Tuesday, July 28, 2009

It Really is a Dry Heat!

As I come in from my evening walk tonight it is a comfortable 98F. Of course I'm in Tucson where the dewpoint is 43F and the humidity 16%. I was reminded of our time just over a week ago in San Antonio, TX where just standing, let alone going on a vigorous walk, you almost needed to hold your arms out to keep rivulets of sweat from running down your arms! BTW, current conditions there (1030pm CDT) are 88F with dew point of 71F and 60% humidity.

One reason it is more comfortable in Tucson is that the monsoon circulation has left us for the moment. Normally starting around July 4th and lasting about 10 weeks, rain comes to the desert, delivering about half our annual rainfall (about 12") in that time. The reasons are complicated, but with the subtropical "Bermuda High" in the right place and another high pressure area near the 4-corners area, air circulation is right to bring up moisture from the Gulf of Mexico, and with the daytime heating in the desert, sometimes violent thunderstorms result. During this time, the air is more humid, but it also doesn't get as hot as it can while dry. As a result, yesterday and today were cloudless for the first time since our return, and for my commute home it was a toasty 106F!

The photos above were shot from our roof yesterday - the infrared shots show off the thunderheads of the July storms, which have, for the moment, moved off to New Mexico, which I verified with a satellite image. The lower image shows a few fair weather cumulus hanging down towards old Mexico past the Santa Rita Mountains south of town.

I've gotten into the habit of taking evening walks after Melinda takes off from work. Five weeks ago it was common to see folks and families out for an evening stroll about sunset. But the last couple nights not a soul - 98F must be over their limit!

1 comment:

Anonymous said...

I don't like it when people say that.. "It's just a dry heat!" Well, it's still hot, nevertheless!! And I don't do any 'evening strolls' until about 2am. I need to move to Alaska... or Siberia, maybe. :P