severe weather thunderstorms, tornadoes, hurricanes, etc…
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Severe Weather Thunderstorms, Tornadoes, Hurricanes, etc…. In this section, we will learn…. - PowerPoint PPT PresentationTRANSCRIPT
Severe WeatherSevere WeatherThunderstorms, Tornadoes, Thunderstorms, Tornadoes,
Hurricanes, etc…Hurricanes, etc…
In this section, we will In this section, we will learn…learn…
Tornadoes, hurricanes, blizzards, and thunderstorms are Tornadoes, hurricanes, blizzards, and thunderstorms are severe weather phenomena that impact society and severe weather phenomena that impact society and
ecosystems. Hazards include downbursts (wind shear), ecosystems. Hazards include downbursts (wind shear), strong winds, hail, lightning, heavy rain, and flooding. strong winds, hail, lightning, heavy rain, and flooding.
The movement of air in the atmosphere is due to The movement of air in the atmosphere is due to differences in air density resulting from variations in differences in air density resulting from variations in
temperature. Many weather conditions can be explained temperature. Many weather conditions can be explained by fronts that occur when air masses meet. by fronts that occur when air masses meet.
• E4.3A E4.3A Describe the various conditions of formation associated Describe the various conditions of formation associated with severe weather (thunderstorms, tornadoes, hurricanes, with severe weather (thunderstorms, tornadoes, hurricanes, floods, waves, and drought). floods, waves, and drought).
• E4.3B E4.3B Describe the damage resulting from and the social impact Describe the damage resulting from and the social impact of thunderstorms, tornadoes, hurricanes, and floods. of thunderstorms, tornadoes, hurricanes, and floods.
• E4.3C E4.3C Describe severe weather and flood safety and mitigation. Describe severe weather and flood safety and mitigation. • E4.3D E4.3D Describe the seasonal variations in severe weather. Describe the seasonal variations in severe weather. • E4.3E E4.3E Describe conditions associated with frontal boundaries that Describe conditions associated with frontal boundaries that
result in severe weather (thunderstorms, tornadoes, and result in severe weather (thunderstorms, tornadoes, and hurricanes). hurricanes).
ThunderstormsThunderstorms
• Thunderstorms are most often Thunderstorms are most often associated with a associated with a Cumulonimbus CloudCumulonimbus Cloud
• This is a cloud that forms when This is a cloud that forms when air is forced high into the air is forced high into the atmosphere (against its will)atmosphere (against its will)
• Cold fronts often create this Cold fronts often create this condition condition
• This produces an This produces an UNSTABLE UNSTABLE environmentenvironment
• The process of cooling, The process of cooling, condensing, cloud formation, condensing, cloud formation, saturation and precipitation saturation and precipitation occurs quicklyoccurs quickly
• Cold fronts often create the Cold fronts often create the proper conditions for this to proper conditions for this to occuroccur
Thunderstorm FormationThunderstorm Formation• Thunderstorms have three stages…Thunderstorms have three stages…
– The Cumulous StageThe Cumulous Stage: Warm air rising and condensing : Warm air rising and condensing to form cloudsto form clouds
– The Mature StageThe Mature Stage: Strong updraft of warm, moist air, : Strong updraft of warm, moist air, AND a strong downdraft of wind and precipitation (hail AND a strong downdraft of wind and precipitation (hail and lightning can occur in this stage too)and lightning can occur in this stage too)
– The Dissipation StageThe Dissipation Stage: The surface has been cooled, : The surface has been cooled, cutting off the warm, moist air that “fuels” the storm. cutting off the warm, moist air that “fuels” the storm. Once the precipitation has fallen from the sky, the storm Once the precipitation has fallen from the sky, the storm is over is over
LightningLightning• Lightning is believed to be Lightning is believed to be
created by created by frictionfriction between between the rising updraft and the the rising updraft and the falling downdraft in a falling downdraft in a cumulonimbus cloudcumulonimbus cloud
• This friction creates a This friction creates a separation of charges (kinda separation of charges (kinda like rubbing your feet across like rubbing your feet across the carpet in your socks)the carpet in your socks)
• Eventually there is a Eventually there is a discharge between positive discharge between positive and negative charges, and negative charges, creating a “spark” (kinda creating a “spark” (kinda like touching that doorknob like touching that doorknob and getting a shock)and getting a shock)
• On a larger scale, that On a larger scale, that “spark” is a bolt of lightning“spark” is a bolt of lightning
ThunderThunder
• When lightning strikes, the When lightning strikes, the “bolt” can be as hot as 30,000 “bolt” can be as hot as 30,000 degreesdegrees
• The air surrounding that bolt of The air surrounding that bolt of electricity expands rapidly electricity expands rapidly (remember… warm air (remember… warm air expands), and then contract expands), and then contract quickly as it cools. quickly as it cools.
• Because of the extremely high Because of the extremely high temperatures involved, the air temperatures involved, the air expands and contracts rapidly expands and contracts rapidly enough to break the sound enough to break the sound barrier (767 mph)barrier (767 mph)
• The thunder is a “sonic boom”The thunder is a “sonic boom”
Wind & DowndraftsWind & Downdrafts
• What goes up, must come What goes up, must come down!down!
• Thunderstorms are no Thunderstorms are no different, when warm air different, when warm air rises high into the rises high into the atmosphere, it eventually atmosphere, it eventually cools and comes back down cools and comes back down toward the surfacetoward the surface
• Cumulonimbus clouds can Cumulonimbus clouds can be as tall as 40,000 feet, be as tall as 40,000 feet, so…so…
• It can fall very quickly It can fall very quickly toward the surface, toward the surface, producing strong winds producing strong winds (called downdrafts)(called downdrafts)
HailHail
TornadoesTornadoes
Thought to be the 1Thought to be the 1stst photograph of a tornado (1884) photograph of a tornado (1884)
TornadoesTornadoes
• Violent windstorms that take Violent windstorms that take the form of a rotating column the form of a rotating column of air, or vortex, that extends of air, or vortex, that extends downward from a downward from a cumulonimbus cloud.cumulonimbus cloud.
• Because of the lower Because of the lower pressure in the center vortex, pressure in the center vortex, air near the ground rushes air near the ground rushes into the tornado from all into the tornado from all directions. directions.
• Air streams inward, it is Air streams inward, it is spiraled upward around the spiraled upward around the core until it eventually core until it eventually merges with the airflow or the merges with the airflow or the parent thunderstorm deep in parent thunderstorm deep in a cumulonimbus tower.a cumulonimbus tower.
TornadoesTornadoes• Some tornadoes consist of a Some tornadoes consist of a
single vortex.single vortex.
• However, within many However, within many stronger tornadoes are stronger tornadoes are smaller intense whirls smaller intense whirls known as known as suction vorticessuction vortices, , that orbit the center of the that orbit the center of the larger tornado → larger tornado → Multiple Multiple Vortex TornadoesVortex Tornadoes..– Usually die out in less Usually die out in less
than a minute.than a minute.
TornadoesTornadoes
• Suction vortices are Suction vortices are responsible for most responsible for most of the narrow, short of the narrow, short waves of extreme waves of extreme damage that damage that sometimes are sometimes are through tornado through tornado tracks.tracks.– Most reports of several Most reports of several
tornadoes at once tornadoes at once actually were actually were multiple multiple vortex tornadoesvortex tornadoes..
Supercell StructureSupercell Structure
Tornado DevelopmentTornado Development• Less than 1% of Less than 1% of
thunderstorms produce thunderstorms produce tornadoes.tornadoes.
• Most intense tornadoes are Most intense tornadoes are associated with associated with supercells supercells (big, cumulonimbus cloud (big, cumulonimbus cloud structures)structures)..
• Tornado formation begins Tornado formation begins with the development of a with the development of a mesocyclonemesocyclone..– Mesocyclone-Mesocyclone- Vertical Vertical
cylinder of rotating air cylinder of rotating air that develops in the that develops in the updraft of a severe updraft of a severe thunderstorm.thunderstorm.
Tornado DevelopmentTornado Development
Tornado DevelopmentTornado Development
• The mesocyclone within The mesocyclone within the cloud stretches the cloud stretches vertically and narrows vertically and narrows horizontally, causing winds horizontally, causing winds speeds to accelerate.speeds to accelerate.
• Air stretches downward Air stretches downward until a portion of the cloud until a portion of the cloud protrudes below the cloud protrudes below the cloud base, producing a dark, base, producing a dark, slow rotating slow rotating wall cloudwall cloud..
*See supercell diagram for *See supercell diagram for location.location.
Tornado ClassificationTornado Classification
• Fujita Intensity ScaleFujita Intensity Scale--– Assesses the damage Assesses the damage
produced by a storm as it produced by a storm as it relates to wind speed.relates to wind speed.
• F0- Moderate; 40-72 mph F0- Moderate; 40-72 mph • F5- Severe; 261-318 mphF5- Severe; 261-318 mph
– Path of DestructionPath of Destruction– Duration Duration
• ProblemProblem: Doesn’t take into : Doesn’t take into account for structural account for structural integrity of objects.integrity of objects.
• The ENHANCED Fujita Scale The ENHANCED Fujita Scale (EF – Scale) is now used in the (EF – Scale) is now used in the US. It DOES take into account US. It DOES take into account structural damage (but still structural damage (but still uses a 0-5 numerical scale)uses a 0-5 numerical scale)
Watches & WarningsWatches & Warnings
• Tornado WatchTornado Watch– Conditions are ideal Conditions are ideal
for a tornado to be for a tornado to be created.created.
• Tornado WarningTornado Warning– An actual tornado has An actual tornado has
been sighted in the been sighted in the area or is indicated area or is indicated by weather radar.by weather radar.
Tornado Frequency in the Tornado Frequency in the USUS
Tornado Frequency Around the Tornado Frequency Around the WorldWorld
Cool Tornado PicturesCool Tornado Pictures
HurricanesHurricanes
Hurricane FormationHurricane Formation
• The hurricanes that The hurricanes that strike the Caribbean, strike the Caribbean, Gulf of Mexico and the Gulf of Mexico and the US originate in AfricaUS originate in Africa
• They begin as low They begin as low pressure storm pressure storm systems over land systems over land
• The Trade Winds (one The Trade Winds (one of the systems of global of the systems of global winds) blow them out winds) blow them out over the warm water of over the warm water of the Atlantic Oceanthe Atlantic Ocean
Hurricane GrowthHurricane Growth
• Remember that low Remember that low pressure pulls air in at the pressure pulls air in at the surface…surface…
• and pushes it to higher and pushes it to higher levels in the atmospherelevels in the atmosphere
• Air temperatures at high Air temperatures at high levels in the atmosphere are levels in the atmosphere are colder,colder,
• and the warm, moist air and the warm, moist air over the ocean begins to over the ocean begins to form clouds (BIG form clouds (BIG Cumulonimbus clouds)Cumulonimbus clouds)
• Lots of Latent Heat released Lots of Latent Heat released during condensationduring condensation
• Creates a very unstable Creates a very unstable environmentenvironment
Continued GrowthContinued Growth• Remember that the water Remember that the water
over the Atlantic Ocean over the Atlantic Ocean near Africa is warm (80near Africa is warm (80°F) °F) and has lots of moisture in and has lots of moisture in it (mT air masses)it (mT air masses)
• As precipitation begins, As precipitation begins, the rain and cool the rain and cool downdrafts of the downdrafts of the Cumulonimbus system are Cumulonimbus system are not enough to cut off the not enough to cut off the updraft (it’s too warm)updraft (it’s too warm)
• The warm, moist air The warm, moist air continues to fuel the continues to fuel the system of Cumulonimbus system of Cumulonimbus clouds, making them clouds, making them bigger, and bigger, and bigger, and bigger, and biggerbigger
Hurricane MovementHurricane Movement• Once the growing low Once the growing low
pressure system is out pressure system is out over the warm water of over the warm water of the Atlantic Ocean, the the Atlantic Ocean, the Trade Winds blow it to Trade Winds blow it to the westthe west
• Because the oceans are Because the oceans are relatively smooth, there relatively smooth, there isn’t much to stand in its isn’t much to stand in its way and slow it downway and slow it down
• With 2,000 to 3,000 With 2,000 to 3,000 miles of warm ocean miles of warm ocean water to move across…water to move across…
• the system has the time the system has the time and the fuel to become and the fuel to become severesevere
Tropical Depressions, Tropical Tropical Depressions, Tropical Storms and HuricanesStorms and Huricanes
• Low pressure begins as a Tropical DisturbanceLow pressure begins as a Tropical Disturbance• The low pressure systems that blow out over the The low pressure systems that blow out over the
waters of the Atlantic Ocean begin as Tropical waters of the Atlantic Ocean begin as Tropical Depressions (a low pressure system is in fact a Depressions (a low pressure system is in fact a “depression” of pressure)“depression” of pressure)
• If winds in the system reach 39mph, the system If winds in the system reach 39mph, the system becomes classified as a Tropical Storm (and it is becomes classified as a Tropical Storm (and it is given a name)given a name)
• If the system continues to gain strength and winds If the system continues to gain strength and winds speeds reach 74 mph, it is officially classified as a speeds reach 74 mph, it is officially classified as a hurricanehurricane
Hurricanes, Typhoons and Hurricanes, Typhoons and CyclonesCyclones
• We give different We give different names to Tropical names to Tropical Storms that develop, Storms that develop, depending on their depending on their locationlocation
• In the Atlantic Ocean In the Atlantic Ocean we call them we call them HurricanesHurricanes
• In the Pacific Ocean we In the Pacific Ocean we call the Typhoonscall the Typhoons
• In the Indian Ocean we In the Indian Ocean we call them Cyclonescall them Cyclones
• They are all basically They are all basically the same type of stormthe same type of storm
Hurricane DangersHurricane Dangers
• The most dangerous The most dangerous component of a hurricane component of a hurricane is the “Storm Surge”is the “Storm Surge”
• As the storm makes As the storm makes landfall, a mound of landfall, a mound of ocean water (driven by ocean water (driven by strong winds AND the strong winds AND the “sucking” power of the “sucking” power of the strong low pressure strong low pressure system) is pushed on system) is pushed on shoreshore
• More people die as a More people die as a result of drowning, than result of drowning, than do of strong windsdo of strong winds
Hurricane Classification Hurricane Classification The Safir-Simpson ScaleThe Safir-Simpson Scale
TypeType KNOTSKNOTS MPHMPH millibarsmillibars inches of inches of mercurymercury FeetFeet MeteMete
rsrs DamagDamag
ee
DepressioDepressionn
less less than 34than 34
less less than 39than 39 ------------ ------------ ------------ ------------ ------------
Tropical Tropical StormStorm 35 - 6335 - 63 39 - 7339 - 73 ------------ ------------ ------------ ------------ ------------
Category Category 11
64 - 8264 - 82 74 - 9574 - 95 greater greater than 980than 980
greater than greater than 28.9428.94 3 - 53 - 5 1.0 - 1.0 -
1.71.7 minimalminimal
Category Category 22
83 - 9583 - 95 96 - 11096 - 110 979 - 965979 - 965 28.50 - 28.9128.50 - 28.91 6 - 86 - 8 1.8 - 1.8 - 2.62.6
moderatmoderatee
Category Category 33
96 - 11396 - 113 111 - 111 - 130130 964 - 945964 - 945 27.91 - 28.4727.91 - 28.47 9 - 9 -
12122.7 - 2.7 - 3.83.8
extensivextensivee
Category Category 44
114 - 114 - 135135
131 - 131 - 155155 944 - 920944 - 920 27.17 - 27.8827.17 - 27.88 13 - 13 -
18183.9 - 3.9 - 5.65.6 extremeextreme
Category Category 55
136+136+ 156+156+ less than less than 920920
less than less than 27.1727.17 19+19+ 5.7+5.7+ catastrophcatastroph
icic
A Hurricane’s “Death”A Hurricane’s “Death”• As a hurricane makes landfall, As a hurricane makes landfall,
the supply of warm, moist air the supply of warm, moist air that was fueling it is cut offthat was fueling it is cut off
• As the downdrafts and rain As the downdrafts and rain cool the land, the strength of cool the land, the strength of the updraft slowsthe updraft slows
• Without an updraft, the Without an updraft, the system will dissipate, and system will dissipate, and eventually die out (just like a eventually die out (just like a thunderstorm)thunderstorm)
• This may take days and 100’s This may take days and 100’s of miles of miles
• Hurricane Ike comes to Hurricane Ike comes to Michigan in 2008 (my front Michigan in 2008 (my front yard in Commerce Township) yard in Commerce Township) >>
Hurricane KatrinaHurricane Katrina
• In August of 2005, Tropical In August of 2005, Tropical Storm Katrina developed Storm Katrina developed over the Bahamasover the Bahamas
• As it approached Florida, it As it approached Florida, it developed into a Category I developed into a Category I hurricanehurricane
• It lost some strength over It lost some strength over the land (turned back into a the land (turned back into a Tropical Storm), but picked Tropical Storm), but picked right back up when it right back up when it moved back over the warm moved back over the warm water of the Gulf of Mexicowater of the Gulf of Mexico
Hurricane Katrina Hurricane Katrina • As the storm moved across As the storm moved across
the Gulf of Mexico, it the Gulf of Mexico, it RAPIDLYRAPIDLY developed (from developed (from a Category II to a Category a Category II to a Category V in only 9 hours)V in only 9 hours)
• Wind speeds reached 175 Wind speeds reached 175 mphmph
• A mound of water was A mound of water was pushed toward Louisiana pushed toward Louisiana and Mississippi…and Mississippi…
• even though wind speeds even though wind speeds slowed (to a Category III) by slowed (to a Category III) by the time it made landfallthe time it made landfall
FloodingFlooding• While the storm surge While the storm surge
associated with Katrina associated with Katrina was estimated to be 28 was estimated to be 28 feet above normal sea feet above normal sea levellevel
• In addition, much of the In addition, much of the city is BELOW sea levelcity is BELOW sea level
• A systems of levees A systems of levees and dams were and dams were supposed to protect the supposed to protect the city, but this was too city, but this was too highhigh
• 85% of the city flooded85% of the city flooded
The AftermathThe Aftermath
• The most destructive and The most destructive and costliest natural disaster in costliest natural disaster in the history of the USthe history of the US
• More than $81 billion dollars More than $81 billion dollars in damagein damage
• More that 1800 people died More that 1800 people died (700 still listed as missing)(700 still listed as missing)
• More than 90,000 square More than 90,000 square miles declared a Federal miles declared a Federal Disaster AreaDisaster Area
• More than 3 million people More than 3 million people were left without powerwere left without power
In Addition…In Addition…• There were unforeseen There were unforeseen
economic effectseconomic effects– Gas and Oil production shut-Gas and Oil production shut-
downsdowns– UnemploymentUnemployment– Insurance Company Insurance Company
BankruptciesBankruptcies– Relocation/Flight from the Relocation/Flight from the
regionregion• Environmental EffectsEnvironmental Effects
– Oil SpillsOil Spills– ErosionErosion– SewageSewage– Loss of Marine and Animal Loss of Marine and Animal
lifelife• Looting and ViolenceLooting and Violence