Latitude What is Latitude? Lines of Latitude run horizontally Latitude is measured in degrees. The Equator is 0 degrees Latitude. Lines of Latitude locate places North or South of the Equator. The North Pole is 90 degrees N Latitude, and the South Pole is 90 degrees S Latitude.

Air generally moves from the poles to the equator, this is because air flows from high pressure to low pressure High pressure forms when cold air sinks (at the poles) Low pressure forms when warm air rises (at the equator) But the air doesn’t flow in a straight line

Does the Earth rotate at the same velocity at all points?

https://youtu.be/dt_XJp77-mk https://youtu.be/i2mec3vgeaI Coriolis Effect A phenomenon that causes fluids like, water and air, to curve as they travel across and above Earth’s surface. It is caused by the Earth spinning on its axis This is the reason hurricanes and tornadoes spin counter clockwise in the Northern hemisphere. https://youtu.be/dt_XJp77-mk https://youtu.be/i2mec3vgeaI

As warm, moist air rises, it creates a zone of low pressure, clouds, and precipitation along the equator. 

Jet Streams Narrow ‘rivers’ of air that form about 7 miles above the surface of Earth Typically occur more in the winter when temperatures are more varied The larger the differences in temperature, the faster the wind speed

Planetary winds blow across the entire planet blow at the same speed and direction Some are high in the atmosphere and you cannot feel them on the ground Each hemisphere contains 3 wind belts: Trade winds, Westerlies, and Easterlies

This air flowing back towards the equator produces what are known as the trade winds. Located between 0-30º north and south Called trade winds because many European sailors used these winds for trade The area near the equator where these winds die out is referred to as the doldrums. In the Northern hemisphere they are the Northeast Trade Winds and in the Southern hemisphere they are called the Southeast Trade Winds. Trade Winds Doldrums

The air cools and sinks back down to the surface at about 30°north and south of the equator.  This sinking air produces areas of higher pressure with drier conditions. 30 degrees- sinking air High Pressure Sahara Desert, New Mexico, Arizona, Southern California, etc.

Horse Latitudes The Horse Latitudes lie between 30° and 35° They are known for variable wind mixed with calm

Winds traveling along the surface of the earth from 30 - 60 degrees north and south of the equator are called WESTERLIES. They flow from the west to the east.

The air currents moving from the poles at 90°to 60° north and south of the equator, flow from east to west and are referred to as Polar Easterlies. High pressure over the poles (caused by the sinking cold dense air) causes the air to blow away from the poles toward 60º latitude

Planetary Wind Shift Because the Earth goes through seasons throughout the year, the wind belts can shift slightly But the average shift is only about 10º

Local Winds These winds blow over small areas Unlike planetary winds, local winds can change speed and direction frequently These are the winds we feel on the ground They are influenced by local conditions and local temperature variations

Sea and land breezes are examples of local wind.

Fronts A boundary between two air masses of different density, moisture, or temperature.

Cold Front – a cold air mass replacing a warm air mass When a cold front passes through, temperatures can drop more than 15 degrees within the first hour. Cold fronts generally move from northwest to southeast. The air behind a cold front is noticeably colder and drier than the air ahead of it.

Warm Front When a warm front passes through, the air becomes noticeably warmer and more humid than it was before. A warm air mass is replacing a cold air mass. Generally move from SE to NW . The air is generally warmer and more moist than the air preceding it.

Stationary Front – a front that is not moving When a warm or cold front stops moving, it becomes a stationary front. Once this boundary resumes its forward motion, it once again becomes a warm front or cold front.

Occluded Front – when a cold front takes over a warm front A cold front essentially wraps around a warm front and typically forms a tornado. The warm, humid air rises while the cold front that has wrapped around moves toward the ground. Symbolically, an occluded front is represented by a solid line with alternating triangles and circles pointing the direction the front is moving. .

https://youtu.be/7KDz6dGQ5RE Tornado Alley https://youtu.be/7KDz6dGQ5RE

Fujiti Scale

DAMAGING WINDS Damage from a tornado Damage from a downburst

Jarrell, TX — May 27, 1997

Severe Weather Safety Watches- conditions are favorable Warnings- conditions already exist Examples- Tornadoes, Flooding, Thunderstorms, Blizzards, Winter Mixes and Hurricanes

Severe Weather

Flooding For each foot of rising water, a car weighs 1500 pounds less! As little as 18 inches of water can float a truck! It takes only 12 to 14 inches of water to float a car!

https://youtu.be/k35Gwb0FFU0 Hurricane https://youtu.be/k35Gwb0FFU0

Hurricane Scale

Hurricane vs Tornado https://youtu.be/W0LskBe_QfA

Dry Line is a moisture boundary. A dry line is a boundary that separates a moist air mass from a dry air mass.

Air Mass Map

Weather Front Worksheet