weather systems. quick review what causes wind? what causes wind? answer: uneven heating of the...
TRANSCRIPT
WEATHER SYSTEMS
Quick ReviewQuick Review
• What causes wind?What causes wind? Answer: Answer: uneven heating of the earth by the sun.uneven heating of the earth by the sun.
• Is hot air high pressure or low pressure?Is hot air high pressure or low pressure? Answer: Answer: low pressure.low pressure.
• What about cold air?What about cold air? Answer: Answer: high pressurehigh pressure
• Which type of air rises? Which one sinks?Which type of air rises? Which one sinks? Answer: Answer: hot air (low pressure) rises, and cold air (high pressure) hot air (low pressure) rises, and cold air (high pressure)
sinks.sinks.
Now lets talk about Air MassesNow lets talk about Air Masses
Air MassesA large body of air that has nearly the same temperature and humidity throughout- They have similar properties as the part of the earth’s surface over which they form.
Why are Air Masses Why are Air Masses important?important?
• They can cover an area of thousands of They can cover an area of thousands of square kilometers. square kilometers.
• They are responsible for day to day They are responsible for day to day weather changes.weather changes.
Which way do the winds Which way do the winds blow?blow?
• From ___________ pressure to _____ From ___________ pressure to _____ pressure.pressure.
high low
Do you know what instrument we use to measure air pressure?
A Barometer
CyclonesCyclones
• In the northern hemisphere, once In the northern hemisphere, once wind blows into a low pressure area, wind blows into a low pressure area, it rises in a counterclockwise it rises in a counterclockwise direction; this is called a cyclone. direction; this is called a cyclone. Low pressure areas usually have Low pressure areas usually have stormy weather. stormy weather. ** This is not the ** This is not the same as a tornado**same as a tornado**
AnticyclonesAnticyclones
• Wind also blows Wind also blows AWAY AWAY from the from the centercenter of high pressure. In the of high pressure. In the northern hemisphere, this wind blows northern hemisphere, this wind blows in a clockwise direction. High in a clockwise direction. High pressure areas usually have good pressure areas usually have good weather.weather.
FrontsFronts
• What is a front?What is a front?
• It is a boundary between two air masses of It is a boundary between two air masses of different density, moisture, or different density, moisture, or temperature. temperature.
• There are four types of fronts; can you There are four types of fronts; can you name them?? _____________, ______________name them?? _____________, ______________
_____________, and ___________________________, and ______________
Warm frontCold front
Occluded front Stationary front
Precipitation Along a Cold Front lifting the warm moist air ahead of it
A Closer Examination of the Animation: Initially, the cold air mass wedges into the warmer air mass ahead of it, (separated from each other by the cold front). The lighter warm air is lifted upwards by the denser cold air and if enough water vapor condenses, clouds develop.
Precipitation Along a Warm Front warm moist air overriding colder air
A Closer Examination of the Animation: Initially, a warm air mass (in yellow) nudges against a colder air mass (in blue) ahead of it, (separated from each other by the warm front). The lighter warm moist air behind the front is lifted upward and "overrides" the colder air.
Stationary Front
SEVERE WEATHER
- A thunderstorm is a weather event where there is heavy rain, lightning, thunder roars, and possible hail.
How do they form?-They occur in warm moist air masses and along fronts.-The air is forced upward where it is __________, and condensation occurs forming _________________clouds.-Then __________________ happens in the form of rain or hail. The rain cooled air sinks and strong updrafts of warmer air causes strong winds.
cooledcumulonimbus
precipitation
What is a thunderstorm?
Can thunderstorms cause Can thunderstorms cause damage?damage?
• YES!YES!
• How?How?
• By floodingBy flooding
• Hail damageHail damage
• Wind damageWind damage
• Lightning strikesLightning strikes
What is lightning?
Lightning is a bright flash of electricity produced by a thunderstorm. All thunderstorms produce lightning and are very dangerous. If you hear the sound of thunder,
then you are in danger from lightning. Lightning kills and injures more people each year than hurricanes or
tornadoes; between 75 to 100 people.
What causes lightning?Lightning is an electric current. In a thundercloud, many small bits of ice (frozen raindrops) bump into each other as they move around in the air. All the collisions create an electric charge. Once the cloud fills, with electrical charges, the positive charges form at the top of the cloud and the negative charges form at the bottom of the cloud. Since opposites attract, this causes a positive charge to build up on
the ground beneath the cloud. The grounds electrical charge concentrates around anything that sticks up, such as mountains, people, or single trees. The charge coming up from these points
eventually connects with a charge reaching down from the clouds and - zap - lightning strikes!
Lightning can also form within or between clouds, not just from the cloud to the ground
Lightning also forms within and between clouds.
Thunder is caused by lightning. When a lightning bolt travels from the cloud to the ground it actually opens up a little hole in the air, called a channel. The lightning heats up the air and causes it to expand. Once the lightning is
gone the air collapses back due to quick cooling, and creates a sound wave that we hear as thunder. The reason we see lightning before we hear thunder is
because light travels faster than sound!
Which do you think is hotter, a bolt of lightning, or the surface of the sun?
Lightning- it is 30,000 degrees Celsius. That’s 5 times hotter than the sun!!
What causes thunder ?
Yes, you can use thunder to tell how far away a storm is. Next time you see a storm, count the number of seconds
between when you see the lightning and hear the thunder. Take the number of seconds and divide by 5 and
that will tell you how far away the storm is in miles. For example: If you counted 10 seconds between the
lightning and the thunder, the lightning is 2 miles away!
Can you tell how far away a thunderstorm is?
How do tornadoes form? When thunderstorms develop, a change in wind direction
and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower
atmosphere; this is wind shear. Rising air from the updraft of a thunderstorm tilts the rotating air from
horizontal to vertical. An area of rotation, 2-6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.
Know the Lingo TORNADO WATCH - Tornadoes are possible in your area. Stay tuned to the radio or
television news.
TORNADO WARNING - A tornado is either on the ground or has been detected by Doppler radar. Seek shelter immediately!
Measuring Tornadoes
The Fujita ScaleThe Fujita Scale
F0F0gale tornadogale tornado40-72 mph40-72 mph
Some damage to chimneys; breaks branches off trees; pushes over shallow-Some damage to chimneys; breaks branches off trees; pushes over shallow-rooted trees; damages sign boards.rooted trees; damages sign boards.
F1F1moderate tornadomoderate tornado73-112 mph73-112 mph
Lower limit is the beginning of hurricane-force winds. Peels surface off roofs; Lower limit is the beginning of hurricane-force winds. Peels surface off roofs; mobile homes pushed over; moving autos pushed off roads.mobile homes pushed over; moving autos pushed off roads.
F2F2significant tornadosignificant tornado113-157 mph113-157 mph
Roofs torn off frame houses; mobile homes demolished; boxcars pushed over, Roofs torn off frame houses; mobile homes demolished; boxcars pushed over, large trees snapped or uprooted; light-object missiles generated.large trees snapped or uprooted; light-object missiles generated.
F3F3severe tornadosevere tornado158-206 mph158-206 mph
Severe damage. Roofs and some walls torn off well-constructed homes; trains Severe damage. Roofs and some walls torn off well-constructed homes; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown.thrown.
F4F4devastating tornadodevastating tornado207-260 mph207-260 mph
Well-constructed homes leveled; structures with weak foundations blown off Well-constructed homes leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.some distance; cars thrown and large missiles generated.
F5F5incredible tornadoincredible tornado261-318 mph261-318 mph
Phenomenal damage. Strong frame homes disintegrate or lifted off foundations Phenomenal damage. Strong frame homes disintegrate or lifted off foundations and carried considerable distance; trees debarked.and carried considerable distance; trees debarked.
The geography of the central part of the United States, known as the Great Plains, is suited to bring all of the ingredients together to forms tornadoes. This includes
Texas, Kansas, and Oklahoma. More than 500 tornadoes typically occur in this area every year and is why it is
commonly known as "Tornado Alley".
Where are tornadoes most likely to occur?
What is a hurricane?A hurricane is a huge storm! It can be up to 600 miles across and have strong winds spiraling inward and upward at speeds of 75 to 200 mph. Hurricanes usually lasts for over a week, moving 10-20 mph over the open ocean. Hurricanes gather heat and energy through contact with warm ocean waters. Evaporation from the seawater increases their power. Hurricanes rotate in a counter-clockwise direction around an "eye." The center of the storm or "eye" is the calmest part. It has only light winds and fair weather. When they come onto land, the heavy rain, strong winds and large waves can damage buildings, trees and cars. Similar storms are called typhoons in the Pacific Ocean and cyclones in the Indian Ocean.
How do hurricanes form?Hurricanes form over warm ocean water of 80°F or warmer. The atmosphere must cool off very quickly the higher you go. The wind must be blowing in the same direction and at the same speed to force air upward from the ocean surface. Winds flow outward above the storm allowing the air below to rise. Hurricanes typically form between 5 to 15 degrees latitude north and south of the equator. The Coriolis effect is needed to create the spin in the hurricane.
Saffir-Simpson Hurricane Scale
CategoryWinds
(MPH)Storm Surge
(Feet)Damage
1 74-95 4'-5' Minimal2 96-110 6'-8' Moderate3 111-130 9'-12' Extensive4 131-155 13'-18' Extreme
5 >155 >18' Catastrophic
Can Hurricanes cause Can Hurricanes cause damage?damage?
• Absolutely!Absolutely!
• Storm surges usually cause the most Storm surges usually cause the most damage and deathdamage and death
• Winds can destroy homes and uproot Winds can destroy homes and uproot treestrees
• Extensive rain can also cause major Extensive rain can also cause major floodingflooding
Shallow-Water Coastline
Deep-Water Coastline
What is a storm surge?
Know the Lingo
TROPICAL STORM WATCH - Tropical Storm conditions with sustained winds from 39 -74 mph are possible in your area within
the next 36 hours. TROPICAL STORM WARNING - Tropical Storm conditions are
expected in your area within the next 24 hours.HURRICANE WATCH - Hurricane conditions with sustained winds of 74 mph or greater are possible in your area within the next 36 hours. This WATCH should trigger your family's disaster plan, and protective measures should be initiated. Especially, those actions
that require extra time such as securing a boat and leaving a barrier island.
HURRICANE WARNING - Hurricane conditions are expected in your area within 24 hours. Once this WARNING has been issued,
your family should be in the process of completing protective actions and deciding the safest location to be during the storm
How do blizzards form?A blizzard is a long-lasting snowstorm with very strong winds and intense snowfall. You need three things to have a blizzard; cold air at the surface, lots of moisture, and lift. Warm air must rise over cold air. Blizzards have winds of at least 56 km/h, temperature is below 20 degrees fahrenheit, and visibility is less than 400 meters
Forecasting WeatherForecasting Weather
• What information do you need to What information do you need to know to forecast weather?? know to forecast weather??
• TemperatureTemperature
• WindsWinds
• Air pressureAir pressure
• HumidityHumidity
• PrecipitationPrecipitation
Do you know the scientific Do you know the scientific name for a weather forecaster?name for a weather forecaster?
A A MeteorologistMeteorologist is what is what they’re called.they’re called.
• Meteorologists measure temperature, air Meteorologists measure temperature, air pressure, winds, humidity, and pressure, winds, humidity, and precipitation.precipitation.
• They use Doppler radar, satellites, and They use Doppler radar, satellites, and instruments attached to balloons to get instruments attached to balloons to get their information.their information.
• They gather information from the upper They gather information from the upper atmosphere, as well as from the earth’s atmosphere, as well as from the earth’s surface. surface.
STATION MODEL
Key to Features 1 -- Cold Front 2 -- Warm Front 3 -- Stationary Front 4 -- Occluded Front 5 -- Trough ("TROF") Also used to depict Outflow Boundary ("OUTFLOW BNDRY") 6 -- Squall Line 7 -- Dry Line 8 -- Tropical Wave ("TRPCL WAVE")
A hash mark denotes a change in frontal type, as in the example below.
Note: The hash mark will always be drawn perpendicular to the boundaries. They are not drawn at "triple points" (the intersection of an occluded, cold and warm or stationary front) and where a low pressure center separates the different frontal types
A weather map showing surface-pressure systems, air masses, fronts, and
isobars (in millibars) as solid gray lines. Large arrows in color show air
flow. (Green-shaded area represents precipitation.) Isotherms are similar to isobars, except they show temperature (Not Shown here)
