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February 9, 2023

Many of the latest weather forecast buzzwords — “polar vortex,” “bomb cyclone” — describe natural phenomena that aren’t new, or even necessarily more common than they used to be, even if climate change generally leads to more extreme weather. But the term is more widely used, sometimes accurate, sometimes not.

According to the National Weather Service, polar vortex “is a large area of ​​low pressure and cold air surrounding the poles of the earth. It is always present near the poles, but weakens in summer and intensifies in winter. The term ‘eddy’ refers to counterclockwise airflow that Stay close to the poles.” The polar vortex expands fairly regularly during the northern hemisphere winter, transporting arctic air to the United States.

A bomb cyclone is a rapid pressure drop in a low-pressure air mass — “a drop of at least 24 millibars in 24 hours,” says John Garcum, a meteorologist at McGill University who helped coin the term in the 1980s. Wind speeds rise sharply as the pressure difference, or gradient, between a low-pressure air mass and an adjacent high-pressure air mass increases. This process of rapid intensification is called bomb generation.

atmospheric river According to the National Oceanic and Atmospheric Administration (NOAA), “a narrow region of the atmosphere transports most of the moisture from the tropics to northern latitudes.” “Atmospheric rivers are part of the water cycle in Earth’s oceans and are closely related to water supply and flood risk.”

Some atmospheric rivers cause severe weather conditions, but many others do not, Dr Gyakum said, adding, “Many of these can move and meander across the globe without causing much impact at all.”

A semi-famous example of a powerful atmospheric river is the Pineapple Express, which has been called “because moisture builds up in the tropical Pacific Ocean around Hawaii and can hit the west coast of the United States and Canada with heavy rainfall and snow,” According to the National Oceanic and Atmospheric Administration.

(In 2008, Seth Rogen starred in a comedy film called “Pineapple Express,” in which a drug dealer witnesses a murder and escapes an assassin and a corrupt policeman, but it doesn’t care about the weather. obvious impact.)

The ‘megastorm’ scenario, originally expected to occur every 1,000 years, According to the US Geological Survey, but are now “expected to become more frequent and intense due to climate change.” The name comes from a combination of “AR” (atmospheric river) and “k” (1,000). One such megastorm occurred in California in 1861-62, and there is “no reason to believe that a similar event will not occur again,” according to the agency.



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