A blog named for the muse of Astronomy containing musings by an astronomer

Now this is a cold snap

Posted on January 16, 2009 by admin

We have had a very cold winter this year. We had one cold snap in December where the nighttime lows dropped to -25 Fahrenheit (that’s -31 Celsius for the rest of the world). However, this new cold snap has been a bit more brutal with daytime highs of about -13 Fahrenheit (-25 Celsius) for the last 4 days. It was so cold yesterday morning (January 15, 2009) here in Moorhead that the temperature at the Moorhead airport dipped to -31 Fahrenheit (-35 Celsius) at 8:14am. At our house in town, the thermometer failed.
It listed the outdoor temperature as “OFL” which means “Off Low End” (I think)… so it was colder than -25 Fahrenheit (-32 Celsius). For fun, the kids and I went outside and decided to throw hot tap water into the air to create clouds. When you throw hot water into air that is this cold, it instantly vaporizes, forming a cloud. The video of it isn’t the clearest, but I think it is pretty cool.

Get the Flash Player to see the wordTube Media Player.

On YouTube I found “Sharon in Minnesota” used extremely hot water from a tea kettle and a spray gun, which makes the droplets much smaller and thus gives you a much clearer cloud.

Finally, a much clearer video of the phenomenon with a simple glass of hot water comes from this poor soul in Alaska where they are dealing with weather about 20 degrees colder than us.

I believe what is happening is an extreme form of what happens to your breath becoming visible on a cold day. The water when thrown suddenly gets a relatively large surface area (allowing cooling) and is scattered into small droplets. These droplets have enough energy to transition to a more solid state, which gives us a visible cloud of tiny particles of ice. A few of the larger drops make it to the ground. I’d appreciate some clarification.

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