Monday, November 30, 2009

Cold Winds but Not Much Rain

The intrusion of a strong cold front from New Mexico into southeastern Arionza around 4 am this morning brought an end to the precipitation at lower elevations in eastern Pima County. Strong downslope east winds continue here at the house with gusts estimated 30 to 35 mph. For the 24 hours ending at 7 am 90% of the Pima County alert gauges had measured rain but, even though the event was widespread, amounts were light with the highest amount only 0.47". Here at the house the entire, even with several periods of lightning and thunder, event produced only 0.10". Earlier this morning the strong east winds across the Rincon Mountains produced a sky that reminded me of Colorado - lenticular clouds, a cap cloud sitting on the mountains and a couple of rotor clouds to the west of the mountains. Regardless of the sad amounts of rain, it's nice to have some weather again after so long.

Sunday, November 29, 2009

More on the Southwest Cutoff

Photo above shows early morning rainbow today, Sunday the 29th, to the northwest of the house.

As the 500 mb cutoff dug southward across southern California yesterday, strong and gusty winds deloped in south-central Arizona around mid to late morning on Saturday, November 28th. The winds caused a serious dust storm between Tucson and Phoenix that resulted in wrecks and fatalities on I-10.
CASA GRANDE, Ariz. - Two people are dead after their small sport utility vehicle crashed into a commercial vehicle during a dust storm in south-central Arizona.

The state Department of Public Safety began warning travelers Saturday morning to avoid Interstate 10 near Casa Grande until the dust settled. The wind slowed down by the afternoon, but Public Safety spokesman Harold Sanders said visibility along the interstate from mile post 190 to 216 remained poor.

Sanders says officers are investigating five separate collisions in the area that resulted from Saturday's dust storms, including the one involving the two fatalities. He did not have details on the other collisions.


Finally Some Weather in the Southwest!

A strong and cold cutoff at 500 mb has dug into the Southwest during the last 36 hours, bringing clouds and thunderstorms to the Tucson area. Photo above shows clouds hanging on the west flanks of the Catalina Mountains at sunrise on November 29, 2009. At 7 am I measured only 0.01" but saw some in-cloud flashes and heard rumbles of thunder. This is the first rainfall since October 3rd. Just the smell of moisture in the air is very much welcome!

Wednesday, November 18, 2009

Low temperatures last several mornings

As the photo above shows, we've had another night with clear skies and strong radiational cooling here in Tucson. The low temperatures here at the house (near the Rillito Wash on the north side of Tucson) for the last three mornings have been: Monday Nov. 16 - 26F (39F); Tuesday Nov. 17 - 27F (53F); and Nov. 18 - 36F (48F). The temperatures in parens are the official NWS observed morning lows at Tucson International Airport (TUS). The winds has kept things warmer down south at the airport; whereas, each morning here at the house it has been calm. The remarkable 26F difference between here and the airport on Tuesday morning is the largest that I've observed - beating the previous record of 23F! I also suspect that the temperature down at the Rillito was several degrees cooler than here at the house - so there's the low down.
No measureable rain here since October 2/3 but it does appear there was a sprinkle trace on Saturday the 14th. It did rain on Saturday where we were, 5 NW of Sonoita, as I suspected it would. The orographic forcing there is quite good with S to SW low-level winds.

Friday, November 13, 2009

Showers on the Catalinas

Early morning view looking north to the Catalinas, where the montain tops were also in the clouds. The two 500 mb S/Ws affecting the western US have pulled substantial moisture into Arizona - a nice change from past days this week. Could actually smell moisture when I walked this morning. Showers now obscuring parts of the mountains, where the current POPs of 20 to 30% are not high enough. Will be interesting to see what happens down at lower elevations. We'll be down NW of Sonoita this afternoon through tomorrow and there'll be an excellent chance that we'll finally see a bit of rain (probably 70% chance or greater based on my experiences down there).

Finally a Bit of Weather

Web cam view on Kitt peak showing that the mountain is in the clouds this morning.

Thursday, November 05, 2009

Slight Bit of Weather in Tucson

It has been very dry and mostly tranquil here in Tucson during most of October and early November. October was exceedingly dry with rain at house on only one day (late on the 2nd) that amounted to only 0.05". A weak, upper-level short-wave came by off the Pacific yesterday and produced an afternoon with thick heavy cloud, and some virga and mammatus. A quite dreary afternoon actually.
This morning there are puffy Cu floating around and a few mini-Cbs, as in the photo above. Note the classic Cb structure for this tiny cloud - a clearly distinct updraft area with darkened, flat cloud base, anvil, and snow-crystal virga falling out of the down-shear side of the cloud. Quite an amazing little Cb. That's not a drifting weather balloon above the Cb, but is rather the waning, 3/4 moon. Photo was taken at 8 am this morning (Thursday Nov. 5th, 2009) looking to the west.