FreezingRainTan2

Freezing Rain

Eric P. & Brian R. Tan Class

Introduction Freezing rain is not much different than the rain people experience on a daily basis. It looks like regular liquid water precipitation, but it is quite special in that it is a supercooled liquid water precipitation which freezes upon impact of an object.(2) This can be a truly severe type of weather, and it can have a large impact on the environment and human life.

Dangers One factor that makes rain extremely dangerous is its ability to form a thin film of ice over any object in makes contact with.(2) This quality of freezing rain is famous for encasing telephone poles and tree limbs, making driving treacherous, and interfering with aviation. These things can be devastating to humans and their daily routines. For example, this ice can be very dense and heavy,(7) causing brittle tree limbs and telephone poles to come crashing down onto roads.(7) Commuting to work with downe d tree limbs, power lines and slippery roads can become difficult and potentially life threatening.(7) The dangerous layer of ice that an ice storm leaves behind is known as glaze.(7) Bridges and overpasses are the most susceptible to glaze because they have more surface area for them to become completely frozen.(7) In extreme conditions like these, it is important to always use caution and be aware of surroundings and check for any possibility of glaze underfoot.

Conditions of Formation It might surprise you how simple the formation process of freezing rain can be, compared to how dangerous it has the potential to be. The basic conditions required for the formation of freezing rain are that there must be a high layer of air cold enough for precipitation to occur, followed by a thick layer of warm air underneath, and then a relatively thin layer of subfreezing (below 0 degrees Celsius) air just above the ground.(2) One thing that is fairly interesting about freezing rain is that the precipitation could be formed as snow, or hail, or any other type of precipitation. What makes freezing rain form is that as the precipitation passes through the deep warm layer of air, it must all melt into rain.(1,2) Due to the fact that the lowest subfreezing level of air is so shallow, when the falling rain enters it there is not have enough time for it to freeze into sleet,(1) so the rain drops become supercooled.(1,2) When a raindrop, or any liquid, is supercooled, it means that it has reached a temperature below the freezing point of the liquid, but remain in the liquid state of matter. As the drops fall, they do not freeze(2) but they freeze on contact with any cold object.(1,2) This freezing of the supercooled rain on all cold objects on the ground causes the film of ice to develop,(2) and in turn the longer the ice storm is the thicker the layer of ice becomes.

There are several ways that the conditions for freezing rain production may be created. As a point of reference, when warm moist air is forced over a mass of cooler air, the rising air expands due to the lesser amount of air molecules at higher altitudes and therefore cools adiabatically. Along with that it is being cooled by the fact that higher in the troposphere there is a cooler temperature altogether. This causes cooling air to reach its dew-point, meaning it is holding the maximum amount of water vapor possible. When the air cannot hold anymore water vapor, the vapor condenses into microscopic water droplets on particulates in the air, and they clump together into clouds and cause precipitation to occur.

One example is that during a mid latitude cyclone (MLC) when the cold front is branching off to the south of the low pressure center of the MLC, southerly winds can trigger freezing rain to occur.(4) What happens is that the warm, moist southerly air is forced up, over and behind the cold front(4) causing precipitation to occur. It falls through the warm layer and then becomes supercooled when it has reached the coldest layer caused by the cold front underneath.(4) Under these conditions, light, scattered patches of freezing rain occur behind the cold front.(4) In addition, stationary fronts can lead to freezing rain.(4) In a stationary front, a warm front and cold front are moving parallel to each other, and when the cold front is to the north and the warm front is to the south, freezing rain can form.(4) Winds in the upper level of the atmosphere can be southern winds,(4) pushing some warm, moist air from above the warm front to over the cold front. As this air mass cools, precipitation forms and hits the low cold front air, resulting in a narrow band of freezing rain along the cold side of the frontal boundary.(4) A last way in which freezing rain can occur has to do with northern arctic fronts.(4) Arctic air masses tend to be relatively shallow,(4) likely caused by their high density due to extremely low temperatures. Som e arctic fronts have continental polar air masses behind them.(4) This is one of the reasons why some of the most intense ice storms are cause by arctic fronts,(4) because continental air comes from over land while maritime air masses originate over bodies of water. Bodies of water stay relatively mild when the surrounding climates are cooler but stay cooler in warmer climates, while land masses can have more variable temperatures. This means that the continental polar air is extremely cold, and when it moves south and forces warmer, moister air up, the precipitation falls into an extremely cold layer of arctic air.(4) Bands of freezing rain wider than 50 kilometers can be associated with arctic fronts.(4)

Historical Examples In 1998, January 4-9, north east Cananda, a terrible storm tore through th e region. (6) This disastourous freezing rain storm downed millions of trees, 130 transmission towers, 30,000 utility poles, and 120,000 km of power and telephone lines. Power outages lasted from several hours to four weeks. (6) This storm not only killed or endangered many people, but locked people away from their jobs for weeks. Partially, what made this storm so disastrous was its timing. Never before had a freezing rain storm of this scale ever occured in January.(6) The storm cost 3 billion in repairs, and interfered with 3 million peoples lives. (6) This was the longest freezing rain storm ever on record, lasting 80 hours, and the most devastating in all of Canada's history. (6)(8)(both)

For other examples of ice storm related destruction, visit: []

Safety Winter ice storms can have adverse effects on a community and can cause getting around by any means of transportation to become dangerous and sometimes impossible. This means it is important to always be prepared, which includes to always be checking the news or radio forecasts(3) especially before travelling. Once this first step is taken, if there is a large ice storm which will inevitably not allow for transportation, it is best to stay indoors(3) and to avoid possible overexertion by trying to travel on foot or even shoveling snow(3) in the intense cold weather. Having to stay in doors calls for having an adequate stock of food,(3) and even food that does not require cooking(3) because ice storms can and have caused power failure in the past.(3) Furthermore, an extra supply of heating fuel, candles and matches is also important to have in some of the more intense ice storms.(3) This would allow one to keep warm and light the way in their home because the power loss associated with an ice storm can last for an extended period of days.(3) In addition, to make sure that a house can maintain what heat it has after an initial power failure or loss of heating, having proper insulation(3) and caulking in any openings around windows(3) is vital.

In the less intense ice storms in which traveling in still an option, planning primary and backup routes to get to a destination can be very useful.(3) Having a back up route can be effective in saving time when the original route is backed up or put out of commission by the ice. In addition, when traveling in a more mild storm, winterizing a car(3), such as putting on snow tires can increase safety when traveling in such a storm.

For even more in-depth tips and information, visit: [] or []

Sources 1) Kisner, St even. "Winter Precipitation Types and Their Environments." //National Weather Service - Central Region Headquarters Home Page .// 7 Dec. 2007. Web. 29 Nov. 2010.  .

2) Wilhelmso n, Bob, and Mohan Ramamurthy. "Freezing Rain - Supercooled Droplets Freezing on Impact." //WW2010: the Weather World 2010 Project. // <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">University of Illinois. Web. 29 Nov. 2010. <http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/zr/frz.rxml>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">3) "Winter Ice Storm Saf <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">ety Rules." <span style="font-family: 'Times New Roman',Times,serif; font-size: 16px; line-height: 32px;"> // Mc.vanderbilt.edu //. <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">Vanderbilt University Medical Center. Web. 29 Nov. 2010. <http://www.mc.vanderbilt.edu/ep/resources/WinterStormSafety%20Rules_07nov.pdf>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">4) Wilhelmson, Bob <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">, and Mohan . "Cyclones and Fronts - the Development of Freezing Rain." //<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">WW2010: the Weather World 2010 Project. // <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">University of Illinois. Web. 29 Nov. 2010. <http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/prcp/zr/cond/cyc.rxml>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">5) <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">"Freezing Rain by Tulio Adriano : Weather Underground." //<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">Welcome to Weather Underground : Weather Underground. // <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">2010. Web. 29 Nov. 2010. <http://www.wunderground.com/wximage/viewsingleimage.html?mode=singleimage&orig_handle=TulioAdriano&orig_number=6&handle=TulioAdriano&number=3&album_id=3>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">6) "Historical Ice Storm Related Events." //<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">Ontario Hazards. // <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">Office of Critical Infrastructure Protection and Emergency Preparedness, 08 Mar. 2010. Web. 30 Nov. 2010. <http://ontario.hazards.ca/historical/Ice_Ontario-e.html>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">7) "Weather.com - Storm Encyclopedia - Winter Precipitation: Freezing Rain, Snow, Sleet." //National and Local Weather Forecast, Hurricane, Radar and Report//. <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">The Weather Channel, 2010. Web. 30 Nov. 2010. <http://www.weather.com/encyclopedia/winter/precip.html>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">8) "Freezing Rain." Government, 1995. Web. 30 Nov. 2010. <http://www.nws.wopp.gov>.

<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px;">9) "Deadly Blizzards and Ice Storms: Americans Lose Power While Afghans Sell Their Children For Bread and Coal." //<span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;">DBKP - Death By 1000 Papercuts - DBKP //<span style="font-family: 'Times New Roman',Times,serif; font-size: 16px; line-height: 32px;">. <span style="font-family: 'Times New Roman',Times,serif; font-size: 14px; line-height: 32px;"> 2010. Web. 30 Nov. 2010. <http://deathby1000papercuts.com/2009/01/deadly-blizzards-and-ice-storms-americans-lose-power-while-afghans-sell-their-children-for-bread-and-coal/>.