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The Northeast Snowfall Impact Scale (NESIS) was created to measure snowstorms in the U.S. Northeast in much the same way the Saffir-Simpson Hurricane Scale records hurricane intensity and the Enhanced Fujita Scale with tornadoes. This scale takes into account the very high population of the Northeast, and thus snowfall amounts are often smaller compared to what other areas of the USA would consider significant snowfall amounts.
NESIS was created by Paul Kocin of The Weather Channel and Louis Uccellini of the National Weather Service, classifies storms in one of five ways that range from Notable (the weakest designation) to Significant, Major, Crippling, and Extreme. This helps to measure storms have on the economy and transportation throughout the major cities in the Northeastern United States as well as the country as a whole. [1] [2]
Category | NESIS Value | Description |
---|---|---|
1 | 1 — 2.499 | Notable |
2 | 2.5 — 3.99 | Significant |
3 | 4 — 5.99 | Major |
4 | 6 — 9.99 | Crippling |
5 | 10.0+ | Extreme |
The variables measured on the scale include area, amount of snowfall, and the number of people living in the path of the storm. These numbers are calculated into a raw data number ranging from "1" for an insignificant fall to over "10" for a massive snowstorm. Based on these raw numbers, the storm is placed into one of the five categories. The largest NESIS values result from storms producing heavy snowfall over large areas that include major metropolitan areas. Only three historical storms—the 1993 Storm of the Century, the North American blizzard of 1996, and the January 2016 United States blizzard—are in the Category 5, with a NESIS value higher than 10.
The northeast is the first region in the U.S. to use a system that measures the impact of snowfall because it is so densely populated. The scale also allows for meteorologists to predict how long airport delays caused snowstorms will last and when things will become normal afterward. According to Uccellini, NESIS will be used to reevaluate recent snowstorms and measure their impact and not as forecasts such as the ones that are created for hurricanes.
By using an example of the area from Washington D.C. to Boston, a Notable Category 1 snowfall would have to drop anywhere from 4 to 10 inches of snow to fall in the category. A Category 2 would affect same area but more people with more than 10 inches of snow on Mid Atlantic Seaboard. A Category 3 would bring about 10-20 inches of snow and affect millions of people in the process.
NESIS only takes into account the raw snow totals and impacted population. It does not account for any of the following hazards associated with winter storms:
A theoretical blizzard may only impact enough people with enough snow to rate a category 2 on NESIS, but bring winds of over 70 MPH, paralyzing the region for days as 5–10 foot drifts and windblown debris are removed. Also, NESIS specifically provides for the storm's impact to the entire population of the affected area. This makes it unusable when trying to describe local conditions caused by a storm.
A blizzard is a severe snowstorm characterized by strong sustained winds and low visibility, lasting for a prolonged period of time—typically at least three or four hours. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Blizzards can have an immense size and usually stretch to hundreds or thousands of kilometres.
The North American blizzard of 1996 was a severe nor'easter that paralyzed the United States East Coast with up to 4 feet (1.2 m) of wind-driven snow from January 6 to January 8, 1996. The City University of New York reported that the storm "dropped 20 inches of snow, had wind gusts of 50 mph and snow drifts up to 8 feet high." This storm was a classic example of a nor'easter, but the storm would not have been as historically significant without the presence of the arctic high pressure system located to the north of New York. It was followed by another storm, an Alberta Clipper, on January 12, then unusually warm weather and torrential rain which caused rapid melting and river flooding in the Northeast Floods later that month. Along with the March Superstorm of 1993 and the January 2016 United States blizzard, it is one of only three snowstorms to receive the top rating of 5, or "Extreme", on the Northeast Snowfall Impact Scale (NESIS).
The North American blizzard of 2006 was a nor'easter that began on the evening of February 11, 2006. It dumped heavy snow across the Mid-Atlantic and New England states, from Virginia to Maine through the early evening of February 12, and ended in Atlantic Canada on February 13. The major cities from Baltimore to Boston received at least a foot of snow, with a second-highest amount of 26.9 inches (68 cm) in New York City, the most since at least 1869, the start of record keeping, only broken by the January 2016 United States blizzard nearly 10 years later.
The Early Winter 2006 North American storm complex was a severe winter storm that occurred on November 26, 2006, and continued into December 1. It affected much of North America in some form, producing various kinds of severe weather including a major ice storm, blizzard conditions, high winds, extreme cold, a serial derecho and some tornadoes.
The December 2009 North American blizzard was a powerful nor'easter that formed over the Gulf of Mexico in December 2009, and became a major snowstorm that affected the East Coast of the United States and Canadian Atlantic provinces. The snowstorm brought record-breaking December snowfall totals to Washington, D.C., Baltimore, and Philadelphia.
The March 18–20, 1956 nor'easter was a significant winter storm in the United States that affected the Mid-Atlantic States and southern New England. The storm ranked as Category 1, or "notable", on the Northeast Snowfall Impact Scale. A high-pressure area north of New York State, developing in the wake of another system on March 15–16, provided cold air for the snowfall. It was among a series of snowstorms to affect the region during the month.
The March 18–22, 1958 nor'easter was an unusual late-season and violent winter storm that impacted the Mid-Atlantic and New England regions of the United States. Its snowfall extended from North Carolina through Maine.
The February 9–10, 2010 North American blizzard was a winter and severe weather event that afflicted the Midwest, Mid-Atlantic and New England regions of the United States between February 9–11, 2010, affecting some of the same regions that had experienced a historic Nor'easter just three days earlier. The storm brought 10 to 20 inches of snow across a wide swath from Washington, D.C., to New York City, with parts of the Baltimore metro area receiving more than 20 inches (51 cm). This storm began as a classic "Alberta clipper", starting out in Canada and then moving southeast, and finally curving northeast while rapidly intensifying off the New Jersey coast, forming an eye. The National Weather Service likened this storm to a Category 1 hurricane: "Winds topped 58 mph over part of the Chesapeake Bay, and 40 mph gusts were common across the region as the storm's center deepened and drifted slowly along the mid-Atlantic coast". The storm system, in conjunction with the earlier storm, has been nicknamed "Snoverkill."
The January 1961 nor'easter was a significant winter storm that impacted the Mid-Atlantic and New England regions of the United States. It was the second of three major snowstorms during the 1960–1961 winter. The storm ranked as Category 3, or "major", on the Northeast Snowfall Impact Scale.
The December 1960 nor'easter was a significant early-season winter storm that impacted the Mid-Atlantic and New England regions of the United States. Moderate to heavy snowfall fell from West Virginia to eastern Maine, amounting to 10 in (25 cm) or more in parts of 13 states and peaking at 21.4 in (54 cm) at Newark, New Jersey. The storm was accompanied by strong winds, gusting to over 90 mph (140 km/h) in coastal New England, and left in its wake a dangerously cold air mass. The storm originated in a weak low pressure area which formed over the western Gulf of Mexico on December 10. A secondary low developed over South Carolina on the next day, supported by the merger of two troughs aloft. Sliding southeast of New England, the new storm explosively deepened to become a full-fledged nor'easter, with a minimum central air pressure of 966 mbar. It began to weaken over the Canadian Maritimes.
The March 1960 nor'easter was a severe winter storm that impacted the Mid-Atlantic and New England regions of the United States. The storm ranked as Category 4, or "crippling", on the Northeast Snowfall Impact Scale. Northeasterly flow, combined with the storm's slower forward motion, enhanced snowfall across the region. The cyclone began moving away from the United States on March 5. It took place during a stormy period in the affected region, contributing to record snowfall.
Global weather activity of 2006 profiles the major worldwide weather events, including blizzards, ice storms, tropical cyclones, tornadoes, and other weather events, from January 1, 2006, to December 31, 2006. Winter storms are events in which the dominant varieties of precipitation are forms that only occur at cold temperatures, such as snow or sleet, or a rainstorm where ground temperatures are cold enough to allow ice to form. It may be marked by strong wind, thunder and lightning, heavy precipitation, such as ice, or wind transporting some substance through the atmosphere. Other major non winter events such as large dust storms, Hurricanes, cyclones, tornados, gales, flooding and rainstorms are also caused by such phenomena to a lesser or greater existent.
The December 1969 nor'easter was a strong winter storm that mainly affected the Northeastern United States and southern Quebec between December 25 and December 28, 1969. The multi-faceted storm system included a tornado outbreak, record snow accumulations, a damaging ice storm, and flooding rains.
The 2015–16 North American winter was not as frigid across North America and the United States as compared to the 2013–14 and 2014–15 winters. This was mainly due to a strong El Niño, which caused generally warmer-than-average conditions. However, despite the warmth, significant weather systems still occurred, including a snowstorm and flash flooding in Texas at the end of December and a large tornado outbreak at the end of February. The main event of the winter season, by far and large, was when a crippling and historic blizzard struck the Northeastern United States in late January, dumping up to 3 feet of snow in and around the metropolitan areas. Several other smaller snow events affected the Northeast as well, but for the most part the heaviest snowstorms and ice stayed out further west, such as a severe blizzard in western Texas in late December, and a major late-season snowstorm in Colorado in mid-April.
The 2012–13 North American winter started out somewhat early, as the remnants of Hurricane Sandy brought heavy snow to the mountains of West Virginia in late October. Later, a strong nor'easter affected the weary Northeastern United States, hampering storm recovery efforts and dropping several inches of snow. The rest of the winter featured several other notable events, such as a Christmas winter storm that affected most of the Eastern United States, and the most notable event occurring in early February, when a powerful blizzard struck the Northeast and brought record snow to some areas. During the winter, a weak El Nino was expected to influence weather conditions across the continent.
The 2009–10 North American winter saw several major blizzards affect the Northeastern United States. It refers to winter as it occurred across the North American continent from late 2009 to early 2010. While there is no well-agreed-upon date used to indicate the start of winter in the Northern Hemisphere, there are two definitions of winter which may be used. Based on the astronomical definition, winter begins at the winter solstice, which in 2009 occurred on December 21, and ends at the March equinox, which in 2010 occurred on March 20. Based on the meteorological definition, the first day of winter is December 1 and the last day February 28. Both definitions involve a period of approximately three months, with some variability.
The 2018–19 North American winter was unusually cold within the Northern United States, with frigid temperatures being recorded within the middle of the season. Several notable events occurred, such as a rare snow in the Southeast in December, a strong cold wave and several major winter storms in the Midwest, and upper Northeast and much of Canada in late January and early February, record snowstorms in the Southwest in late February, deadly tornado outbreaks in the Southeast and a historic mid-April blizzard in the Midwest, but the most notable event of the winter was a record-breaking bomb cyclone that affected much of the Central United States and Canada in mid-March. Unlike previous winters, a developing weak El Niño was expected to influence weather patterns across North America. Overall, however, winter of 2018–19 was mild along the mid- and lower parts of the East Coast, the West Coast, and most of the southern Plains. Overall, the meteorological winter of 2018-19 became the wettest on record for the United States.
The December 15–17, 2020 nor'easter was a powerful nor'easter that hammered the Northeastern United States and produced widespread swaths of over 1 foot (12 in) of snow in much of the region from December 15–17, 2020, ending a 1,000+ day high-impact snowstorm drought in much of the Mid-Atlantic and coastal New England regions. The system developed out of a weak area of low-pressure that first developed over the Central United States producing some snowfall before moving eastward, and by December 16, a new, dominant area of low pressure began to develop along the Southeast coast. This low steadily deepened as it moved along and impacted the Mid-Atlantic coastline, prompting several winter-related advisories and warnings for much of the Northeast.