Photo: Mount Washington

Mount Washington is the highest peak in the American Northeast at 6,288 ft. (1916.6 m). It is famous for its dangerously erratic weather, holding the record for the highest wind gust directly measured at the Earth's surface, at 231 mph (372 km/h) on the afternoon of April 12, 1934. It was known as Agiocochook, or "home of the Great Spirit", before European settlers arrived.

The mountain is located in the Presidential Range of the White Mountains, and in Coos County, New Hampshire. It is the third highest state high point in the eastern U.S., after Mount Mitchell, North Carolina (6,684 ft; 2,038 m) and Clingmans Dome, Tennessee (6,643 ft; 2,025 m). While nearly the whole mountain is in the White Mountain National Forest, an area of 59 acres (within a radius of approximately a quarter mile), above 5,500 feet (1690 m) and including the summit, is the whole of Mount Washington State Park.

Mount Washington has notoriously erratic weather. This is partly due to the convergence of several storm tracks, mainly from the South Atlantic, Gulf region and Pacific Northwest. The vertical rise of the Presidential range, combined with its north-south orientation, makes it a significant barrier to westerly winds. Low-pressure systems are more favorable to develop along the coastline in the winter months due to the relative temperature differences between the Northeast and the Atlantic Ocean. With these factors combined, winds exceeding hurricane force occur an average of 110 days per year. From November to April, these strong winds are likely to occur during two-thirds of the days.

Mount Washington holds the record for directly measured surface wind speed, at 231 mph (372 km/h), recorded on the afternoon of April 12, 1934. Phenomena measured via satellite or radar, such as tornados, hurricanes, and air currents in the upper atmosphere, are not directly measured at the Earth's surface and do not compete with this record, although a tornado or hurricane would qualify if it was directly and accurately measured. Mount Washington's record low of −47 °F (−44 °C) was recorded on January 29, 1934. On January 17, 2007, after a major winter storm, a weather observation registered a windchill value of -77 °F (-61°C) at the mountain. Snowstorms at the summit are routine in every month of the year, with snowfall averaging 645 cm (21 feet) per year.

The primary summit building was designed to withstand 300 mph (480 km/h) winds; other structures are literally chained to the mountain. In addition to a number of broadcast towers, the mountain is the site of a non-profit scientific observatory reporting the weather as well as other aspects of the sub-arctic climate of the mountain. The extreme environment at the top of Mount Washington makes using unmanned equipment problematic. The observatory also conducts research, primarily the testing of new weather measurement devices. The Sherman Adams summit building, which houses the Observatory, is closed to the public during the winter and hikers are not allowed inside the building except for emergencies and pre-arranged guided tours.

The first regular meteorological observations on Mount Washington were conducted by the U.S. Signal Service, a precursor of the National Weather Service, from 1870 to 1892. The Mount Washington station was the first of its kind in the world, setting an example followed in many other countries.

The Mount Washington Observatory reoccupied the summit in 1932 through the enthusiasm of a group of individuals who recognized the value of a scientific facility at that demanding location. The Observatory's weather data have accumulated into a valuable climate record since. Temperature and humidity readings have been collected using a sling psychrometer, a simple device containing two mercury thermometers. Where most unstaffed weather stations have undergone technology upgrades, consistent use of the sling psychrometer has helped provide scientific precision to the Mount Washington climate record.

[Source: Wikipedia]

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Photo: Mt. Washington Observatory