Weather

1. Weather Ch 13 p. 448

2. L1 What is weather? A atmospheric condition Short term changes One certain place One certain time Can change quickly

3. Weather Variables Meteorologist are scientist that study and predict weather Air temperature & Moisture (rain fall/humidity) Humidity is the amount of water vapor in the air Air pressure-force placed on objects below a column of air Wind speed and direction Cloud coverage Dew point-temp at which air is saturated and condensation can occur

4. Clouds & Fog Clouds are water droplets or ice crystals in the atmosphere Types of clouds: Stratus-flat, white, layered, low altitude; Cumulus-fluffy, heaps or piles, mild altitude; Cirrus-wispy and high altitude As air cools, water vapor condenses and forms water droplets-the water droplets block and reflect light making them visible as clouds Clouds that form close to Earth’s surface are called fog- can reduce visibility

5. Water Cycle Sun sends thermal energy to heat water on Earth’s surface Evaporation: as water increases heat, water vapor rises into the atmosphere Most water vapor rises from oceans Condensation: as water vapor cools, water droplets form Precipitation: liquid/solid water falling from the atmosphere (rain, snow, hail, sleet) See pic p. 455

6. L2 Weather Patterns Cool air - close molecules = higher pressure/weight Warm air - distant molecules = lower pressure/weight High pressure system: large body of circulating air with high pressure at the center and low pressure outside-air moves away from center and dense air sinks bringing clear skies and fair weather See pic p. 459 Low pressure system: large body of circulating aid with low pressure at the center and high pressure outside-air moves upward then cools and forms clouds (condensation) -brings precipitation See pic p. 459

7. Air Masses Map p. 460 Large bodies of air that have uniform/same temperature, humidity, and pressure - patterns created Forms when a large high pressure system lingers over an area for days. As high pressure comes in contact with Earth, the air takes on the temp and moisture of the surface below it. Can cover the entire country

8. Types of Classification based on temp & moisture Continental air masses (over land) can be Polar (cold and dry) or Tropical (hot and dry) Arctic and Antarctic air masses (near poles are cold and dry) Maritime air masses form over oceans: Tropical-Western Atlantic, Gulf of Mexico, Eastern Pacific Polar-Northern Atlantic and Pacific See pics p. 461

9. Fronts Pics p. 462-463 A boundary between two air masses-characterized with drastic changes in temp, humidity, clouds, wind, and precipitation. Cold moves faster than warm fronts. Cold: cold goes under warm which rises & cools forming clouds/storms; gusty wind changes direction; temps decrease Warm: warm towards cold; warm rises creating a blanket of clouds causing steady rain; wind shifts direction; temps increase Stationary: either cold or warm front stalls for days; cloudy and rainy Occluded: either cold or warm front is blocked; one front moves fast & catches another front; rainy

10. Thunderstorms “Electrical Storms” Warm temps, moisture, and rising air (low pressure) are required. Stage1: Cumulus-air moves away from ground causing rapid cumulus cloud growth, then air reverses Stage2: Mature-heavy wind,rain and lightning Stage 3: Dissipation-everything decrease in size and strength Positively & negatively charged particles crash and create electricity (lightning) Molecules near lightning expand & contract causing thunder

11. Lightning Electric discharge between Earth and the atmosphere Heat nearby air more than 50,000 degrees Can move cloud to cloud, cloud to ground, ground to cloud Most are from cloud to ground - each bolt only striking one location Average of 51 deaths a year due to lightning

12. Tornadoes Violent, whirling column of air in contact with the ground-over 250 mph-usually last only a few minutes but can last for hours Invisible funnel clouds are produced in thunderstorms-you only see the debris in the funnel cloud Pic p. 465 Most tornadoes occur in the US than anywhere else on Earth. The central Great Plains experience the most in the US (Nebraska-Texas) “Tornado Alley” In this area, cold-dry Canadian air collides with warm-wet Gulf air. AMSTI Lab

13. Fujita Scale Tornadoes are classified on the Fujita Scale based on damage caused F0-light damage like broken tree branches and street signs F1-F4-moderate damage like torn roofs, derailed trains, cars turned over F5-incredible damage like demolishing concrete & steel buildings, pulling bark off trees, and flattening neighborhoods

14. Hurricanes Intense tropical storms with winds above 75 mph Most destructive storms on Earth- up to 150 times larger than tornadoes Form over warm tropical oceans in late summer through fall An eye (open area) is in the center - very calm weather Most damage is from strong winds and floods (rain and ocean surge) Once it moves over land, it decreases in strength

15. Other names? US- hurricane Asia- typhoon Australia- cyclone These are the same type of storms - just different location and name Analyze pics p. 466

16. Blizzard Violent storm characterized by freezing temps, strong winds, and blowing snow Swirling snow reduces visibility Freezing temps increases frostbite and hypothermia Weight of ice tears down power lines and small trees

17. NWS US National Weather Service issues watches and warnings for all storms Watch- means severe weather is possible Warning- means severe weather is already occurring Have a plan BEFORE the storm! If told to evacuate, LEAVE!

18. How to protect yourself? Thunderstorms - stay inside and away from windows, metal, and electricity Tornadoes - get to the lowest area and cover yourself with a mattress Hurricanes - get far away from large bodies of water, have a boat/raft Blizzard - stay inside with multiple layers of clothing and blankets Have safety items for all storms: flashlight, charged phones/computers, medicines, water, and non-refrigerated food Have a buddy system to always check on one another Call 911

19. L3 Weather Forecasts p. 470 Meteorologist study and predict weather Use special instruments and knowledge of past weather events Instruments measure conditions in the atmosphere Instruments: thermometers (temp), barometers (air pressure), psychrometers (humidity), and anemometers (wind) Satellites also send infrared pics of Earth to use for weather forecast (predictions)

20. Doppler Radar Specialized radar that detects precipitation as well as the movement of small particles in the atmosphere (which determines wind speed) Very useful in determining speed and direction of tornadoes and thunderstorms Modern meteorologists enter all this info in a computer to create predictions US government uses the internet to exchange weather knowledge throughout each day. Predictions are made public through internet, tv, radio, and newspaper. Weather apps alert public immediately

21. TEST TIME Review p. 478 Main Ideas Complete Review p. 479-481 Study Quizlet Know vocabulary Study!