Meterology

Air Mass

A large body of air with generally uniform temperature and humidity.

Continental Air Masses

Air masses that originate over land and are dry.

Maritime Air Masses

Air masses that originate over oceans and are moist.

Arctic Air Masses

Air masses that originate from the arctic or antarctic and are very cold.

Polar Air Masses

Air masses that originate over high latitudes of both land and sea and are not as cold as arctic air masses.

Tropical Air Masses

Air masses that originate over the lower latitudes of both land and sea and are warm and hot.

Front

The boundary between two air masses that meet but do not mix.

Warm Front

Occurs when a warm air mass approaches a cold air mass and gradually climbs up and over it, resulting in cloudy weather with gentle steady rain.

Cold Front

Occurs when a cold air mass approaches a warm air mass, shoving the warm air up and out of the way, resulting in thunderstorms or heavy rain.

Stationary Front

Occurs when both a warm and cold air mass approach each other and stop moving, resulting in rain along the entire front.

Occluded Front

Occurs when a cold front advances and overtakes a warm front, resulting in strong wind, heavy rain, and tornadoes.

Isolines

Lines drawn on a map connecting data points of the same value.

Isotherms

Lines connecting points of equal temperature.

Isobars

Lines connecting points of equal air pressure.

Wind speeds

Wind speeds are faster when the isobars are closer.

Air Pressure

Air moves from areas of high pressure to low pressure.

High Pressure Systems

Wind moves clockwise and out due to the Coriolis effect/forces, cooler air temp, rising pressure, clear, nice weather.

Low Pressure Systems

Wind moves counterclockwise and in due to the Coriolis effect/force, warmer air temp, falling pressure, poor, humid weather.

Coriolis Effect

As the Earth spins, it causes the wind and waters to deflect; Northern hemisphere - deflects right, Southern hemisphere - deflects left.

Hurricanes

Location - over water; Duration - Days to weeks; Damage - Heavy rain, flooding, wind; Pressure - Low pressure; Peak season - June-November; Warning times - days to weeks in advance; Wind Speed - 74-157+ mph; Most affected areas - coastal states; Category system - Saffir Simpson; Call Typhoons in India and w. Pacific oceans; Hurricanes are named.

Tornadoes

Location - over land (most form when cool and warm air collide); Duration - Minutes, up to an hour; Damage - Strong winds, thunderstorms, hail; Pressure - Low pressure; Peak season - March - July; Warning times - Little to no warning; Wind Speed - up to 300 mph+; Most affected areas - Midwest/interior states; Category system - Enhanced Fujita Scale; Tornadoes are not named.

Relative Humidity

Relative Humidity - the amount of water vapor in the atmosphere compared to the amount of water vapor the air could hold.

Saturated Air

When the air is holding as much moisture as it can, it's said to be saturated. Condensation will occur at 100% relative humidity.

Units of Relative Humidity

Units - Percentage.

Dewpoint

Dewpoint - the temperature at which relative humidity is 100%. Condensation must occur.

Examples of Dewpoint

Examples - Morning Dew, Frost, Clouds - water vapor on cloud condensation nuclei.

Temperature and Dewpoint Relationship

The closer the temperature and dewpoint, the higher the relative humidity.

Units of Dewpoint

Units - Celsius (C) and Fahrenheit (F).

Finding Relative Humidity and Dewpoint

Measured using a Sling Psychrometer.

Dry Bulb Temperature

Dry Bulb Temperature = air temperature.

Wet Bulb Temperature

Wet Bulb Temperature = how much evaporation occurred.

Wet Bulb Depression

Wet Bulb Depression = the difference between dry and wet bulb temperatures.

Use of Wet Bulb Temperature

Dry Bulb temperature and Wet Bulb Depressions are used to determine relative humidity and dew point - chart.

Station Models

A station model is a representation of all the different parts of weather over a location.

Barometric Pressure

Barometric pressure is expressed in 'shorthand' millibars.

Air Pressure

This location's air pressure is currently 1019.6mb.

Wind Direction

Where the wind comes from, expressed by the direction the staff is pointing.

Wind Speed

How fast the wind is blowing, expressed in knots.

Wind Speed Measurement

Each full feather is 10 knots, each half feather is 5 knots, and each triangle is 50 knots.

Current Wind Speed

This location's wind speed is 15 knots.

Cloud Formation

Clouds form when evaporated water rises in the atmosphere, cools, attaches to small particles, condenses to form tiny water drops, which combine to form cloud droplets and ultimately clouds.

Cirrus Clouds

Wispy clouds that form at higher elevations, made mostly of ice crystals.

Stratus Clouds

Flat layered clouds that may obscure the sky, occurring at mid-low altitudes.

Cumulus Clouds

Fluffy and puffy clouds usually seen on sunny days, occurring at mid to low altitudes.

Weather Maps

Describe weather conditions at particular locations, providing information about pressure systems, fronts, air mass movement, temperature, etc.

Wind Direction on Weather Map

From what direction would the wind be blowing if you were standing on the pink dot?

Air Pressure on Weather Map

What would be the possible air pressure on the green dot?

Temperature Comparison

If the temperature at B is 79 degrees, would the temperature at A be warmer or colder?

Front Movement

Which direction is front 'X' moving?

Fastest Wind Speed

At which dot is the wind speed the fastest?

Stormy Weather Area

Which area would contain stormy weather?

Weather Map Functionality

How does this map show the weather at each particular location?

Leeward Side

Typically, as a system moves towards and over a mountain, the cloud and weather will dissipate, causing the leeward side to be considered dry.

Cup Anemometer

This instrument measures wind speed.

Barometer

Measures air pressure.

Weather Vane

Tells us wind direction and points in the direction where the wind is blowing.

Psychrometer

Allows us to find relative humidity and dew point.

Radiosonde

Collects weather data from areas in the troposphere.

Hydrologic Cycle

Describes how water moves through Earth systems.

Evaporation

Liquid water is heated into a gas and rises in the atmosphere.

Transpiration

Plants take up water from the soil and release it as gas from their leaves.

Condensation

Water vapor is cooled down (to the dew point) and becomes a liquid again.

Precipitation

Liquid water falls down from the sky as rain, snow, etc.

Surface Runoff

Liquid water on the surface travels downhill toward lower elevations.

Infiltration

Liquid water being absorbed into the ground.