Unusual Weather Phenomena Photo Gallery – Part 3

2008-07-03 22:35:58.000 – Matthew Morin,  Space Grant Intern

Since the beginning of my internship with the Mount Washington Observatory back in February, I’ve taken advantage of the opportunity to photograph a wide variety of unusual weather phenomena. I recently compiled the best of the best of these pictures and used them in two of my observer comments. Additionally, I used my knowledge of meteorology to include a discussion of how these phenomena form. As my internship winds down, I have a few more interesting photos to share with you all. So here it is… part 3 of Matt’s Unusual Weather Phenomena Photo Gallery.

Kelvin-Helmholtz Wave Cloud
Back in February I took several pictures of a breathtaking Mount Washington-style sunset. As if the stunning winter scenery wasn’t enough, I later found out that I had also captured an interesting cloud formation. Kelvin-Helmholtz Waves, or K-H Waves, form as a result of wind shear in a narrow cloud layer. Faster winds at the top of the cloud layer drag crests of the wave faster than the associated troughs. This type of turbulence creates waves similar to those found in the ocean.

Mammatus Cloud
One cloud formation that I thought I would never see while atop Mount Washington is mammatus. It was my misconception that mammatus only form under the anvils of mature cumulonimbus clouds. I figured seeing mammatus meant severe weather was nearby. However, mammatus cloud formations can be found in many different non-severe cloud types such as stratiform clouds, as seen in the photograph I took last May. Nonetheless, mammatus form as a result of moisture-laden air sinking at different rates. The more moisture in the parcel of air, the more opportunity for evaporative cooling in the sub cloud layer which leads to a faster descent. The outcome of this complex process is drooping cotton ball shaped clouds.

Gravity Wave
Picture the wave created by a rock being thrown into water. This type of moving wave can also be found in the atmosphere in the form of a cloud disturbance known as a gravity wave. Gravity waves form as a result of a trigger that forces air to move in the vertical direction. In most cases, topography is the trigger that forces air in a stable environment to first rise then sink back to and past the equilibrium point. The result is a ripple in the clouds which is best seen in a stratiform cloud layer.

With only one and a half shifts remaining, I don’t expect to create a fourth edition to this series. However, given the unique atmospheric conditions created and experienced by Mount Washington, I won’t totally reject the notion of seeing and photographing more types of unusual weather phenomena.

Matthew Morin,  Space Grant Intern