Weather!

1. Weather! Matt Aufman NSF North Mississippi GK-8 November 2005 NSF North Mississippi GK-8

2. 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

3. 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

4. So, the air’s ability to hold water vapor _____ as the temperature of the air _____. NSF North Mississippi GK-8

5. 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

6. Which type of air holds more water vapor. Warm air or cold air? • 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

7. 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

8. Cloud Cover Symbols • You will often see the circles drawn on a weather map NSF North Mississippi GK-8

9. 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

10. Air Masses There are two types of air masses: 1. Continental Polar air masses 2. Maritime Tropical air masses NSF North Mississippi GK-8

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. Weather Maps: Pressure & Temperature NSF North Mississippi GK-8

23. Weather Maps: Doppler Radar Maps NSF North Mississippi GK-8

24. 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

25. 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

26. 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