WINTER WEATHER CHAPTER 4.6 The winter months in New York City can be brutal. They are often characterized by periods of extremely cold temperatures and by storms that haul in large amounts of snow, ice, sleet, and freezing rain in addition to strong winds. The number of storms per season, the amount of snow from each storm, and prolonged periods of extreme cold can take a toll on people, buildings, infrastructure, and the economy. Hazardous wintry conditions also induce dangers like traffic accidents, power outages, and hypothermia and frostbite. WHAT IS THE HAZARD? SNOW and ICE The term heavy snow generally means snowfall accumulating to a depth of four inches or more within 12 hours or less, or six inches or more within 24 hours. Sleet is pellets of ice composed of frozen or mostly frozen raindrops, or refrozen partially melted snowflakes. Freezing rain is precipitation that falls as rain, but freezes on contact with a surface, forming a glaze of ice. The severity of a winter storm depends on temperature, wind speed, type of precipitation, accumulation rate, and timing. A storm that occurs during early winter, when trees still have leaves, may result in more downed trees and power lines due to the additional weight of snow and ice. Our city can experience a variety of winter storms: The intensity of a winter storm can be classified by meteorological measurements and societal Snow showers are brief, intense periods of snowfall impacts. The Northeast Snowfall Impact Scale resulting in accumulations of one inch or less. (NESIS) characterizes and ranks high-impact Northeast snowstorms – those with large areas of A blizzard is a severe snowstorm with winds snowfall accumulations of 10 inches and greater. of 35 mph or greater and snow and blowing The National Climatic Data Center developed this snow that reduce visibility to less than one- scale because the transportation and economic quarter mile for three hours or longer. impacts of Northeast snowstorms can significantly affect the rest of the country. The index uses A snowsquall is moderate to heavy population data and meteorological measurements snowfall accompanied by strong, gusty to gauge a storm’s impacts on society. winds and, sometimes, lightning. N ESIS SCALE Thundersnow events are snow accompanied by thunder and lightning. N otable Signficant Major Crippling Extreme Ice storms occur when freezing rain 1 2 3 4 5 results in dangerous accumulations of ice, usually one-quarter inch or more. WINTER WEATHER 111 TPO FIVE SNOWSTORMS IN NEW YORK WIN TER WEATHER EXTREMES IN NEW YORK CITY CITY FOR SNOW ACCUMULATION The largest snowstorm to hit New York City occurred on DATE INCHES OF SNOW NESIS February 11-12, 2006, bringing in a total of 27 inches of snow. RATING The month with the most snowfall is February 11 27 inches 3 February 2010: 37 inches fell. to 12, 2006 One of the worst winters for snow was 1996-1997, December 26 26 inches 2 when snowfall totaled 76 inches. to 27, 1947 The coldest day of the year was recorded on February 9, March 12 to 21 inches 4 1934, with temperatures dipping 15 degrees below zero. 14, 1888 The coldest month was recorded in February February 25 21 inches 3 1934, with an average temperature of 20°F. to 26, 2010 December 26 20 inches 3 to 27, 2010 So URCE: WEATHER 2000/FORECAST RESEARCH Winter storms are frequent here. Since 1798, New York ocean. Areas right next to the shoreline are often City has experienced 19 snowstorms with snowfall slightly warmer during colder months, but wind-chill totaling 16 inches or more. One was Extreme, five temperatures along the shore may be lower than were Crippling, five were major, one was significant, temperatures several miles inland, due to stronger and one was notable. The remaining six historical winds near the water, even if the actual air temperature snowstorms did not qualify for a NEIS rank. is higher. Neighborhoods with lower population density, greater natural cover, and less heat-absorbing asphalt may be a few degrees cooler, though this EXTREME COLD effect is less pronounced during colder months. While snow and ice are the defining features of A National Weather Service (NWS) wind-chill chart winter storms, wind gusts and frigid temperatures reports the temperature felt on exposed skin due can accompany these weather events. Extreme to the combination of air temperature and wind cold can occur independent of storms. speed. When conditions warrant, the NWS issues wind-chill advisories or wind-chill warnings for the Extended periods of subfreezing temperatures are New York City region. An advisory is issued when most common here between December and March. wind-chill values are expected to fall to between An extreme cold event typically involves an extended 24°F and minus 15°F. A warning is issued when period with temperatures at or below 32°F. As the values are expected to fall to minus 25°F or below. temperature drops and wind speed increases, heat drains from our bodies more rapidly. This “wind- According to the New York City Panel on Climate chill effect” can make a person feel even colder. Change, the city experiences an average of 72 days per year with temperatures at or below 32°F. This In general, New York City experiences less severe annual average is projected to decrease by the 2020s cold due to the urban heat island effect (explained to 52 to 58 days and by the 2050s to 42 to 48 days. in the “Extreme Heat” profile) and proximity to the 112 NYC’s Risk LaNDSCAPE WIND CHILL CHART (Source: NWS) Temperature (ºF) Calm 40 35 30 25 20 15 10 5 0 -5 -10 -15 -20 -25 -30 -35 -40 -45 5 36 31 25 19 13 7 1 -5 -11 -16 -22 -28 -34 -40 -46 -52 -57 -63 10 34 27 21 15 9 3 -4 -10 -16 -22 -28 -35 -41 -47 -53 -59 -66 -72 15 32 25 19 13 6 0 -7 -13 -19 -26 -32 -39 -45 -51 -58 -64 -71 -77 20 30 24 17 11 4 -2 -9 -15 -22 -29 -35 -42 -48 -55 -61 -68 -74 -81 25 29 23 16 9 3 -4 -11 -17 -24 -31 -37 -44 -51 -58 -64 -71 -78 -84 30 28 22 15 8 1 -5 -12 -19 -26 -33 -39 -46 -53 -60 -67 -73 -80 -87 35 28 21 14 7 0 -7 -14 -21 -27 -34 -41 -48 -55 -62 -69 -76 -82 -89 Wind (mph) 40 27 20 13 6 -1 -8 -15 -22 -29 -36 -43 -50 -57 -64 -71 -78 -84 -91 45 26 19 12 5 -2 -9 -16 -23 -30 -37 -44 -51 -58 -65 -72 -79 -86 -93 50 26 19 12 4 -3 -10 -17 -24 -31 -38 -45 -52 -60 -67 -74 -81 -88 -95 55 25 18 11 4 -3 -11 -18 -25 -32 -39 -46 -54 -61 -68 -75 -82 -89 -97 60 25 17 10 3 -4 -11 -19 -26 -33 -40 -48 -55 -62 -69 -76 -84 -91 -98 Frostbite Times Where, T= Air Temperature (ºF) V= Wind Speed (mph) 30 minutes 10 minutes 5 minutes Wind Chill (ºF) = 35.74 + 0.6215T - 35.75(V0.16) + 0.4275T(V0.16) WHAT IS THE RISK? The NYC Department of Health and Mental Hygiene (DOHMH) reports nearly 200 hypothermia-related Accumulations of snow and ice, as well as cold hospital admissions and emergency department temperatures, can impact public health, public visits on average each year from 2005 to 2010. safety, buildings, infrastructure, and the economy in ways that range from inconvenient to grave. Another serious condition brought on by extreme cold is frostbite: a freezing of the body’s outer tissue, most commonly the nose, ears, cheeks, chin, fingers, PEOPLE AT RISK: HEALTH and perSONAL SAFETY and toes. Symptoms include numbness, tingling or stinging, aching, and skin discoloration. Frostbite Power outages caused by winter storms – typically, can cause permanent damage to body tissue and in when trees topple onto power lines or the weight severe cases may result in the need for amputation. of ice brings power lines down – can trigger a cascade of problems. For example, during power Exposure to cold can also exacerbate chronic illnesses, outages, people living without backup power are such as asthma and other respiratory diseases. at increased risk. If a winter storm interrupts the supply of fuel oil, natural gas, steam, or electricity Another threat is carbon monoxide poisoning. Home to building heating systems, the drop in building appliances, notably gas kitchen ranges and space temperatures can put occupants’ health at risk. heaters emit carbon monoxide if not properly ventilated. While carbon monoxide poisoning can happen any One risk is hypothermia. When exposed to cold time of the year, the danger is greater during winter. temperatures for an extended period, our bodies lose heat faster than we can generate it, causing Icy conditions may contribute to falls and other our internal temperature to drop. Symptoms injuries for people who venture outdoors. Snow include shivering, fatigue, loss of coordination, and ice storms can be especially hazardous blue skin, dilated pupils, slow pulse and breathing, for people who work outdoors, those who are and loss of consciousness. Death can result. homeless, and other vulnerable populations. WINTER WEATHER 113 Falling icicles from buildings can be dangerous in a dense city such as New York. In the winter of 2013-14, icicles formed on 1 World Trade Center, and some fell, from The Urban Green Council created computer models of representative buildings to determine great heights.