Wind

How Wind blows 

 Air is constantly on the move. Warm air rises and cold air moves down. This movement of air from a high pressure area to a low pressure area causes the wind to blow. 

Wind

 

 

 

  Effect of pressure on wind

 The greater the difference  in pressure between the two areas, the fiercer the wind will be. 

Role of sun in wind blowing

The sun plays a very vital role in these movements. The sun heats the the earth unevenly. For example, the equator is always very hot because the sun's rays shine directly down at it. However, the sun rays hit the remainder of the earth at varying degrees or angles.

Coriolis force

Because the earth rotates from west to east, winds blowing toward the equator have a tendency to curve toward the east. This is known as Coriolis force.

Wind belts

Due to this force, the general circulation of the atmosphere is made up of winds that go around the earth in wind bands called wind belts. There are six of these wind belts. "Wind is the movement of air over the earth's surface". Wind can blow slowly and gently or it may blow so hard and fast that it smashes buildings and pushes over large trees.

 Wind as a part of weather

 Local winds arise only in specific areas on the earth. For instance, Chinooks are warm winds that blow down the side of a mountain. In Alberta, Canada, a Chinook can raise the temperature by 20°C (36°F) in just a few minutes.

Witch's wind

 In Southern California in the United States, there is a hot dry wind called the witch's wind, or Santa Ana, which can keep brush fires burning for days. 

Haboob wind

In the Sudan, there is a strong wind called the haboob which whips up sandstorms. 

Willy Willy wind Horricane

In Australia there is a hurricane called the willy-willy. In the kite shapes which follow are names of more local winds as well as other words related to the wind. 

Horrican

 

 

 

 

Wind and Temperature

 When the air around us alters from cold to hot and vice versa the air moves and this movement is called the wind. Very often on a cold, blustery winter's day, we hear the weather forecaster make mention of the wind chill factor. What does it mean? What actually happens is that the air temperature and the wind combine to make the air feel colder than the actual temperature reading. As an example, if the outside temperature was -10°C (14°F) and the wind speed was 20 kmh (12 mph) the wind chill would make it feel like the temperature was -19°C (-1°F).

Beaufort wind scale

 In 1805 an Englishman named Sir Francis Beaufort devised the Beaufort wind scale. The scale is a series of numbers ranging from 0 to 17 that are used to indicate wind speeds. 

Wind speed

Wind speed is a feature of wind that is used in forecasting weather. In most countries, including Canada, wind speeds are measured in kilometres per hour while in the United States they are stated in miles per hour. 

Effect of wind on weather

Winds effect our weather a great deal. If you watch a flag blowing in the breeze you can judge from which direction the wind is blowing. North winds are cold while south winds usually mean warm weather. East winds often mean a cloudy day is in store. West winds are usually warm and we can be somewhat certain of blue skies. The flags that follow are all blowing toward the west. Wind is moving air. Strong winds are fast-moving air; gentle breezes are air that moves slowly. Air moves because the Sun warms some places more than others, creating differences in air pressure. Warmth makes air expand and rise, lowering air pressure. Cold makes air heavier, raising pressure. Winds blow from areas of high pressure to areas of low pressure, which are called lows. The sharper the pressure difference the stronger the winds blow. 

Winds in Northern Hemisphere

In the Northern Hemisphere, winds spiral in a clockwise direction out of highs, and anticlockwise into lows.

Winds in Southern Hemisphere

 In the Southern Hemisphere, the reverse is true. A prevailing wind is a wind that blows frequently from the same direction. Winds are named by the direction they blow from. For instance a westerly wind blows from the west.

Winds in tropics

 In the tropics the prevailing winds are warm, dry winds. They blow from the northeast and the southeast towards the Equator. In the mid-latitudes the prevailing winds are warm, moist westerlies. 

Tornadoes

Tornadoes, or twisters, are long funnels of violently spiralling winds beneath thunderclouds. Tornadoes roar past in just a few minutes, but they can cause severe damage. Wind speeds inside tornadoes are difficult to measure, Supercell cloud but they are believed to be over 400 km/h. 

Thunder clouds

Tornadoes develop beneath huge thunderclouds, called supercells, which occur along cold fronts. England has more tornadoes per square kilometre than any other country, but they are usually mild. 

Tornado Alley in Kansas

 Tornado Alley in Kansas, USA, has 1000 tornadoes a year. Some of them are immensely powerful. cloud base Tornadoes are especially destructive in central USA but they can occur wherever there are thunderstorms. 

Origin of  Tornado

A tornado starts deep inside a thundercloud, where a column of strongly rising warm air is set spinning by high winds roaring through the cloud’s top. As air is sucked into this column, or mesocyclone, it corkscrews down to the ground. 

 Incredible tornado

A tornado may be rated on the Fujita scale, from gale tornado inconceivable tornado.
 An incredible tornado can lift a house and carry a bus hundreds of metres. In 1990 a Kansas tornado lifted an 88-car train from the track and then dropped it in piles four cars high. In 1879, a Kansas tornado destroyed an ron bridge and sucked up a river beneath it. 

Hurricanes 

Hurricanes are powerful, whirling tropical storms. They are also called willy- willies, cyclones or typhoons.  Hurricanes develop in late summer as clusters of thunderstorms build up over warm seas (at least 27°C).  As hurricanes grow, they tighten into a spiral with a calm ring of low pressure called the ‘eye’ at the centre.  Hurricanes move westwards at about 20 km/h. They strike east coasts, bringing torrential rain and winds gusting up to 360 km/h.  Officially a hurricane is a storm with winds exceeding 119 km/h.  Hurricanes last, on average, 3-14 days. They die out as they move towards the Poles into cooler air. 
 Each hurricane is given a name in alphabetical order each year, from a list issued by the World Meteorological Organization. The first storm of the year might be, for instance,  A satellite view of a hurricane approaching Florida, USA. Notice the yellow eye in the centre of the storm. Hurricane Andrew.  The most fatal cyclone ever was the one that struck Bangladesh in 1970. 
It killed 266,000 with the flood from the storm surge - the rapid rise in sea level created as winds drive ocean waters ashore.  A hurricane generates the same energy every second as a small hydrogen bomb. Each year 35 tropical storms reach hurricane status in the Atlantic Ocean, and 85 around the world.