Monday, April 06, 2009

Very strong, local temperature gradients this morning

Had a very interesting walk this morning.

When I left the house at 5:40 am the temp in the back yard was42F. It was distinctly cooler as I walked down into the slightly lower elevations along the Rillito Wash. It was calm during the first half of the walk.

As I headed back up hill away from the wash I passed through a very sharp temperature gradient (micro or meso scale warm front). I estimate that the temperature jumped from about 45F to ~65F within about 10 to 20 feet. There were the lightest of winds stirring about at this "warm front."

As I progressed on back toward the house the wind speeds were gradually increasing, and the wind was about 15 kt and gusty when I reached the house around 6:40 am. The temperature on my return was 60F.

I note that the official NWS low temp at the airport appears to have been 56F just after midnight this morning.

Also of interest is that the low here yesterday morning (Sunday April 5th) was 32F - this may likely be the last reading at or below freezing for the 2008/2009 cool season here at house.