Weather and Climate – More snow from “Lake Effect” in US with Global Warming « 3B Meteo

Weather and Climate – More snow from “Lake Effect” in US with Global Warming « 3B Meteo

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Lake Effect Snow, that's what it is
Lake Effect Snow, that’s what it is

It has been defined as one of the most intense snowstorms of recent years on the state of New York; but it is the whole area of ​​the Great Lakes that is grappling with intense and record-breaking snowfalls. The weather warning is in effect for more than 6 million people in six Great Lakes states: Wisconsin, Michigan, Indiana, Ohio, Pennsylvania and New York.

This dynamic is the consequence of a massive irruption of cold air which is affecting much of North America up to Texas and Mexico. The images arriving from the affected area show cars and towns literally buried in snow; in Orchard Park the snow cover reached 195cm, possibly a record for snowfall in 24 hours. But notable accumulations are recorded in Hamburg (187 cm) and Blasdell (180 cm). Buffalo Airport with 43cm of snow in 24 hours broke the previous daily record from November 2014 of 20cm. In 2014 the snow in the city was much higher and is remembered as one of the worst snowfalls ever.

This area is known for very heavy snowfall around the time Lake Effect Snow develops. In fact, the cold air arriving from Canada flows over the relatively warmer water of the lake which is charged with humidity, generating clouds and precipitation. The most consistent precipitation occurs in contact with the mainland due to the friction generated by the orography on the wind. The greatest rainfall occurs close to the hills. The major snowstorms for the Lake Effect Snow occur between late autumn and early winter when the air-water temperature difference is greatest, the lakes are not frozen so there is a greater supply of humidity. The necessary ingredients for this snowfall are: a significant vertical thermal gradient, moderate atmospheric instability, humid air at low to medium altitudes from the west/southwest and relatively warm lake water temperatures. The direction of the wind is very important because the more westerly the wind is, the greater the stretch of lake it crosses, therefore the air mass becomes more loaded with humidity. The direction of the wind also determines which areas will receive snow so that sometimes some points can receive a lot of snow and contiguous localities little or even none. These types of phenomena also occur in other parts of the world such as Scandinavia and Japan.

Numerical models predict more snow to occur for ‘Lake Effect’ as the region warms and ice cover decreases. Greater evaporation can in fact lead to an increase in rainfall on neighboring areas. Years with much less than normal ice cover appear to have become more frequent in the past two decades, especially in Lakes Erie and Superior. Since 1973, the number of freezing days (duration) on all five Great Lakes has decreased; the Great Lakes remain frozen 8 to 46 days fewer than in the early 1970s. The decreases in Lakes Ontario and Superior are also statistically significant.

In a 2009 work by Kunkel et al, total snowfall decreased in many parts of the USA. The Pacific Northwest has seen a decline in both total snowfall and the percentage of precipitation falling as snow. Parts of the Midwest also saw a decrease while an increase occurred in the Great Lakes area. These snowfalls can coexist in a warmer world at least until there is enough cold air blowing over the lakes (Burnett et al 2003, Andresen et al. 2012). Provided, however, that temperatures due to greenhouse gases do not continue to increase above a certain threshold, beyond which “lake effect” snow would be less likely to turn into rain. It is not the episode itself but the trend to make it clear that climate change is influencing this type of phenomenon.

mean rate of change in total snowfall 1930-2007 (from Kunkel et al)
mean rate of change in total snowfall 1930-2007 (from Kunkel et al)

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