Thursday, December 20, 2007

The meeting of Farenheit and Celsius

Brrrrr....2pm and the temperature was hovering at a chilly -45ºF (-42.8ºC) this afternoon. What most Alaskans would term as "real cold" arrived this week. This is when the thermometer plunges to the point where the Fahrenheit and Celsius scales cross paths---the magical number of -40ºF (-40ºC).

I snapped the above shot when I was out snowshoeing on a trail just down the hill from my house in mid-afternoon. Only 200 vertical feet higher up at the house it was a balmy -28ºF (-33.3ºC) -- almost 20 degrees warmer. And if you go up higher in the hills the readings were even warmer. The dense, cold air sinks to the low lying areas (or valley bottoms) and sits there until clouds or a warm breeze can scour it away. The deep cold is going to be short lived but the forecast is for temperatures to remain from around zero and below for a while.

The sun at high noon peers through the thickening ice fog.

This time of the year the sun barely climbs above the horizon for a few hours and provides absolutely zero warming. So the temperatures will not budge upward until a warmer airmass arrives. This is different from more southerly latitudes where the heat from the sun will warm things up during the day. We wont see any heating effect from the sun until sometime in late January. So during mid-winter in far north its pointless to forecast afternoon high and nighttime low temperatures because the high and low for the day can occur at anytime.