Weather EffectsWeather EffectsHoward Middle SchoolHoward Middle School

66thth grade grade

Earth ScienceEarth Science

FloodsFloods Floods can happen at any time, Floods can happen at any time,

anywhere.anywhere. What causes floods?What causes floods?

– Single heavy rainfallsSingle heavy rainfalls– Days of moderate Days of moderate levels of rainlevels of rain– Melting of snow and iceMelting of snow and ice– The breaking of a dam The breaking of a dam or leveeor levee– Ocean waves arriving Ocean waves arriving onshoreonshore

FloodsFloods Large-scale flooding often occurs Large-scale flooding often occurs

during seasons with exceptionally high during seasons with exceptionally high rainfall.rainfall.

Or springtimes that produce large Or springtimes that produce large snowmelt.snowmelt.

Dams and levees Dams and levees

are built along are built along

waterways to waterways to

prevent such prevent such

events.events.

FloodsFloods Floods that result from short periods of Floods that result from short periods of

extremely heavy rain are known as extremely heavy rain are known as flash flash floods.floods.

One common place for flash floods is the One common place for flash floods is the desert.desert.

HurricanesHurricanes A hurricane is a severe tropical storm, A hurricane is a severe tropical storm,

and those that hit the U.S. typically and those that hit the U.S. typically originate in the Caribbean Sea, the Gulf originate in the Caribbean Sea, the Gulf of Mexico, or the Atlantic Ocean.of Mexico, or the Atlantic Ocean.

Hurricane Katrina

HurricanesHurricanes In other parts of the world, hurricanes In other parts of the world, hurricanes

are also known as tropical cyclones and are also known as tropical cyclones and typhoons.typhoons.

Hurricanes form in areas of warm Hurricanes form in areas of warm tropical water where there is moisture tropical water where there is moisture and an absence of strong winds.and an absence of strong winds.

Formation of a HurricaneFormation of a Hurricane

HurricanesHurricanes Hurricanes can produce high winds, Hurricanes can produce high winds,

heavy rains, and flooding.heavy rains, and flooding. In the U.S., hurricane season runs from In the U.S., hurricane season runs from

June – November.June – November.

HurricanesHurricanes

Hurricanes have winds of at least 74 Hurricanes have winds of at least 74 miles per hour that swirl around a miles per hour that swirl around a clam center, known as the eye.clam center, known as the eye.

HurricanesHurricanes The eye is usually about 20-30 miles in The eye is usually about 20-30 miles in

diameter, while the entire diameter of diameter, while the entire diameter of the hurricane may extend to 400 miles.the hurricane may extend to 400 miles.

HurricanesHurricanes The Saffir-Simpson Hurricane Scale The Saffir-Simpson Hurricane Scale

classifies hurricanes into categories classifies hurricanes into categories based on their wind speed, from a based on their wind speed, from a category one (less than 95 mi/hr) to a category one (less than 95 mi/hr) to a category five (more than 155 mi/hr).category five (more than 155 mi/hr).

HurricanesHurricanes Hurricanes are low-pressure events.Hurricanes are low-pressure events. Along ocean fronts, this low pressure can Along ocean fronts, this low pressure can

create a storm surge that brings large create a storm surge that brings large amounts of ocean water onshore, with amounts of ocean water onshore, with waves reaching up to several meters waves reaching up to several meters high.high.

HurricanesHurricanes Storm surges cause significant damage Storm surges cause significant damage

during strong hurricanes, due to the large during strong hurricanes, due to the large amount of water and flooding.amount of water and flooding.

Hurricanes Hurricanes are given are given names in names in alphabetical alphabetical order order (excluding (excluding letters Q, U, letters Q, U, and Z) with and Z) with the name of the name of the first one the first one each year each year starting with starting with the letter A.the letter A.

HurricanesHurricanes The World The World

Meteorological Meteorological Organization rotates Organization rotates six lists of names and six lists of names and reuses names every reuses names every sixth year. The name sixth year. The name of a particularly deadly of a particularly deadly or costly hurricane is or costly hurricane is retired from the lists, retired from the lists, and a new name is and a new name is selected to take its selected to take its place.place.

TornadoesTornadoes A tornado is a violently rotating column of A tornado is a violently rotating column of

air that is in contact with both the ground air that is in contact with both the ground and a cloud layer.and a cloud layer.

It is usually seen as a funnel cloud and It is usually seen as a funnel cloud and can have winds as strong as 300 mi/hr.can have winds as strong as 300 mi/hr.

TornadoesTornadoes Meteorologists use the Fujita-Pearson Meteorologists use the Fujita-Pearson

scale to rate the severity of tornadoes scale to rate the severity of tornadoes based on resulting damage and based on resulting damage and assumed wind speeds.assumed wind speeds.- F-0 – less than 73 F-0 – less than 73

mi/hrmi/hrtoto

- F-5 – 261-318 F-5 – 261-318

mi/hrmi/hr

TornadoesTornadoes

A tornado’s high winds and low A tornado’s high winds and low pressure can cause the windows of pressure can cause the windows of buildings to blow outward.buildings to blow outward.

TornadoesTornadoes

Compared to any other Compared to any other country, the U.S. country, the U.S. experiences the greatest experiences the greatest number of tornadoes.number of tornadoes.

About 1,000 tornadoes About 1,000 tornadoes are reported here per are reported here per year on average, year on average, resulting in approx. 80 resulting in approx. 80 deaths and more than deaths and more than 1,500 injuries.1,500 injuries.

TornadoesTornadoes Many of these tornadoes occur in Many of these tornadoes occur in

“Tornado Alley,” a region of the central “Tornado Alley,” a region of the central U.S. that includes Texas, Oklahoma, U.S. that includes Texas, Oklahoma, Kansas, Nebraska, and S. Dakota.Kansas, Nebraska, and S. Dakota.

Tornadoes can form at any time of the Tornadoes can form at any time of the year, but are mostyear, but are most

common between common between

March – August.March – August.