Friday, March 9, 2012

Graupel-- huh?!

(March 8, 2012. Photo courtesy: Marcie M. from Keys, OK. Picture shows a hybrid of ice. This could be considered as graupel...maybe...)

"It's hailing! Wait, I think it's sleet. Uhm, this can’t be snow, uhm, it's uhm…"

If you muttered this to yourself yesterday, you aren't alone!

Yesterday during the cold rain you may have seen graupel (a word the spell checker doesn't even like!) for the first time in your life-- so what is it?

Graupel could be considered part rain, sleet and snow, and it's rare in Oklahoma. In layman's terms, it's a bit of an ice hybrid.

Graupel forms during cold precipitation.

Cold, above ground temperatures cause the precipitation to begin as snow, remaining mostly frozen from cloud level to near the surface. The snow gradually melts above the ground while rain or sleet attempt to freeze to the melting snow.

The rain exists in what's called a "supercooled" state-- water in a liquid form below 32 degrees as it adheres to what's left of the snow. (Supercooled water/moisture is common in clouds.)

You can end up with a compact, smallish icy/snow pellet. It's hard to nail down the precipitation type from viewer pictures alone, and it's debatable whether you call it graupel, sleet, and/or ice pellets. Melting doesn't help identifying the precip type either.

Across Oklahoma, nearly all forms of precipitation fell yesterday in the cold weather: a few flurries were reported west, sleet covering the road in eastern Oklahoma, some small hail fell during "pulse" type storms during the morning. A few reports of the icy slush/maybe graupel came in as temperatures dropped.

Enjoy the pictures on this page... George

(Below: The Wilson family in South Tulsa sent in these pictures of the melting mess. It's difficult to tell whether it's sleet, small hail, ice/snow pellets or graupel.)

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