Air Masses and Fronts/Severe Weather

Doppler radar maps

Show location, intensity, and the movement of precipitation.

satellite maps

Show clouds and cloud movement. Satellite maps can also show temperature, humidity, and wind speeds at various altitudes.

NWS

National Weather Service - a governmental agency that supplies us with weather data and maps.

NOAA

National Oceanic and Atmospheric Administration: a governmental agency that supplies us with weather data and maps.

isobar

Lines that connect points of equal air pressure. It comes from the latin words "isos" and "baros" that mean "equal weight".

air mass

A large body of air that has similar temperatures and moisture throughout.

continental

An air mass that is dry because it forms over land.

maritime

An air mass that is wet/moist because it forms over water.

tropical

An air mass that is warm because it forms from areas that are always warm.

polar

An air mass that is cold because it forms from areas that are always cold.

front

It is the boundary that forms between two different air masses.

These occur in the middle latitudes because there are both warm and cold air masses there.

warm front

The warm air mass overtakes the cold air mass because the warm, less dense air moves over the cold air and gradually replaces it.

This brings drizzly precipitation

It is clear and warm when it is gone.

cold front

The cold, more dense air moves under the warm air mass and pushes it up.

This moves fast and it brings thunderstorms, heavy rain, or snow.

Cold weather follows a cold front.

occluded front

A faster moving cold air mass overtakes a slower moving warm air mass and forces the warm air mass up. The cold air mass continues until it meets another cold air mass that is warmer.

The cold air mass then forces this air mass to rise. (A warm air mass sandwich)

Has cool temperatures and large amounts of precipitation.

stationary front

Cold air mass meets a warm air mass and does not move much.

Weather similar to a warm front (drizzly precipitation).

thunderstorms

They are small, intense weather systems with strong winds, heavy rain, and lightning and thunder. They occur along cold fronts.

2 things necessary for thunderstorm to form

1.the air near the Earth's surface must be warm and moist.

2.The atmosphere must be unstable

(•The air surrounding the rising warm air mass is colder.

•This causes the warm air to rise rapidly.)

lightning

Is a large electrical discharge between two oppositely charged surfaces. It can occur from cloud to cloud or cloud to ground.

thunder

Is the sound that results from the rapid expansion of air along the lightning strike. This happens because of the extreme heat from the lightning (30,000o C or about 60,000o F).

tornado

Is a small, rotating column of air that forms during thunderstorms.

75 % of a all tornadoes occur in the U.S. The U.S. averages around 1,000 tornadoes per year.

tornado formation

Wind travels in two different directions.

The air between begins to roll.

The "roll" turns vertically and begins to rotate because of the updrafts.

It turns into a funnel and touches the ground.

vortex

The center of a tornado.

waterspouts

Tornadoes that form over water.

Tornado Alley

An area east of the Rocky Mountains. It is mainly in Texas, Oklahoma, and Kansas that experiences the highest number of tornadoes per year.

This happens because the cool dry air (north) meets warm moist air (south).

Fujita Scale

The scale used to measure tornadoes. The scale goes from the lowest, F0, to the highest, F6. A F6 has never happened.

Hurricane

A storm spinning counterclockwise with winds greater than or equal to 74 mph.

eye

The calm, low pressure center of a hurricane .

eye wall

The area surrounding the eye. It is dense and the strongest and most intense part of a hurricane.

rain bands

The spiral bands of clouds surrounding the eye wall. The largest part of a hurricane.

storm surge

A large surge of water near the coast. This causes the most damage.

Saffir Simpson Scale

The scale used to measure a hurricane's wind intensity.

tropical storm

A storm spinning counterclockwise with winds between 39 and 73 mph.

tropical depression

A storm spinning counterclockwise with winds less than 39 mph.