Recent Hoarfrost and Soft Rime Photos
UPDATE 1/18/10: Check out some more talk & pics about hoarfrost associated with the widespread fog in the Midwest on this blog entry.
I talked this time last year about the differences between hoarfrost and rime, the main difference being that the latter forms only on the side of objects which is opposite the direction the wind is coming from. Local storm chaser Ron "R-Factor" Shawley took some great photos and videos of trees encased in hoarfrost over the weekend in Vinco, PA.
ELVIS TORNADO, KEY WEST COLD RECORD AND MORE AT RIGHT IN J'S BREAKING WEATHER NEWS
A lot of people assume this is snow, but snow generally doesn't stick to trees well, certainly not encircling their branches. Hoarfrost isn't freezing fog (see below) and actually all "frost" on objects is hoarfrost though it's generally not called that until there is a large accumulation (technically accretion) of it. Ron took this closeup:
Hoarfrost can come with or without snow, in this case there was plenty of snow on the ground but what was in the trees at one time had been blown out, and the high winds and extremely low temperatures (below zero on the mountain) caused a large accumulation of hoarfrost. Unlike "rime" which is generally hard and icy In this video he shows how it is soft like snow:
We also got hoarfrost pictures recently from Monroe, Ohio, Dayton Ohio, and even Ireland.
But I believe this picture from New Jersey on Christmas day shows "soft rime" - not hoarfrost because it looks like needles and has only accumulated on one side of the braches (carried by the wind as fog passed by, as opposed to spontaneously forming all around the object), both unique factors according to WikiPedia.
This makes me question whether what I saw last January was really hoarfrost or soft rime. Maybe if the wind is calm then soft rime can form around the object and not on the windward side?
So to summarize:
Hoarfrost = Frost = Soft, Formed on Object without fog (like dew)Rime = Ice deposit caused by fog freezing on the object, usually hard and windward but can be needles and all around
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