Presentation on theme: "Section 2 and 3 Weather Patterns"— Presentation transcript:
1Section 2 and 3 Weather Patterns Chapter 13Section 2 and 3Weather Patterns
2Pressure SystemsAir pressure = weight of the molecules in a large mass of air. (2 TYPES)1) HIGH pressure systemCool air massesMore “weight” because cool => molecules are closer together. (Sinking air at center.)Air moves clockwise – away from center.Associated w/ clear skies and fair weather.
3Pressure Systems cont. Warm air masses. 2) Low Pressure SystemWarm 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!!!
4(areas of air pressure). Always remember …Winds blow fromHIGH to LOW(areas of air pressure).
5Air Mass: large body of air that has uniform temp 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.
65 ways AIR MASSES are classified ~ 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 & humidWinter – heavy snowfall
7Air masses not constant … Change as they move from land to ocean and from ocean to land.Remember: if over land (“continental”) = dryif over ocean (“maritime”) = moistureif POLAR = cold tempif TROPICAL = warm temp
84 kinds!!! Pictures on P. 462 – 463 FRONTS Definition: Boundary between 2 air masses of different density, moisture, or temp.4 kinds!!! Pictures on P. 462 – 463
9cold air advances toward warm air. Cold air wedges under warm air. 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
102.)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.
113.)Occluded Front *Need 3 air masses. *Usually 2 cold fronts close off a warm front from the surface.*Usually precip
124.)Stationary FrontBoundary between air masses stops advancing. (They are stuck – days of precip.)Represented by alternating blue and red lines w/ triangles and semicircles.
13Severe Weather Heavy rains, lightening, thunder, hail, etc. 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 warningHail and / or Wind DamageLightening strikes
14Lightning: 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 objectPos. and Neg. join ….Makes the flash.
15THUNDER Results from: the rapid heating of air around the lightning then it rapidly cools and contracts.Makes a sound wave = thunder
16Types of Severe Storms Produced by thunderstorms 1.)Tornado:Produced by thunderstormsWhirling, violent wind that moves over narrow strip of landFunnel Cloud – in airTornado – called this when it touches ground!!Fujita Classification F1 – F4 moderate damage, F5 incredible damage!
172.)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 energydisappears
18How Hurricane forms … 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, thunderstorms4) Winds > 116 km/hr = hurricane.
19Parts of Hurricane Eye – center w/ clear skies and light wind. Eyewall RainbandsP. 466Pictures of damage?
20Blizzards: conditions must be 1. Winds 56 km/h2. Temp is LOW3. Visibility is less than 400 m. in falling or blowing snow.4. Conditions persist for 3 hours or more.1. Winds 56 km/h2. Temp is LOW3. Visibility is less than 400 m. in falling or blowing snow.4. Conditions persist for 3 hours or more.
21Severe Weather SafetyWATCHES: 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)
22Assign: Sect 2 Questions P. 468 (1-8)Next up …reading Weather Maps
23Section 3 : Weather Forecasts Meteorologists:person who studies the weather.Takes/uses measurements of temperature, air pressure, winds, humidity, and precipitation to:Used to make weather mapsThe maps allow them to make predictions about future weather patterns.
24Measuring the Weather 1) Surface Report Def: describes a set of weather measurements made on Earth’s surface.Weather Stations – instruments that report:temp, air pressure, humidity, precip, & wind direction/speed. (weather VARIABLES)
25Measuring weather cont. 2) Upper-air ReportDef: describes wind, temp, & humidity conditions ABOVE Earth’s surface.Measured by a RADIOSONDE (carries weather instruments)Many km high in atmosphere in a weather balloon.pictures of weather balloon
26Measuring weather cont. 3) Satellite / Radar ImagesInfrared ImagesHow much thermal energy stored is in atmosphere.Cloud heightAtmospheric tempsDoppler Radar –Detects precipitationMovement of small particles (used to approximate wind speed)Important tool during severe storms
27Station Models Data gathered at Earth’s surface Used to make a map w/ symbols called Station ModelThis info entered into computer w/ the data collected from atmosphere - used to make forecasts (what is coming or happening to the weather)
28How Temperature and Pressure are represented on the maps … 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.
29Know how to read a Weather Map P. SR – 46 Weather Map SymbolsP. 473 Weather Map
30End of Chapter 13 Read Chapter if you haven’t. Make your note cards or foldables.Study them every night from now until the test.