Wednesday, January 16, 2008

Good radar link

Here is a good link to follow precip moving our way.


And here's another good link to follow temperature/dew point/wet bulb temperatures.

Speaking of temps, I'm a little concerned by this bright sunshine which was beating down until about 30 minutes ago.

Temps up to 42, but dewpoint still just 12.

2 comments:

hamcdani said...

I am not very weather savvy, so sorry if this question is ridiculous, but what does the dew point have to do with anything?

Also, what has to happen for it to snow? I know most people know the answer to that question but I don't.

Skip Foster said...

Good question. I answered it some extent in this post here:

http://sfosterstar.blogspot.com/2008/01/weather-update-big-one-or-big-rain.html

Technically, the dew point is the temperature to which air must be cooled in order for it to become saturated.

In layman's terms, the dew point -- much like relative humidity -- measure the dryness of the air.

When dew points are low, precipitation that falls through the air causes the actual temperature to fall. So, if it's 35 degrees with a dewpoint of 10 and it starts precipitating, the air will cool to below freezing.

Regarding snow, it's a complex question, but basically you need subfreezing temperatures through all levels of the atmosphere. Freezing rain occurs when it's cold at the surface, but warm in upper levels. Hope that helps!