Sky Islands

I was looking for an inexpensive vacation last week that offered lots of sun and interesting weather features--well I found one --Tucson, Arizona.

Perhaps my most interesting weather experience was ascending one of the "sky islands" - the Santa Catalina Mountains northeast of Tucson. Starting around 2500 ft in the Tucson metro area, one can take the Catalina Highway/Sky Island Scenic Byway to 9,157-foot Mt. Lemmon over about 25 miles (see map). This topographic "island" within the Sonoran desert provides a wide range of climatic and weather conditions, with temperature dropping and precipitation increasing with height.

We started in Tucson under sunny skies and temps about 55F--surrounded by Saguaro and other cacti. The Saguaro are the cacti that are so often used to represent the Southwest (one is shown in the figure below), but they really only found in southern Arizona and Mexico--they can't handle below freezing temperatures for any length of time. By around 4ooo ft the Saguaro were gone--just too cold.


Weaving up the road, the vegetation and climate changed rapidly, and by around 5000 ft we started to see some SNOW in shaded areas. By 6500 ft there was loads of snow and we had entered a pine forest--reminding me of the eastern slopes of the Cascades. Moving higher, the snow got deeper (perhaps 3-6 inches at 7500 ft) and the air temperature was probably around 35F. So in 45 minutes one goes from desert to snow and a northern-type forest...there is even a ski area at the top!

Average rainfall is roughly 12 inches in Tucson (slightly wetter than eastern Washington) to 30 inches at the Mt. Lemmon site (slightly drier than Bellingham).

But the weather excitement didn't end there. On Tuesday, Dec 22, a cold front was approaching central Arizona, with a low center to the north--the result was a large pressure difference over the region with winds accelerating to 40-50 mph. We were out hiking in Saguaro National Park as the wind hit and the most extraordinary thing was the rapid loss of visibility (see pic). The situation got very bad on I10 south of Phoenix where winds blew over agricultural fields. (it has been a very dry year...Tucson only has received about half their normal 12 inches a year). The result was a severe dust storm that resulted in over 20 accidents on I10, a death, and the temporary closure of the road (graphic).

The adaption of the plants and animals to the dry conditions is really extraordinary, including the ability of big cacti to store tons of water and the dual usage of cactus needles for both protection and shading. I was not a little disappointed about human adaption down there...lots of large vehicles and relatively few solar panels.



And my family's adventure in Tucson was really enhanced by the very nice bed and breakfast we stayed at: a place called Azure Gate. Friendly, helpful people and extraordinary food.

Finally, what about our weather? Our sunny period ends today...and tomorrow will bring increased clouds and a few sprinkles. Then a few weak systems in store...but nothing of any note for several days. Unfortunately, for active weather lovers the influence of El Nino will now become more significant...and that means that weakened and split systems will be more frequent than normal...and snowpack should be below normal.