Clouds and Weather (1939)

full and inspiring objects of nature but clouds and cloud forms may have a practical value as well well they should study of cloud changes loud as weather sign changes in weather and clouds are caused by the passage of the different air masses in wind systems called cyclones this true cyclone not a tornado is a great counter clockwise wind system perhaps 2,000 monde I am atrophies about 600 miles a day the center of the advancing world is an area of low barometric pressure between areas of higher pressure we have cold air east north and northwest of the center with a warm sector to the south a warm front with easterly then southerly winds beyond the warm sector a cold front where south winds ships to northerly where warm moist air overrides cold air there is precipitation rain or snow now along a line cuts through the center of the cyclone let's watch these fronts go by starting where the air pressure is high let us watch for three or four days while a cyclone patties think of the space above this imaginary warm front line is filled with a mass of advancing warm air flowing up over a dome or ridge of heavier cold air this warm air is more and as it is listed and cooled different cloud forms develop at different altitudes as the warm front of the Earth's surface approaches there is rain or snow this precipitation is generally steady and light to moderate fair weather follows as we enter the warm sector here warm air ascends and presently clouds begin to form as the weather grows warmer these clouds grow heavier and as the cold front approaches they become dense and threatening breaking in heavy rain as the cold front passes this is the so called squall line these cloud tend to dissipate as the northwest winds bring in cold air and finally we're back where we started in a high-pressure area so much for the phases of the typical weather cycles which is most pronounced in winter less so in spring and fall and often interrupted in summer now let's study the cloud types that usually mark the progress of such a cycle starting after the passing of the cold front we have cirrus clouds sometimes called mares tails these wispy clouds of ice particles are the highest of all floating at an elevation of 25 to 30,000 feet above the earth the wind is from the northwest the parameter which tells air pressure is high temperature cools cirrus clouds may be followed by cirrostratus which may merge into civil cumulus sometimes called mackerel sky next not quite so high we may have altocumulus clouds meanwhile the wind is northerly temperature cool barometer still high next we find Alto stratus clouds not so high generally with northeast winds falling barometers and steady or slowly rising temperature as the warm front approaches the wind swings to the east with nimbus clouds and rain or snow as the warm front passes the wind bears to a southerly direction shifts in wind indicate what part of the cyclone we are entering then the sky clears and we have fair and warm weather for perhaps a day with southwest winds and steady or slowly falling barometers scattered cumulus clouds appear at an altitude of 5000 feet or more gradually becoming heavier as the temperature rises as the cold front approaches the cloud's often rise suddenly into threatening Thunderhead mountains of cumulonimbus clouds towering to a height of possibly 30,000 feet as the tip of the sloping cold front passes nimbus clouds form at the base of the cumulonimbus storm clouds and heavy showers occur these are normally briefs but violent rainstorm the temperature falls abruptly while the cold front is passing the wind shifts to the northwest the barometer rises and we may have a rainbow soon thereafter the storm clouds give way to fractal cumulus clouds which rapidly blow away the squeak sector of fair and cool weather and the cycle is complete so you see clouds have a story