Weather and Severe Storms

The Sun provides the energy that drives Earth’s weather by unevenly heating the

land and water, and by heating the equator and poles by different amounts.

http://www.youtube.com/watch?v=6hD52H7rQak The Sun as the driving force behind for wind and water currents and earth’s temperatures

Air masses, of different temperature and humidity, move from areas of high pressure to

areas of low pressure, creating wind.

Why would the area indicated in the map below be considered unseasonably warm?

•Look at the jet stream.

•Since the jet steam is so far north, the warm tropical air from the South would come further north

Climate is the long term pattern of temperature and precipitation in an area

Weather is the short term variations in temperature, humidity, air pressure, and wind.

http://www.climatecentral.org/videos/web_features/climate_vs_weather

Weather happens every day, but only some days have storms

Storms vary depending on their temperature, if they are coming off the ocean or continent, and the season.

The severity of the storm depends on whether or not they strike a populated area.

Examples of severe storms

•Thunder and lightning storms•Tornadoes•Hurricanes•Blizzards

•For the test you need to be able to:• distinguish one storm from another and • identify why they only form in certain areas of

world during certain times of the year

Thunderstorms•What is it? A storm with thunder and lightning and typically also heavy rain or hail.

•What causes a thunderstorm?• Moisture, unstable air, and lift. • You need moisture to form clouds and rain. You need

unstable air that is relatively warm and can rise rapidly. Finally, you need lift. This can form from fronts, sea breezes or mountains.

When are thunderstorms most likely to occur?Thunderstorms can occur year-round and at all hours. But they are most likely to happen in the spring and summer months and during the afternoon and evening hours. Why?

•Warm, moist air rises, forming cumulus, then cumulonimbus clouds.

•The water vapor condenses, it collects together and forms rain drops or hail.

•As rain or hail falls, a downdraft is created, which cuts off rising warm air and stops the storm.

Thunderstorm FormationThunderstorm Formation

Lightning•Uneven electrical charges occur in a cloud as rain drops and hail move in a convection current in the cloud.

•The lightning occurs in an attempt to equalize the uneven charges.

Tornadoes

Tornadoes•What is a tornado?A tornado is a violent rotating column of air extending from a thunderstorm to the ground.

Other Names for Tornadoes•Tornado comes from the Spanish word, tronada, which means “thunderstorm.” Other names for tornadoes are twisters, dust devils, whirlwinds, waterspouts, and cyclones.

R- Dust Devil, Center- Water Spouts, L- Fire Devil

•In severe thunderstorms, winds are moving in different directions and at different speeds at different heights.

•This difference in wind direction and wind speed is called wind shear.

Wave Clouds (or Tsunami Clouds, or Kelvin-Helmholtz Clouds) seen in

Van Gogh’s “Starry Night” painting

•A strong updraft tilts the wind shear and produces rotation inside the tornado. A funnel cloud appears.

Tornado AlleyTornado Alley Tornadoes in the U.S. are most likely to Tornadoes in the U.S. are most likely to

occur in a region known as Tornado occur in a region known as Tornado Alley.Alley.

Did Dorothy from the Wizard of Oz live in “Tornado Alley?”

Any place thunderstorms occur, a tornado can happen.

In the United Kingdom, Polar continental air mixes with Tropical Maritime air

producing tornadoes

Tornado Categories

• The Fujita-Pearson Tornado Intensity Scale or F-scale ranks tornadoes by their wind speed.

• F0- winds 40-72 mph• F1- winds 73-112 mph• F2- winds 113-157 mph• F3 – winds 158-206 mph• F4 – winds 207-260 mph• F5 – winds > 261 mph

Tornado Precautions

•Go to a basement, if you have one.•Get in the innermost room of your house. Avoid rooms with windows. Bathrooms are good.

•Crouch with arms above your head.• If outside, lie in a ditch or get under a bridge.

• If you live in an area with a frequency of tornadoes, listen to forecasts.

Hurricanes

Hurricanes• What is a hurricane?

Hurricanes are a system of strong winds spiraling inward and upward at speeds of 75 to 200 mph counterclockwise around a low pressure center

• Swirling air rises and cools, forming clouds and precipitation• Hurricanes form over warm (82 degree +) water and have

winds 74+ mph

Formation of a Hurricane•Hurricanes are storms that form over tropical waters. The hurricanes that affect the eastern coast of the United States form off the western coast of Africa where the water is warm, the air is humid, and the winds converge.

•Hurricanes start out as a group of storms that begin to rotate when they meet converging winds. These storms create violent seas that send more moisture into the air. The water vapor rises and helps the wind increase in speed. If the storm holds itself together for 24 hours, we call it a tropical disturbance.

Tropical Disturbance

Tropical Depression

•Tropical cyclones are areas of low pressure that develop over tropical waters. We call them tropical depressions if their wind speeds are more than 25 mph and less than 38 mph.

•A tropical disturbance becomes a tropical depression if it lasts more than 24 hours.

Tropical Storm

•A tropical depression becomes a tropical storm when its winds rise above 38mph.

• It is called a tropical storm if the winds are between 39 and 73 mph.

Hurricanes

•A tropical storm becomes a hurricane when its winds exceed 73 mph.

Hurricane Categories

•Category 1 – Winds between 74- 95 mph•Category 2 – Winds between 96- 110 mph•Category 3 – Winds between 111-130 mph•Category 4 – Winds between 131-155 mph•Category 5 – Winds above 156 mph

                                                    

• Hurricanes can be very big, even as big as the state of Ohio! They can be seen from outer space.

• The entire formation and life of a hurricane takes days or weeks.

• Because hurricanes seldom travel in straight paths, meteorologists predict several paths.

• Hurricanes usually lose power as they travel over land.

• Hurricanes destroy beaches, buildings, and vegetation.

• Hurricanes bring strong winds, heavy rain, storm surges, flooding, and tornadoes.

Hurricane Facts

Hurricane Protection

•Watch weather forecasts.•Board up all windows and doors•Have bottled water, food, batteries, medicine, and important documents

•Call someone and let them know where you are

•Photograph valuables for insurance•Take care of your pets

Hurricane Isabel

Hurricane AndrewHurricane Andrew

The path of Hurricane Andrew over three consecutive days The path of Hurricane Andrew over three consecutive days can be seen below.can be seen below.

Super Storm SandySuper Storm Sandy

BlizzardsBlizzards

A blizzard is a long-lasting snowstorm with very strong winds (35+ mph) and intense snowfall.

When and where do blizzards occur?When and where do blizzards occur?

They are common in winter when the jet stream travels They are common in winter when the jet stream travels south and a cold northern air mass comes in contact with a south and a cold northern air mass comes in contact with a warmer, semi-tropical air mass.warmer, semi-tropical air mass.

When the cold, continental polar air mass When the cold, continental polar air mass travels over a lake, it can pick up more travels over a lake, it can pick up more moisture and produce “Lake Effect” snow moisture and produce “Lake Effect” snow blizzardsblizzards

Lake Effect SnowLake Effect Snow

Blizzards & Ice Storms

Review1. Which is larger, a hurricane or a tornado?2. Which moves faster, a hurricane or a tornado?3. Which lasts longer?4. Where do hurricanes form?5. Where do tornadoes form?6. What do we call the area of the US that has a

high occurrence of tornadoes?7. How long do tornadoes last?8. How long do hurricanes last?9. Name two precautions in the event of a tornado.10.Name two precautions in the event of a

hurricane.

Severe WeatherSevere Weather

Spring or Summer

Type of Storm Where FormsTypical Time of

YearSafety Rules

Thunderstorms

Tornado

Hurricane

Within large cumulonimbus clouds

Spring, early summer

Evacuate or move inside a well-built building.

Seek shelter, avoid trees and water.

Cumulonimbus cloud

Move to a storm shelter or basement if possible; stay away from windows and doors.

Over warm ocean water

Late summer and into autumn

WEATHER SERVICE MAPSWEATHER SERVICE MAPS

ISOTHERMS are lines joining ISOTHERMS are lines joining places on the map that have the places on the map that have the same TEMPERATUREsame TEMPERATURE–Do you see the connection between Do you see the connection between “isotherm” and “thermometer”“isotherm” and “thermometer”

ISOBARS are lines joining places ISOBARS are lines joining places on the map that have the same AIR on the map that have the same AIR PRESSUREPRESSURE–Iso means “equal”Iso means “equal”

–Bar means “pressure”Bar means “pressure”Why doyou think it’s called a barometer?Why doyou think it’s called a barometer?

WEATHER SERVICE MAPSWEATHER SERVICE MAPS