Excessive Heat Warning Today

Scattered clouds over the Catalinas at a bit after 5:00 am MST this morning.

There was little to report yesterday, with no CGs over southeastern Arizona and no rainfall reported across the ALERT network. Very dry here, and I'm starting to water some of the plants.

Map above shows NWS warnings and advisories in effect today: Purple shows excessive heat warning areas; orange indicates heat advisories; red regions are under Red Flag warnings for high wildfire threats; and gray areas have air quality advisories in place. Tucson is just within the purple area - note that at airport at 7:00 am this morning temperature was 87 F and winds were gusting over 30 mph.

The morning 500 mb analysis (above from SPC) shows the western anticyclone is elongated from northern Baja northeastward to southern Wyoming. The morning TWC/TUS sounding (below, also from SPC) indicates fairly dry conditions with little CAPE. Winds aloft are westerly to northerly, while winds below 700 mb are southeasterly and fairly strong, so some gusty afternoon winds likely.

Plumes from the 06 UTC GEFS for QPF at the airport (above) indicate a dry week ahead, as does the 06 UTC WRF-GFS forecast from Atmo - below, for period ending at 5:00 am next Friday the 13th of September.

Hot And Dry

View looking east this morning at 5:50 am MST.

Another totally suppressed day re CG flashes southwest US and northern Mexico - as per CG flashes plot above from Atmo and Vaisala.

At 500 mb this morning (above from SPC) a large anticyclone covers the West. Current forecast from TUS for the airport below - hot and dry, with excessive heat warning today and tomorrow.

Summer Overview

Storm over the Catalina foothills on 25 July at 4:00 pm MST.

First, a look at August in detail. Plots above and below show total August rainfall observations across the ALERT network. The driest region covers most of the metro area northwest to Oro Valley. There are three sites that reported over 3 inches of rainfall for the month, and many sites had over 2 inches. Here at the house I measured only 0.78" inches, which was the fifth driest August since 1999.

Back to June - we had 1.75" of rain during the last part of the month. This was the third wettest June here since 1999.

July was another wet month, with a total here of 3.72" - this was the 7th wettest July since 1999 here.

There were 23 days here when I noted that thunderstorms had occurred during the summer (my hearing is bad, so there were probably a few more that I missed). One of these was marginally severe and blew apart our front gate (on 18 July).

Total summer rainfall here was 6.25", which was 10th wettest summer since I started my records. The driest summer was in 2013 (1.51" total), while the wettest here was in 2021 (10.98").

Light Showers

Pre-sunrise color at about 5:10 am MST looking toward the Rincons this morning, the first day of September.

Plot of detected CG flashes through 1033 UTC last night shows thunderstorms occurred over western parts of eastern Pima County yesterday afternoon.

ALERT observations show widely scattered amounts of 0.04" and more, with most reports on northwest side of the Catalinas. Here at house there was a brief shower that left 0.03" in the gauge. I did not hear any thunder. The airport reported a thunderstorm with gusts to 53 mph and 0.07" of rain; Atmo had 0.02"; while DM did not report any rainfall.

The 500 mb anticyclone (above from SPC) is centered over Colorado this morning, with a hint of an inverted trough to our east. The morning sounding (below, also from SPC) continues to be not very impressive, but with some CAPE above 700 mb. I was wrong about yesterday's sounding and showers here, so I'll just say that I'll be surprised, again, if we have showers here today.

The 12 UTC WRF-HRRR forecast through midnight tonight (above, from Atmo) forecasts little for all of Pima County. Current NWS forecast is shown below.

End of August

View toward the eastern Catalinas at 6:00 am MST this morning.

Plot of detected CG flashes (from Atmo and Vaisala, through 0733 UTC last night) indicates some scattered thunderstorm activity in eastern Pima County yesterday, mostly over and near the mountains. The ALERT observations below (through 7:00 am this morning) tell the same story. The airport and DM reported thunder but no rain. No rain here or at Atmo. There may have been thunder here, but I did not hear it.

The 500 mb analysis (above, from SPC) this morning shows light winds across the Southwest, with the anticyclone center far to the north over Idaho. The morning sounding (below, also from SPC) has about an inch of PW and little to no CAPE. Winds are light and variable below 300 mb. I would not expect low elevation storms with this sounding, barring an increase in PW during the day (which is not forecast by models).

However, both the 12 UTC WRF-HRRR (above through midnight) and the NWS (current forecast below) disagree and forecast chances for storm at lower elevations and the airport. So, I will be interested to see what happens later today and this evening.

More Sprinkles

Nice pre-sunrise color this morning looking toward Redington Pass at 5:50 am MST.

Yesterday was very suppressed over most of southern Arizona. Plot of detected CG flashes (above through 0813 UTC last night - from Atmo and Vaisala) shows no thunderstorm activity over eastern Pima County.

There were morning sprinkles and showers yesterday across the Catalinas and far southern parts of the ALERT network. There was a Trace here, as well as at DM and the airport.

At 500 the main anticyclone center has shifted to the Carolinas this morning and there appears to be a weak circulation over Nevada, as well as an inverted trough over western Arizona and southern California (above analysis from SPC). Wind speeds remain quite light at 500 mb. The morning sounding is relatively dry and quite stable (below, also from SPC).

Plumes for QPF at the airport from the 06 UTC GEFS (above) indicate a quiet ending of the month for August. The 12 UTC WRF-HRRR forecast through midnight (from Atmo - below) indicates little rainfall over much of Arizona, including Pima, Santa Cruz, and Cochise Counties.

Light Sprinkles

Some color on the Catalinas at 6:00 am this morning.

There were a couple of small clusters of CG flashes in eastern Pima County near the mountains yesterday afternoon - plot of CG flashes through 0803 UTC last night shown above (from Atmo and Vaisala). May have been thunder here, but I didn't hear it.

Limited reports of light rainfall amounts across the Alert network through 7:30 am this morning (above and below). There was a very light sprinkle and Trace here late yesterday afternoon.

The morning 500 mb analysis (above from SPC) shows the anticyclone has weakened significantly and moved over the southeastern US. Pattern is very chaotic over the Southwest with slight height gradients and light/variable winds.

Morning sounding from TWC/TUS has appeared (below, also from SPC), so the office must have received a helium shipment. Sounding shows moisture and some CAPE above 700 mb. There are southwest winds of 20 to 30 kts above 500 mb, but light and variable winds below. The current morning forecast from the Forecast office for the airport is shown at bottom.