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

2. 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.

3. 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.

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

5. 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.

6. NSF North Mississippi GK-8  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?

7. 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.

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

9. 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

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

11. 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

12. 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

13. 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

14. 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 a cold or warm front

15. 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

16. 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.

17. 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

18. 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

19. 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

20. 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

21. 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

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

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

24. 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

25. 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

26. 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 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 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