BC: By Elizabeth Harris Mrs. Scott's Class 2nd block
FC: Weather Booklet
1: Contents Air Pressure and Density Pg 2 Jet Streams Pg 3 Types of Air Masses Pg 4-5 Types of Fronts Pg 6-7 Types of Pressure Systems Pg 8-9 Types od Global Winds Pg 10-11 Types of Thunderstorms Pg 14-17 Tornadoes, their classifications and safety Pg 18-21 Tropical Cyclones Pg 22-23 Stages of Development of Tropical Cyclones and their classidications Pg 24-25 Hurricane Safety Pg 26-27 Storm Surge Pg 28-39
2: Air Pressure and Density Air pressure is caused by the air above exerting a force on the air below. Air pressure is the greatest near Earth's surface. When the temperature increases the particles of air move farther apart. Density decreasess as temperature increases. If density remains constant then air pressure increases temperature increases and vice versa.
3: Jet Stream The differances in temperature, pressure, and density preoduce fast, high-altitude winds called jets streams. They normally are found in the upper atmosphere and normally move west to east in the uper-mid latitudes. They affect the strengh of weather systems by moving air masses from one place to another.
4: Air Masses An air mass is a large body of air theat takes on the characteristics of the area that it is covering also called the source region. When they move they take on the characteristics of the new source region. | Air Mass Modififcation They are not permanent because wind currents move them frome one region to another. The process where they exchange heat and moisture with the surface that it is traveling over, is called air mass modification.
5: Classifying Air Masses Maritime = wet Continental = dry Tropical = warm Polar = cold Arctic = very cold
6: Fronts Fronts form when two air masses with differnet characteristics collide and seperates two air masses of different densities. There are four different types of fronts: cold, warm, stationary, and occluded. They can be thousands of kilometers and cause sudden changes in weather. | Cold Fronts Cold fronts are when cold and warm air masses collide and the cold air mass take over. The dense air forces force the warm air up. The rising cool air condenses and forms clouds, rain and sometimes thunderstoms. On a weather map, they are a blue solid line with triangles that point to the direction that the front is moving.
7: Warm Fronts A warm front happens when a warm air mass takes over a cold air mass. Warm fronts spread clouds and precipitation over a wide area. On weather maps, a warm front is a red solid line with semicircles pointing in the direction it is moving.
8: Stationary Fronts A stationary or stalled front forms when two air masses meet and stall or do not move. There normally are no major differences in temperature or pressure. Sometimes light winds and precipitation come with stationary fronts. They are represented on a weather map with a red and blue segmented line with blue triangles pointing to the warm air and red semicircles pointing to the cooler air.
9: Occluded Front Occululed fronts occur when cold air masses overtake a warm front. A warm front contains a cold air mass and warm air is forced between the two cold air massas. Strong and heavy winds occur with occluded fronts. On a weather map, they are a purple line with alternating triangles and semicircles.
10: Pressure Systems When air rises, air pressure decreases and when air sinks, air pressure increases. When air rises or sinks, high or low pressure form in the atmosphere. These areas are known as pressure systems and air moves around the center of them in a circular motion. | High-Pressure Systems The Coriolis effect in the northern hemisphere causes air to move in a clockwise direction and in a counterclockwise direction in the southern hemisphere. The air spreads out from the center when it reaches Earth's surface. They normally indicate decent weather because clouds are not formed.
11: A wave cyclone affects the weather across areas in the middle latitudes like the mid-Atlantic states. | Low-Pressure Systems They move in a counterclockwise direction in the northern himisphere and a clockwise direction in the southern hemisphere. | Air raises to the center, then up and air from outside replaces the raising air. Low-Pressure systems come with clouds and precipitation. A wave cyclone affects the weather across areas in the middle latitudes, like the mid-Atlantic states.
12: Global Wind Systems There are three major wind systems in each hemisphere, they are the trade winds, prevailing westerlies and the polar easterlies. The wind directions in the north and south hemispheres are reversed. | Trade Winds They are located 30 degrees at the north and south latitudes. This area is called the horse latitudes and the winds are generally light. The air sinks and moves toward the equator and is warmed by the sun. The air rises and travels back toward its origin, where it cools, sinks and moves again toward the equator. This is called a convection current and is repeated endlessly. The raising air causes clouds and precipitation. Tropical rain forest and most moist areas are found along this belt.
13: Polar Eaterlies They are found between 60 degrees latitude and the poles. They bring cold air and in the northern hemisphere blow from the northeast to the southwest. In the southern hemisphere, they flow from the southeast to the northwest. | Prevailing Weasterlies They are located between 30 and 60 degrees north and south latitudes. They are named for the direction they are blowing. They normally blow from the west and move east to the poles. In North America, they blow from the southwest to the northeast because of the Coriolis effect and greatly affect the movement of weather systems across the US and Canda.
14: Thunderstorms They develop when a cumulus cloud grows into a cumulonimbus cloud and temperature and humidity are at optimal levels for a storm and precipitation to happen. The cloud must be lifted by unequal heating at the Earth's surface or an advancing front and the lower atmosphere must contain alot of moisture. The air that surrounding the cloud, has to be unstable or colder than the cloud.
15: Mountain Thunderstorms They form when air is going over a mountain. Frontal Thunderstorms They form as a result of oncoming cold fronts causing cold air to push the warm air up extremely fast. A line of thunderstorms can form along the edge of fronts (sometimes warm fronts). | Air-Mass Thunderstorms An air-mass thunderstorm rises because of the unequal heating of Earth's surface, which is normally during mid -afternoon. Sea-breeze Thunderstorms They form in summer, in tropical and subtropical coastal regions. They are caused by major tempeture gradients between air over land and water.
16: Supercells They develop when a very large temperature gradient is between the upper and lower parts of the storm. They normally occur when cold fronts move with upper-level, low-pressure systems that contain parts of cold air. The results can be a very violent storm with major,rotating updrafts,and can reach speeds of 240 km/h. Supercells only occur in 10% of thunderstorms that occur each year. | Severe Thunderstorms Powerful thunderstorms produce hail, tornadoes, and winds that can be mores than 160 km/h.
17: Lightning It is a electrical discharge caused by quick movement of air in a cumulonimbus cloud. A lightening bolt heats the air to 30,000 degrees C which is five times greater than the surface of the sun. It causes hundreds of injuries and deaths per year and about 7,500 forest fires. | Hail Hail is a form of precipitation that falls in the form of balls of ice. The precipitation freezes and begins to fall, then an updraft brings it back up and it grows larger. This process continues till the hail is to heavy and it falls to the ground. It can destroy crops and cause $1,000,000,000 in damage each year.
18: Tornados A tornado is a violent, whirling column of air that touches the ground.
19: Tornados Classification Weak tornadoes (F0 and F1) are 80% of all the tornadoes, have a path of up to 5 km, have wind speeds 97 to 185 km/h and last about one to ten minutes. Strong tornadoes (F2 and F3) make up about 19% of all tornadoes, have a path of 24 km or more, have wind speeds from 177 to 330 km/h and last twenty minutes or more. Violent tornadoes (F4 and F5) make up 1% of tornadoes, have a path of 80 km or more, have wind speeds of 322 km or higher and last an hour or more.
20: Tornado Safety If you are in a home or building, go to a designated shelter area like a basement. If an underground shelter is unavailable, move to an inside room or hallway on the lowst level of the building and try to get under a heavy or sturdy piece of furniture. Stay away from windows. Get out of cars and do not try to out run a tornado in them. If you are outside or in a vehicle, lie flat in a nearby ditch or depression in the ground. Mobile homes are not good protection from tornadoes and you should leave then immediately.
22: They are large, rotating, low-pressure systems that form over tropical oceans since they get energy from warm water. | The low-pressure system begins to rotate counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. They start moving faster around when more air enters, rises and lets energy into the system. The lower the air pressure the stronger the storm. | Tropical Cyclones Tropical Cyclones are some of the most powerful storms on Earth.
23: Distribution of Tropical Cyclones There are two things responsible for the formation of a tropical cyclone and that is warm water and water distubance which causes air to rise. In North America they are called hurricanes. They most often stike during late sumer and early fall, when tropical oceans contain the greatest amount of heat and energy.
24: Stages of Development The first stage of a tropical cyclone is a tropical disturbance which is what causes air to rise. The disturbance begins to rotate around an area of low pressure and starts the next stage of development called a tropical depression. When the wind speed at the center of the cyclone goes above 65 km/h, the depression is classified as a tropical storm. If air pressure continures to go down and wind speed reach 120 km/h, the depression is classified as a hurricane.
26: Hurricane Classification The Saffir-Simpson hurricane scale ranks hurricanes according to their wind speed, air pressure in the center, and the amount of property damage that my happen. | Hurricane Scale A catagory 1 hurricane has wind speeds of 119 to 153 km/h and it causes mild to moderate damage. A catagory 2 hurricane has wind speeds of 154 to 177 km/h and it causes mild to moderate damage. A catagory 3 hurricane has wind speeds of 178 to 209 km/h and it is considerd highly damgerous. A catagory 4 hurricane has wind speeds of 210 to 250 and are considerd deadly. A catagory 5 hurricane has wind speeds of 250 km/h or higher and is considered deadly.
27: Hurricane Hazards Most of the damage caused by hurricanes comes from strong winds. The most powerful winds are normally found in the eyewall which is normally about 40 to 80 km wide. Winds which are more than 60 km/h are found hundreds of km from the storm eye.
29: Hurricane Safety Turn the refrigorator to the coldest setting and open it if necassary. Turn of all things if told to by authorities. Unplug small appliances and turn off propane tanks. Fill bathtubs and large containers with water for sanitary purposes. Stay away from windows and doors. Try and get in small interior rooms. Close interior doors and secure external doors. Go to the first floor and lie under a sturdy object.
30: Storm Surges The strong winds of hurricanes are the biggest factor in the creation of storm surges near costal areas. They are mounds of ocean water moved by hurricane-force winds that come onto land. They can be as tall as 6 m above sea level and cause major damage to property. Water damage from hurricanes can also happen inland because heavy rain can cause flooding.