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Chapter 15: Weather Systems
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1. The Weather around Us
2. The Science of Weather: From
Folklore to Forecasting
3. Air Masses
5. Midlatitude Cyclones
4. Frontal Systems
and Tornadoes
6. Severe Weather: Thunderstorms
7. Severe Weather: Hurricanes
Learning Objectives• Students will explain concepts related to weather systems.• Students will recognize the role of technology in our knowledge of
weather patterns and forecasts.• Students will classify air masses based on their locations.• Students will compare and contrast warm, cold, and occluded
fronts.• Students will synthesize the development of mid-latitude cyclones
and frontal systems.• Students will describe the process of thunderstorm, tornado, and
hurricane formation.• Students will recognize when/where tornadoes are most likely to
occur.• Students will place hurricanes within the context of the Earth
system.
The Weather around Us
The Good Earth/Chapter 15: Weather Systems
Would you want to be riding in one of these vehicles?
On average, 2-3 U.S. weather disasters per year cause more than a billion dollars in damage and threaten numerous lives.
Today, more than 100 million residents make the South the most heavily populated region in the U.S.
People are migrating to Florida, Georgia, and N.C. more than any other state.
Most people are migrating from states that have low incidences of extreme weather events (New York, Illinois, New Jersey).
The Good Earth/Chapter 15: Weather Systems
The Weather around UsWeather = the state of the atmosphere at any given time
and place.
Extreme weather can threaten lives, disrupt transportation, and cause billions of dollars in destruction.
Billion dollar weather disasters, 1980-2005.
The Weather around Us
• Almost 3 times as many people die from extreme temperatures than any other weather related causes.
• More than 26,000 people in Europe died in 2003 during hottest summer on record there (104°F or more).
• Extreme weather events can change these statistics (e.g. Katrina killed over 1,000 people)
• Extreme heat – “…underrated and least understood of the deadly weather phenomena.”
The Good Earth/Chapter 15: Weather Systems
Weather-related fatalities.
The Weather around Us• Can extreme heat, tornadoes, hurricanes, and other weather phenomena
be stopped?
− No, but meteorologists work to provide timely warnings.
− Hurricane Katrina – most expensive disaster in U.S. history.
− Over $100 billion in damage.
The Good Earth/Chapter 15: Weather Systems
Hurricane Katrina approaches the Louisiana coast, August 28, 2005.
Weather Systems Self Reflection Survey
The Good Earth/Chapter 15: Weather Systems
Answer the following questions as a means of uncovering what you already know about weather systems:
1. Explain three examples of how the weather influences your daily life.
Weather Systems Self Reflection Survey
The Good Earth/Chapter 15: Weather Systems
Answer the following questions as a means of uncovering what you already know about weather systems:
2. Describe your ideal annual weather conditions.
Weather Systems Self Reflection Survey
The Good Earth/Chapter 15: Weather Systems
Answer the following questions as a means of uncovering what you already know about weather systems:
3. Describe the most extreme weather event you have experienced.
Go back to the Table of Contents
Go to the next section: The Science of Weather: From Folklore to Forecasting
The Good Earth/Chapter 15: Weather Systems
The Science of Weather: From Folklore to Forecasting
The Good Earth/Chapter 15: Weather Systems
Mankind has been trying to make sense of the weather since ancient times.
Meteorology is the study of the atmosphere and its weather.
1637 – Descartes published first scientific text on weather, but had no tools to make measurements.
By the 1700’s the technology caught up:
- 1643 first barometer
-Gabriel Fahrenheit (1714) and Anders Celsius (1742) invented first Mercury thermometers
- hygrometer (measures humidity) invented a few decades later
A paradigm shift in our understanding of weather occurred.
The Good Earth/Chapter 15: Weather Systems
With the development of communications devices information on weather from multiple sources became
available, and patterns in weather data began to emerge.
-Weather systems migrate from west to east
-Fair skies are associated with high-pressure
-Rain often accompanies low-pressure systems
U.S. National Weather Service was established in 1870
By 1872 it was creating national weather maps
By 1878 daily observations were being collected at hundreds of sites and relayed cross-country by telegraph
The Science of Weather: From Folklore to Forecasting
Not until early 1900’s did Norwegian scientists identify the concepts of air masses and frontal systems
The Good Earth/Chapter 15: Weather Systems
• Air masses = large volumes of air with similar temperature and pressure.
• Frontal systems = locations where air masses interact.
• Few gas molecules exist here.
These concepts allowed meteorologists to use raw temperature and pressure data to predict weather over large regions.
The recognition of these basic types of air masses and their motions made it possible to develop rules for the evolution of weather systems.
Later these rules were turned into mathematical equations that could be programmed into computers to produce forecasts
The Science of Weather: From Folklore to Forecasting
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
The Bergen school (the Norwegian scientist who identified the concepts of air masses and frontal systems) looked at individual weather cases and drew general conclusions about weather. Which of the following types of reasoning did they use:
a.Inductive Reasoning
b.Deductive Reasoning
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
Once the rules of weather evolution were established, scientists anywhere could readily apply these rules to predict future weather patterns. This is an example of:
a.Inductive Reasoning
b.Deductive Reasoning
The Good Earth/Chapter 15: Weather Systems
The Science of Weather: From Folklore to ForecastingToday, all weather
information and data come from the NWS.
NWS processes over 1 million surface, air, and satellite weather observation every day.
Two GEOS (geostationary operational environmental satellite) satellites in orbit provide weather coverage for 60% of the planet’s surface.
Over 100 Doppler radar sites nationwide used to track changes in regional storms.
Doppler can detect dangerous swirling winds.
Satellite weather image for North America
Weather Systems Checkpoint 15.3
How are the following four key principles of science evident in the brief history of meteorology in this section?
1) Phenomena can be explained by natural causes.
2) Explanations are tentative.
3) Science is based on empirical observations.
4) Explanations should be testable.
The Good Earth/Chapter 15: Weather Systems
Go back to the Table of Contents
Go to the next section: Air Masses
The Good Earth/Chapter 15: Weather Systems
Air Masses
Air Mass = a large region of the lower troposphere that has relatively uniform temperature and moisture
content.
The Good Earth/Chapter 15: Weather Systems
Their nature depends on their source area and changes that occur as they travel.
Air masses are identified by their temperature and the moisture characteristics of the underlying surface.
-Polar air masses found at high latitudes
-Tropical air masses found near equator
-Maritime air masses develop above oceans and are wetter
-Dry air masses form over continents
No clear boundaries between these air masses – they can migrate
Air Masses
The Good Earth/Chapter 15: Weather Systems
Locations of air masses. cA = continental Arctic/Antarctic; cP = continental polar; cT = continental tropical; mP = maritime polar; mT = maritime tropical.
Northern Hemisphere Southern Hemisphere
Air Masses
The Good Earth/Chapter 15: Weather Systems
Types of Air Masses:
• cA – forms over permanent snow or sea ice. Extremely cold, dry air that may move south.
• cP – forms over northernmost portions of N. America, Europe, and Asia. Cold and dry but not as cold as cA masses.
• cT – forms over continental interiors. Hot, dry air that is modified as it moves east or north.
• mP – form in the N. Atlantic and Pacific and Southern Oceans. Cool, moist air that affects NE and NW states in the U.S. Warmer than cP air. Bring rains to the coasts of Washington, Oregon, and snows to the inland mountains.
• mT – move inland from the tropical Pacific Ocean, Gulf of Mexico, and tropical Atlantic Ocean. Hot and humid. Brings hot humid summers to SE states.
Air Masses
The Good Earth/Chapter 15: Weather Systems
Air masses of North America
Circles show source areas and arrows show where the air mass moves after it forms.
Source areas and paths can influence weather patterns across North America.
Weather Systems Checkpoint 15.5
The Good Earth/Chapter 15: Weather Systems
Of the five most common types of air masses, which ones most directly affect the area where you live?
Air Masses
The Good Earth/Chapter 15: Weather Systems
Air masses can gain or lose heat and/or moisture as they move from one location to another.
Air masses are principally modified by:
- Temperature of the underlying surface
- Topography of the underlying surface
Examples:Air heated by warmer land surface will begin to rise. It is unstable and will rise until its temperature matches the surrounding atmosphere.
Air that is forced up over topography will cool and moisture will condense. Condensation removes moisture leaving dry air (rainshadow effect).
Air MassesLake effect is
common in states south and east (downwind) of the great lakes.
Dry cP air masses pick up moisture as they cross the warmer waters of the lakes. When the air mass arrives at the southern lake shore it cools, saturates, and precipitates.
The Good Earth/Chapter 15: Weather Systems
Weather Systems Checkpoint 15.7
The Good Earth/Chapter 15: Weather Systems
Imagine that you had a device that would constantly monitor the characteristics of an air mass as it moved from its source region to another location. Draw some idealized graphs illustrating how some key characteristics of the mT and CP air masses would change.
Go back to the Table of Contents
Go to the next section: Frontal Systems
The Good Earth/Chapter 15: Weather Systems
Frontal Systems
The Good Earth/Chapter 15: Weather Systems
The boundary between one air mass and another is a front.
Frontal systems – pairs of relatively narrow, long, slightly curved regions where air masses interact.
Frontal systems bring clouds and precipitation and changes in moisture, temperature, pressure, and wind direction.
Weather patterns typically associated with a cyclone (low-pressure system) over the central U.S.
When warm and cold fronts merge, they form an occluded front.
Frontal Systems
The Good Earth/Chapter 15: Weather Systems
Cold fronts are represented by blue triangles, warm fronts by red semicircles.
Both symbols “point” in the direction of air movement.
Cloud cover occurs in advance of the cold front, adjacent to the warm front, and around the occluded front.
Warm maritime tropical air from the gulf of Mexico lies in between the two fronts.
Which direction is this frontal system moving?
West to east.
Frontal Systems
How are wind direction, temperature, clouds, and precipitation affected by a passing frontal system?
The Good Earth/Chapter 15: Weather Systems
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
Use this map to answer the following questions:
1. The map illustrates the relative positions of a warm front and a cold front. Where is the warm front located?
a) Between A and B
b) Between C and D
c) At E
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
Use this map to answer the following questions:
2. Where is it raining?
a) A and B
b) B and C
c) C and D
d) B and D
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
Use this map to answer the following questions:
3. Which location is in a maritime tropical air mass?
a) A
b) G
c) E
d) H
Weather Systems Conceptest
The Good Earth/Chapter 15: Weather Systems
Use this map to answer the following questions:
4. Which location will become warmer in the next 12 hours?
a) A
b) B
c) C
d) D
Frontal Systems
The Good Earth/Chapter 15: Weather Systems
Advancing Cold Fronts:
• Warm air is displaced up and over an advancing cold front
- The warm air is less dense and therefore lighter than the cold air
- Cold fronts slope steeply
- The rising air undergoes rapid cooling and condensation in a narrow region above the cold front
- Condensing water vapor fuels formation of tall cumulonimbus clouds that usually produce heavy but short-lived rains
A squall line is a linear pattern of thunderclouds that may accompany a
rapidly advancing cold front.
Above: Squall line in the Gulf of Mexico.
Frontal Systems
The Good Earth/Chapter 15: Weather Systems
Advancing Warm Fronts:
• Weather changes are not as severe
- The warm air does not rise as rapidly
- Warm fronts slope gently
- Warm fronts move more slowly and the associated rain may last longer than with a cold front
- Warm fronts extend over a larger area
- Temperatures and humidity rise
- Winds change direction
Occluded front. A cold air mass overtakes a warm air mass.
Nimbostratus clouds generate precipitation along an occluded
front.
Weather Systems Checkpoint 15.12
The Good Earth/Chapter 15: Weather Systems
Use the Venn diagram provided here to compare and contrast the characteristics of warm fronts and cold fronts. Identify at least 10 features, write them in the table, and put each of their corresponding numbers in the correct location on the diagram.
Cold front Warm front1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Go back to the Table of Contents
Go to the next section: Midlatitude Cyclones
The Good Earth/Chapter 15: Weather Systems
Midlatitude Cyclones
The Good Earth/Chapter 15: Weather Systems
Midlatitude cyclones are regional-scale low-pressure systems formed between 30° and 60° N or S.
• This is where continental polar and maritime tropical air masses collide to form frontal systems
• This collision zone migrates south during winter and north in the summer
• Can be 1-2 km (621 – 1242 miles) across
• Can affect much of the continent for up to a week
• Midlatitude systems tend to dominate weather patterns in the U.S.
• Midlatitude cyclones develop where surface irregularities (mountains or water boundaries) cause a local sideways-acting force to distort a front
• The front is transformed as warm air pushes northward and cool air pushes south, generating a counterclockwise rotation
Midlatitude Cyclones
The Good Earth/Chapter 15: Weather Systems
A midlatitude cyclone
(a)At the point where a low-pressure system (cyclone) interacts with neighboring high-pressure systems, a midlatitude cyclone forms. It is centered over the low-pressure system and is characterized by warm (red) and cold (blue) fronts. Cloud cover concentrates over the fronts and low-pressure center.
(b)Classic comma-shaped cloud pattern associated with midlatitude cyclones. Central U.S., Christmas Eve, 1997.
Midlatitude Cyclones
The Good Earth/Chapter 15: Weather Systems
a. A cyclone forms.
Three stages in midlatitude cyclone development over the U.S.
b. The cyclone reaches mature stage, with well-developed warm and cold fronts.
c. The cyclone begins to weaken as warm and cold fronts merge to form an occluded front.
Weather Systems Checkpoint 15.14
The Good Earth/Chapter 15: Weather Systems
Examine the image at right. Where is the low-pressure system at the center of the cyclone? What type of front is represented by the line of clouds extending toward the Gulf of Mexico?
Go back to the Table of Contents
Go to the next section: Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Severe weather (as defined by NWS) has one or more of the following elements:
A tornado
Damaging wind speeds (more than 58 mph)
Penny sized or larger hail
Only 10% of all the 100,000 thunderstorms that form over the U.S. each year have these conditions.
Most thunderstorms are around 16 miles across and last less than 30 minutes.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Moisture in the atmosphere + warm air + a lifting mechanism = a thunderstorm!
The life cycle of a thunderstorm.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Lightening! Lightening joins two centers of opposite charge associated with a thunderstorm. Cloud to ground lightening – negative charges in a cloud are connected to positive charges on the ground. Cloud to cloud
lightening – opposite charges in one or more cloud are connected.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Thunderstorms can occur anywhere in the U.S. but their causes vary by region:
Central or eastern portion of the states – isolated afternoon thunderstorms in warm summer months when moist air rises. They are typically brief and associated with a single large cloud called a cell. Warm land surface heats the overlying air, causing it to rise, condense, and generate a thunderstorm.
Eastern U.S. – thunderstorms associated with midlatitude cyclones. Severe storms from a series of cumulonimbus clouds called supercells. They are associated with frontal lifting along a cold front between cP and mT air masses. Most common during spring and early summer.
Rocky Mountains – related to orographic lifting.
Florida – warm maritime air rises due to several lifting mechanisms.
Thunderstorms are rare in Pacific coast states because weather is influenced by cool ocean more stable air.
Weather Systems Conceptest
Updrafts responsible for the formation of thunderstorm clouds are most likely to occur with which combination of conditions?
The Good Earth/Chapter 15: Weather Systems
a. Low-level warm, moist air; upper-level warm, moist air
b. Low-level cool, dry air; upper-level warm, moist air
c. Low-level warm, moist air; upper-level cool, dry air
d. Low-level cool, dry air; upper-level cool, dry air
Weather Systems Checkpoint 15.20
The Good Earth/Chapter 15: Weather Systems
Rank the three thunderstorm components (air temperature, moisture, a lifting mechanism) in order of their significance in causing thunderstorms. Justify your ranking.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Tornadoes = narrow, funnel-shaped spirals of rapidly
converging and rotating air that form in association with
thunderstorms.
Near-circular low-pressure systems that rotate
counterclockwise in the Northern Hemisphere
Pressure gradient is much more intense for tornadoes
Tornadoes generate the strongest natural winds on
Earth!
People have been “storm chasing” for about 50 years. Tourists pay companies to get them into tornado prone areas to get footage of
tornadoes. Groups of tourists will pile out of minivans and cheer as a tornado rips apart a
farmhouse. Is this sensible?
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
The worst tornado outbreak in U.S. history – April 3, 1974.
Tornadoes were spotted from Canadian border all the way down to Gulf coast, and from Illinois to Virginia.
A total of 148 tornadoes touched down in 13 states.
330 people killed, over 5,000 injured.
A massive single tornado threw two tractor-trailers onto the roof of a bowling alley in Xenia, OH as the storm sped through at 50 mph.
33 people killed, 1300 buildings destroyed in Xenia that day.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Tornadoes are ranked on the Fujita intensity scale, which places them in a category based on the destruction they
cause.
Rule of thumb: Weak tornadoes can tear shingles off the roof of a house, strong tornadoes can tear the roof off a house, and
violent tornadoes can tear up the whole house.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Union City, OK tornado May 1974.
a. Early stage
b. Mature stage
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Characteristics of tornadoes:
• Funnels are less than 2,000 feet wide
• Average funnel velocities are 31 mph, with highs of 125 mph
• Path of destruction typically 3-16 miles long
− Some may stay on ground for over an hour and travel over 62 miles
Tornadoes follow the path of their parent thunderstorms (most travel east or northeast, as they are often associated with midlatitude cyclone thunderstorms.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
a. Early stage. Friction slows winds near surface. Higher wind velocity moving upward from the surface. Contrasting vertical wind speed generates counterclockwise winds about a central horizontal axis.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
b. Updraft stage. Updrafts below a thunderstorm draw spiraling horizontal winds upward to form a mesocyclone within the larger storm cloud. These are rotating thunderstorms that can be seen on radar (up to 6 miles across).
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
c. Tornado stage. Rotation in the mesocyclone forms small intense spiraling winds within a newly formed tornado. These winds then extend downward from a cloud base toward the ground surface.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Why do you think U.S. tornado fatalities have declined in the past 50 or so years?
Better forecasting and warnings.
Severe Weather: Thunderstorms and Tornadoes
The Good Earth/Chapter 15: Weather Systems
Tornado Alley. The U.S. is home to the majority of the world’s tornadoes, averaging about 1200 per year. These states have an annual average of more than 5 strong to violent tornadoes, 1950-
1995.
Tornadoes occur when thunderstorm activity is at an optimum across much of the nation.
More common in Gulf coast and SE states in early spring, migrates to Great Plains in late spring.
Weather Systems Checkpoint 15.24
The Good Earth/Chapter 15: Weather Systems
Explain why the number of tornadoes counted each year has increased, while the number of days with at least one tornado sighting has remained essentially unchanged for several decades.
Go back to the Table of Contents
Go to the next section: Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Hurricane Katrina was the worst natural disaster to strike the United States in the last century.
Are we doomed to repeat history? Can a hurricane strike the same place twice?
More than 1,300 people died
An estimated $100 billion in damage in communities in Louisiana, Mississippi, and Alabama
Much of the damage had long been predicted – A dozen major hurricanes had made landfall along coastal Louisiana in the last century
Government reports, scientific articles, and newspaper stories had all predicted what would happen if a major hurricane made landfall near New Orleans
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Who should address the issue?
Scientists – best equipped to determine the probability and destruction of a hurricane, but no funds or resources to do much about it.
Government – have power and funds for levees or evacuation plans, but don’t always understand the seriousness of the threat.
“We learn from history that we learn nothing from history.” George Bernard Shaw
New Orleans before and after Katrina.
Blue areas = flooded areas
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Key observations of Katrina:
Large size
Dense mass of clouds surrounding central clear “eye”
Swirling spiral pattern of clouds
Centered over the ocean (Gulf of Mexico)
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Hurricanes originate in areas of the world’s oceans where the temperature is greater than about 80°F. Hurricanes are most common in the summer
seasons of each hemisphere.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
What are hurricanes:
High winds
Heavy rainfall
Storm surges (elevated water levels) along coastlines
Not all hurricanes make land fall
Biloxi, Mississippi before and after Katrina.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
North Atlantic hurricane season June 1 – November 30
Hurricanes only develop over warm (>80°F) water down to ~200 ft
Needs sufficient evaporation and condensation to foster large volume of moisture to foster growth of huge cloud masses
Warm surface waters move north from equator in the summer in N. Hemisphere creating optimal hurricane conditions
Development of Atlantic hurricanes that make landfall:
2-3 weeks prior to landfall – Cloud mass develops over warm ocean water. Most storms generated in east Atlantic take about 3 weeks to reach the coast of N. America
Katrina – developed in west Atlantic near the Bahamas.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Hurricanes begin to grow when warm, humid air is forced aloft.
The rising air cools and condenses to form cumulus clouds that will develop into cumulonimbus cells.
Earth’s rotation imparts a counterclockwise rotation to the storm in the Northern Hemisphere. This rotation is zero at the equator, therefore the majority of hurricanes originate between 10° and 20° N or S of the equator.
To maintain wind speed, inflow of air into developing low-pressure system must be matched by outflow of air in the upper troposphere.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
1-2 weeks prior to landfall – Tropical depression develops (winds 23-39 mph). After about 5 days this develops into a tropical storm (winds 39-74 mph). Finally, a hurricane develops (winds at least 119 mph).
Air pressure is lowest in the eye, where warm air is rising.
The lower the pressure inside the hurricane, the faster the winds.
Hurricanes will continue to grow in size and intensity as long as underlying water temperature remains above 80°F.
Precipitation concentrates within 124 miles on either side of eye, releasing up to 20 billion tons of water per day.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
3-7 days before landfall – Atlantic hurricanes are driven west by prevailing winds at 6-16 mph.
Florida and Texas experience more landfalls than any other state.
Hurricane may turn parallel to the east coast or pass south of Florida to strike the Gulf Coast or Caribbean islands.
2-3 days before landfall – The likely landfall site is identified.
Evacuations should be in full gear by now.
1-2 days before landfall – Size and slow motion of hurricanes means their impact is drawn out over several days.
Effects can reach coast before worst affects from the eye.
Measurements are made off coast by buoys to gather info about eye
Waves over 100 feet high during Katrina
Predicted landfall site of Katrina. It hit within 19 miles of the predicted site.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Winds in the NE quadrant blow onshore, piling up water in a storm surge.
Surges cause ~90% of the damage in coastal areas.
Can potentially reach inland areas up to 6-12 miles from shore.
Katrina – water reached heights of 30 feet above sea level in NE quadrant of storm.
Winds in NW quadrant blow offshore. In the case of Katrina, winds in NW quadrant pushed water from Lake Pontchartrain (located NW of the city) over levees into the city.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Hurricanes can take days to make their way onshore.
Hurricanes lose intensity over land because of frictional drag and loss of a moisture source.
Damaging winds near the core have speeds similar to F1-F3 tornadoes.
Can rain up to 24 inches of rain in just a few days over inland regions.
Water causes major erosion and damage from flooding.
Erosion from hurricane Ivan eroded most of N segment of Chandeleur islands, LA. In box – lighthouse.
Severe Weather: Hurricanes
The Good Earth/Chapter 15: Weather Systems
Katrina – category 3 hurricane
In 1973 in Bangladesh – Cyclone pushed onshore from Bay of Bengal
22-foot storm surge produced widespread flooding on the low lying plain
300,000 deaths
Weather Systems Checkpoint 15.26
The Good Earth/Chapter 15: Weather Systems
Draw a diagram that illustrates how the four components of the earth system (atmosphere, biosphere, hydrosphere, and geosphere) interact during a hurricane.
Weather Systems Checkpoint 15.27
The Good Earth/Chapter 15: Weather Systems
Use the Venn diagram provided to compare and contrast the features of midlatitude cyclones, tornadoes, and hurricanes. Identify at least 12 features.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
Tornadoes Midlatitude cyclones
Hurricanes
The End
Go back to the Table of Contents
The Good Earth/Chapter 15: Weather Systems