a large body of air that has the same temperature and humidity throughout classified according to where they originate during the time the air mass.

•a large body of air that has the same temperature and humidity throughout

•classified according to where they originate

•during the time the air mass is over an area, it determines the weather of that area

Originates over the ocean

humid air mass (m) (maritime)

Originates over the land

dry air mass (c) (continental)

Originates in cold air

cool air mass (P) (Polar)

Originates in warm air

warm air mass (T) (Tropical)

Maritime Tropical Atlantic (mT)

•moves northward across eastern US

•brings mild, cloudy winters and hot humid summers with hurricanes and thunderstorms

small balloon carried observatory that carries a radio transmitter that sends out signals about air pressure, temperature, and humidity

fronts: boundary between two air masses having different temperatures and humidity

•warm air overtakes cool air

•warm air rises

•brings hot, humid days and precipitation over a large area

•cold air overtakes warm air

•cold air forces warm air up

•brings strong storms (squall) with clear days following

•two cold masses sandwich a warm mass

•warm air rises between them

•brings strong winds and heavy rains

•does not move

•small-area storms formed by the strong upward movement of warm, moist, unstable air

•always accompanied by lightning, thunder, and usually rain

•formed from cumulonimbus clouds

Air-mass thunderstorm:

•form in warm, moist air mass

•occur in spring and summer- last less than 1 hour

•single, widely scattered

Frontal thunderstorm:

•occur in lines along a frontal surface

•stronger and may last several hours

•can produce heavy rain and flooding

Lightning:

•a discharge of electricity from a thundercloud to the ground, or cloud to cloud, or ground to cloud

•temperature inside lightning flash can reach 28,000°C

•at this temperature, air expands explosively-sudden expansion makes thunder!

an intense tropical low-pressure area with sustained winds starting at 75 mph

storm surge: currents formed when hurricanes pile water up along the shore and blow it inland

most damaging part of a hurricane

eye: central area of sinking air; 15 to 20 km wide

Eye of hurricane Floyd

•Winds most violent just outside the eye

http://www.weather.com/web/newscenter/specialreports/hurricanes/inside/elements.html

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Tropical depression: wind speeds up to 38 mph; some circular rotation at surface

Tropical storm: wind speeds from 39-74 mph; can be named, shows drop in pressure, distinct rotation

Hurricane: wind speeds up to 75 mph

Movement of Air in a Hurricane

There are sometimes gaps in between these bands where no rain is found. In fact, if one were to travel between the outer edge of the hurricane to its center, one would normally progress from light rain to dry back to slightly more intense rain again over and over with each period of rainfall being more intense and lasting longer until reaching the eye. Upon exiting the eye and moving towards the edge of the hurricane, one would see the same events as they did going in, but in opposite order.

A schematic of this banding feature can be seen in the diagram above. The thunderstorms are now organized into regions of rising and sinking air. Most of the air is rising, but there is a small amount found in between the thunderstorms that is sinking.

a narrow, funnel-shaped column of spiral winds that extends downward from the cloud base and touches the ground

•strongest winds between 360 and 500 km/hr

•funnel less than 500 m across

•always travel with a parent thunderstorm at speeds ranging from 40 to 65 km/hr

funnel is a mixture of clouds and dust

pressure gets lower in center

air flows toward the funnel and cools to dew point- drops form

lowering of condensation level due to low pressure causes cloud to funnel Extremely low

pressure-when it touches ground, acts like a giant vacuum

Waterspout: tornados over the water- weaker than tornados

Tornados usually occur during spring and summer and most likely occur in late afternoon

Fujita Scale: scale used for categorizing tornados

Meteorologists interpret weather information from:

satellites

commercial aircraft

weather balloons

weather stations around the world

Radar: electronic device that transmits radio waves in the form of a beam

Data is collected and put into a central computer at the National Weather Service

•data includes: winds, temperature, pressure, humidity, clouds, precipitation

•Makes a computer model (copy of the atmosphere in computer

•Maps are made and forecasts are reported to local stations across the country

•Weather forecasts are issued by the Weather Service at 10 am, 4 pm, 9pm, and 4 am. Forecasts are updated more often during severe weather.

watch: threat of storm conditions within 24-36 hours

warning: due to strike within 24 hours