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Section 2 and 3 Weather Patterns Air pressure = weight of the molecules in a large mass of air. (2 TYPES) 1) HIGH pressure system Cool air masses More.

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Presentation on theme: "Section 2 and 3 Weather Patterns Air pressure = weight of the molecules in a large mass of air. (2 TYPES) 1) HIGH pressure system Cool air masses More."— Presentation transcript:

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2 Section 2 and 3 Weather Patterns

3 Air pressure = weight of the molecules in a large mass of air. (2 TYPES) 1) HIGH pressure system Cool air masses More weight because cool => molecules are closer together. (Sinking air at center.) Air moves clockwise – away from center. Associated w/ clear skies and fair weather.

4 2) Low Pressure System Warm air masses. Less dense => air molecules are farther apart. Air moves counter clockwise – towards the center. Air rises at center which then cools and water vapor condenses. Associated w/ cloudy weather and sometimes precip. *Know how to compare and contrast the two!!!

5 Winds blow from HIGH to LOW (areas of air pressure).

6 Air Mass: large body of air that has uniform temp., humidity, and pressure. Takes on the temp, etc. of the surface where it formed. Ex. Air mass over tropics will be warmer than an air mass that develops over the North Pole. Ex. Air mass that develops over land is dryer than an air mass that develops over water.

7 1) Arctic Air Masses = bitterly cold, dry air. Form Siberia & Arctic – kind that causes neg. temps. 2) Continental Polar Air Masses = fast moving, cold & dry. Cold temps in winter & cool weather in summer. 3) Maritime Polar Air Masses = cold & humid. Bring cloudy, rainy weather. 4) Continental Tropical Air Masses = hot & dry. Bring clear skies and high temps. 5) Maritime Tropical Air Masses = Hot & humid. Summer – hot & humid Winter – heavy snowfall

8 Change as they move from land to ocean and from ocean to land. Remember: if over land (continental) = dry if over ocean (maritime) = moisture if POLAR = cold temp if TROPICAL = warm temp

9 FRONTS Definition: Boundary between 2 air masses of different density, moisture, or temp. 4 kinds!!! Pictures on P. 462 – 463

10 1.) Cold Front: cold air advances toward warm air. Cold air wedges under warm air. (think snow plow) Represented by blue lines w/ triangles on weather map (When temp diff is large, thunderstorms or tornados can form.) *Brings drop in temp, clouds, precip, wind & severe storms

11 2.)Warm Front: Form when lighter, warmer air advances over heavier, colder air. Represented by red lines w/ semicircles on weather map. * Brings rising temps, steady rain & a change in wind direction.

12 3.)Occluded Front *Need 3 air masses. *Usually 2 cold fronts close off a warm front from the surface. *Usually precip

13 4.)Stationary Front Boundary between air masses stops advancing. (They are stuck – days of precip.) Represented by alternating blue and red lines w/ triangles and semicircles.

14 Thunderstorms: Heavy rains, lightening, thunder, hail, etc. Occur in Warm, moist, air masses and along fronts (boundaries!!!) Sinking, rain cooled air and strong updrafts of warmer air cause the strong winds. To be severe – winds 89 m/hr or more. Damage: Flash Floods – happen w/out warning Hail and / or Wind Damage Lightening strikes

15 Sinking, rain cooled air and strong updrafts of warmer air Cause clouds to become charged. Forms a current between these charged clouds and ground or object Pos. and Neg. join …. Makes the flash.

16 Results from: the rapid heating of air around the lightning then it rapidly cools and contracts. Makes a sound wave = thunder

17 1.)Tornado: Produced by thunderstorms Whirling, violent wind that moves over narrow strip of land Funnel Cloud – in air Tornado – called this when it touches ground!! Fujita Classification F1 – F4 moderate damage, F5 incredible damage!

18 2.)Hurricanes: (150,000 x larger than tornado) *The most POWERFUL storm. *Large, swirling low-pressure formed over the Atlantic Ocean (Called Typhoons in Pacific Ocean and Cyclones in Indian Ocean.) *Must have at least 119 km/hr. *As long as it is over water, gains strength and continues … – water provides energy for storm – once it hits land, its source of energy disappears

19 1) Low pressure system over ocean. 2) Tropical Depression forms = thunderstorms w/ winds bt. 37 – 62 km/hr. 3) Tropical Storm – air continues to rise … winds > 63 km/hr, thunderstorms 4) Winds > 116 km/hr = hurricane.

20 Eye – center w/ clear skies and light wind. Eyewall Rainbands P. 466 Pictures of damage?

21 1. Winds 56 km/h 2. Temp is LOW 3. Visibility is less than 400 m. in falling or blowing snow. 4. Conditions persist for 3 hours or more. Blizzards: conditions must be 1. Winds 56 km/h 2. Temp is LOW 3. Visibility is less than 400 m. in falling or blowing snow. 4. Conditions persist for 3 hours or more.

22 WATCHES: issued when conditions are favorable for severe weather like tornadoes, thunderstorms, winter storms … WARNINGS: severe weather conditions already exist (may be moving into our area)

23 P. 468 (1-8) Next up … reading Weather Maps

24 – Meteorologists: person who studies the weather. Takes/uses measurements of temperature, air pressure, winds, humidity, and precipitation to: – Used to make weather maps – The maps allow them to make predictions about future weather patterns.

25 1) Surface Report Def: describes a set of weather measurements made on Earths surface. Weather Stations – instruments that report: temp, air pressure, humidity, precip, & wind direction/speed. (weather VARIABLES )

26 2) Upper-air Report Def: describes wind, temp, & humidity conditions ABOVE Earths surface. Measured by a RADIOSONDE (carries weather instruments) Many km high in atmosphere in a weather balloon. pictures of weather balloon

27 3) Satellite / Radar Images Infrared Images How much thermal energy stored is in atmosphere. Cloud height Atmospheric temps Doppler Radar – Detects precipitation Movement of small particles (used to approximate wind speed) Important tool during severe storms

28 Data gathered at Earths surface Used to make a map w/ symbols called Station Model This info entered into computer w/ the data collected from atmosphere - used to make forecasts (what is coming or happening to the weather)

29 Isobars – line that connects areas of equal atmospheric pressure. Help indicate where areas of High and Low- pressures are … Lines closer together means stronger winds … Isotherms – line that connects areas of equal temperature.

30 P. SR – 46 Weather Map Symbols P. 473 Weather Map

31 Read Chapter if you havent. Make your note cards or foldables. Study them every night from now until the test.


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