Severe Weather

There are many types including:  Lots of rain  Lightning  Hurricanes  Hail  Tornadoes  Cyclones  Blizzards

Thunderstorm Thunderstorm – brief heavy storm with rain, thunder, lightning, and strong winds Stages: 1. Cumulus stage – warm air rises to form clouds 2. Mature stage – the sever weather occurs 3. Dissipating stage – storm decreases

Lightning Lightning – the discharge of electrical charges  It occurs when ice and water in clouds rub together causes charges to build up The positive charges - at the top of cloud The negative charges - at the bottom of the clouds When too much builds up the electrons travel to the ground  As the electricity heats the air next to it, it expands quickly making thunder

Hurricanes Hurricane – a tropical storm with winds are more than 74mph that spiral in toward the center  Range from category How it forms:  Warm moist air over ocean rises and forms clouds  Clouds rotate counter clockwise (in north)  A low pressure forms in the center as the hot lighter air rises and pushes cold heavy air out of the way

Parts of the hurricane 3 layers of thick cumulonimbus clouds – spiraling upward around the center The eye – the center of the storm  Calm and clear The eyewall – part bordering the eye  Highest winds are here

Internal Hurricane Structure

Dangers of hurricanes Storm surge – rising sea levels with large wave  As air in center rises it pulls ocean water upward – as it travels onto land it creates storm surges Wind damage – determined by speed of wind, how buildings are constructed, etc.

Cyclones Cyclone – an area with low pressure that has winds moving toward the rising air in the center of an are  Occurs in the mid-western US  Also - what hurricanes are called in the Indian ocean

Cyclone formation 1. It starts where warm and cold air move parallel but in opposite directions 2. A piece of the cold front moves faster creating a wave 3. The fast moving cold overtakes the warm front and starts to spin

Tornadoes Tornado – rotating column of fast moving wind that is visible a funnel shape  Occur mostly in late spring and early fall  Winds up to 400mph Formation: 1. Hot dry air moves up and meets with cold air moving down 2. Air starts to spiral 3. It may develop a funnel shape If it does touch – it wanders haphazardly and can rise and touch down again

How does the Enhanced Fujita Scale work? EF 0 Gale Tornado: miles per hour (mph) Some damage to chimneys. Tree branches broken off. Shallow-rooted trees uprooted. EF 1 Moderate Tornado: mph Roof surfaces peeled off. Mobile homes overturned. Moving autos pushed off roads. EF 2 Significant Tornado: mph Considerable damage. Roofs torn off frame houses. Large trees snapped or uprooted. Light object projectiles generated. EF 3 Severe Tornado: mph Severe damage. Roofs and some walls torn off well-constructed homes. Most trees in forests uprooted. Heavy cars lifted off ground. EF 4 Devastating Tornado: mph Well-constructed houses leveled. Structures blown off weak foundations. Cars thrown and large projectiles generated. EF 5 Incredible Tornado: 200+ mph Strong frame houses lifted off foundations and disintegrated. Automobile-sized projectiles fly through the air in excess of 100 mph. Trees debarked.

Blizzards

Ice storms

Measuring weather in lower atmosphere We measure to try to predict future weather events Thermometers – temperature Psychrometer – humidity Barometer – air pressure Anemometer – wind speed Wind vein – wind direction

Rain Gauge

Sling Psychrometer

Mercury Barometer

Anemometer

Wind vein and Wind Socks

Measuring weather in upper atmosphere Radiosonde – many instruments lifted by balloon Doppler Radar – uses reflected radio waves to determine velocity and location of weather Weather satellites – create images of weather Computers – used for doing the math and store data for comparisons

Radiosonde

Satellite

Doppler Radar

Computer Models

Forecasting weather Use weather maps and models to put collected information in a picture  To try to predict but - these are limited and not always accurate Map includes:  Have different symbols and colors to represent specific weather  Have isotherms – line connecting equal temperatures  Have isobars – lines connecting equal pressures

Measuring Wind

Cloud Cover

Isotherms

Isobars

Issuing weather alerts Watch – when conditions are ideal for sever weather Warning – when weather has been spotted

Trying to control the weather Used techniques like cloud seeding  Cloud seeding – process of introducing condensation or freezing nuclei into a cloud to force precipitation Purpose – either increase rain, decrease rain, reduce lightning It did not work Still are working on it to try to improve the process