Unexpected AZ Weather

Author:

Renee M

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Today the temp at 9:30 AM was 85 ° F and the sky was completely cloudy. Usually, even with cloud cover, the temp would be in the 90s. Right now, at noon, the temp is 75 ° and we've had light rain with little wind for 2 hours. I think most Arizonans who've been here more than a few years aren't too surprised by this weather, but I figure most of the country expects us to always have daily highs of 105 to 120 °.

Unlike most of the mountain west and even Northern AZ, we are having our summer monsoon season. All monsoon means is a big change in wind direction. We do get a little rain and higher humidity, but there are no 5" per day rainstorms. During the summer, we sort of shift into the subtropics where there are prevailing Easterly Trade Winds. The rest of the year we are back in the temperate westerly winds, by the winter, instead of passing north of us, we get the same storms that hit Southern CA.

On the edge of the subtropics, we don't get a 180 ° wind shift, just 90 ° with winds out of the south that bring moisture from the gulf of CA, (Sea of Cortez). Because of temp rise of up to 30 ° per day, we seldom use relative humidity; RH is dependent on temp and would be constantly changing. We use the absolute humidity expressed as the dew point, the temp when the RH is 100%. In late May and early June, we are very dry; the dew point is around 25 ° F. As the monsoon starts to shift the dew point rises. We are officially in monsoon season went the dew point is above 60 ° (I think) (maybe 56 °?) for three days in a row.

Other things happen that, I think, are rare in the NE at least. The dew point has been 65 ° all day; it's predicted to go down to 59 ° by tomorrow night. At 75 ° and 65 ° dew point the RH is 71% (I'm surprised it's that low; 10 ° temp drop and the RH is 100%!). The non back east thing is that we have rain at such a low RH. Maybe the atmosphere cools with elevation faster than back east. The fairly low clouds must be around dew point or lower.

The good news for me is I got to watch the TdeF, do some chores then ride (easy) 12 miles without being hot at all. I was riding in light rain for about 10 mins. Usually, to avoid heat exhaustion, I have to be home by about 9 AM and that's being uncomfortably hot; stopping by 8 AM feels much better!

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Comments

I grew up in the Imperial Valley, CA

Which gets monsoon weather in September. I always hated it. I'd rather have 115F with a dew point around 40 than 90F with dew point at 75!!! But it did make for nice dewy mornings and riding across the desert before it got warm was glorious. Unfortunately, the monsoons arrived usually just as school started. :(

Now I live in the desert mountains of Riverside County and it stays pretty dry all year round. Even when it is raining, it is often fairly dry air at ground level and we sometimes get luvia, which is where the rain evaporates before it hits the ground. :) And it can hail out of a nearly clear sky, which is weird.

Hugs,
Erin

= Give everyone the benefit of the doubt because certainty is a fragile thing that can be shattered by one overlooked fact.

Global weather change is funny thing :-)

It started with cancellation of "Global Warming" conference in DC due to anomalous cold :-)
In Europe it's even more funny as Spain got itself nice dry desert due to installation of wind turbines along the coasts. Alps are not getting enough cold air from the North due to all windfarms in Scandinavia. Solar panels in Germany also contribute some nice side effects.
For me it is real fun to listen to all the experts who are unable to predict tomorrow's weather better than random number generator predicting effects of change due to CO2 emissions for next 200 years :-)
BTW, CO2 can theoreticaly contribute to about 0.01% of "green house" effect, and about 99.8% of said effect is due to H2O in the air.
Additionally, contemporary models can give you about +/- 30% accuracy in predicting temperatures in _enclosed_ system with just two water phase change effects inside and exactly known amounts of heat supplied and removed. With six such phase changes with very rough approximations of heat supplied and removed from Earth surface we can expect at best something like +/- 150% accuracy. Which means that by slight changes to some of the guetimates of some of the constants we can get any result from Hell freezing over to whole Earth evaporating in next hour.
Four different weather services predict for the place I live in four different temperatures for tomorrow ranging from 15Â°C to 30Â°C with precipitation from torrential rain to sunny without clouds :-)
Add to this need to tripple worldwide electricity production to allow Americans to ejoy air conditioning or heating in their electric cars... Basically, I want to join that bandwagon and get myself couple of billion dollars fighting global weather change :-)