Freezing+Rain-Purple

**Freezing Rain**  Gabrielle K. and Michael A.   Purple Class

Introduction Freezing rain is supercooled droplets that freeze on impact (2). For rain to be considered supercooled, it must be below its freezing point (o°C) but not frozen (1). The rain cannot freeze because it does not have a condensation nuclei to form on, as it is falling quickly (1). The rain is supercooled at or below 0C but it has not frozen because it does not have a condensation nuclei to form on (1). It is most commonly found in a narrow band on the cold side of a warm front, where surface temperatures are at or just below freezing (2). These storms are the result of the accumulation of freezing rain (2). Later on, you will learn in more depth about the dangers, conditions of formation, historical examples, and safety of freezing rain.

media type="youtube" key="S-vCY2OkG_0" height="315" width="420" The dangers of driving in freezing rain.

Dangers Freezing rainstorms can be the most destructive of winter weather phenomena (2). They are often the cause of car accidents, power outages and personal injuries (2). It is also extremely dangerous for planes and helicopters(1). Freezing rain can form on on these vehicles, which can jam rotars or engines, and distort the balance of the plane. (1). Intense ice storms can halt a region in just hours, which affects the people living there (4). Freezing rain is almost invisible on smooth surfaces and people often don't know that it's there. The sidewalks become slick when covered with the frozen rain and people can easily slip and get hurt (4). Many more fractured hips, ankles, and wrists are recorded at times when there is freezing rain (5). People can be injured in a freezing rain storm by falling down stairs, falling off of loading docks, slipping on sidewalks, and on icy ground when they get out of their cars (5). As freezing rain accumulates the roads can become completely covered in in ice, making car accidents very common (4). This also puts commuters at an extra risk, as they could be hit by an out of control car (4). The weight of the ice from the frozen rain can damage telephone poles and electrical wires, adding the extra threat of electricution to the direct threats of the ice (4). Heavy buildup of ice can also bring down trees and communication towers, which can fall on people, vehicles or houses (6). Freezing rain is an example of a winter storm (6). Winter storms are regarded as deceptive killers because most deaths caused by them are indirectly related to the storm (6). For example, if freezing rain caused a car accident, and a person was killed in the car accident, freezing rain would be the deceptive killer, as it has caused the accident (6).

Conditions of Formation Freezing rain develops as falling snow, which encounters a layer of warm air deep enough for the snow to melt, changing it to rain (2). As the rain continues to fall, it passes through a thin layer of cold air just above the surface and cools to a temperature below freezing (2). As there is no condensation nuclei, the drops supercool instead of (2). When the supercooled drops hita surface (be it pavement, powerline or plane) they instantly freeze, forming a thin layer of ice (2). The development of freezing rain can happen on any surface exposed to air (1). Freezing rain usually results from warm, moist air surging into colder air (8). Most regularly, the overrunning occurs when warm, moist air flows up and over a warm front related to a mid-latitude cyclone (8). The air that rises cools and water vapor condenses producing a thin band of freezing rain ahead of the front (8). The band is frequently wrapped around and behind the low pressure center by counterclockwise winds flowing around the cyclone (8). Another area of freezing rain is often found behind the cold front (8). Freezing rain forms as winds from the south at upper levels push the warm, moist air up and over the cold front, which produces rain that falls into the colder air (8). Freezing rain associated with the cold front is typically light and broken up (8). Stationary fronts can also be associated with creating freezing rain (8). The stationary front separates cold air to the north from the warm, moist air in the south (8). In this case, freezing rain will develop as upper-level winds, which are usually light and southwesterly, that push the warm air over the colder air of the stationary front (8). This produces a narrow band of freezing rain on the cold side of the front's boundary (8).

Click here here //to learn more about the formation of freezing rain.// //Or, click here to see a freezing rain animation. Once you get to the site, make sure to click "Continue to active figure," and then click on the freezing rain tab to watch freezing rain form!//

Historical Examples Freezing rain's most prominent effects are felt in Northern and Southern areas of the world. A storm in Northern Idaho brought over 8 inches of ice through freezing rain in January of 1961 (3) In Medford, Oregon just 0.13 inches of precipitation, much of which was freezing rain, caused over 140 accidents in Rogue Valley on December 11th and 12th 2009 (9). The event was preceded by several consecutive days that had temperatures under 15 degrees F, which cooled the ground below freezing, causing the ice to stay frozen longer than it would have normally (9). //Click// //[|here] for several historical examples of freezing rain in Ontario. // Click this link to see a weather map of the Medford, Oregon area from December 11th, 2009. It shows the pressure and wind speeds of the area. Safety There are some safety precautions to take if you drive during freezing rain. Firstly, only travel if it is necessary (5). You can't slip on the sidewalk if you don't walk on it! If you must drive, drive carefully, and wait for the roads to be sanded/salted before driving. (5 & 7). When it is safe, test your brakes, to know how they will respond when you try to stop (5). If you come upon an accident, park in a safe area and use the emergency flashers (5). Don't offer assistance until it is safe, as cars approaching the scene could loose control and add to the car accident (5). These safety precautions are for freezing rain, and should always be followed in this type of weather. If freezing rain is predicted to hit where you are, get extra supplies like food and blankets, so you don't have to try and get them during the storm (7). As in any winter storm, avoid overexertion in freezing rain conditions (6). Strain from the cold when combined with hard work could cause a heart attack (6). Sweating from this labor can lead to chill and hypothermia--low body temperature (6). If you are caught outside, seek shelter immediatley (6). If you cannot find a shelter, look for somewhere to protect yourself from the wind and rain, like a cave, and try to build a fire if you know how (6). If you are caught in a vehicle, stay in it and make yourself visible to others (6). Be careful not to use up your car battery (by leaving your lights on for extended periods of time) as you will not be able to start your car again if it the battery is dead. If you are in a building or at home, stay inside and get heat from a fireplace or wood stove as the power can go out as a result of ice from the freezing rain building up on power lines and telephone poles (4 & 6). Make sure to eat and drink so, you can stay hydrated and have energy just in case (6).

Sources 1.) “Freezing Rain.” //Glossary of Meteorology//. American Meteorological Society, n.d. Web. 10 Jan. 2012. . 2.) “Freezing Rain: Supercooled droplets freezing on impact.” //WW2010//. University of Illinois, n.d. Web. 9 Jan. 2012. . 3.) "Freezing Rain & Ice Storms." //Weather Almanac//. Advameg.inc. Web. 12 Jan. 2012.  4.)“Dangers to People: injuries and automobile accidents.” //WW2010//. University of Illinois, n.d. Web. 11 Jan. 2012. . 5.) Lesperance, Martin. “Freezing Rain.” //Safete//. Safety Health Publishing, 1997. Web. 15 Jan. 2012. . 6.) “Winter Storms... are deceptive killers.” //National Weather Service//. U.S. Department of Commerce, n.d. Web. 17 Jan. 2012. . 7.) “Freezing Rain.” //Winter Storms//. Scholastic.com, n.d. Web. 17 Jan. 2012. . 8.) “Cyclones and Fronts: the development of freezing rain .” //WW2010//. University of Illinois, n.d. Web. 17 Jan. 2012. . 9.) Keene, Shad. “Freezing Rain in Medford, Oregon: Analysis of a High-Impact Event.” //Medford, Oregon Weather Forecast Office//. National Weather Service, n.d. Web. 18 Jan. 2012. .