Weather lesson


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Weather lesson

  1. 1. Weather Lesson
  2. 2. Objectives • Learn about Weather Instruments • Learn about Highs and Lows • Learn about Winds  Global and Local • Learn about Air Masses • Learn about Fronts • Learn how to Read and Draw Station Models • Learn how to draw isolines (lines of equal value on maps) • Learn about Severe Weather and Clouds
  3. 3. Weather Instruments (click below the picture)
  4. 4. High and Low Pressures • Barometric (Air) pressure is the weight of the air above you. It is measured with a barometer. Isobars are lines of equal pressure used on a weather map to show air pressure. The unit for isobars is millibars (mb). Two Types of Pressure: • Low (L): also called a Cyclone – Air rises in a low as winds converge at the surface – The air cools as it rises and creates clouds that can produce precipitation • High (H): also called an Anticyclone – Air sinks and diverges away from a central point at the surface – The air warms as it subsides (goes down) which doesn’t allow for cloud formation (clear skies are present)
  5. 5. Highs and Lows Northern Hemisphere • Low (L) spins counter clockwise • High (H) spins clockwise Southern Hemisphere • Low (L) spins clockwise • High (H) spins counter clockwise What Causes the spin (deflection) which is named the Coriolis Effect? Answer: Earth’s Rotation
  6. 6. We ALWAYS go HIGH  LOW
  7. 7. Winds (are always named based on where they are coming from NOT where they are going to) Example: A North wind is coming from the North BUT is heading South Global • We live in the Prevailing Westerlies Local • Sea Breezes and Land Breezes • Valley Breezes and Mountain Breezes • Local breezes are caused by differences in specific heat capacity of different materials (i.e., how quickly or slowly a substance absorbs heat and holds onto it).
  8. 8. Local Winds Sea Breeze • During the day, land heats up quickly and generates a Low pressure center where the warm air begins to rise. As the warm air rises the cooler air from the sea moves in to fill the space and creates a breeze from the sea  Sea Breeze Land Breeze • During the evening as the sun goes down the land that heated quickly is now going to cool quickly and become cooler than the water temperature. When that happens, the low pressure is now over the water and the higher pressure from the cooler land fills in the space from the rising warmer air over the ocean creating a breeze from the land  Land Breeze
  9. 9. Air Masses Air Mass: a body of air with similar temperature, pressure, and humidity. • Terms for Air Masses: – Maritime (m)  related to the water, so moist air – Continental (c)  related to land, so dry air – Arctic (A)  related to really, really, really cold air – Polar (P)  related to really cold air – Tropical (T)  related to warm air • As indicated above, the location of origin is indicated with a lowercase letter and the temperature of the air mass is indicated with an uppercase letter.
  10. 10. Fronts Front: a boundary between Air Masses • Four Types of Fronts: 1. Cold 2. Warm 3. Occluded 4. Stationary • Fronts occur when two different air masses meet. Very violent weather systems can and are formed when two different air masses meet. • Violent storms include: Severe Thunderstorms and Tornadoes.
  11. 11. Station Models Station Model (SM): symbol on a weather map that describes the weather of a particular area using symbols. • Pressure on a station model is always ONLY 3 digits. So, a conversion must be done when placing the number on and then reversing that process when taking from station model. – 1013.2 mb  on SM would be 132 • Remove decimal and get rid of the 10 – 999.5 mb  on SM would be 995 • Remove decimal and get rid of the 9 – 124 on SM  would be 1012.4 mb • Add decimal between last two digits and add a 10 if the first digit is <5 – 895 on SM  would be 989.5 mb • Add decimal between last two digits and add a 9 if the first digit is >5. • Click on the picture to the right to practice reading station models.
  12. 12. How to Draw Isolines (lines of equal value on a map) Click on the Picture
  13. 13. Severe Weather and Clouds (click on each picture to learn about the different types) Make sure to take notes and write down the features of each.