Today, @gwhizkids asked a great question about what causes the extreme weather on the summit of Mount Washington.

 

Certainly Mount Washington is not the tallest peak on the East Coast (For one, Mt. Mitchell in North Carolina stands at 6,683 feet, topping us by 395 feet!). But, Mount Washington is the tallest peak north of North Carolina and east of the Mississippi River. In fact, the next tallest mountain west of here is Harney Peak in South Dakota with an elevation of 7,242 feet. So what does that have to do with our extreme weather?

 

On average throughout the year, Mount Washington sees winds predominantly out of the WNW direction. Looking at the terrain to our west, you can see there is a distinct funneling effect. As the air rushes toward the summit, not only is it funneled toward the mountain by the surrounding terrain, but it’s also forced to rise up and over the summit. When there is not much around for miles to inhibit this flow of air, it will cruise along until being forced and “molded” by the terrain.

 

What happens when you compress air or water? It accelerates! This is known as the Venturi Effect (which incorporates Bernoulli’s Principle). As the air is forced to rise over the summit, it is squeezed between a stable layer of air, known as the tropopause, and the mountain. As a result, the speed of the flow increases, and significantly accelerates the winds on the summit.

 

 

 Mount Washington also lies in the center of 3 main storm tracks. A lot of the extreme weather we see simply has to do with our location. Below is a 10 year climatology of over 1,000 low pressure systems. As you can see, New England is the “tailpipe” of the United States, with areas of low pressure traversing the region all the time.

 

Perhaps this is what makes Mount Washington so unique. It’s certainly not nearly as tall as peaks in the Western United States, but the ample access to moisture, location, prominence, and surrounding terrain forcings contribute to some of the most extreme weather conditions ever observed. Rime ice growth at rates of up to 10”+ per hour, high winds, low temperatures, and dense blowing snow are just a taste of the conditions that Mount Washington has to offer.