Weather Forecasts

The National Weather Service counts on two sources for information:

RadarWeather Balloon

•Data collected from the atmosphere•Data collected from the Earth’s surface

In order to forecast the weather, meteorologists make measurements of:temperature

windsair pressurehumidityprecipitation

Instruments used to measure precipitation:

Snow GaugeRain Gauge

Instrument used to measure temperature:

Thermometers

Instrument used to measure humidity:

Psychrometer

Instrument used to measure wind speed

Anemometer

Instrument used to measure wind direction:

Wind Vane

Instrument used to measure air pressure:

Barometer

When meteorologists gather up data, it is recorded on a map using a combination of symbols, forming a STATION MODEL.

Isobars are lines that connect equal atmospheric pressure .

These lines show the areas of high and low pressure.

Air flows in a clock-

wise direction

on the surface of the Earth.

Cold, dense air sinks to

the surface of the Earth. Airs flows in

a counter clock-wise

direction at the surface

of the Earth.

LWarm, less dense air

rises forming clouds

Pressure Changes with Temperature

Pressure Gradients•There are many areas of high and low pressure above the Earth’s surface due to uneven surface heating creating pressure gradients.

Air moves from high pressure to low pressure forming winds.

•The closer the isobars, the stronger, the winds blow.•The more spread out the isobars, the gentler the winds.

Fronts are draw as lines and symbols.

Stationary Front

Occluded FrontWarm Front

Cold FrontHHigh Pressure

LLow Pressure

45°C

28°C

29°C

25°C

40°C

Which direction is the warm front moving?

What will happen to the weather in Denton?

Airs flows in a counter clock-wise direction at the surface of the Earth.

LWarm, less dense air

rises forming clouds

Air flows in a clock-wise

direction on the surface of

the Earth.

Cold, dense air sinks to the surface

of the Earth.

STATION MODEL is created when data that is collected is recorded on a map using a combination of symbols.

There are many areas of high and low pressure above the Earth’s surface due to uneven surface heating creating pressure gradients.Air moves from high pressure to low pressure forming winds.

Air flows in a clock-wise direction on the surface of the Earth in High Pressure areas.Airs flows in a counter clock-wise direction at the surface of the Earth in Low Pressure areas.

Symbols for Fronts

Cold, dense air sinks to the surface of the EarthWarm, less dense air rises forming clouds

The closer the isobars, the stronger the winds blow.The more spread out the isobars the gentler the winds.

Isobars are lines that connect equal atmospheric pressure .