Saturday, December 20, 2008

April 12, 1934 Weather Map of Northeastern US and Maritimes

Image courtesy

On April 12, the wind actually blew from the southeast—an unusual direction for Mt. Washington, given the westerlies that dominate the region’s climates. However, a southeasterly wind adds another effect to the region’s cauldron of wind-accelerating phenomena. The land between Mt. Washington and the coast to its southeast, about sixty miles away, is flat until it reaches the Conway region, where the White Mountains form the Mt. Washington Valley, which extends north and passes just to the east of Mt. Washington. A southeast wind, then, faced no obstructions from the coast to the mountains until the Mt. Washington Valley began funneling it, increasing wind speed as air molecules sped up to escape the constraints of the valley wall.

The southeast wind was thus particularly strong due to its unusual interaction with the topography on that side of the mountain. West winds on Mt. Washington, no matter how strong they may be, are not funneled horizontally because the terrain to the west of the mountain is relatively flat, so is very unlikely that they could ever reach such a high speed. The Big Wind happened as a consequence of local topography exacerbating longterm meteorological effects associated with mountains and the middle latitudes.

Geomorphological Effects

Such persistent weather trends and their resulting harsh climate have dramatically influenced the geoecology of the Presidential Range. One of Mt. Washington’s most striking features, especially for such a relatively small mountain, are the prominent glacial cirques on its eastern face. The two largest and most famous are Tuckerman and Huntington ravines, famous in the northeastern United States as backcountry skiing and ice climbing meccas. They are named for a pioneering botanist and surveyor who were active on the mountain’s flanks. While Huntington Ravine is far rockier and has a sheer interior face, both have the classic U-shape of glacial cirques. Worn down by the thrust and weight of alpine glaciers that flowed off the main ridge during a succession of ice ages, they adjoin onto the wider Mt. Washington Valley running north to south, which culminates at Pinkham Notch (notch is New Hampshire vernacular for a glacial valley). Here, a massive continental glacier carved another U-shaped valley through a weak spot in the topography as it slowly moved south.

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