2Objectives Define and described air masses. Define and describe weather fronts.Be able to name winds and air massesUnderstand differing cyclonic systems and how to prepare for related emergencies.Compare high and low pressure systems.Read, label and analyze a weather map.
3Air MassesLarge areas (blobs) of air that have the same weather, temperatures and humidity and air pressureAir Mass Types - Named for where they come FROMWeather changes occur with changes in air masses
4TYPES of Air Masses The Bergeron Classification System maritime Tropical (mT)- humid/moist air & warmcontinental Tropical (cT)- dry air & hotmaritime Polar (mP)- humid/moist air & coldcontinental Polar (cP)- dry air & coldcontinental Arctic (cA)- dry air & very coldThere are no mA air masses
8Air Mass Army AnalogyThink of air masses as an army front (the army is BEHIND the frontline)At the Front there is FIGHTING and lots of VIOLENCE (stormy weather)Behind the front (inside the air mass) the general sits on his duff and watches the goings-on while enjoying the nice weather!
10Cold Front Cold dense air pushes warm air out of the way Cold fronts move very quickly and bring short periods of rain/thunderstormsLower temperatures are behind the frontSYMBOL – the direction of the “arrows” points towards the direction the front is MOVING
13Warm FrontWarm air moves up the cold front as it slowly displaces the cold airWarm fronts move slowly, and bring many days of steady precipitationHigher temperatures are behind the frontSYMBOL – direction of “half-moons” is the direction the front is moving
16Stationary FrontThe air from the warm front and cold front meet, but do not moveThese fronts have the same weather as warm frontsSYMBOL – warm and cold fronts are moving in opposite directions, thus making a stationary condition
18Occluded FrontsSometimes a colder or cooler front follows right behind a warmer front. A warm air mass pushes into a colder air mass (the warm front) and then another cold air mass pushes into the warm air mass (the cold front). Because cold fronts move faster, the cold front is likely to overtake the warm front. This is known as an occluded front.Remember moving in the same direction and combind or included.
19There are two types of Occlusion I. In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front, and plows under both air massesII. In a warm occlusion, the air mass overtaking the warm front is not as cool as the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air.
21Vocabulary Prevailing Westerlies- typical west wind at this latitude Trade winds- prevailing wind from east below Florida's latitudeJet stream- high altitude, high speed “river of air”Storm track- path of a storm
23The CycloneA Cyclone is any low pressure system that has a counterclockwise rotation(In the Northern Hemisphere)
24Types of Cyclones: Tornado- a small, compact storm with strong winds AKA:TwisterWilly-Willy (Australia)
25Types of CyclonesHurricane- A large, organized storm with strong winds and heavy rainAKATyphoon- in the Pacific
26Types of CyclonesMid Latitude Low- a low pressure system in the middle latitudesWe live in the middle latitudes (30-50 degrees North & South)Comma shaped ,AKANor’ Easter (North Easter)Alberta Clipper
27Prevailing Winds Push weather around In N.C., the prevailing winds come from the westMost of the time our winds come from the west (therefore) our weather will usually come from the westSometimes we will get wind from the Northeast, which usually brings extreme weather.“Nor’ easters”
28A nor'easter is a type of macro-scale storm along the East Coast of the United States and Atlantic Canada, so named because the winds come from the northeast atlantic, especially in the coastal areas of the Northeastern United States and Atlantic Canada. But their reach can be down into the atlantic southeast. The precipitation pattern is similar to other extratropical storms. Nor'easters also can cause coastal flooding, coastal erosion, hurricane force winds, and heavy snow. Nor'easters can occur at any time of the year but are mostly known for their presence in the winter season
29Windward and Leeward Winds Rain Shadow Windward SideLeeward Side
30A rain shadow is a dry area on the mountainside facing away from the direction from which the wind comes. The mountains block the passage of rain-producing weather systems, casting a "shadow" of dryness behind them. Warm moist air is "pulled" by the prevailing winds over a mountain. Then it condenses and precipitates and the dry air moves foreword leaving a rain shadow behind the mountain. Usually a desert.
32The Mid Latitude Low N L S This weather system starts when cool and warm air masses meet.Then a Low develops over the interface.LS
33The Low continues to spin, creating a warm front and a cold front.
34Rain will fall in front of the warm front and right on top of the cold front.
35HurricanesMassive storms with a size that can be more than 300 miles in diameter.Feed on warm waterBiggest danger is the storm surge in coastal areas
36High Pressure CellsA high-pressure area is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment.High-pressure areas are generally associated with cooler, drier air as well as clearing skies due to their formation within areas of atmospheric subsidence, or areas of large scale air descent.A low pressure area is commonly associated with inclement weather, while high pressure area is associated with light winds and fair skies.Clockwise
37Low Pressure CellsWind is initially accelerated from areas of high pressure to areas of low pressure.[Stronger areas of low pressure are associated with stronger winds.The stronger the pressure difference, or pressure gradient, between a high pressure system and a low pressure system, the stronger the windA low pressure area is commonly associated with inclement weather, while high pressure area is associated with light winds and fair skies.Counter-clockwise
43Tornadoes form from very powerful thunderstorms (cumulonimbus clouds) These are funnel shaped columns of spiraling winds that extend down to the ground from the base of a cloudThe winds move into a tornado (low pressure), and can reach a maximum of 318 mph!Spin COUNTER CLOCKWISE (like a hurricane)The actual funnel is made by water droplets (clouds) and dust
44Tornadoes are especially dangerous because it is so difficult to predict where they will form Damage is usually along a narrow path where the tornado traveledThey usually last less then one hourMost fatalities are caused by flying debrisTornadoes are rated on the Fujita scale (F0 – F6)An F6 is very rare, and can have wind speeds up to 318 mph
52For those of you who aren't familiar with tornadoes, here is a short glossary to help you understand. Fujita Scale: Scale used to measure wind speeds of a tornado and their severity.F1: Laughable little string of wind unless it comes through your house, then enough to make your insurance company drop you like a brick. People enjoy standing on their porches to watch this kind.F2: Strong enough to blow your car into your house, unless of course you drive an Expedition and live in a mobile home, then strong enough to blow your house into your car.
53F3: Will pick your house and your Expedition up and move you to the other side of town. F4: Usually ranging from 1/2 to a full mile wide, this tornado can turn an Expedition into a Pinto, then gift wrap it in a semi truck.F5: The Mother of all Tornadoes, you might as well stand on your front porch and watch it, because it's probably going to be quite a last sight.F6: Is theoretical and has never been reported.It is known as “the finger of god’ or “the finger of fate.” The implication, is that the power and destructive force is incalculable and unguided.
55Meteorologist: A rather soft-spoken, mild-mannered type person until severe weather strikes, and they start yelling at you through the TV: "GET TO YOUR BATHROOM OR YOU'RE GOING TO DIE!“Storm Chaser: Meteorologist-rejects who are pretty much insane but get us really cool pictures of tornadoes. We release them from the mental institution every time it starts thundering, just to see what they'll do.Moore, Oklahoma: A favorite gathering place for tornadoes. They like to meet here and do a little partying before stretching out across the rest of the Midwest.
56Bathtub: Best place to seek shelter in the middle of a tornado, mostly because after you're covered with debris, you can quickly wash off and come out looking great. Severe Weather Radio: A handy device that sends out messages from the National Weather Service during a storm, though quite disconcerting because the high pitched, shrill noise just as an alarm sounds suspiciously just like a tornado. Plus the guy reading the report just sounds creepy. Tornado Siren: A system the city spent millions to install, which is really useful, unless there's a storm or a tornado, because then of course you can't hear them.
57Storm Cellar: A great place to go during a tornado, as it is almost 100% safe, though weigh your options carefully, as most are not cared for and are homes to rats and snakes.May-June: Tourist season in Oklahoma, when people who are tired of bungee jumping and diving out of airplanes decide it might be fun to chase a tornado. These people usually end up on Fear Factor.
58Mobile Home: Most people are convinced mobile homes send off some strange signal that triggers tornadoes, because if there's one mobile home park in a hundred mile radius, the tornado will find it.Twister: Slang for 'tornado' and also the title to a movie starring Helen Hunt, which incidentally everyone thought was corny and unrealistic until May 3rd, 1999.
59TORNADO RECORDS· Highest Recorded Wind: 318 mph, Bridge Creek/Moore, OK, May 3, **· Widest Observed Path: 2.5 miles, Hallam, NE, May 22nd,· Longest Observed Path: 219 miles, Tri State Tornado, March 18, 1925.
60Additionally, here are some phrases you might want to learn and be familiar with: "We'll have your electricity restored in 24 hours," which means it'll be a week.“We're going to be out for a week, so buy a lot of supplies and an expensive generator," means it's going to be on in twelve hours, probably as soon as you return from Wal-Mart."It's a little muggy today." Get outta town. It's getting ready to storm."There's just a slight chance of severe weather today, so go ahead and make your outdoor plans." Ha. Ha ha ha ha.
62The BIG STORM TIP of the day: When your electricity goes out, and you go to bed at night, be sure to turn off everything that was on before it went out, or when it is unexpectedly restored in the middle of the night, every light, every computer, your dishwasher, your blow dryer, your washing machine, your microwave and your fans will all come on all at once. 1) You'll just about have a heart attack when they all come on at the same time, waking you from a dead sleep. And 2) Your breakers will blow, leaving you in the dark once again.
63Thunderstormssmall area storms formed by the strong upward movement of warm, moist airusually occurs ahead of a cold front as the colder, denser air shoves the warmer air upwardThis forms the cumulonimbus clouds that produce thunderstormsThese storms are accompanied by heavy rain, thunder, lightning, sometimes hail, and can also produce tornadoes
64All thunderstorms produce lightning Lightning is the discharge of huge amounts of static electricity (think of walking across a carpet in your socks and then touching something-ZAP)Lightning can travel from the cloud to the ground, cloud to cloud, or even from the ground to a cloud!Thunder is the result of the air quickly expanding from the heat of the lightning bolt (causes a sound wave)You cannot have lightning without thunder!!
65Supercell Thunderstorm formations – will form SEVERE storms and tornadoes! THIS IS ONE BIG STORM SYSTEM!