“Freezing rain is a type of precipitation that begins as snow at higher altitude, falling from a cloud towards earth, melts completely on its way down while passing through a layer of air above freezing temperature, and then encounters a layer below freezing at lower level to become supercooled. This water will then freeze upon impact with any object it encounters.[1] The ice can accumulate to a thickness of several centimetres, called glaze ice. The METAR code for freezing rain is FZRA.” -from Wikipedia
(image from the Wikipedia Free Commons)
It’s a beautiful, clear, sunny day here in Virginia. Thin filmy clouds, no wind, just an all-around nice day. But the weather forecast is for the dreaded “wintry mix” starting tonight and lasting all day tomorrow, with most of it being freezing rain.
I hate winter. I hate being cold and I especially hate frozen precipitation of any kind.
What the heck is “supercooled” anyway? I know roughly that it’s water that is below the freezing temp, but which is still liquid.
“A liquid below its freezing point will crystallize in the presence of a seed crystal or nucleus around which a crystal structure can form. However, lacking any such nucleus, the liquid phase can be maintained all the way down to the temperature at which crystal homogeneous nucleation occurs. The homogeneous nucleation can occur above the glass transition but can be supercooled at standard pressure down to its crystal homogeneous nucleation at almost 231 K (−42 °C).[1] If cooled at a rate on the order of 106 K/s, the crystal nucleation can be avoided and water becomes a glass. Its glass transition temperature is much colder and harder to determine, but studies estimate it at about 165 K (−108 °C).[2] Glassy water can be heated up to approximately 150 K (−123 °C).[1] In the range of temperatures between 231 K (−42 °C) and 150 K (−123 °C) experiments find only crystal ice.” – from Wikipedia
Ummm … okay. I have no idea what most of that means, but there it is.
Prior to the invention of the telegraph in 1837, weather forecasting was essentially not happening. The nice weather that I am seeing today, back then, would have given no hint of the misery that is going to happen tonight and tomorrow. Even today, it’s amazing that we get such horribly accurate predictions of doom.
“Imagine a rotating sphere that is 12,800 kilometres (8,000 mi) in diameter, has a bumpy surface, is surrounded by a 40 kilometres (25 mi)-deep mixture of different gases whose concentrations vary both spatially and over time, and is heated, along with its surrounding gases, by a nuclear reactor 150,000,000 kilometres (93,000,000 mi) away. Imagine also that this sphere is revolving around the nuclear reactor and that some locations are heated more during one part of the revolution and other locations are heated during another part of the revolution. And imagine that this mixture of gases continually receives inputs from the surface below, generally calmly but sometimes through violent and highly localized injections. Then, imagine that after watching the gaseous mixture, you are expected to predict its state at one location on the sphere one, two, or more days into the future. This is essentially the task encountered day by day by a weather forecast.” – Bob Ryan of WRC-TV and previously the Today Show (quote taken from Wikipedia)
To make this post vaguely related to photography, look at this (old) picture from NOAA of Hurricane Hugo. I think the photo is just as beautiful as a lot of modern art that I’ve seen. Appearance completely divorced from meaning (pure misery down below).
-Julie
