A quiet day most of the day with no sign of the explosive developments that were indicated to occur in the U of AZ models, causing some excitement in the Dept there. Not a shred of Cumulus clouds appeared on the Catalina Mountains until mid-afternoon. Then, fairly quickly things looked more promising for rain, as in shots 2, 3 and 4 showing a Cumulus turret that exploded upward. The instability of the day, indicated in the models, was finally being unleashed! The time lapse movie from the U of A is even more dramatic (here).
But this Cumulus congestus cloud quickly converted into a long, thin Cumulonimbus, and was not followed by others as hoped for. Only its glaciated head survived, drifting non-chalantly across Oro Valley. No rain made it off the Catalinas, either, as can happen with this type as the mid and upper portions dribble light showers away from the mountains.
So, nothing in the daytime…
But then during the early nighttime hours, things began to happen. By nightfall lightning was occurring to the NE, and a cell developed right over Catalina/Oracle Road about 8:30 PM. An extremely close lightning “pop and explode” strike hit here about 8:45 PM, but no rain was falling! Odd, since the radar indicated the edge of the thundercell was in my neighbor’s yard practically.
The cell drifted away toward the west, its intense rainshaft visible in the night light of Oro Valley. You can see from the rainlog.org site that some folks got blasted, one site in Rio Vistoso reporting 0.70 inches. The Pima ALERT data, showing amounts in the mountains, is here. Pig Spring, a little northeast of Charoleau Gap was the “winner” at 0.43 inches.
Sprinkly rain occurred a time or two overnight; in fact, its raining right now (R—, “R triple minus” for exceedingly light rain, 6:07 AM.) And check this cloud-radar 12 h loop from IPS Meteostar. You will see how the rain was all around us last night, though light, something the U of AZ model (WRF-GFS) had picked up on yesterday in forecasting an active night rain situation in SE AZ.
One factor that kept things at bay, and my Seattle friends won’t believe it, was the “cool air” yesterday, the high temperature only reaching 95-97 F here, about 10 degrees cooler than the previous day. Really, it felt quite comfortable I thought. That cool air really put the damper on convection, or, restrained the damper conditions than could have been.
Of course, these model breakdowns have to do with how accurate the initial conditions are. The U of AZ experts, in their late morning assessments of data that have arrived at 5 AM AST and later, or other local data from water vapor sounders, spend a lot of time seeing which of the two models they run on their Beowulf Cluster had the best starting conditions. They can then estimate what the differences might be in the model output imagery, and which model did the best job given the starting errors, always present to greater and lesser degrees.
Today, the model run from last night’s data have little rain in the Catalina area today, though storms approach from the Ne in the evening hours similar to yesterday. But the mods don’t think they survive the trip from the White Mountains and Rim to here, dying out about the time they reach the Catalinas.
As we have seen, this kind of close call can’t be taken too literally. So, the best forecast has to be generalized, in my opinion, to a chance of a thundershower in the mid-afternoon through the early nighttime hours. If you see Cumulus clouds piling up over the Catalinas by noon, the chances will be much greater for rain in the Catalina area today or early tonight (he sez).
Tomorrow is thought to be a wetter day here. Always, “tomorrow” it seems.