Isolated Storms Yesterday

Light shower along the foothills at about 3:00 pm MST yesterday afternoon. It was fairly suppressed yesterday, with few thunderstorms over eastern Pima County - below shows plot of detected CG flashes for 24-hours ending at 1203 UTC this morning (from Atmo and Vaisala).

Only 12 sites across the ALERT network reported rainfall during the 24-hours ending at 8:00 am this morning. Another July day with nothing in the gauge here.

This morning the 500 mb analysis (above from SPC) shows that main circulation center of the large anticyclone is very near the Four Corners. The morning TWC/TUS sounding remains less than impressive (below). There is nice CAPE, if BL could mix out to 600 mb. The easterly steering flow has increased to 20 to 30 kts. However, the 12 UTC WRF-RR forecasts little rainfall in Pima County through midnight tonight (second below), with no precipitation over the Catalinas or Rincons.

Play It Again

Thunderstorm in foothills yesterday afternoon about 4:30 pm MST - had thunder here at house from this storm but only a sprinkle of rain. There was quite a bit of lightning activity  in western part of greater metro area - as per plot of detected CG flashes (below - from Atmo and Vaisala) through 0803 UTC today.

Scattered rainfall reports across the ALERT network (above and below) - areal coverage was about 60 percent as per ALERT and also MesoWest. We again had only 0.01" in the gauge. There were three reports of just over half an inch. So it was a fairly active storm day.

This morning's sounding (above from NCAR RAP) is similar to past few mornings. There is some CAPE above 700 mb. But, steering winds have weakened to around 15 kt from the southeast, so it will be interesting to see if mountain storms can propagate into lower elevations. The 12 UTC WRF-RR run at Atmo indicates very limited activity in Pima County (below shows total precipitation forecast through midnight tonight).

Light Shower Last Evening

View last evening with some raindrops on the camera lens.

The ALERT plots ending at at 7:00 am MST this morning show that a few sites received 0.04" or more during past 24 hours. Atmo reported 0.09", we had 0.01", and airport and DM both had a Trace but with thunder and wind gusts around 40 mph. Here at house we had a single CG flash around 8:30 pm and a long rumble of thunder. Plot of detected CG flashes (second below) shows that most thunderstorm activity was out west across central Pima County.

The large, 500 mb anticyclone continues to dominate much of the western half of the country (above). It is forecast to wobble around, centered near the Four Corners for next week or so.

The morning sounding from TWC/TUS (above) remains relatively dry below 600 mb, with a sliver of CAPE. Speeds of the steering winds from the east have increased a bit. But, the sounding continues less than impressive. There may be hope that Hurricane Estelle will develop and pass close enough to the GoC to push higher amounts of low-level moisture into southeast Arizona by the middle of next week.

The 12 UTC run of the WRF-RR model at Atmo forecasts only streaky, light rainfall this afternoon - forecast below shows amounts through midnight tonight.

Isolated Showers

Another scenic sunrise for Tucson today - above view from about 5:30 MST.

Thunderstorms yesterday stayed mostly on the mountains - as  plot of detected CG flashes (above from Atmo and Vaisala) for 24-hours ending at 0103 am this morning shows.

Rainfall reports from MesoWest (above for 24-hours ending at 7:41 am - show only isolated, light amounts at low elevations (nothing here at the house). The NWS outlook for heavy rain and flooding yesterday (see graphic at bottom of previous post) was a serious over-forecast.

This morning's sounding remains much the same as past few days - little moisture below 700 mb, slight CAPE, and very light winds below 200 mb. The 12Z WRF-RR forecast, from Atmo, for composite radar echoes valid at 4:30 pm today (below) keeps storms at low elevations mostly out around the edges of the metro area. So it goes.

 

Forecast Differences Today

Nice view of Catalinas and heavy clouds just before sunrise this morning.

Post is late today because I had a morning appointment over on the east side of the city.

Plot of detected CG flashes (below - from Atmo and Vaisala for 24-hours ending at 0133 MST this morning) shows that yesterday was another with virtually no thunderstorm activity within Pima County.

This morning's sounding (12 UTC above) again indicates little CAPE and light variable winds - how long can this go on? Sounding is most conducive to another round of strong outflows, along with light showers. Yesterday the airport reported max gusts to 46 mph from the southeast around 7:30. The outflow did bring a nice temperature drop of almost 20 F, which was quite welcome.

Forecasts here from the 12 UTC WRF-RR runs: above composite radar echoes at 6:30 pm today, and below total rainfall through midnight. The line of echoes moving through the metro area will likely bring strong gusts from the east to southeast - how strong? I can't really say for sure, but sounding indicates potential for 45 to 55 mph winds.

The model forecast (below) also indicates light precipitation amounts across much of eastern Pima County through midnight.

 Thus, the WRF forecast is much different than the NWS Forecast office outlook (second below) issued at 8:00 am this morning, which warns of possible heavy rains and flooding across southeast Arizona. Once again, time will tell.

July Grinds On

View above, with contrail streak, from a bit before 6:00 am MST. Thunderstorms mostly avoided Pima County yesterday, as did rainfall - plot of detected CG flashes for 24-hours ending at 0803 UTC this early morning (below, from Atmo and Vaisala).

The 500 mb plot is truly a mess this morning - the 250 mb chart provides a better depiction of current features. Three anticyclone centers of circulation extend from Arkansas to northwestern Sonora. An inverted trough in the easterlies is over the southern end of the GoC.

The morning sounding at TWC/TUS continues to be unimpressive - limited moisture, no CAPE and a chopped up wind profile. The 14 UTC plot of total precipitable water (below) shows higher moisture content lurking just south of 30 degrees north - need a feature to kick these values up into Arizona. Remnants of Bonnie are around 140 degrees west, while intensifying Hurricane Darby (now a high-end Category 3 storm) is just west of 120 degrees.

The 12 UTC WRF-RR forecast manages, somehow, to develop isolated nighttime storms over parts of eastern Pima County - forecast above valid at 10:00 pm tonight.

Current heat warning for today. from the NWS Forecast Office, is shown below.

Continued Dry Here

Storms around yesterday with a rumble of thunder here from the northeast. Just a sprinkle here - not enough to wet the courtyard.There were gusty outflow winds several times during afternoon and evening. Of note was a gust to 49 mph at the airport just before 8:00 pm MST.

Plot of detected CG flashes (from Atmo and Vaisala - above) for 24-hours ending at 803 UTC last night. Not the classic Tucson donut hole is very pronounced. Precipitation (below from MesoWest) is for 24-hours ending at 7:00 am this morning. Reports on the mountains, but with some isolated rain reports around metro area.

This morning's TWC/TUS sounding (above) is as bad as it can get - no winds, no CAPE. The 12 UTC WRF-RR forecast indicates only isolated storms over the mountains at 5:00 pm this afternoon. It's July but you sure wouldn't know it without looking at the calendar.

Chance For Showers

Pink cirrus and dark lower clouds about 5:15 am this morning. Very warm start to the day - when I returned from my morning walk at 6:30 am MST it was 82 F here. The plot of detected CG flashes (below from Atmo and Vaisala - for 24-hours ending at 0803 UTC) shows that thunderstorms returned to southeastern Arizona yesterday - perhaps a flash or two just inside Pima County.

This morning's sounding remains unimpressive, as per past several days. There are, however, some relatively strong east winds from 300 to 700 mb. If storms develop off to the east this afternoon, the steering flow will try to move them our way.

The 12 UTC WRF-RR forecast run at Atmo indicates that this is what will happen, with storms moving west over much of eastern Pima County. Forecast of composite radar echoes (above) is valid at 7:30 pm this evening. The storms produce strong outflow winds and some light rainfall - as per two forecasts below from same WRF-RR run.

At bottom is an outlook graphic for today from the NWS Forecast office.