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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
Weather Instruments(click below the picture)
http://www.weatherwizkids.com/weather-instruments.htm
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)
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
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).
Local WindsSea 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
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.
FrontsFront: a boundary between Air Masses• Four Types of Fronts:1. Cold2. Warm3. Occluded4. 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.
Station ModelsStation 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.
How to Draw Isolines(lines of equal value on a map)
Click on the Picture
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.