FRONTS AND STORMS

1. FRONTS AND STORMS

2. Weather Changes as air masses move Forms when air sits for many days Large volume of air Covers thousands of miles Air Mass Same temperature and humidity in different locations At the same altitude

3. Earth is cold Air is cold Earth is wet Air is moist As air mass moves It brings its Temperature and moisture to new location

4. Air masses are named according to the area where they form First part of the Name: Continental – means the air mass formed over land, air is dry Maritime – means the air mass formed over water, air is moist Second part of the name: Tropical – means the air mass formed near the equator, air becomes warm, gains energy from land or water Polar – means the air mass formed far from the equator, air becomes cool, loses energy to the cold land or water

5. How do air masses move ? Air masses can travel away from regions where they form. They move with the global pattern of winds. In most the United States, air masses generally move from west to east. They may move along with the jet stream. In more complex and changing patterns They bring their temperature and moisture to their new location. Can cause weather to change

6. FRONTS Boundary between air masses Clouds form Weather becomes cloudy or stormy

7. Moves slow, brings many hours of rain or snow. After front passes air is warmer Produces cloud covered skies high cirrus clouds Symbol Warm Front Warm air moves up and over a mass of denser and colder air

8. Moves quickly, very steep After front passes air is cooler and often very clear Produces cumulonimbus clouds and precipitation Brief, heavy storms are likely Symbol Cold Front Cold dense air is moved forward, warmer air is pushed upward

9. Occurs when air masses meet, or when cold or warm fronts stop moving, boundary is in same location Clouds cover the sky for days at a time Symbol Stationary Front May become a warm or cold front, depends on which air is pushed down

10. High Pressure System • Large and change slowly • Water droplets evaporate, so clouds often disappear • Calm air or gentle breezes • Generally brings clear skies • Is formed when air moves all the way around a high pressure center

11. Low Pressure System • Air moves inward toward the low pressure and then up to higher altitudes • Is a large weather system that surrounds a center of low pressure • Air moves faster • Produces stormy weather • Northern hemisphere air circles in a counter clockwise direction • They often happen along the boundary of warm and cold air masses

12. Low – Pressure Systems can become storms Warm water makes it bigger and stronger Land or cool water makes them weak and lose energy Move westward with the trade winds Strike b/w August and October Tropical Low Pressure system Winds blowing at speeds of at least 120Km/Hr. Hurricanes Formed over the Indian Ocean or Western Pacific called Typhoons or Cyclones

13. FORMATION OF HURRICANES • Bands of heavy clouds and rain spiral inward toward the eye • Center is called the EYE of the hurricane • The center is calm because the air moves downward • Air moves quickly around and upward • Tall ring of cumulonimbus clouds form the eye wall • The ring produces heavy rain and tremendous winds

14. EFFECTS OF HURRICANES • Strong winds • Heavy rain • May produce Tornadoes • Rivers may overflow and flood nearby areas • Can create a storm surge

15. STORM SURGE • Destructive and deadly • Huge mass of ocean water • Produces LARGE WAVES that can move back up rivers and flood their shores

16. VERTICAL AIR MOTION CAN CAUSE SEVERE STORMS THUNDERSTORMS ARE STORMS WITH Lightning Thunder

17. Rising humid air forms a cumulus cloud which eventually forms into cumulonimbus cloud The downdraft created, produces heavy rain or hail Ice particles form in the low T near the top of the cloud FORMATION OF THUNDERSTORMS The ice particles fall and pull cold air down

18. EFFECTS OF THUNDERSTORMS • Flash Floods • Strong Winds • Hail • Heavy Rain • Lightning

19. TORNADO • Most common are small and last only a few minutes • May lift dust and debris from the ground • Violently rotating column of air • Stretches from a cloud to the ground • Moves along the ground in a winding path • Column may rise off the ground and then come down in a different place

20. EFFECTS OF TORNADOES Most common can pick up and slam dirt and small objects Large tornadoes can knock over large trees 20% can lift cars off the ground Tear roofs off houses 1% can lift or completely demolish sturdy buildings

21. Weather forecasters use advanced Technologies Scientist who studies weather To predict weather they look at past and current conditions Uses maps to display a lot of information at once METEOROLOGIST Use technology to gather information

22. Isobars: Lines that connect places with the same air pressure. Isotherms: Lines of equal temperature. Pressure systems WEATHER DATA H L Precipitation Fronts B G Y R

23. FORECASTING • Is complicated • Short forecasts are the most accurate (3 days) • Fast changing weather is less accurate (storms)

24. COMPUTERS IN WEATHER • Important tool for forecasting weather • Scientists study the computer forecasts then apply their knowledge and experience • Combine many types of data to forecast what might happen next • Can create maps when weather stations send in data

25. GATHERING WEATHER INFORMATION Ground Stations Gathers data from just one place Small area surrounding the station Satellites Gathers data from a large area Surface of Earth below