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Severe Weather.

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Presentation on theme: "Severe Weather."— Presentation transcript:

1 Severe Weather

2 Thunderstorms & Lightning

3 Thunderstorm Development
Thunderstorms need: moisture warm air lifting capability (fronts, sea breeze, mountains) Cumulus clouds (white, puffy) form from lifting air and develop into cumulonimbus clouds

4 Lightning Results from buildup and discharge of electrical energy between + and – areas within a rising cloud Lightning rapidly heats the surrounding air, causing a shock wave we hear as thunder Three types: Within cloud Between cloud Cloud-to-ground

5 Thunderstorm Formation
Lightning Formation



8 Hurricane Life Cycle Start as pre-existing low pressure systems, called tropical waves, over warm ocean waters Evaporating ocean waters and heated air rise and develop thunderstorms Storms begin to swirl around the low pressure center due to the Coriolis Effect (spinning of the Earth)

9 Hurricane Structure Eye – sinking air in the center of the storm forms a calm, cloud-free eye that can be 20 – 40 miles across Eyewall – dense thunderstorms surrounding the eye; strongest winds Rainbands – thunderstorms and clouds that spiral outward from the center; spin counter- clockwise in the northern hemisphere

10 Hurricane Stages Tropical Depression – strengthening tropical wave; winds less than 34 mph Tropical Storm – continued strengthening; winds between 35 – 73 mph; named Hurricane – when winds reach 74 mph; eye forms Hurricanes lose energy when they make landfall, or emerge into colder waters

11 Notice how this hurricane got worse over the dark red (warmer water) and finally died when it got over the colder water.

12 How Do You Measure a Hurricane?
Hurricanes are measured by their speed and it is split into categories The categories range from one to five, with one being the weakest and five being the strongest The classification of hurricane systems is called the Safir- Simpson Hurricane Scale

13 Safir-Simpson Hurricane Scale
Category One 74 to 95 MPH Category Two to 110 MPH Category Three to 130 MPH Category Four to 155 MPH Category Five Winds greater then 155 MPH Note: Hurricanes of Category Three or above are considered major hurricanes.

14 A storm surge is the change in sea level produced by wind pushing the water up onto the shore. It is the MOST damaging part of a hurricane.

15 Important Hurricane Terms
A Hurricane Watch occurs when a hurricane is possible within 36 hours The storm is being tracked to predict where it may hit A Hurricane Warning is issued when it the storm is expected to hit within 24 hours Evacuation may be needed

16 Hurricane Safety Tips Know if the location you are in is a safe zone or whether evacuation may be needed Protect windows and glass with plywood Turn off utilities Have a supply kit including first aid, water, canned goods, battery powered radio, blankets, etc. After evacuation, do not return until it has been declared safe


18 What is a Tornado? A tornado is a violently rotating column of air extending between, and in contact with, a cloud and the surface of the earth Tornadoes can come one at a time or in clusters They can also vary in size, length, width, direction of travel, and speed

19 Tornado Formation Changing wind direction and increased wind speed prior to a thunderstorm creates an invisible, horizontal spinning effect in the lower atmosphere Rising warm air within the thunderstorm tilts the spinning air upward into the storm The vertical spinning column of air begins to rotate the thunderstorm, and a tornado soon forms

20 Formation Waterspout

21 The Enhanced Fujita Scale
EF to 85 MPH EF to 110 MPH EF to 135 MPH EF to 165 MPH EF to 200 MPH EF Over 200 MPH

22 How Do You Measure a Tornado?
Since February 1, 2008 tornadoes have been measured based on the Enhanced Fujita Scale (EF) This scale helps determine the speed of a tornado from weakest to strongest

23 Tornado Facts Waterspouts – tornadoes that form over water; usually weaker than land tornadoes Tornadoes can be transparent, and only appear when dust and debris get picked up into the funnel Tornadoes can occur anywhere on Earth, but are most common in “Tornado Alley” in the central United States


25 Tornado Safety Tornado Watch – conditions are right for tornado development Tornado Warning – one has been sighted or indicated in the area; take shelter If inside – stay away from windows, get in a central room or basement If outside – seek shelter, get out of cars and get on the ground or in a ditch

26 More Severe Weather Flash Floods
Heavy rainfall over a short period of time; causes most fatalities during thunderstorms Hail Strong vertical winds within thunderstorm clouds (updrafts) carry rain drops to heights where they freeze; once they get too heavy they fall to the ground

27 SUN SAFETY The Sun’s ultraviolet radiation can cause health risks, including skin cancer Surfaces like snow, water, and beach sand can double the effect of UV radiation


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