Storm Systems

Forecasting the Weather

Spring Storm Systems

Low pressure on 3/26/09

sparked a line of strong to

severe thunderstorms along

the cold front

Snow showers occurred in the

cold air behind the cold front

Thunderstorms

Developing—physicalgeography.net

Mature—physicalgeography.net

Severe Weather in the Southeast

Severe Weather • Severe Thunderstorm—winds stronger

than 58 mph, hail larger than ¾ inch, funnel clouds, or tornadoes sighted

• Severe Thunderstorm Watch—issued when a severe thunderstorm may develop

• Severe Thunderstorm Warning—issued when a severe thunderstorm is occurring

Watches and Warnings are issued by the National Weather Service www.weather.gov

Watches and Warnings from www.weather.gov

Tornadoes

• Tornadoes happen more during the Spring

• Cold air and warm air collide, begin rotating, and form tornadoes

FSmith, 1991

Tornado Alley

June 8th is National Tornado Day

Cold & Dry

Warm & Moist

cP

mT

cP

mT

Tornado Videos

• http://www.ny1.com/content/top_stories/12

5647/the-science-behind-a-tornado

• http://www.brainpop.com/science/weather/

tornadoes/

Tornado Safety

• Head to the basement or an interior room

• Wait for storm to pass

Lightning

NASA.gov

Lightning is

• Electrical discharge in the atmosphere

• From the separation of + and – charges in a cloud

• Able to reach 54,000° F (30,000° C)

http://www.brainpop.com/science/w

eather/thunderstorms/

• How lightning forms

Types of Lightning

http://www.nssl.noaa.gov/primer/lightning/images/ltgtypes_schematic.jpg

Lightning Safety

• Do not stand under a tree

• Do not be the tallest object in an open area (duck down)

• Lightning Striking a Tree

Hail

8 inches in diameter in Vivian, South Dakota (14

inch circumference) on July 23, 2010

New Record Holder!

http://www.youtube.com/watch?v=ECn3u0Bon7w Apr 7, 2010 ... Running through a hail storm

http://www.ultimatechase.com/Hail

_Video.htm

• http://www.youtube.com/watch?v=Hy9MV

VF_3k8

• http://dsc.discovery.com/videos/storm-

chasers-running-the-hail-gauntlet.html

Flash Flooding Turn around, don’t

drown!

Flash Floods

• occur rapidly in a local area with little warning

• accounts for most fatalities (in North America) because they are unexpected

www.newprophecy.net/2007part1.htm

Summer Storm Systems

• Thunderstorms

• Hurricanes

• Flash Floods

Hurricanes

• Form over warm oceans as tropical storms

• Winds over 74 mph

• Storm center = eye

• Ranked by Saffir-Simpson Categories 1—5

• Hurricane Season is June 1 to November 30

http://www.hurricanekatrina.com/

Hurricane Safety

• Emergency Family Plan

• Emergency Supply Kit

• Food & Water

• Batteries, radio, flashlight

• Essential documents & phone numbers

Autumn Storm Systems

• Rain

• Thunderstorms

• Late—season snowstorms

• Hurricane season continues to Nov. 30th

Winter Storm Systems

• Cold weather low pressure systems

• Often produce frozen precipitation

Nor’easters & Blizzards • Nor’easters have NE winds and arctic air,

causing heavy snow to fall along the East Coast

• Blizzards are severe winter storms with wind speeds over 35 mph for 3+ hours and heavy, blowing snow

Ice Storms—more common than blizzards in the USA

http://www.danzfamily.com/archives/blogphotos/07/818-tulsa-ice-storm-dec-9-2007.jpg

Ice storms produce over 0.25 in of freezing rain, causing tree, power line, and

structural damage

J.R. Carmichael, Dec. 2005

Lake Effect Snow

• Evaporation of warm lake water condenses to form clouds

• Heavy snow falls in bands downwind of the lake

http://www.mygtv.net/wp-content/uploads/2008/12/lake_effect_snow.jpg

http://scienceblogs.com/bushwells/LakeEffectSnowRadar.jpg