Weather!

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# Weather - PowerPoint PPT Presentation

Weather!. Matt Aufman NSF North Mississippi GK-8 November 2005. Relative Humidity. The relative humidity tells us how “full” of moisture the air is at the time of measurement.

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### Weather!

Matt Aufman

NSF North Mississippi GK-8

November 2005

NSF North Mississippi GK-8

Relative Humidity

• The relative humidity tells us how “full” of moisture the air is at the time of measurement.
• For example, 90% relative humidity means that at that moment the air is holding 90% of the maximum amount of water it could.

NSF North Mississippi GK-8

If the air is at 100-percent relative humidity, sweat will not evaporate into the air. As a result, we feel much hotter than the actual temperature when the relative humidity is high.

NSF North Mississippi GK-8

So, the air’s ability to hold water vapor _____ as the temperature of the air _____.

NSF North Mississippi GK-8

SO….
• Cold air cannot hold as much _____ _____ as warm air.

Draw this.

Cold air is more dense than warm air.

NSF North Mississippi GK-8

• What does it mean when we say that the relative humidity of the air is 50%, 75%, 100%?
• Which type of air (cold or warm) is heavy and dense? Why?
• Which type of air (cold or warm) is light?  Why?

NSF North Mississippi GK-8

Draw a picture of cold air that has a relative humidity of 50 %.  Write a short paragraph that explains your picture.
• Draw a picture of warm air that has a relative humidity of 70 %.  Write a short paragraph that explains your picture.

NSF North Mississippi GK-8

Cloud Cover Symbols

• You will often see the circles drawn on a weather map

NSF North Mississippi GK-8

High and Low Pressure Areas

• High pressure causes air to sink
• Usually results in several days of clear sunny skies
• Air rises in low pressure areas and forms water droplets
• Usually results in rain and storms

NSF North Mississippi GK-8

Air Masses

There are two types of air masses:

1. Continental Polar air masses

2. Maritime Tropical air masses

NSF North Mississippi GK-8

Fronts

A front is the boundary separating air masses of different densities

• Fronts extend both vertically and horizontally in the atmosphere

NSF North Mississippi GK-8

Fronts: Five Types of Fronts

1.Cold Front: The zone where cold air is replacing warmer air

• In U.S., cold fronts usually move from northwest to southeast
• Air gets drier after a cold front moves through

NSF North Mississippi GK-8

Fronts: Five Types of Fronts

2.Warm Front: The zone where warm air is replacing colder air

• In U.S., warm fronts usually move from southwest to northeast
• Air gets more humid after a warm front moves through

NSF North Mississippi GK-8

Fronts: Five Types of Fronts

3.Stationary Front: When either a cold or warm front stops moving

• When the front starts moving again it returns to either being acoldor warm front

NSF North Mississippi GK-8

Fronts: Five Types of Fronts

4.Occluded Front: Formed when a cold front overtakes a warm front

• This occurrence usually results in storms over an area
• In U.S., the colder air usually lies to the west

NSF North Mississippi GK-8

Fronts: Five Types of Fronts

5.Dry Line (Dew Point Front): Boundary separating a dry air mass from a moist air mass

• This occurrence can result in tornadoes being formed
• Usually found in western part of U.S.

NSF North Mississippi GK-8

Clouds: Five Types of Clouds

1. High-Level Clouds: Usually found at greater than 20,000 ft.

• Usually made of ice crystals
• Examples include Cirrus, Cirrostratus

NSF North Mississippi GK-8

Clouds: Five Types of Clouds

2. Mid-Level Clouds: Usually found between 6,500 and 20,000 ft.

• Usually made of water droplets, but can be made of ice
• Example is altocumulus

NSF North Mississippi GK-8

Clouds: Five Types of Clouds

3. Low-Level Clouds: Usually found lower than 6,500 ft.

• Low, lumpy clouds that produce weak to moderate precipitation
• Examples include Nimbostratus and Stratocumulus

NSF North Mississippi GK-8

Clouds: Five Types of Clouds

4. Vertically developed: These clouds are thick and puffy and extend very far upwards

• Examples include Cumulonimbus and Fair Weather Cumulus
• Ordinary Cumulus clouds can quickly become Cumulonimbus clouds that start strong thunderstorms

NSF North Mississippi GK-8

Clouds: Five Types of Clouds

5. Other: These are miscellaneous clouds

• These clouds do not really fit into any category, and all have different characteristics
• Examples include billow clouds, contrails, mammatus, orographic, and pileus

NSF North Mississippi GK-8

Weather Maps: Pressure & Temperature

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Weather Maps: Doppler Radar Maps

NSF North Mississippi GK-8

Summary

• Temperature: Usually in °F, need to convert to °C
• High pressure areas cause sunny weather; low pressure areas cause rain and storms
• Two Types of air masses:

1. Continental Polar

2. Maritime Tropical

NSF North Mississippi GK-8

Summary (continued)

• Five types of fronts:

1. Cold

2. Warm

3. Stationary

4. Occluded

5. Dew Point (Dry Line)

• Five types of clouds:
• 1. High Level
• 2. Mid Level
• 3. Low Level
• 4. Vertically developed
• 5. Miscellaneous

NSF North Mississippi GK-8

Sources

• Palmer, Chad and Evans, David. May 20, 2005. Occluded fronts can
• signal weakening of storm. Accessed 28 October 2005. http://www.usatoday.com/weather/tg/wofront/wofront.htm
• Palmer, Chad and Kepple, Kevin. May 20, 2005. High-pressure systems
• brings sunny days. Accessed 27 October 2005.
• http://www.usatoday.com/weather/tg/whighp/whighp.htm
• Palmer, Chad and Kepple, Kevin. May 20, 2005. How low pressure
• systems affect weather. Accessed 27 October 2005. http://www.usatoday.com/weather/tg/wlowpres/wlowpres.htm
• Weather World 2010, University of Illinois. No date of publication
• given. Reading and Interpreting Weather Maps. Accessed 21 October 2005. http://ww2010.atmos.uiuc.edu/(Gh)/guides/maps/home.rxml

NSF North Mississippi GK-8