Extreme Weather: From Heat and Cold Waves to Storms

LAST MODIFIED:

POSTED: 10 June 2020

• Climate and Weather Extremes

• lowest recorded air pressure at sea level: 870 mbar (25.7 in); during Typhoon Tip (1979), Pacific Ocean
• highest air pressure at sea level: 1084 mbar (32.02 in); Agata, Siberia
• lowest air temperature (world): -89°C (-129°F); Vostok, Antarctica
• lowest air temperature (North America): -63°C (-81°F); Yukon, Canada
• highest air temperature (world): 58°C (136°F); Al Aziziyah, Libya*
• highest air temperature (North America): 57°C (134°F) Death Valley, California
• highest wind speed (world): 372km/h (231mph); Mt. Washington, New Hampshire


• hottest U.S. cities (average A): Key West, FL (78.0°); Honolulu, HI (77.5°); Miami, FL (76.6°); Fort Lauderdale, FL (75.7°); West Palm Beach, FL (75.3°)
• hottest U.S. cities (ave. Jul. max. T): Palm Springs, CA (108.3°); Yuma, AZ (107.0°); Phoenix, AZ (106.0°); Las Vegas, NV (104.17deg;); Tucson, AZ (101.0°)
• coldest U.S. cities (average T): Fairbanks, AK (26.7°); Anchorage, AK (36.2°); International Falls, MN (37.4°); Duluth, MN (39.1°); Caribou, ME (39.2°)
• coldest U.S. cities (ave. Jan. min. T): Fairbanks, AK (-19.0°); International Falls, MN (-8.4°), Grand Forks, ND (-4.3°); Alamosa, CO (-3.7°), Williston, ND (-3.3°)
• snowiest U.S. cities: Truckee, CA (203.4"); Marquette, MI (179.8"); Steamboat Springs, CO (173.3"); Oswego, NY (153.3"); Sault Ste. Marie, MI (131.2")


• top of troposphere: -60°C (-80°F)

* this observation on 13 Sep 1922 was long considered the world's highest temperature. But the World Meteorological Organization (WMO) deemed int illegitimate in 2012. The current record for world's highest temperature is the Death Valley measurement. is the

For comparison, temperatures on other planets in our solar system:

Planet	day time	night time
Mercury	427°C	-173°C
Venus	480°C (900°F)
Mars	20°C	-140°C




• Heat Waves and Droughts

• heat waves occur when strong upper atmospheric high pressure systems become locked over a region for an extended period of time
• definition: there is no uniform definition worldwide, but the WMO describes a heat wave when the daily maximum temperature exceeds the typical average maximum temperature by 5 °C (9 °F) for five or more consecutive days.
  

  heat index: heat index says how hot the air feels, taking relative humidity into account; when air warms beyond a certain threshold (about 70°F) , humid air feels warmer than dry air. The effect becomes more severe with increasing T. The apparent T of hot air that we feel depends on how much sweat can evaporate from the skin (evaporation requires energy that is taken from the surrounding air). In hot, humid air, sweat cannot evaporate and cool the skin. Humans are then more easily overcome by heat exhaustion.

  
  
• The most intense and widespread heat wave ever to occur in the U.S. took place during the summer of 1936 (during July and August). Fifteen state absolute-maximum temperature records still stand today as a result of this heat wave. Readings of 120°F or higher were recorded in Arizona, Arkansas, California, Kansas, Oklahoma, South Dakota, Texas, and, incredibly, North Dakota, where the temperature peaked at 121°F.
• The American Southwest, already the hottest region of the United States, experienced its highest temperatures ever during late June and early July 1994. From West Texas to Arizona most weather stations attained their all-time maximum temperatures, including Midland, Texas (116°); El Paso (114°); Albuquerque, New Mexico (107°); and Roswell, New Mexico (114°). Santa Fe, normally cool even in summer because of its 7000-ft elevation, reached 100° for the first time in recorded history. Five state records were broken or tied in Nevada (125°), Arizona (128°), New Mexico (112°), Texas (120°), and Oklahoma (120°).
• heat bursts: rare and interesting events, characterized by a sudden increase in temperature, often lasting for no more than a few minutes, and usually occur in the vicinity of thunderstorms (mostly at night); (e.g. 1977 Antalya, Turkey, rise from 100° to 158° in 2 min).
• urban heat island effect: Humans can cope with heat during the day if nighttime T fall below a certain threshold (80°F). The urban heat island effect often prevents this: paved ground retains heat during the night and prevents the ground from cooling as much as soil would. The lack of vegetation that would release cooling water at night during respiration is also missing. The use of air conditioners to cool houses inside heats the air outside further.
• the increased use of air conditioning during heat waves taxes already strained electrical power grids. This increases the risk of damaging power outages. To prevent damage, some el. energy companies cut off power to customers during rolling blackouts.
• NB⁽¹⁾: heat waves can be hazardous to air traffic. On June 26, 1990 a heat wave in Phoenix, AZ drove the temperature to 50°C (122°F). The extreme heat lowered the air density to the point where aircraft lift was reduced. Officials suspended aircraft takeoffs at Sky Harbor Airport.
• in the U.S., heat waves have been the top severe weather killer in the last 20 years, leading before hurricanes and floods. In the U.S. more people die from heat waves than from exposure to cold and winter storms taken together.

NOW READ THIS? TIME Magazine, Nov 9, 2015: 165-170°F - The heat index, which combines heat and humidity, forecast for parts of the Persian Gulf by 2100, if carbon dioxide emissions continue to grow at the current rate.

• Cold Storms

• when arctic air spreads unusually far south
• the greatest cold wave in modern U.S. history occurred during the first two weeks of February 1899. For the first and only time, temperatures fell below zero in every state of the Union, including Florida, where Tallahassee dropped to an unbelievable -2°. In Mobile, Alabama, the reading of -1° was a full 13 degrees colder than the previous records low of 12°. Even tropical Havana, Cuba, was affected of Feb 14, when the temperature did not rise above 54°. In New Orleans the lowest reading was 6.8°, and ice floes choked the Mississippi River and even drifted into the Gulf of Mexico. Three inches of snow fell in New Orleans. The arctic outbreak spread south out of Canada on Feb 7, dropping temperatures to -61° in Montana and -59° in Minnesota.
• ice storms: winter storm; when rain falls at the same time as ground temperatures remain below freezing. The damage from ice storms is usually more severe than that caused by snowstorms, wreaking havoc to electric powerlines, highways, and forests.
• the Siberian Express in 1983/1984 was responsible for one of the coldest winters on record across North America (see Case Study 1) since reliable records began in 1931.
• wind chill factor: How cold the wind makes us feel is expressed in the wind-chill factor (formulated in 2001).
  On a cold day, a thin layer of warm air molecules form close to our skin, thereby protecting it from the surrounding cooler air and from rapid transfer (loss) of heat. Once a wind starts to blow, the insulating layer is swept away, and heat is rapidly removed from the skin. The faster the wind blows, the greater the heat loss. To access the chart at Wikipedia click here and the the wind chill wikipedia page
• Blizzards: Canada and the U.S. have different criteria to call a cold storm a blizzard. In the U.S., the criteria are:
  • sustained wind speeds 56 km/h (35 mph) or larger
  • blowing snow
  • visibility of 0.25 mi or less
  • lasting for at least 3 h
  Canada also makes a wind chill of less that -25°C (-13°F) a criterion but has less restrictions on sustained wind speed (40 km/h) and visibility (1 km)
• link the the National Weather Service page on biggest snowstorms in the U.S.



• Clouds and Precipitation

• cloud: a region where moisture condenses (droplets are 1/3 of human hair)
• fog: cloud at surface


• clouds reflect incoming sunlight, hence cooling the Earth's surface during the day
• clouds trap heat coming from the Earth's surface, hence heating it at night.


Cloud lifting mechanisms:
• convective lifting (e.g. on islands)
• frontal lifting (between air masses)
• convergence lifting (air has nowhere to go but up)
• orographic lifting (air rising up a mountain)


cloud names by shape:
• cumulus: puffy, cauliflower like
• stratus: thin, sheet-like
• cirrus: wispy, featherlike curls


cloud names by altitude:
• high (>7km) cirro
• mid (2-7km) alto
• low (<2km) no name

add "nimbus" or prefix "nimbo" if cloud produces rain (e.g. cumulonimbus)

• Rain, Snow and Hail

Clouds/fog:
• when moist air rises, water vapor eventually condenses
• need preexisting liquid or solid aerosols as condensation nuclei
• droplets (about 2µm across) form around condensation nuclei
• droplets suspended in clouds

Rain:
• droplets in cloud collide and coalesce (grow)
• eventually droplets are too large to float and fall as rain
• droplets at least 0.5,, in diameter; typical rain drops are 2mm in diameter and fall at 20km/h

Sleet:
• if rain falls through cold air near the ground, freezes

Drizzle:
• droplets smaller than 0.5 mm in diameter
• most drizzle falls from stratus clouds
• drizzle may also form near the surface when rain fell through unsaturated air aloft and partially evaporated on its way down
• virga: rain that never hits the ground (visual as streaks or "rain streamers" emerging below clouds) as a result of rapid evaporation (very common in San Diego skies)

Snow:
• cold clouds contain mix of very cold droplets and tiny ice crystals
• water droplet evaporate faster than ice (because water molecules are less tightly bound to water droplet than to ice)
• moisture then condenses around ice crystals, leading to growth of hexagonal snowflakes
• if air below cloud is very cold, snow falls in powder-like flakes
• if air is close to melting T (0°C), large, wet clumps of snowflakes fall
• if air is above 0°C, snow transforms to rain

Hail:
• in clouds with strong updraft (e.g. thunderstorm), ice crystallizes to ice balls at high levels where T is below freezing
• hail falls over a few minutes, in a typically 2-10km long streaking in the direction a storm moves
• most hailstones are pea-sized though the largest recorded stone reached a diameter of 14cm and weighed 700g.
• in the U.S., most hail storms happen in the tornado alley (see below) from Texas through Oklahoma into Kansas and north



• Air Masses

air mass: a large body of air (can be > 1500km across) with similar T and humidity in every horizontal direction (same altitude) moved about by winds aloft forms over a large flat area (source region) with only light surface winds (calm) ideal source regions: areas with high surface air pressure (e.g. ice- and snow-covered arctic plains in winter, subtropical oceans in summer) Classification by latitude (arctic/polar/tropical) and surface type (continental/maritime) air masses relevant to weather in the U.S. cA: continental Arctic; very cold, dry, stable cP: continental Polar; cold, dry, stable mP: maritime Polar; cool, moist, unstable cT: continental Tropical; hot, dry, stable air aloft; unstable surface air mT: maritime Tropical; warm, moist; usually unstable


NB⁽¹⁾: the character of cP is different in winter and summer. In winter, over very cold areas (T=-20°C; -4°F), the cooling effect from low surface temperatures is stronger than the heating effect from sinking air in a high pressure system (adiabatic heating). Cold air is then trapped near the surface below warmer air aloft. This causes the formation of an inversion layer. Over large cities, pollutants can accumulate within a few days, lowering visibility and air quality.

The characteristic of an air mass changes when it leaves the source regions and moves over new areas. For example, an unstable mP air mass loses moisture when it moves east and crosses the Rocky Mtns. It then travels over a cold, elevated plateau that chills the surface air and slowly transforms the lower level into dry, stable cP.

Lake-Effect Snow: this phenomenon often occurs November through January along the eastern shores of the Great Lakes (and up to 50 km inland). The Midwest is often dominated by clear cP air. If this air moves east, the still warmer lakes warm the air from below, which then becomes unstable. During warming, the air picks up moisture that condenses to fog after the air starts to rise. The air can rise further to form clouds that bring heavy snow falls as they move eastward.


• Fronts

• weather changes drastically when one air mass replaces another
• front: boundary between air masses



stationary front: two air masses butt up against each other nearly no movement of air toward the front surface winds parallel to front but in opposite directions on each side of the front winds aloft usually parallel to front




cold front: cold air mass pushes underneath a warm air mass steeply sloped front warm T ahead of front, cold T behind it marked drop in air pressure near the front air cools quickly, rises very high, condenses and produces thunderstorms, violent weather extent of precipitation confined to vicinity of front and immediately behind it cirrus clouds driven by winds aloft are far ahead of the front NB(1): The passage of a cold front can be quite spectacular. Though no temperature records are available, it is reported that temperatures dropped nearly instantaneously from a balmy 40s°F to 0°F when a cold front moved through Illinois on Dec. 21, 1936.




warm front: warm air mass moves on top of cold air mass shallow slope of front warm front move about half as fast as cold fronts cold T ahead of front, warm T behind it air expands, cools, condenses causing precipitation extent of precipitation widespread, far ahead of front cirrus clouds driven by winds aloft are far ahead of the front




occluded front: when a cold front catches up with or even overtakes a warm front warm front gets lifted up and loses contact with surface cooling and condensation leads to further precipitation most violent weather when cold front is just overtaking warm front cold occlusion: (shown in example) when cold air behind occluded front is colder than air in front of warm front (typically more violent) warm occlusion: when cold air behind occluded front is warmer than air in front of warm front


how to locate a front near the surface: sometimes difficult but things to look out for are
• sharp temperature change over short distance
• changes in air moisture content (dew point)
• shift in wind direction
• changes in air pressure
• clouds and precipitation patterns



• Wave Cyclones

In mid-latitudes, the weather commonly reflects the movement of a large low-pressure air mass that moves from west to east. The polar front theory is a simplified model of how some extratropical/mid-latitude cyclones develop. The polar front is the stationary boundary between the Polar and Ferrel circulation cells near 60° latitude. Air from the north gets deflected westward by the Coriolis effect, while air from the south gets deflected eastward. Air starts to circulate counterclockwise around a center, creating a mid-latitude cyclone or wave cyclone. Wave cyclones can also form along other stationary front.



Stages of a wave cyclone: initially two air masses shear past each other along a stationary front. This sets up a cyclonic wind shear. under the right conditions, an indentation, or "wave" develops along the front a warm front develops on the leading side, a faster-moving cold front develops on the trailing side of a developing low-pressure center the indentation becomes more pronounced, and air circulates in a counterclockwise path (it becomes a cyclone). The low pressure near the center intensifies the faster cold front starts to occlude the warm front, from the center outward. The weather is most severe where the occlusion occurs the cyclone feeds on 1) the transfer of potential energy of sinking cold air into kinetic energy and 2) on the release of latent heat by rising warm air when occlusion is complete, the cyclone dissipates. This happens when the triple point where the three fronts (cold, warm, occluded) meet are too far away from the center to feed the cyclone.




DID YOU KNOW? Some wave cyclones can develop to large powerful storms. An example in the eastern U.S. is the 1993 "White Hurricane" (see case studies for this and other powerful winter storms).


Powerful storms can destroy large stretches of forests. For example, a storm with 130-knt-winds (150 mph) in January 1921 flattened 8 times as many Douglas firs in Washington and Oregon (wind throw) as Mt. St. Helens destroyed on its flanks during its May 18, 1980 eruption (pyroclastic flows). (see case studies for more examples)


• Storms

• storm: an episode of severe weather, when winds, rainfall, snowfall, and in some cases lightning become strong enough to be bothersome and even dangerous.
• storms form where large pressure gradients develop (e.g. across fronts)
• storms form locally where warm, moist air rises
• rising air leads to condensation -> release of latent heat
• release of latent heat warms air that rises further still until it becomes cools enough to form clouds (cumulonimbus)
• warm, moist bottom air that follows near the surface feeds the storm
• once cloud become thick enough, rain starts to fall, causing a downdraft when rain is heavy
• storm eventually dissipates



• The Nor'Easter (in the Northern Hemisphere)

The Nor'Easter is a large, powerful mid-latitude, hence extratropical (wave) cyclone that develops or intensifies into a powerful storm off the eastern seaboard then moves northeast along the coast (e.g. Japan, U.S. east coast). The mid-latitude cyclone developing in the U.S. is called Hatteras Low (after the area where it forms). It often feeds on the warm Gulf Stream to rapidly intensify.

occurs in late winter/early spring (but can occur Oct - Apr) usually most intense of the coast of New England typically develops in the south and is steered northeast by the jet stream often accompanied by rapid drop of central pressure some Nor'Easters may possess the characteristics of a tropical hurricane, e.g. it can have a calm "eye" Main characteristics of a Nor'Easter: gale force northeasterly winds on the northern side of the storm's center high waves and significant coastal erosion due to the large extent of the storm over open ocean heavy precipitation; often blizzards along the northern perimeter, the counterclockwise flowing cyclone is fueled by bringing cool, moist air (mP) from the northeast (allows heavy precipitation). This makes Nor'Easters different from other extra-tropical cyclones main difference from hurricanes: it is a cold-core low-pressure system, thriving on cold air




NB for the interested(1): often, the U.S. Nor'Easters are preceded by a situation where a slow-moving, cold continental anticyclone (H pressure system) that formed further north drifts to the east to park over Newfoundland. The anticyclone then captures the cool, moist mP air and brings it ashore along its southern perimeter. A stationary front separates this air from warmer air further south (mT air brought in from the Gulf of Mexico). North of the front, northeasterly winds provide damp weather with drizzle, rain and snow. When upper atmospheric conditions are right, storms develop along the front, are pushed eastward by the Jet Stream and intensify to become Nor'Easters (see also section on wave cyclones).





DID YOU KNOW? Perhaps the most (in)famous Nor'Easter is "the perfect storm" in October 1991 (described in a book and movie). The storm initially developed as a Nor'Easter. It captured an unnamed hurricane, moved south and then fueled on the warm Gulf Stream to develop into a category 1 hurricane before making landfall in Nova Scotia. It caused waves up to 30 m in the open ocean and had a storm surge of > 10 m that caused extensive coastal erosion (see case studies that also describes other, more typical Nor'Easters).




• Recommended Reading

• "Extreme Weather" by Christopher C. Burt, 2004, Norton&Comp, ISBN: 0-393-32658-6
• ⁽¹⁾"Meteorology Today" by C. Donald Ahrens, 2003, Thomson Brooks/Cole, ISBN: 0-534-39771-9
• ⁽²⁾Wild, R., 2011, A Review of Global Heavy Snowfalls and Blizzards in 2003. Int. J. Meteo., 36 (362), 201-204.
• ⁽³⁾Wild, R., 2011, A Review of Global Heavy Snowfalls and Blizzards in 2004. Int. J. Meteo., 36 (362), 205-210.
• ⁽⁴⁾homepage of British Meteorologist Richard J. Wild

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• World's Remarkable Snowstorms and Blizzards^(2,3,4)

U.S.

02/07/03: Heavy snow caused an accident in western Michigan, involving 60 cars and tractor trailers. One person was killed and eight others seriously injured. The incident took place in blinding snow on I-94, just north of the Indiana border. Other northern and eastern districts of the U.S. also saw heavy snowfall. Many cities including Washington, D.C. and Baltimore received a snowfall of 15 cm.

02/15/03-02/17/03: A 3-day snowstorm that caused 24 deaths affected north-eastern districts of the U.S.. Between 40 and 90 cm of snow fell across many areas between Washington, D.C. and Boston, MA. The heavy snow forced the closure of airports in the region as runways and roadways were impassable. The region experienced its snowiest winter in over 7 years.

03/06/03: Heavy snow fell across Massachusetts. The snowstorm caused an accident of 100 cars on I-95, just south of Boston.

04/07/03: A snowstorm affected the Plains and north-eastern districts of the U.S.. The snow was blamed for an accident that left 7 people dead in Pennsylvania. Up to 15 cm of snow fell in places.

12/06/03-12/07/03: Heavy snow affected north-eastern parts of the country causing 11 deaths. Western parts of Maine sustained a snowfall of 100 cm, New York had 48 cm, while Boston, MA sustained 45 cm. Power supplies were cut off to many thousands of households and travel was severely disrupted. Hundreds of flights from New York's LaGuardia Airport were cancelled. The snowfall in Boston was the largest snowfall in the city in the month of December for 28 years.

12/09/03-12/10/03: A snowstorm hit many states across the country. The snowstorm affected the Sierra Mtns. of California, Minnesota, Wisconsin, Iowa and Missouri. Snowfall between 15 and 25 cm in many districts.

12/13/03: Oklahoma and Kansas sustained a snowfall up to 30 cm in places.

12/15/03-12/16/03: Heavy snow covered many north-eastern areas of the country. At least 7 people died. In New York City, 15 cm of snow fell.

12/26/03: In Utah, a snowstorm deposited a snowfall of 75 cm on the mountains, while in areas around Salt Lake City, 30 cm of snow fell. The snow caused widespread chaos as tree branches collapsed on to powerlines bringing blackouts to over 50,000 people.

12/30/03-12/31/03: A snowfall gave Las Vegas, NV the first good covering of snow in 5 years. Around 2-4 cm of snow fell on the famous gambling city. Further to the west and north in Oregon and California, snow also occurred. In the Sierra Nevada Mountain Range, CA snow fell up to 60 cm.

01/03/04: Nearly 1 m of snow fell on parts of Colorado. The snow caused an air crash and an avalanche to occur closing the Vail Pass.

01/06/04-01/07/04: Seattle, WA sustained the worst snowstorm in 7 years. The snow caused traffic chaos and closed hundreds of schools.

01/26/04-01/28/04: heavy snow affected the Midwest and NE districts. Washington, D.C. received 18 cm of snow, while New York City received 33 cm.

02/05/04: Heavy snow fell in parts of the Midwest and Arkansas. The snow caused hundreds of schools and offices to close.

02/14/04-02/15/04: at least 5 people died as a snowstorm caused power cuts and flight cancellations in parts of Texas. Wet snow that fell across North Texas forced approximately 70 flight cancellations at Dallas-Fort Worth International Airport.

02/25/04: The Sierra Nevada Mountain range of Northern California received a snowfall of 60 cm in places.

02/27/04-02/28/04: Snow caused problems in the eastern parts of the country. North and South Carolina were the worst affected areas as up to 30 cm fell in many places including Charlotte, NC. This was the heaviest snowfall in the area for 16 years. A snowstorm also affected Utah, In the higher region of the state, up to 120 cm of snow fell.

03/16/04-02/17/04: heavy snow affected the North East of the country. Buffalo, NY was one of the hardest hit areas, with a snowfall of approximately 40 cm.

04/13/04: An unusual late-season snowfall fell across parts of southern Indiana and the western parts of Kentucky and Tennessee. In Jackson, TN it was the latest late-season measurable snowfall on record. In Kentucky, there were six fatalities in traffic accidents due to snowfall.

09/21/04: heavy snow fell across Denver, CO. Over high ground in Colorado, up to 42 cm occurred.

09/25/04: In Anchorage, AK, 15 cm snow fell. This snowfall was the heaviest snowfall for any single day in the month of September.

10/27/04: In California, record-breaking snowfall occurred in the Sierra Nevada Mountain range. A snowfall of 120 cm had already fallen by 27 October 2004, which was the greatest cumulative snowfall in the month of October since records began in 1945. The previous record was 90 cm in October 2000.

11/02/04-11/03/04: heavy snow affected the South Plains. The snowfall caused 12,000 customers in the Panhandle and South Plains to lose their electricity. In the Lubbock area, 30 cm of snow fell.

11/20/04-11/21/04: In Southern California, up to 90 cm of snow fell over the mountains east of Los Angeles. The heavy snow stranded 10 campers on a peak on the San Jacinto Mountain range west of Palm Springs.

11/23/04-11/25/04: Central and northern parts of New Mexico, Illinois, Michigan, Missouri and South Dakota sustained heavy snow, particularly across the mountains. In Missouri, Kansas City ground to a halt with a snowfall of 20 cm.

11/28/04: Thousands of passengers were grounded at the Reno-Tahoe International Airport as a snowstorm struck Nevada. The snowstorm brought as much as 46 cm of snow to the Sierra Nevada Mountain range with 15 cm falling in Reno.

12/12/04-12/14/04: Heavy snow fell across the northern Plains and the Great Lakes area. Approximately 60 cm fell over parts of northern Wisconsin. In western maryland, 20 cm of snow fell.

12/19/04-12/20/04: Blizzard-like conditions occurred over much of Michigan and Indiana, with 40 cm of snow falling in places.

12/25/04: Cleveland, Ohio, Indiana, Kentucky, idaho and South Texas received snow, with Corpus Christi, TX recording a snowfall of 11 cm. it was only the second time in history that Corpus Christi had seen a White Christmas. In Victoria, TX, snow fell to a depth of 32 cm, making it the first White Christmas on record. In Cleveland, OH, 50 cm of snow fell.

12/26/04-12/28/04: Across the northeast, snow fell up to 45 cm high across parts of North Carolina, new York and Massachusetts. Across the Sierra Nevada Mountains in California, 2 m of snow fell. Reno, NV sustained its heaviest snowfall in a decade, causing the local airport to shut down.

01/05/05: Reno, NV endured the largest snowstorm to hit the area in 15 years.

01/08/05: In the San Bernadino Mountains, CA 200 vehicles were stranded in snow after 1 m of snow fell across the area.

01/14/05: The mountains of Hawaii sustained a heavy snowfall. Mauna Kea reported having a snowfall of 15 cm.

01/19/05: in the Piedmont areas of North Carolina and Virginia, snow fell up to 7 cm, producing traffic jams in the Raleigh-Durham area. The snow stranded more than 3,000 children overnight in schools.

01/22/05-01/23/05: large parts of the north and northeastern areas of the country had a snowstorm that seriously curbed road and air travel and cut power to thousands of customers. The cities of Chicago, New York, Boston, Philadelphia and Washington were badly hit. On the 22nd, a 747 cargo plane skidded off a runway at JFK Airport, New York. The "blizzard of 2005" caused snowfall accumulations exceeding 30 cm in much of the State of New England, with as much as 97 cm in some areas of Massachusetts, Maine, New Jersey and Maryland. In New York City, 45 cm of snow fell, while New Jersey saw a snowfall of up to 53 cm.

02/01/05: the state of Colorado sustained a snowfall of 60 cm.

03/01/05: Heavy snow brought large areas of the East Coast to a standstill. Areas worst hit by the snowstorm were North Carolina, Virginia, New Jersey and Pennsylvania. Up to 20 cm of snow fell at Mount Mitchell, NC.

Canada

01/20/03: Parts of Newfoundland experienced a blizzard that shut down schools and government services, as well as cause delays and cancellations at St. John's airport.

04/26/03: In Calgary, emergency medical services responded to 263 calls, approximately 100 more than average, after a snowstorm paralyzed parts of Calgary causing major damage to trees and some buildings. Up to 65 cm of snow fell in places.

11/12/03-11/13-03: Heavy snow affected SE Canada, including Quebec. The snow caused widespread chaos.

02/19/04-2/20/04: In areas of Nova Scotia and Prince Edward Island, snow fell up to 90 cm. In the city of Halifax, the 1-day snowfall record of 51 cm set in 1944 was broken.

08/18/04: Snow pellets fell on parts of downtown Winnipeg. according to Environment Canada, Winnipeg had no previous evidence of snow falling in August.

10/16/04-10/17/04: Eastern districts of Manitoba received 15 cm of snow on Saturday just north of the Tans-Canada Highway, causing some power failures north of Anola. On Sunda, in northern alberta, 18 cm of snow fell, while 15 cm of snow fell in Saskatoon, Saskatchewan.

11/13/04-11/14/04: Up to 50 cm of heavy, wet snow blanketed Nova Scotia over the weekend, leaving more than 100,000 homes and businesses without power and temporarily shutting down Halifax International Airport.

01/22/05-01/23/05: Heavy snowfall affected parts of Nova Scotia, where it was reported that snowdrifts up to 3 m high occurred in places.

Mexico

01/31/04: Heavy snow affected the north central state of Zacatecas. The snow forced a number of schools to close.

12/31/04: Heavy snowfall occurred in the states of Chihuahua and Zacatecas.

Iceland

11/06/04: Heavy snowfall affected the country. Jan Mayen, to the north-east of Iceland received 60 cm of snow in just 6 h.

Russia

01/08/03: A blizzard on the island of Sakhalin left 6 people dead. Many of the victims were found buried beneath snow drifts as high as 2m.

06/03/03: People in Moscow were astonished to see snowflakes faulting from the skies upon leaving their houses during the morning period. The phenomenon lasted for only a few minutes and the snowflakes melted immediately upon reaching the ground.

02/14/04: A record snowfall in Moscow caused the collapse of a roof of a swimming pool leaving at least 25 dead and over 100 injured.

02/18/04: Heavy snow fell in the Elbrus region of Russia and Georgia. The snow trapped 200 vehicles on the Georgian Military Highway in the east of the state.

02/22/04: Snowstorms in Vladivostok shut down ferry links and the airport as snow fell constantly for 12 h.

Scandinavia

10/19/03-10/20/03: Heavy snow fell across western Finland.

12/21/03-12/22/03: Blizzards left at least 2 people dead and 100,000 more without power in parts of Denmark, Finland and Sweden. The snow caused 80 separate traffic accidents on 12/21 in Finland alone.

02/12/05-02/13/05: scandinavia had a major snowstorm that left many homes without power in Sweden. The worst affected region was the eastern Baltic coast, especially around Stockholm. In Denmark, the main airport at Copenhagen was closed for landings on the 12th.

Ireland and Great Britain

01/18/05: heavy snow fell in eastern parts of the Republic of Ireland, with Dublin Airport seeing several flights cancelled or delayed during the morning period. The main runway was closed for 30 min to allow workers to clear snow and ice that had accumulated.

Belgium, Netherlands and Luxembourg

01/26/04-01/28/04: Heavy snow fell across parts of France, Belgium, Germany and Luxembourg. The snow cased many flight cancellations and travel disruption across Belgium.

03/04/05: A rare snowstorm blanketed the Netherlands, disrupting flights at Amsterdam's Schiphol Airport. The heaviest snowfalls were in the northwestern province of Friesland, where 50 cm of snow fell, the highest level in March for 25 years.

Germany

12/16/03: Snow caused numerous traffic accidents, resulting in 1 fatality and 17 injuries. Police reported at least 100 road accidents in the southern states of Bavaria and Baden-Württemberg.

02/23/05: Heavy snow shut down major airports in Europe, including Munich, Germany and both of the major airports in Paris, France. In parts of the Czech Republic, 40 cm of snow fell, with the main D5 highway west of Prague blocked after several trucks collided. Vienna, Austria received 30 cm of snow.

03/04/05: The heavy snowstorm in the Netherlands also affected Germany as almost all of the country was covered.

Austria

01/05/04: Heavy snow fell in Vienna causing travel disruption. Up to 20 cm of snow fell across the country.

11/20/04-11/21/04: A snowstorm affected Moscow, Austria and the Ukraine over the weekend. In Austria, thousands of homes lost their electricity, as up to 30 cm fell in places.

France

01/06/03: A rare snowfall in southern France shut down two airports. Flights to and from the southern cities of Nimes and Montpellier were cancelled. Several major highways linking France and Spain across the Pyrenees Mnts. were closed. Up to 5 cm of snow fell across the area.

02/27/04-02/28/04: Heavy snow affected many parts of Europe, including Belgium, Netherlands, Italy and France. The Mediterranean resorts of Nice and Antibes turned white, which even included the beaches. Approximately 1,500 lorries were stranded near the French-Spanish border because the road into Spain from the town of Biriatou was closed due to heavy snowfall.

03/10/04: Heavy snow caused the cancellation of the fourth stage of the Paris-Nice cycling race.

05/09/04: Parts of the northeast of the country sustained heavy snow causing thousands of homes to lose their electricity. Many mountainous roads across the area closed due to a snowfall of 30 cm falling above 900 m.

02/23/05: While heavy snow fell in many parts of Europe, snow also fell in areas where snow is rare, for example Nice.

Spain

01/23/03: Heavy snow affected the Balearic Islands.

02/27/04-02/28/04: Snowfall closed nearly 30 mountain passes and even blocked several motorways. The snow caused between 2,000 and 3,000 motorists to be stranded.

03/01/05: Heavy snow caused problems in the country, grounding flights on Madrid and Barcelona and disrupting train services.

03/04/05: A state of alert was declared due to heavy snowfall, with Mdrid recording its heaviest snowfall in 15 years.

Italy

01/24/04-01/25/04: Snow fell across Rome, giving a dusting on the ground. This was the first time in 4 years that the Italian capital had seen snow.

02/27/04-02/28/04: Many parts of northern and central Italy experienced heavy snow. The Cities of Genoa, Bologna and Florence were shrouded in snow.

01/26/04: Hundreds of motorists were stranded by heavy snow and ice on a motorway in southern Italy forcing local authorities to call in the army to remove snowbound vehicles and take their occupants to safety. Local authorities faced a barrage of criticism from many motorists why spent 2 days and nights in their vehicles on the snowbound A3 autostrada between Salerno and Reggio Calabria without receiving help. In the western Mediterranean, snow fell for the first time in decades, with 8 cm of snow falling at Mahon on the island of Menorca. Snow also forced the closure of mountain roads on the island of Mallorca.

North Africa

01/25/04-01/27/04: The heaviest snow since the year 1950 fell on the Algerian capital, Algiers. Several areas in the north of Algeria, in particular the Mediterranean oil port city of Skikda, were cut off after 2 days of snow. On the 27th, 13 people died and 47 others were injured, mostly in snow related road accidents as snow up to 15 cm fell in places. Over the Atlas Mountains, Morocco, up to 2 m of snow fell.

The Balkan

12/25/03: Blizzards affected many parts of Romania, Serbia and Bulgaria.

01/24/04-01/25/04: In many parts of Romania and Bulgaria, heavy snow caused chaos as some areas sustained the heaviest snowfall in 20 years.

02/13/04-02/14/04: Snow caused widespread disruption in parts of Romania.

01/23/05: In Albania, 8 people were killed in an traffic accident during a blizzard near the northern town of Qafa e Bualit.

01/25/05: Heavy snowfall affected road and maritime traffic throughout Croatia. Snow forced the shutdown of some roads to trucks, including the central town of Gorski Kotar, where a snowfall of 64 cm occurred. Traffic was also affected by the snow on the highway between Zagreb and Split as well as in the northern region of Bijelovar, and between Rijeka and Zadar. In macedonia, 1 person was killed and 3 were injured in one of some 200 traffic accidents reported around the country because of heavy snow. The snow blocked roads and isolated villages and towns. In neighboring Kosovo, 2 people were killed and 9 were injured in traffic accidents caused by snow.

02/05/05: Heavy snow and blizzards affected eastern Romania leaving roads and schools closed. In the county of Constanta on the Black Sea coast, snowdrifts up to 2 m high brought traffic to a standstill.

02/23/05: Blizzards affected Bosnia, Austria and Montenegro.

Greece

02/19/03: Heavy snow left nearly 80 villages around the country cut off.

03/17/03: Heavy snow fell in the southern Peloponnesian region.

02/13/04-02/14/04: Parts of southern Greece were hit badly with snow, particularly close to the capital Athens. Snow fell up to 10 cm across the city as it forced the closure of schools and courthouses, as Athens transport network ground to a halt. Athens Airport was forced to close and many flights were cancelled.

03/04/05: The heavy snowfall in northern and central Greece cut off dozens of mountain villages, blocked roads and closed some schools. Italy too experienced extensive snow in places.

Turkey

12/18/03: Heavy snow fell across parts of Turkey, forcing schools to close and roads to become blocked including the capital, Ankara.

01/09/04-01/12/04: A period of cold, snowy weather claimed 10 lives. The heavy snowfall isolated nearly 2,000 villages.

01/24/04-01/25/04: Heavy snow brought traffic to a standstill on the roads of Istanbul. More than 500 traffic accidents occurred on the snow-covered roads. Up to 50 cm of snow occurred in some areas of western Turkey. The snow brought down many powerlines causing 65% of Istanbul to lose power. NB: the original reference cites that this happened in Istanbul, the capital of Turkey. Since Ankara is the capital of Turkey, this note may apply to Ankara instead. NASA's Earth Observatory website states that an estimated dozen lives were lost due to the temperature and snow, many due to being trapped in their cars by deadly conditions and severely restricted visibility. authorities even shut down the Bosporus, the main maritime route between the Black Sea and the Marmara Denizi, because of strong winds and heavy snowfall. The Bosporus is also called the Istanbul Strait.

02/13/04-02/14/04: 35 cm of snow fell over Istanbul.

11/23/04-11/25/04: At least 13 people were killed, roads were blocked and hundreds of villages were isolated due to a heavy snowstorm. A 6-year old boy in the central Aksaray province lost his life when the roof of his home collapsed under the weight of the snow. More than 900 villages in central and eastern Anatolia suffered power cuts because of the heavy snowfall. Many schools closed for 2 days in Yozgat, just 150 km east of the capital, Ankara, due to the heavy snowfall.

Jordan

02/24/03: Heavy snow fell across parts of Jordan, Israel and Lebanon. This was the heaviest snowfall in the region since 1950. Locally, over 20 cm of snow accumulated, disrupting transportation and closing schools and business throughout the region.

02/14/04: snow blanketed much of Jordan, Israel and parts of Lebanon. Snow lay up to 2-3 cm across Jerusalem. The snow caused powerlines to collapse in Lebanon, while motorists using the mountainous highway from Beirut to Damascus, the Syrian capital, were urged to use snow chains.

02/09/04: snow fell in the capital Amman and neighboring countries, for example Israel. In Lebanon, snow blanketed Mount Lebanon above 700 m and the Bekaa Valley region. Snowploughs were used to try and keep the road open between Beirut and Damascus.

Persian Gulf

12/30/04: The United Arab Emirates had the first recorded snowfall across the al-Jiys mountain range.

Iran

02/19/03: Parts of the country reported snow for the first time in three years.

02/09/04: northern parts of the country and the capital Tehran received record breaking snowfall. Certain districts received snowfalls up to 150 cm, the heaviest snow to fall in the area in 10 years.

Pakistan

01/02/05: Abbottabad, a hill resort town about 70 km northwest of Islamabad sustained heavy snow. Quetta, capital of the southwestern Baluchistan province received the heaviest snow in 20 years.

01/22/05-01/23/05: The northern city of Islamabad experienced the first snowfall in the nearby hills in 6 years.

02/11/05: Remote northern areas of the country, where the Himalaya, Karamoram and Hindu Kush mountain renges meet, were cut off, as roads were buried under 60 cm of snow. The Chitral Valley was the worst affected with 50 people confirmed dead due to onset of several avalanches.

Afghanistan and Central Asia

02/03/05: Heavy snow in Tajikistan caused a house to collapse in the Nurobod district of central Rasht Valley, killing 9 people and seriously injuring 3 others. In Afghanistan, an Afghan passenger jet with 104 people on board disappeared from radar during a snowstorm. The Kam Air Boeing 737 took off from the western Afghan City of Herat bound for the capital Kabul, but was unable to land due to heavy snow.

02/10/05: Heavy snow affected Tajikistan causing roofs to collapse on schools, homes and even hospitals. Tavildara had as much as 2 m of snow.

India

12/28/03: Heavy snow fell over the high ground in the Himalayan foothills cutting off the Kashmir Valley from the rest of the country.

05/06/04: An unusual late-season snow fell across the Kashmir region along the border of India and Pakistan. The snow trapped 20,000 nomads in the Himalayan area of Kashmir.

China

02/18/04: Heavy snow affected the Xinjiang Uygur Autonomous Region. The heavy snow caused traffic disruption and delayed flights.

12/19/04-12/20/04: The northeastern Liaoning province was plagued with heavy snow causing traffic chaos.

12/31/04: Heavy snowfall caused flight cancellations in Shanghai.

02/16/05-02/18/05: Heavy snow affected the southern Xinjiang Uygur Autonomous Region. In Sangzhu Village in Pixian County, snow fell to a depth of 70 cm, killing livestock and causing houses to collapse.

03/06/05: Taiwan had an unexpected 9-hour heavy snowfall that closed highways and caused considerable inconvenience to the local residents.

Vietnam

01/05/03-01/06/03: Parts of northern Vietnam were blanketed by snow. In Ha Giang province, 5-15 cm of snow fell. This was the heaviest snow ever reported to have fallen in that area.

Korea

03/04/04: Snow of up to 60 cm blanketed the central region of South Korea forcing schools to close and brought traffic to a standstill. This amount of snow was the largest 1-day snowfall in March since the Korean Meteorological Administration began maintaining meteorological records since 1904. The snowstorm deposited more than 18 cm of snow in the capital Seoul.

01/15/05-01/16/05: Eastern parts of the country were battered by heavy snowfall. Up to 56 cm fell in the Gangwon and North Gyeongsang provinces by midday on the 16th. Pusan's Kimhae International Airport was forced to close to all flights due to the snow.

Japan

12/20/03: Snow brought parts of western and central Japan to a standstill. Nagoya City in central Japan saw its heaviest snowfall in 38 years with a total of 9 cm. The snow proved perilous for travelers as the snow delayed flights and the 'bullet train'.

01/14/04-01/15/04: Heavy snow caused the cancellation of 170 flights on the 14th and 95 flights on the 15th.

12/31/04: Tokyo experienced the first New Year's Eve snowfall in 21 years. The snow caused chaos on roads and led to the cancellation of some flights.

01/15/05-01/16/05: The regions of Kanto and Tohoku, especially towards the Pacific coast, were badly hit by snow. Approximately 50 cm of snow fell in places.

02/01/05: The country was hit by a severe snowstorm causing traffic chaos. Domestic flights were forced to cancel and train services were suspended or delayed in northern and western areas of the country. The worst affected area of japan was on the north side of Honshu where up to 90 cm of snow occurred. On the southern Japanese Island of Shikoku, the city of Kochi sustained snow for the first time in 20 years.

03/04/05: 3 cm of snow accumulated in downtown Tokyo. It is the first time since 1998 that more than 1 cm of snow has covered the country's capital.

New Zealand

07/06/03: heavy snow fell across southern districts of the North Island. The heavy snow caused significant power loss to many areas with up to 30 cm falling in places.

Peru

07/11/04: Heavy snowfall in the south left thousands of people homeless. The snow also killed many livestock. Many areas were isolated, forcing helicopters to drop food and clothes to villages in the high mountains.

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• Case Studies A: Wave Cyclones in the U.S. and Europe

The 1993 "White Hurricane"
Between March 12-15, an immense cyclone covered the eastern U.S. from Florida to Maine and from the Appalachian Mountains to the Atlantic coast. Hurricane-force winds gusted to over 160 km/h (100 mph) driving a blizzard with snow and sleet into the eastern seaboard and sending storm surges into coastal areas. The storm caused 238 fatalities from Cuba to Canada, 48 sailors were lost and damages exceeded $800 Mio. The hardest hit area was Florida where over 50 tornadoes killed more people than Hurricane Andrew did in 1992.
The unusually large and late winter wave cyclone was fueled by the fact that three air masses collided to the south of the Great Lakes. Toward the east, a warm, moist mT air mass from the Gulf of Mexico advanced on a cold air mass. On the western side, the southward undulating jet stream steered a cold cP air mass from the north, pushing it under the warm air mass from the Gulf.
This storm rivaled the legendary blizzard of March 1888 that brought wind gusts up to 135 km/h (85 mph) and snow drifts of up to 6 m (20 ft) deep and killed 400 people.
This storm was part of a wet winter and spring that set the stage for the great 1993 Mississippi flood in August (the costliest regional flood and one of the costliest natural disasters in U.S. history).

European Storm Lothar 1999
Storm Lothar on December 25, 1999, a storm with wind gusts of 272 km/h (168 mph), caused more than $6 billion in damages, killed at least 27 people and flatten in excess of 100 millions of trees (10 million in Switzerland alone). Worst hit was France which lost 140 Mio m³ worth of wood, southern Germany lost 35 Mio m³ and Switzerland 13 Mio m³ (the total losses in Europe amounted to 200 Mio m³).

European Storm Kyrill 2007
Storm Kyrill on January 18, 2007, the largest European storm since Lothar, had wind gusts of 225 km/h (139 mph), killed 47 people (13 in Germany and 11 in UK) and caused damages estimates at $10 billion from the Czech Republic to Ireland. The storm knocked down major power pylons and caused structural damage to Berlin's newly opened central railway station.

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• Case Studies B: The 1983/1984 Siberian Express

The winter of 1983/1984 was one of the coldest on record across North America. In early December, a cold cP air mass covered most of the northern and central plains. Far to the north, a huge bitter cold cA air mass formed over the Canadian Northwest Territories. A upper-level ridge (high pressure) form over Alaska, pushing strong northerly winds (associated with the polar jet stream) along its eastern side. This allowed the cA air to be carried south over the prairie provinces of Canada. A portion of this cold air broke away and swirled as an anticyclone into the U.S., accompanied by 45 knt (52 mph) winds (the Siberian Express). Temperatures dropped to some of the lowest readings ever recorded for December. E.g. on Dec. 22, Elk Park, MA recorded an unofficial -53°C (-64°F), only 4°C higher than the all-time low of -57°C (-70°F) for the contiguous U.S. (recorded at Rogers Pass, MA on Jan. 20, 1954). The high pressure system eventually stretched across North America into the Gulf of Mexico. By Dec. 24, the sea-level pressure at Miles City, MA reached an incredible 1064 mbar (a new record that topped the old mark of 1063 mbar set in Helena, Ma on Jan. 10, 1962). By Dec. 24, arctic air covered almost 90% of the U.S.. Hard freeze caused $100s Mio in damage to the fruit and vegetable crops in Texas, Louisiana, and Florida. On Dec. 25, 125 record low temperature readings were set in 24 states. That afternoon, it was colder in Atlanta, GA (-13°C) than in Fairbanks, AK (-12°C). By Jan. 1, 1984, the extreme cold eased, only to return 10 days later. On Jan. 18, an all-time records low pf -54°C (-65°F) was recorded at Middle Sinks, UT. On Jan. 19, temperatures at the airports in Philadelphia and Baltimore plummeted to a new low of -22°C (-7°F). The Siberia Express episodes where them followed by one of the warmest Februarys on record (most states east of the Rockies were affected by a heat wave fueled by warm, humid air from the Gulf of Mexico).


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• Case Studies C: Some Examples of Nor'Easters in the U.S.

The Great Blizzard of 1888 (The Great White Hurricane)
• March 11-14
• one of the most severe blizzard in U.S. recorded history
• central low pressure near Cape Cod at 982 mbar
• snowfalls of 100-125 cm (40-50 in) in New Jersey, New York, Massachusetts and Connecticut
• sustained wind speeds of over 72 km/h (45 mph)
• snow drifts > 15 m (50 ft)
• cost of damage: $1.2 billion (2008)
• 400 fatalities (200 in New York alone)
• min. T of -14.4°C (6°F) and daytime average of -12.8°C (9°F) at New York's Central Park (coldest ever for March)
• paralyzed East Coast from Chesapeake Bay to Maine and Canada; telegraphy infrastructure disabled

The Halloween 1991 "Perfect Storm"
• perhaps the most (in)famous Nor'Easter in the U.S.
• unusual Nor'Easter that moved south and later developed into a category 1 hurricane before making landfall in Nova Scotia
• on the track south, the storm absorbed short-lived subtropical hurricane Grace (the last one in the 1991 season) that developed earlier and unusually far north
• fueled by warming tropical moisture from the Gulf Stream, it became a category 1 hurricane after it turned in an unusual counterclockwise loop
• central low pressure during the hurricane stage at 980 mbar; sustained wind speed at 120 km/h (75 mph)
• cost of damage: $ 208 Mio (1991) mostly in Massachusetts and New Jersey
• 12 fatalities, including 6 onboard the Andrea Gail
• the lowest pressure was reached on Oct 30 at 972 mbar
• a Canadian buoy reported a wave height of 30.7 m (100.7 ft); U.S. NOAA buoys 100-150 km farther south reports sustained wind speeds of 91 km/h (49 knt) and 117 km/h (63 knt) and significant wave heights (average high waves) of 12 m (39 ft) and 9 m (31 ft)
• 10 m (30 ft) storm surges caused severe beach erosion along the coast
• heavy rain and extensive flooding inland

The December 1992 Nor'Easter⁽¹⁾
• central low pressure over New Jersey on Dec. 11 at 988 mbar
• cost of damage: $100s Mio
• developed an eye similar to that of a hurricane
• strong northeasterly winds from Maryland to Massachusetts
• huge waves pushed by hurricane-force winds (78 knt/ 90mph in Wildwood, NJ)
• extensive damage to beaches, beach front homes seawalls and boardwalks in New Jersey
• heavy snow and rain for several days; coupled with high winds and high tides caused extensive coastal flooding
• flooding of coastal highways, including parts of New York's subway

The March 1997 Nor'Easter
• late March
• 1-3 ft of snow over portions of the northeast

The February 11, 2006 Blizzard

Photo:NASA/GOES Satellite

central low pressure 971 mbar estimated damages: $5 Mio fatalities: 3 as a consequence of the snow developed an eye similar to that of a hurricane heavy snow from Virginia to Maine and into Canada; upward of 32 in in some places major northeast cities from Baltimore to Boston received > 1 ft of snow, with all-time largest amount in New York City (26.9 in; since at least 1869 when records began) 1 m (3 ft) high storm surge, whipped by 95 km/h (60 mph) winds, lead to coastal flooding, particularly in Massachusetts offshore wave of up to 8 m (25 ft) main airports closed (JKF, La Guardia in New York) or most flights cancelled (90% at Logan Airport in Boston)

Scientists contend that, at least in New York, the use of the term blizzard is not appropriate because the conditions for blizzards were not met (high wind speeds, low visibility).

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• Additional Resources

study guide to book chapter 13
not-for-credit online quiz for practice testing (do not request edit access!)

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1. true
2. false

1. true
2. false

1. warm air pushes beneath cold air
2. warm air climbs on top of cold air, causing local thunderstorms
3. warm air climbs on top of cold air, causing extensive rainfall
4. warm air pushes past cold air along a sharp line

1. exactly along the front
2. behind the front
3. well in advance of the front

1. sustained wind speeds 35 mph or higher
2. blowing snow
3. power outage longer than 12 h
4. visibility 0.25 mi or less
5. lasting for at least 3 h