than the cyclone in determining weather sequence2 for the progressive motion of the cyclone depends largely upon the strength of the anticyclone4 ,,ocean ,,storms ,sir ,napier ,shaw1 who has written much on the weather of the ,british ,isles1 may be quoted here4 ,anyone who is interested in the weather is always on the lookout for 'lows' and is very keen to know whether he is going to be on the south of the centre or the north of it4 ,he is1 of course1 interested in the anticyclone too1 because as long as an anticyclone is there1 there cannot be a depression2 but it is the depression which has the life and movement about it1 giving it a claim to the attention of everybody who wants to know what the weather and its changes are going to be4 ,this has been recognized from the very earliest days of weather maps with isobars4 ,the depressions which pass over our shores 7,great ,britain7 mostly come from the west4 ,some of them come all the way from ,america2 one or two have been traced from the west coast of ,africa and so have crossed the ,atlantic twice1 first to the westward and then to the eastward4 ,some have come all the way from a sort of parent 'low' in the ,north ,pacific ,ocean4 ,so general is the tendency for 'lows' to go eastward that it was thought at one time1 particularly by the ',new ,york ,herald1' that their departure from the ,american ,coast and subsequent arrival on our own shores could be notified by cable1 and we 7the ,british7 might thus be forewarned of their approach1 some three or four days in advance4 ,the attempt was made by the ',new ,york ,herald' acting in co-operation with the ,meteorological ,offices of the ,united ,kingdom and ,france4 ,but a depression keeps to no beaten track2 it has as many paths for its centre as there are lines in a bundle of hay4 ,though groups can be picked out there are many strays1 and1 moreover1 the depression changes its shape and intensity while it travels1 so that if you lose sight of it for a day you cannot be at all sure of its identity4 ,illustration3 ,,fig4 #f4 ,,notos--,,the ,,south ,,wind ,,transcontinental ,,storms ,if there is so much uncertainty in forecasting the path of a disturbance at sea1 how much more uncertain must it be on land8 ,elaborate statistics of the average daily movement of various types of storms have been officially published4 ,the average speed of storms 7not wind speeds7 across the ,united ,states is #aa metres per second or #be miles an hour4 ,storms travel more rapidly in winter than in summer1 about half again as fast2 that is1 summer storms travel #bj miles1 and winter storms #cj miles1 an hour4 ,illustration3 ,,fig4 #g4 ,,lips--,,the ,,southwest ,,wind ,the paths vary widely2 from the ,gulf storms moving northeast and ,west ,indian hurricanes recurving on the southern coast1 to the storms from ,alberta and the west which move south and east4 ,ten types of storms1 classified according to the place of origin1 are recognized by the official forecasters of the ,united ,states4 ,these are ,north ,pacific1 ,alberta1 ,northern ,rocky ,mountain1 ,colorado1 ,central1 ,south ,pacific1 ,texas1 ,east ,gulf1 ,south ,atlantic and ,west ,indian ,hurricanes4 ,a better nomenclature would be 7#a7 ,alberta1 7#b7 ,washington1 7#c7 ,kootenay1 7#d7 ,utah1 7#e7 ,kansas1 7#f7 ,california1 7#g7 ,texas1 7#h7 ,louisiana1 7#i7 ,florida1 and 7#aj7 ,hurricanes4 ,,hurricanes ,type #aj is the general class of tropical storms occurring chiefly in the summer and fall which1 drifting west1 slowly work northward4 ,similar storms are the typhoons and baguios of the ,east ,indian and ,china ,seas4 ,the path and point of recurvature will be determined by the position of the ,bermuda ,hyperbar1 that is1 the seasonal anticyclone of the ,atlantic4 ,this accounts for the swinging east and north of these tracks as the season progresses2 for the hyperbar is slowly displaced east1 the maximum displacement occurring in ,september4 ,illustration3 ,,base ,,map ,,by ,,goode ,,fig4 #h4 ,,all ,,storms ,,lead ,,to ,,new ,,england ,individual anticyclones also influence individual hurricanes4 ,thus a hurricane passing west over ,havana1 will go farther west if a vigorous high is spreading southeast over the ,gulf ,states4 ,and when this high passes seaward1 the hurricane will work around the southwest quadrant of the high1 recurving and moving northeast4 ,,storm ,,rendezvous ,altho storms originate or are first detected in nine different sections1 it is a fact worth mentioning that they all leave the ,united ,states in the vicinity of ,new ,england or ,nova ,scotia4 ,some of the southern depressions starting near the coast1 pass to sea south of ,new ,york1 but in general an observer standing on ,plymouth ,rock can virtually encompass within a radius of #ejj kilometres1 #cjj miles1 the paths of ninety per cent of the storms that traverse the country4 ,thus a storm that originates in ,texas 7#g7 will probably pass close to ,cape ,cod4 ,likewise1 types 7#c7 and 7#e72 while the other types may pass a little to the north or south4 ,see ,chart1 ,paths of ,storms4 ,,storm ,,paths ,forecasting then would seem to be very easy2 for one would only have to know the place of origin of the storm and the rate of travel1 to foretell exactly the time of arrival4 ,unfortunately these are only the average paths2 and as with most mean values1 represent a value not often experienced in fact4 ,these paths then are not paths which any given storm will follow4 ,one must recall the story of the operating surgeon who gave the average age of his patients in the operating room as #ce4 ,there were but two patients1 one #fi years old and the other #a year old4 ,illustration3 ,,fig4 #i4 ,,zephyros--,,the ,,west ,,wind ,as a matter of fact the path of any individual depression depends upon several factors1 some of which are3--the prevailing eastward drift of the air2 the extent and motion of some anticyclone advancing before the ,,low2 the duration and speed of relatively dry cold tongues of air from the north2 and the supply of water vapor brought from southern waters by south winds4 ,a depression can make little headway if to the north or east the normal path is blocked by what is known as a stagnant ,,high4 ,so therefore1 if the anticyclone is a slow mover1 a ,texas storm1 which would normally pass not far from southern ,new ,england1 may be deflected farther north than when the ,,high moved rapidly east4 ,so too1 with the storms which originate in the western part of the country4 ,a slow moving ,,high will prevent the ,,low following it1 from moving east at a normal rate along the usual path4 ,anticyclones then1 are the real weather controls4 ,there are various types1 but all drift from the north or west4 ,occasionally they enter the country from the ,pacific1 but the great majority come from ,alberta and move leisurely southeast1 often reaching the ,south ,atlantic ,states2 but more frequently recurving and passing to the north4 ,,stagnant ,,highs ,,highs are sometimes reinforced and this results in what is called a stagnant ,,high4 ,a good illustration of such a slow moving ,,high and its consequences occurred during the last week of ,january1 #aibb4 ,a surge of cold air from ,alberta or farther north reached the international boundary ,january #bast and spread slowly eastward1 reaching the ,great ,lakes on the #bdth and the ,st4 ,lawrence ,valley two days later4 ,then seemingly it halted or moved slowly westward1 retrograding4 ,in three days1 that is1 on the #bith1 the centre of the ,,high was apparently #ejj miles west of where it had been on the #bgth4 ,after the #bith it followed a normal track1 moving slowly southeast1 reaching the ,atlantic near ,long ,island4 ,meanwhile a depression on the south coast of ,texas on the #beth1 moved across the ,gulf of ,mexico1 passing over ,southern ,florida on the #bgth and advanced steadily northeast1 reaching ,cape ,hatteras in #bd hours4 ,owing to the presence of the anticyclone referred to above1 the depression recurved off ,hatteras4 ,the result was a memorable snow storm in ,northern ,virginia and ,maryland4 ,at #h p4m4 ,january #bgth1 there had been a fall of #e cms4 7#b inches74 ,within the following twenty hours the average depth in the city of ,washington was #ff cms4 7#bf inches74 ,the weight of the snow caused the collapse of the roof of the ,knickerbocker ,theatre and the death of #ig persons4 ,the total snowfall in various coast cities was3 ,raleigh #bd cms499 ,richmond #dh ,washington #ga ,baltimore #fg ,wilmington #df ,philadelphia #ca ,trenton #bg ,new ,york #ah ,new ,haven #h ,boston #a 99,note3 ,to convert to inches multiply by #j4d4 ,the table shows clearly how the snow was formed4 ,on the east side of the ,,low a stream of air1 relatively warm1 carried a load of water vapor1 approximately #ac grams in each cubic metre4 ,illustration3 ,,base ,,map ,,by ,,goode ,,fig4 #aj4 ,,paths ,,of ,,high ,,and ,,low1 ,,great ,,snow ,,storm ,,of ,,january #bg-bh1 #aibb ,this current was steered around the north side of the ,,low and met the north-northeast wind4 ,under the new conditions the air saturated could hold only #b or #c grams2 and so condensation and heavy precipitation resulted4 ,the region of maximum snowfall was near ,washington1 and it will be seen that there is a proportional decrease north and south4 ,the snowfall at ,washington was the heaviest ever known at that city4 ,unlike most storms1 there was no strong cold northwest wind blowing into the depression4 ,the temperature rose slowly4 ,it was less a contrast of winds than a steady slow outward push of the anticyclone1 and the consequent turning of the path of the cyclone eastward4 ,,laws ,,of ,,forecasting ,buys ,ballot's ,law4 ,if you stand with your back to the wind the pressure decreases toward your left1 and increases toward your right4 ,for navigators1 this law is more generally expressed in the words of the ,hydrographic ,office on ,cyclonic ,storms4 ,since the wind circulates counter-clockwise in the northern hemisphere1 the rule in that hemisphere is to face the wind1 and the storm centre will be at the right hand4 ,if the wind traveled in exact circles1 the centre would be eight points 7#ij degrees7 to the right when looking directly in the wind's eye4 ,but the wind follows a more or less spiral path inward which brings the centre from eight to twelve points 7#ij to #ace degrees71 to the right of the wind4 ,the centre will bear more nearly eight points from the direction of the lower clouds than from the surface wind4 ,illustration3 ,,fig4 #aa4 ,,skiron--,,the ,,northwest ,,wind ,the law given on the preceding page is named after ,c4 ,h4 ,d4 ,buys ,ballott1 a ,dutch meteorologist4 ,it was announced in a paper published in the ,comptes rendus in #aheg4 ,two ,american writers on the ,winds1 ,j4 ,h4 ,coffin and ,william ,ferrell1 had however earlier found the law to hold4 99 99 99 99 99 ,while most of us study storms from a window at home and are not called upon to handle a ship in a storm1 yet it may not be out of place to include here the diagram of the winds in an ideal storm and give the rules for maneuvering4 ,see ,figure #ab4 ,the ,winds in an ,idealized ,storm4 ,the rules apply only to storms in the northern hemisphere4 ,right or dangerous semicircle1--,steamers3 ,bring the wind on the starboard bow1 make as much way as possible1 and if obliged to heave-to1 do so head to sea4 ,sailing vessels3 ,keep close-hauled on the starboard tack1 make as much way as possible1 and if obliged to heave-to1 do so on the starboard tack4 ,left or navigable semicircle1--,steam and sailing vessels3 ,bring the wind on the starboard quarter1 note the course and hold it4 ,if obliged to heave-to1 steamers may do so stern to sea2 sailing vessels on the port tack4 ,on the storm track in front of center1--,steam and sailing vessels3 ,bring the wind two points on the starboard quarter1 note the course and hold it1 and run for the left semicircle1 and when in that semicircle manoeuvre as above4 ,on the storm track1 in rear of center1--,avoid the center by the best practicable route1 having due regard to the tendency of cyclones to recurve to the southward and eastward4 ,illustration3 ,,from ,,hydrographic ,,office ,,fig4 #ab4 ,,the ,,winds ,,in ,,an ,,idealized ,,storm ,,wind ,,and ,,altitude ,the law of the turning of the wind with altitude4 ,a casual observation of the lower clouds where no means of measuring small angles is available will not usually show any difference between the motion of the clouds and the surface wind2 but with the upper clouds the case is different1 and one readily detects a difference4 ,several thousand observations with various agencies1 such as kites and pilot balloons and more especially measurements made with theodolites and nephoscopes1 show that there is a definite twist to the right with elevation4 ,the amount of the deflection is shown in ,figure #ac4 ,turning of the ,wind with ,altitude4 ,here the average yearly values are given for directions and velocities4 ,thus if the mean wind direction at ,blue ,hill is from a point a little to the north of west1 #cjf grads or #bge degrees1 and the mean velocity #g metres per second2 the clouds at #ajjj metres elevation will move from #cab or #bhj degrees and at a speed of approximately #aa metres per second 7#bd miles an hour74 ,these however1 are average values4 ,in individual cases the difference between surface winds and stratus clouds may be considerably greater4 ,it may be as much as #ahj degrees2 that is1 the cloud may move directly opposite to the wind4 ,in general there will be a difference of #aj to #bj degrees4 ,,wind ,,and ,,rain ,the law of wind direction1 approximate cooling and rain4 ,when the lower clouds are moving from the north or northwest1 without sharply defined edges1 the ,,low is east or northeast of the observer2 and rain or snow is not likely unless there is a rapidly falling temperature4 ,illustration3 ,,turning ,,of ,,wind ,,with ,,altitude1 ,,blue ,,hill ,,fig4 #ac4 ,,turning ,,of ,,wind ,,with ,,altitude ,when a stream of warm air with a high absolute humidity flows north on the east side of a ,,low1 and a cold northwest wind follows quickly after the ,,low1 rain or snow may be expected4 ,any rapid chilling of warm1 moist air produces cloudiness and rain or snow2 but a cold stream blowing into a warm area will not produce as much rain as a warm stream blowing into a cold area4 ,,duration ,,of ,,wind ,the average duration of wind from various directions is as follows3 ,from the north about #af hours each week2 from the northeast1 the same2 from the east1 #aa hours2 from the southeast1 #aj hours2 from the south1 #bd hours2 from the southwest1 #bg hours2 from the west1 #cc hours2 and from the northwest #ca hours4 ,during an individual disturbance lasting about #cf hours1 we may have #h hours of southwest wind2 #d hours of west wind1 backing during the next #d hours to south2 #b hours of south wind2 #b hours of southeast wind2 #b hours of east wind2 #h hours northeast wind and #d hours north wind1 #b hours northwest1 when it may be considered that a new pressure distribution prevails4 ,the above values hold only for a storm moving with normal velocity4 ,,lows are often blocked by slow moving ,,highs in advance4 ,in such cases the duration of east winds is greater4 ,,the ,,winds ,,of ,a ,,year ,the following table shows the marked increase in the prevalence of northwest and west winds during winter months1 the decrease in north winds during ,july1 the increase in northeast winds in ,may1 also in east winds2 the increase of south and southwest winds in ,july2 and the falling off of southeast winds in ,december4 ,see ,table1 page #gb4 ,in cities near the ,atlantic ,coast1 a continuance of northeast wind1 especially in the fall and winter months1 results in frequent altho not necessarily heavy rains4 ,on the other hand a period of continued northwest and west wind is a dry period4 ,in summer1 southeast and east winds bring fog and cooler weather2 while southwest winds are favorable for the development of thunderstorms4 ,,winds ,,of ,a ,,year ,,table ,i4--,number of ,hours the ,wind ,blows from ,different ,directions4 ---------------------------------------- ---------------------------- ,jan4 ,mar4 ,may ,july ,sept4 ,nov4 ,year ,feb4 ,apr4 ,june ,aug4 ,oct4 ,dec4 ,boreas 7,n7 #ih #gd #ga #gj #fj #dj #ei #ei #fg #hj #hb #if #hej ,kaikias 7,,ne7 #da #df #fe #id #aja #ee #gi #gi #gg #ia #dh #cj #hai ,apheliotes 7,e7 #cd #cg #eb #eh #fc #dh #ea #ea #eb #eh #cd #ca #egf ,euros 7,,se7 #cg #cg #de #da #ed #de #fb #fb #eb #de #ci #cd #ecd ,notus 7,s7 #hb #ff #ie #ii #adc #aee #abh #abh #aah #ic #ha #fe #abde ,lips 7,,sw7 #aab #gg #ha #gi #aah #agj #ace #ace #acc #ajh #aai #aca #adjb ,zephyros 7,w7 #ahj #agg #aee #abe #ajg #acg #abe #abe #ajh #aca #afi #aid #agcb ,skiron 7,,nw7 #afj #afb #ahc #aed #ih #id #aje #aje #aac #ach #adh #afc #afjg ---------------------------------------- ---------------------------- ,illustration3 ,,fig4 #ad4 ,,velocity ,,of ,,summer ,,and ,,winter ,,winds ,,in ,,metres ,,per ,,second ,,the ,,sea ,,breeze ,when the weather has been clear and moderately warm for two or more days1 and the winds are light and variable1 there may occur on the third day a moderate wind from the east1 known as the sea-breeze4 ,this occurs during anticyclonic conditions4 ,preceding the sea-breeze1 the winds are very light1 there are no clouds1 and the temperature rises rapidly during the forenoon4 ,this heating is due to a slow dynamic compression as the air slowly descends and the surface air does not flow away4 ,there is no cooling because there is no evaporation due to air movement4 ,the absolute humidity is low1 often less than ten grams per cubic metre4 ,cumulus clouds do not form because there is no uplift of the lower air and consequently no chance for condensation of whatever water vapor may be present4 ,no thunder-heads form notwithstanding the heat4 ,the heat1 while dry1 is nevertheless extremely trying to men and animals4 ,relief comes in the early hours of the afternoon by the arrival of the sea-breeze4 ,the usual explanation of the origin of the sea-breeze is that the land being excessively warm1 the air over a relatively cool ocean moves in to take the place of the warm and therefore lighter air1 which it is assumed has risen4 ,unfortunately for this explanation1 the air over the land has not risen2 but on the contrary is falling slowly4 ,again the sea-breeze does not begin at the place where the temperature contrast is greatest1 namely1 just inside the shore line2 but comes in from the sea4 ,nor does the flow extend far inland1 which would be the case if there were up-rising currents4 ,the sea-breeze is very shallow1 generally not extending upward more than #bjj metres1 and often not above #ajj metres4 ,it does not penetrate far inland1 as a rule not more than #ae kilometres1 #i miles4 ,the sea-breeze is probably caused by a slow descent of dry1 warm air1 on an incline sloping from northeast to southwest4 ,as it reaches the surface it is twisted more to the right2 that is1 becomes an east wind4 ,it carries inland with it some of the air over the ocean which is much cooler and heavily saturated4 ,,muggy ,,days ,there are certain days1 more noticeable in summer than at other times1 when the air is heavily laden with water vapor2 and there is little or no cooling of the body due to evaporation4 ,we perspire freely but as the sweat does not evaporate1 there is a constantly increasing amount of water on the skin4 ,illustration3 ,,fig4 #ae4 ,,blue ,,hill ,,observatory ,,during ,,ice ,,storm1 ,,november #bi-cj1 #aibb ,it is not altogether a question of temperature1 for another day may have as high or even higher temperature4 ,it is essentially a matter of ventilation4 ,on muggy days we are somewhat in the condition of the unfortunate prisoners in the ,black ,hole at ,calcutta4 ,they did not die by poisoning1 as has generally been accepted1 that is1 lack of sufficient oxygen and an excess of carbon dioxide2 but because they were unable to keep the skin sufficiently cool4 ,there was no ventilation2 no movement of the air and the body became over-heated and exhaustion followed4 ,no matter how much water there may be on the skin if the surrounding space is saturated1 one feels oppressed4 ,a vigorous fanning of the air helps evaporation and cools us4 ,that is why a brisk northwest wind routs a muggy condition4 ,,castilian ,,days ,john ,hay wrote of such days spent in ,spain4 ,we who live in a land where the winds are more boisterous1 occasionally experience what we call a perfect day4 ,such days have easterly winds of two metres per second or less than five miles an hour4 ,the temperature is midway between freezing and normal body temperature or about #gj deg4 ,f4 ,the relative humidity is approximately #ge and the absolute humidity #ab grams per cubic metre4 ,the table on page #gb explains the paucity of perfect days4 ,the gusty1 boisterous winds1 ,skiron and ,zephyros1 blow too frequently4 ,perhaps certain of our national characteristics may be traceable to this flow of the air and our climatic environment4