Let's Learn To Predict The Weather (1962)

[Music] what kind of weather is coming you've probably asked yourself that question many times have you ever tried to predict the weather perhaps your grandparents can remember when people depended on weather sayings to help them predict the weather from experience they had learned that a ring around the sun or moon usually meant that rain is coming soon they also relied on the old Rhymes rainbow in the morning sailor take warning but weather sayings didn't explain why weather changes took place we know that weather changes may happen within a few hours or a day or two to help us try to predict the weather we're going to make use of weather facts about clouds winds and air pressure let's think first about air pressure air pressure is caused by the weight of the air above you we measure air pressure with this kind of instrument called a barometer we can show how this barometer works by looking inside it here is the inside of the barometer under the pointer we can see the metal Bellows as as the air pressure changes it pushes on the Bellows with more or less Force this makes the pointer move showing the air pressure on a dial now let's do an experiment to show how a barometer indicates air pressure by pumping air into this jar we can increase the air pressure in it air is blowing out of this tube as the air pressure in increases in the jar the pointer on the barometer moves to the right now the pump is drawing air into the tube so that we can take air out of the jar the air pressure inside the jar is going down the pointer moves to the left when the air pressure is falling here is another type of barometer that draws a graph of changing air pressure let's see the graph this barometer made during a change in weather that took several hours this graph shows that the air pressure dropped and then rose again the sky was clear when the pressure was highest and the day was cool but dark clouds appeared in the sky about the same time that the air pressure began to drop it was quite low just before rain began to fall but shortly before the rain ended the air pressure began to rise a rising barometer usually indicates that Skies will soon be clearing because the air pressure is not Rising as high as it was before this is a sign that warm air is replacing the cool air warm air weighs less than cool air and so exerts less pressure so you can see how observing changes in air pressure can help you predict the weather now let's see how winds help us predict the weather cold winds often come from the north as this air moves South it brings cold weather and often snow or rain because air is usually warm that comes from the tropical regions of the South Winds from the south often bring warm weather especially in summer when warm moist air meets cool air clouds will form and Rain may fall when one kind of air is in contact with another kind of air and replacing it the wind may change direction over a period of a few hours when such changes occur you can suspect that a storm is on its way winds indicate many things about weather to come now let's see how clouds can help you predict tomorrow's weather these high curly clouds are called cirrus clouds cirrus clouds are made of ice crystals and are about 4 to 8 Mi above you lower clouds that form in layers are called stus clouds Straus clouds are formed when moisture in a whole layer of air changes into clouds these heaped up clouds that look like puffy rolls of cotton are cumulus clouds cumulus clouds form when air currents rise rapidly and cool by expansion then the moisture in them changes into clouds if more and more moisture gathers in the white cumulus clouds they may grow into large dark cumulon nimbus clouds that are sometimes called thunderheads these towering clouds can bring severe thunderstorms this rain is falling from a Nimbo stus cloud above this town it is a type of strus cloud in which more and more moisture gathered until it began falling out as rain Nimbo Straus clouds and cumulonimbus clouds are rain clouds recognizing the different types of clouds can also help you predict the weather this is because clouds usually go over us in a certain order when certain kinds of weather changes are taking place for example suppose where you are the weather weather is cool but warm air is pushing away the cool air what kinds of clouds would you expect to see suppose you were right here looking up at the clouds passing by first you would see feathery cirrus clouds over you next come seratus clouds these are high thin clouds made of ice crystals they are the clouds that produce the ring around the Moon and Sun as the air keeps moving over you you see lower Straus clouds and soon a light rain might Begin to Fall usually Nimbo stratus clouds come overhead next it is from these Nimbo stratus clouds that heavy rains can fall when the rain is over you can expect fluffy cumulus clouds to appear soon as air is heated by the ground and air currents rise and and cool now the warmer air has pushed away the cooler air let's see what the order of clouds is when dry cool air pushes aside moist warm air again where the two kinds of air meet clouds have formed as the warm air is pushed aside by the cooler air first you see feathery cirrus clouds you can't tell whether warmer or cooler weather is coming yet but when you next see the high cumulus clouds and then the Towering thunderheads you know that cool air is pushing aside the warm air the thunderheads cumulonimbus clouds can be expected to bring heavy rains and thunderstorms when the clouds pass by and the rain is over fluffy cumulus clouds appear again now the weather is cooler because cool air has pushed away all the warmer air Now by putting together what you know of clouds winds and air pressure you can try to predict the weather suppose the day is fair with a few low cumulus clouds in the sky the the wind is from the Northwest air from that direction is usually dry and cool the barometer is steady or perhaps Rising with these conditions You can predict that fair weather will continue suppose on a warm day you see high clouds far to the Northwest slowly moving toward you and they are cumulus clouds the kind that form when cool air replaces warm air the wind where you are is blowing from the southwest this is almost opposite to the direction of the cloud movement remember winds change direction when one kind of air meets and replaces another you notice the barometer is falling a sign that a storm is coming now you can predict that it is probably going to rain as the cool air from the north meets and replaces the warm moist air from the South in this way you can try to predict the weather then it might be fun to compare your prediction with predictions that are made at the weather bureau by meteorologists who study the weather although there are many factors that affect the weather you will find that the more you know and understand about changing air pressure winds and clouds the better you will be able to predict the weather