Glaze Ice vs. Rime Ice on the Summit
2017-03-28 22:06:31.000 – Caleb Meute, Weather Observer/ Meteorologist
Another system is winding down atop the Rockpile and temperatures are beginning to fall in its wake. As of my last observation, the temperature was sitting just above freezing, but that will soon change as a cold front charges into New England. An unimpressive snow pack over the summit has dwindled to an average of 5 inches thanks to 24 hours with the mercury sitting above freezing. Before temperatures rose above the freezing mark, several hours elapsed with the mercury hovering just below freezing which led to some thick accrual of glaze ice.
Glaze ice up here can accrue at alarming rates, especially when the winds are strong and the temperatures are just below the freezing mark. When you combine the glaze forming from freezing fog blowing over the summits with freezing rain, this is especially true. Yesterday morning, freezing rain was falling at a moderate intensity while combining with 40-50 mph winds and thick freezing fog. As a result, glaze formed on all surfaces at rates between 3 and 5 inches per hour! This lasted for only a few hours, but there are shifts where it lasts for much longer periods of time, which can make our job quite hectic. Glaze is a much harder ice than rime ice, which is more common here on the summit. When rime is accruing very fast up here, simply hitting the posts beneath the instruments is usually enough to free them. Glaze ice requires us to chip away at it, which can take significantly longer than it does with rime. As temperatures fall from freezing towards below zero readings, the consistency of the ice changes. Glaze turns to a hard rime as temperatures fall, and eventually as it gets colder, the rime becomes very soft and feathery. The soft and feathery rime can even blow off the instrumentation at times, without our intervention. I feel lucky that I was asleep yesterday while Mike was on observations dealing with the 3-5 inches of glaze per hour. I most definitely jinxed myself though and now it is safe to assume that each night on my next shift will warrant heavy glaze ice accumulations.
With the spring season upon us, days are getting longer and I am beginning to see the sun again! At least when we are not in the fog… This means that my phone will hate me again until I actually buy a camera to photograph the amazing scenery up here. Here is a picture of a sunset from this past week. I am looking forward to being awake for these in the coming months!
Caleb Meute, Weather Observer/ Meteorologist