After the unusually chilly weekend for June, the nice weather of the past few days is a welcome change. Unfortunately, the same system that kept temperatures under 70 degrees here Saturday and Sunday brought serious cold and snowy weather to the Presidential Range of New Hampshire, including Mount Washington.
The weather atop New England’s highest peak, sitting at 6,288 feet above sea level, is often dramatically different than the weather in the valley below. Mount Washington is frequently cited as having the world’s most extreme weather and this isn’t necessarily hyperbole.
Although we experience weather here on the ground, that weather is made up of a large interaction between layers of air from the surface all the way up to the tropopause, at roughly 30,000 feet.
There are several factors that bring the extreme weather to the summit of Mount Washington. Most notably, the summit is the highest peak in the area and sticks up into the atmosphere without anything to slow down the wind. The lack of trees at this height is included in this equation of extreme weather. Once you get above about 4,200 feet, the landscape changes to mainly rocks, moss and lichens, and small plants.
Indeed the flora of Mount Washington is more conducive to the alpine regions of the subarctic.
Without anything to slow down the wind, it can blow quite hard and frequently reaches speeds over 100 miles per hour. Mount Washington boasts the second-fastest recorded wind speed on Earth at 231 miles per hour.
There’s a scientific principle called the Venturi effect, whereby fluids get squeezed and move faster. Air is a fluid; as the air flows through the Presidential Range, the mountains tend to squeeze it. Since Mount Washington sits above everything else, it feels the Venturi effect most dramatically.
There is also an additionally squeezing of the air from above the summit of Mount Washington. Higher up, the tropopause meets the stratosphere. Although the jet stream itself is up much higher, lower-level jet streams can form at around 5,000 feet, producing dramatic wind.
For every thousand feet of height, the temperature decreases by roughly 3.5 degrees, so by the time you get to the top of Mount Washington it’s much colder than the valley below. This weekend, the cold air mass and the wind brought wind chills in the single digits along with more than an inch of snowfall.
Mount Washington’s position in New Hampshire and frankly much of New England is at the confluence of many different jet stream patterns. This is one of the reasons why the weather in New England is often so variable and why Mount Washington’s weather is particularly extreme.
Strong polar and subtropical jet streams and even a fast zonal or west-to-east pattern will often pass through that part of New Hampshire, bringing the often-extreme weather Mount Washington and New England are known for.