11/4/2022 0 Comments Seasonal precipitation totalsPrecipitation increases by 10 to 40 percent when the Pacific decadal oscillation is positive. La Niña events lead to drier than normal conditions, while El Niño events do not have a correlation towards dry or wet conditions. Inland, often less than 10 inches (250 mm) falls a year, but what precipitation falls during the winter tends to stay throughout the season. Across western sections of the state, the northern side of the Seward Peninsula is a desert with less than 10 inches (250 mm) of precipitation annually, while some locations between Dillingham and Bethel average around 100 inches (2,540 mm) of precipitation. The northern coast of the Gulf of Alaska receives up to 150 inches (3,800 mm) of precipitation annually. On average, Anchorage receives 16 inches (406 mm) of precipitation a year, with around 75 inches (1,905 mm) of snow. South central Alaska does not get nearly as much rain as the southeast of Alaska, though it does get more snow. Juneau averages over 50 inches (1,270 mm) of precipitation a year, while other areas in southeast Alaska receive over 275 inches (6,980 mm). Meteorological scientists have observed that La Niñas have become more frequent over time. Furthermore, global La Niña meteorological events are generally associated with drier and hotter conditions and further exacerbation of droughts in California and the Southwestern and to some extent Southeastern United States. There is also evidence that global warming is leading to increased precipitation to the eastern portions of North America, while droughts are becoming more frequent in the western portions. The El Niño–Southern Oscillation affects the precipitation distribution, by altering rainfall patterns across the West, Midwest, the Southeast, and throughout the tropics. Large thunderstorm areas known as mesoscale convective complexes move through the Plains, Midwest, and Great Lakes during the warm season, contributing up to 10% of the annual precipitation to the region. Over the top of the ridge, the jet stream brings a summer precipitation maximum to the Great Plains and western Great Lakes. Equatorward of the subtropical ridge, tropical cyclones enhance precipitation across southern and eastern sections of the country, as well as Puerto Rico, the United States Virgin Islands, the Northern Mariana Islands, Guam, and American Samoa. ĭuring the summer, the North American monsoon combined with Gulf of California and Gulf of Mexico moisture moving around the subtropical ridge in the Atlantic Ocean bring the promise of afternoon and evening air-mass thunderstorms to the southern tier of the country as well as the Great Plains. The snow to liquid ratio across the contiguous United States averages 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water. Low pressure systems moving up the East coast bring cold season precipitation to the Mid-West and Northeast states, as well as Great Salt Lake and the Finger Lakes region. During the winter, and spring, Pacific storm systems bring Hawaii and the western United States most of their precipitation. Late summer and fall tropical cyclones bring precipitation which falls across the Gulf and Atlantic states. The characteristics of United States rainfall climatology differ significantly across the United States and those under United States sovereignty.
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