Severe+Rain-Purple

Severe Rain and Thunderstorms Lamia F. and Madison I. Purple

**Introductio****n**

A thunderstorm is a strong disturbance in the atmosphere that can bring heavy rain, thunder, and lightning to the areas covered by the clouds (2). The usually storm cloud is a cumulonimbus cloud, low flying, gray, puffy, and rain bearing. Often times these storms being chaos to the affected areas and have many after effects. The forming of theclouds is complex a nd requires many specific conditions in order to be complete (1).

**Conditions of Formations** In order for severe thunderstorms to form, there must be warm moist air. Thunderstorms occur anywhere that warm moist air has absorbed enough heat to make the air less dense than the surrounding air. This is most commonly along cold front, as well as anywhere daytime heating forms hot air near the earth's surface. First, the warm air rises, begins to cool, and water vapor reaches dew point and therefore starts to condense into tiny droplets that form clouds. Next, condensation in the clouds release the latent heat of evaporation, adding heat to the rising air. This decreases the density and allows it to rise higher in the atmosphere. The rising air is called an //updraft//, the updrafts start to build clouds to 6km. Further rising and cooling causes more condensation and formation of ice-crystals --> this releases more latent heat which builds the cloud up to 12km. Drops of water and ice form grow in size by coalescence or joining together with each other. Eventually, the cloud becomes too large and cannot be supported by the air mass. As a result //downdrafts// form on the leading edge of the cloud. At a mature thunderstorm updrafts and downdrafts operate side by side within the cloud. This is also the most dangerous stage of the cloud, there are high winds, heavy rain, thunder, lightning, possible hail and tornado development. Eventually, the storm reaches a stage when down drafts drag in so much cool dry air that it prevents further updrafts. Without updrafts, the rain stops. Thunderstorms can be single cell with only one cloud mass, or it can be multiple cells with several clouds along the same place (1). There are two types of thunderstorms, air mass storms and frontal storms. Air mass storms form over warm and humid areas, such as the Florida Peninsula. Rain falls from the upper part of the cloud but heavy downdrafts cause no more rain to be formed. Frontal thunderstorms occur over moderate regions, such as Eastern and Central US. These storms approach before a cold front. During formation, denser air causes warmer, more humid air to rise creating convective clouds that lead to rain. When the cloud releases precipitation, the strong downdrafts it also releases cause more humid and warm air to rise, feeding the storm. Thus, the frontal storm becomes much more dangerous than an air mass storm. Super cells are usually a product of frontal thunderstroms. These extremely strong weather conditions can bring hail, flash floods, high winds, and tornadoes (2). media type="youtube" key="exlVSEPEXKc" height="315" width="420" ^ Above is a video further explaining the formation of a thunderstorm (4).

**Dangers**

Severe rain and thunderstorms can bring many hazards to an area, such as lightning, floods, and tornadoes. Tornadoes, which are commonly the product of thunderstorms in the midwest US, are extremely dangerous. They bring strong winds, and can pick up and throw anything in its path including homes, people, etc (3).Lightning is electric discharge from clouds that cause thunder. Lightning occurs in all thunderstorms and is caused by an imbalance of electric charge between the cloud and the ground. The electricity is discharged as a volt of lightning. Lightning can go cloud to ground, ground to cloud, or cloud to cloud. The discharge of electricity during lightning heats up the air surrounding the bolt, causing a rapid expansion of air. This explosion causes the sound we call thunder. Lightning has the ability to start brush fires and lead to many other dangers (8). To learn more about the formation and dangers of lightning, click on the link below: http://environment.nationalgeographic.com/environment/natural-disasters/lightning-profile/ Flooding and winds can knock over telephone poles, causing the water to become electrically charged. In addition flooding can cause water systems to become dirtier, and a danger for people to drink (5).



**Historical Examples**

Historically, thunderstorms have been known to be dangerous, lethal weather that create fear in people. On December 8, 1963 and May 5, 1995 these fears proved true. Passengers on a flight back from Puerto Rico on December 8, 1963 were expecting to land in Philadelphia that evening. As they were flying through Dover, Delaware they encountered a thunderstorm. Lightning struck the plane, causing it to crash from a height of 5,000. All 81 passengers in this plane tragically died. Now, planes are engineered to survive a lightning strike, making this fatal story one of learning as well (7).

Out of what seemed like nowhere, on May 5, 1995, Fort Worth, Texas saw towering cumulonimbus clouds and knew danger was approaching. What happened next was too fast for anyone to react. Softball sized hail began to crash towards the ground and massive flash flooding occurred. Winds reached speeds of 60 to 70 miles per hour. Twenty million dollars of damage came from this storm along with over 20 deaths, and more than 100 injuries. This tragic day in Texas was one of the costliest thunderstorms in US history (7).

**Safety**

If you know a storm is on it's way, prepare by stocking up on the necessities such as bottled water, canned foods, flashlight, medical care if needed, etc or leave the area. If there is a flood as a result of the heavy rainfall, stay indoors until further notice and avoid moving water at all costs (5). Once the storm has passed, listen for announcements made by local authorities and follow their more specific instructions (8).

Many safety measures are needed in order to stay safe throughout a thunderstorm. Different locations require different safety precautions. Some general advice for each is listed below: //Overall:// - stay tuned to weather forecasts - cancel all outdoor activities //Indoors: -// stay off phone //-// stay away from windows //-// use flashlights //-// unplug electronics, specifically computers. If there is lightning, the electricity can easily travel through the wires. - avoid taking showers or baths because sometime lightning can travel though the plumbing if it hits the house - hide in a cellar or basement (in case of tornado) - boil water before drinking (in case of a flood) //Driving:// - reduce speed because the high winds and rain can distract you while driving - go to the shoulder of the road - put on emergency flashers - remain in car - don't touch metal, as it is a strong conductor of electricity - avoid roads covered in water. The water could be electrically charged from prior lightning strikes //Outdoors: -// stay low - if possible, find shelter - get away from trees, tall objects, metal, and water because they attract lightning - boats and swimmers should get to land and as far from water as possible. - if in a group, spread out. If you do this, you become less of a target for lightning. - **If your hair beings to stand up, this indicates that lightning is about to strike. Drop to knees, bend forward, put hands on knees, crouch down. Don't lie flat on the ground -- this creates a bigger target (3)** media type="youtube" key="CUnN2FcAV4M" height="315" width="420" ^ Above is a video explaining the safety precautions, in detail, describing what one should do in case of a flood (6).

For more information on dangers and safety precautions on flash flooding, check out: http://www.srh.noaa.gov/lub/swaw/pns/flash_flooding_pns.php

**Sources**

1. Michna, Paul. "Severe Thunderstorms." //Earth Science Australia//. Web. 18 Jan. 2012. .

2. Lerner, Lee, and Brenda Wilmouth Lerner. "Thunderstorm." //Gale Error Page//. Gale, 2008. Web. 9 Jan. 2012. .

3. "Weather News: Forecast, Maps, Radar, & Storm Report - USATODAY.com." //News, Travel, Weather, Entertainment, Sports, Technology, U.S. & World - USATODAY.com//. 9 Aug. 2005. Web. 11 Jan. 2012. .

4. //Thunderstorm Formation//. By Britannica. //Youtube//. Britannica, 1 May 2009. Web. 11 Jan. 2012. .

5. National Weather Service. "Flood and Flash Flood Definitions." //National Weather Service Southern Region Homepage//. National Weather Service. Web. 18 Jan. 2012. .

6. LRCA Video. "National Flood Safety Awareness Week." __Youtube__. 10 Mar. 2011. LRCA. 2012 .

7. The Weather Channel. "Historical Thunderstorms." __Weather__. The Weather Channel. 11 Jan. 2012 <http://www.weather.com/encyclopedia/thunder/history.html>.

8. Lerner, K. Lee, and Brenda Wilmouth Lerner. "The Gale Encyclopedia of Science." __Gale__. 2004. Gale Group. 12 Jan. 2012 <go.galegroup.com/ps/aboutEbook.do.actionstring=do_display_ABOUT_Page&inps=true&prodIa=GUrL&Usergroupname=min_m_wellhigh&searchtype=basicsearchform&doc_d_gale%7ca7800787677763-&contentsegment=9780787677763>.