PORTLAND, Ore. (KOIN) — An infrequent and rarely visible cloud formation rolled across Portland’s skyline like a set of waves Wednesday morning.
KOIN 6 Meteorologist Kelley Bayern reports that the wave-like clouds are known as Kelvin-Helmholtz clouds, which form when a top layer of clouds is whipped up by faster wind speeds.
“Surfs up,” Bayern said. “Caught some Kelvin-Helmholtz wave clouds out this morning over the city. These happen occasionally and don’t last more than 15 or so minutes. They are caused by turbulent winds that roll due to wind shear. Pretty neat.”
Meteorologist Jon Bonk with Portland’s National Weather Service told KOIN 6 News that although these clouds aren’t necessarily rare, it is uncommon for all the proper conditions to align in the Pacific Northwest for them the clouds to be visible. In addition to the assorted layers of atmospheric moisture and wind speed required for the clouds to form, the fleeting phenomenon also has to occur during the right time of day and on a day with limited cloud cover.
“It’s rare that we get such a good view of them …” Bonk said. “It’s not uncommon, it’s more that everything has to come together just right to provide that breaking wave shape.”