SCIENCE NEWS

Thunderstorms

What are thunderstorms? A storm which contains lightning and thunder

Why Study Thunderstorms ? Fatalities Injuries Property Damage Crop Damage

Weather related deaths in the u.s.

Weather damage cost in the U.S.

According to NOAA’s National Weather Service The US has sustained 90 weather related disasters over the 29 years Total cost of all 90 events? $700 billion

ILLINOIS According to NOAA, 2008 Summary of Hazardous Weather Fatalities, Injuries, and Damage Costs by State Fatalities 35 Injuries 48 Property Damage $ 227.14 million Crop Damage $ 41.04 million Total - $ 268.18 million

Average number of days per year with thunderstorms

FACTS OCCURANCES FEATURES 2000 in progress at any one time 100,000 per year in the United States Most frequent in Florida and eastern Gulf Coast region FEATURES Cumulonimbus clouds Heavy rainfall Lightning Occasional hail

All thunderstorms need Moisture - source typically over water, cloud formation & rain Lifting- mechanism for condensing moisture to release its latent heat Unstable air- rising air warmer than the surrounding air, produce upward growing clouds and vertical updrafts keep precipitation suspended

2 Types of Thunderstorms Classified by lifting mechanism 1. Air mass - unequal heating of surface Mountain : Orographic lifting Sea breeze : difference between land/water storage & release of thermal energy 2. Frontal – advancing cold fronts and more rarely warm front

Stages of development 3 distinct stages make up a t-storm

Cumulus stage Warm, humid air rises vertically and condenses into a cumulus cloud Large amounts of latent heat are release inside the cloud As the cloud grows, particles eventually get heavy enough to fall also sides of the cloud evaporates forming a downdraft No precipitation during this stage

Cumulus Stage

Mature stage The appearance of a downdraft Updraft/downdraft is called a “cell” An “anvil” top appears as the updrafts hit the tropopause Heavy rain possible in this stage Strong/gusty surface winds

Mature Stage

Dissipation Downdrafts basically choke out the updrafts Cuts off the warm, moist air which is the energy supply for the storm Light rain only

Dissipating Stage

Multi cell thunderstorms If new thunderstorms forms due to downdrafts from the air mass, they are called “multi cell” thunderstorms Most severe storms & ordinary storms are multi cell storms

Multi cell Thunderstorm

Thunderstorm hazards Hail Collision of super cool water drops forms layers Cause extensive & quick damage Largest Aurora, Nebraska 6/03 7 in diameter & 18.75 in circumference almost a soccer ball

Lightning & Thunder Charge differences between the thunderstorm and ground can cause lightning strokes of 30,000°C, and this rapid heating of air will creates an explosive shock wave called thunder, which requires approximately 3 seconds to travel 1 kilometer

Lightning Stroke Development Charge layers in the cloud are formed by the transfer of positive ions from warmer hailstones to colder ice crystals. When the negative charge near the bottom of the cloud is large enough to overcome the air's resistance, a stepped leader forms. A region of positive ions move from the ground toward this charge, which then forms a return stroke into the cloud.

Lighting Several names, such as forked, bead, ball, and sheet lightning describe forms of the flash Distant, unseen lightning is often called heat lightning

2007 Lightning Fatalities 45 lightning fatalities Above the 10-year average of 44 fatalities. For the 9th consecutive year, Florida was hardest hit with 11 fatalities Illinois 1 fatality

ANY QUESTIONS?

HOMEWORK QUIZ? Read Ch 13 p 344- 349 Ch 13 Study Guide Due Tues 4/28 Ch 12 test corrections due TR 4/30

Good References http://www.eoearth.org/article/Thunderstorm USE THIS FOR SEVERVE TSTROMS http://images.google.com/imgres?imgurl=http://www.srh.noaa.gov/jetstream//tstorms/images/tstrm_climo.jpg&imgrefurl=http://www.srh.noaa.gov/jetstream//tstorms/tstorms_intro.htm&usg=__m-1V4Sh8B9WBA8zbbPFfGZaPnM0=&h=577&w=641&sz=126&hl=en&start=3&um=1&tbnid=qQOw5qoo0zZh-M:&tbnh=123&tbnw=137&prev=/images%3Fq%3Daverage%2Bnumber%2Bof%2Bdays%2Bwith%2Bthunderstorms%2Bin%2Bthe%2Busa%26hl%3Den%26sa%3DN%26um%3D1