Bell Ringer 2/21/17 Create a circle map on what you know about WEATHER

Unit 3 Air Masses and Severe Weather

Air Pressure & Wind Air Pressure & Wind 2/21/2017

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Air pressure - the pressure exerted by the weight of air above Exerted in all directions (up, down, and sideways) Air pressure doesn’t just push down on an object, it pushes all around the object (High or low?) *

Barometer: device used for measuring air pressure Unit: millibars (mb) inches of mercury Torricelli: invented the mercury barometer in 1643 https://www.youtube.com/watch?v=GRxglLS1YWI *

The unequal heating of earth’s surface generates pressure differences Solar radiation is the ultimate energy source for wind *

Isobars lines on a map that connect places of equal air pressure A pressure gradient The spacing of isobars shows the amount of pressure change over a given time *

Closely spaced isobars: indicate a steep pressure gradient and high winds. Widely spaced isobars: indicate a weak pressure gradient and light winds. *

Winds blow counterclockwise Winds blow outward and clockwise Low Pressure Centers High Pressure Centers AKA Cyclones Anti-cyclones Pressure Behavior Pressure drops Pressure increase Wind Behavior Winds blow counterclockwise Winds blow outward and clockwise Weather Associated Severe and stormy Fair and Sunny Symbol “L” that is RED “H” that is BLUE *

Wind is a result of horizontal differences in air pressure Air flows from areas of high pressure to areas of lower pressure. *

https://www.youtube.com/watch?v=aiYyCurh_SU

Jet streams are fast-moving rivers of air Speed: 120 and 240 kilometers per hour Direction: West-to-east direction. https://www.youtube.com/watch?v=WAve9PlK4Gg https://www.youtube.com/watch?v=CgMWwx7Cll4 https://www.youtube.com/watch?v=huweohIh_Bw *

Direction Labeled by the direction from which they blow Ex: winds blowing from the Southeast. Tool: Wind Vane *

Anemometer Measures how fast wind is blowing *

Air Masses & Fronts Air Masses & Fronts 2/22

Chapter 20 Air Masses

Probing Questions Refer back to heating of land and water activity Now lets look at heating of land and water on a global scale! (continental and maritime) Go back to solar radiation. Warmer at the equator. (Tropical and Polar) at equator and poles.

Air Mass An air mass is a big body of air that is characterized by similar temps and moisture When an air mass moves out of the area it formed over, it keeps the same temp and moisture conditions As it moves, the characteristics of an air mass change and so does the weather in the area it moves over

Classifying Air Masses Air masses are classified by temperature and surface area over which they form

Classifying Air Masses NAME P – Polar LOCATION High Latitudes towards the poles TEMPERATURE Cold Temps T – Tropical Low Latitudes towards the equator Warm Temps C – Continental Over land mass Cold or warm, depending on the latitude M – Maritime Over water

Four Basic Types of Air Masses cP – Continental Polar dry and cool cold and dry in winter and summer cT – Continental Tropical dry and warm hot, drought-like conditions mT – Maritime Tropical wet and warm source of precipitation in the United States mP – Maritime Polar wet and cold mild, humid, unstable cold air from Canada

Weather in North America is influenced by continental polar and maritime tropical air masses

Probing Questions Probe to get to that air masses move (wind) and the space between two air masses is the front.

Fronts When two air masses meet boundary separating the two air masses.

Warm Front A warm front – warm air moves into an area formerly covered by cooler air Warm air glides up over a cold, dense air mass Weather Conditions: Light to moderate rain

Cold Front Cold air mass moves into an area occupied by warmer air. Weather Conditions: Thunderstorms

Stationary and Occluded Fronts stationary front: The surface position of the front does not move (steady rain for days) occluded front: when an active cold front overtakes a warm front

Winds blow counterclockwise Winds blow outward and clockwise Low Pressure Centers High Pressure Centers Centers of Low Pressure High Pressure AKA Cyclones Anti-cyclones Pressure Behavior Pressure drops Pressure increase Wind Behavior Winds blow counterclockwise Winds blow outward and clockwise Weather Associated Severe and stormy Fair and Sunny Symbol “L” that is RED “H” that is BLUE *

​Tornadoes & Thunderstorms

-Thunderstorms -Tornadoes -Hurricanes Severe Storms -Thunderstorms -Tornadoes -Hurricanes

Thunderstorms -Is a storm that generates thunder and lightning -Frequently produces gusty winds, heavy rain, and hail Associated with cumulonimbus clouds

Lightning: results from the build up and discharge of electric energy between positively (ground) and negatively (clouds) charged area -Thunder: the sound of rapidly expanding gases usually associated with lightning https://www.youtube.com/watch?v=G7GbOFlFODE https://www.youtube.com/watch?v=jM8h60S1GsM

Occurrence and Development At any given time, there are an estimated 2000 thunderstorms in progress on Earth Mostly in the tropics Development Thunderstorms form when warm, humid air rises in an unstable environment 3 Stages

3 Stages Cumulus: build up of clouds and moisture Mature: Heavy rainfall, most active time Dissipating: light rain, storm is calming down

Tornadoes Tornadoes - violent low pressure windstorms that take the form of a rotating column of air (vortex). The vortex extends downward from a cumulonimbus cloud producing rain and hail Move counterclockwise https://www.youtube.com/watch?v=oQPBjQHG8gc https://www.youtube.com/watch?v=V-Xbj0aEkRQ

Occurrence, Development, and Intensity of Tornadoes 770 occur each year Tornado Season April to June Associated with severe thunderstorms Intensity Fujita Tornado scale Based on the amount of damage

Incredible and Speechless Damage Fujita Tornado Scale Category Winds (MPH) Winds (KPH) Damage F0 <73 <116 Light damage F1 73-112 116-180 Moderate Damage F2 113-157 181-254 Considerable Damage F3 158-206 254-332 Severe Damage F4 207-260 333-419 Devastating Damage F5 >260 >419 Incredible and Speechless Damage

Tornado Warnings vs. Watches Watches : Possibility of a tornado to be developed in the area Warning: Tornado has been seen by people or indicated by radar

Hurricanes 2/24/2017 HURRICANES

Indian Ocean – Cyclones Most powerful storm on Earth Hurricanes Whirling tropical cyclones (low pressure system) producing winds of at least 119 km per hour (73 mph) US – Hurricanes Pacific – Typhoons Indian Ocean – Cyclones Most powerful storm on Earth

Occurrence and Development of Hurricanes Form between 5 and 20 degrees north and south latitude Season: June 1 to November 30th Development of Hurricanes Hurricane develop most often in the late summer when water temperatures are warm enough to provide the necessary heat and moisture to the air Low Pressure: Spins counterclockwise

Eye: Center of storm, warmest part, winds cease, rain ceases Parts of a Hurricane Eye: Center of storm, warmest part, winds cease, rain ceases Eye wall: Strongest winds and rain Spiral Rain Bands: extend out from the eye wall https://www.youtube.com/w atch?v=Wk_FVXVnE2I

Categorized on the Saffir- Simpson Scale (based on wind speed) Hurricane Intensity Storm Surge: is a dome of water that sweep across the coast caused by the hurricane’s winds Categorized on the Saffir- Simpson Scale (based on wind speed)

Hurricane Warning and Watches Hurricane Watch: could see hurricane related hazards within 48 hours Hurricane Warning: Could see hurricane winds within 36 hours

Weather Symbols