Rains Close By Yesterday

View of Catalinas yesterday afternoon at a bit before 3:00 pm MST - thunderstorms stayed mostly to east and south of metro area.

ALERT plots for 24-hours ending at 7:00 am this morning. Cluster of reports from sites near Redington Pass and also scattered reports across south half of network, with most reports being quite light. Nothing here at the house except for a couple of gusty outflows. Airport reported thunder and Trace with gusts to 36 mph during the afternoon. All-in-all a pretty bland day with respect to the forecasts for an active day (see previous post).

Plot of detected CG flashes for 24-hours ending at 1400 UTC (7:00 am) this morning (above, from Atmo and Visala) shows the storm activity from yesterday afternoon, as well as some unusual, early morning storms near Yuma - thunderstorms are even occurring over the south part of California this morning!

The morning 500 mb analysis (above) shows a weak closed low along California coast and a trough eastward across Arizona. The large anticyclone over central US has no well-defined circulation center this morning.

The morning TWC/TUS sounding plot (below) has moistened considerably  below 700 mb compared to yesterday (see previous post) and there is a fair amount of CAPE. Winds are light and variable below 400 mb, so there is no distinct steering flow.

The 12 UTC WRF-RR forecast verified reasonably well for Pima County yesterday, and I grabbed its forecast of precipitation through midnight - second below. Even though the sounding looks favorable, the model again keeps the storm activity fairly restricted and mostly in Cochise County. I would expect a more active day, especially over and near the mountains - time will tell.

Difficult Forecast Today

Middle cloudiness over the Catalinas and metro area this morning, a bit before 8:00 am MST.

This morning's 500 mb analysis (above from NCAR RAP)  shows the anticyclone still centered far to our east over the Missouri Bootheel. A massive ridge extends from Hudson Bay southward to central Mexico. Most of the trough that was to our northwest has pulled away to the northern Plains, leaving a weak piece of trough over central California.

The morning sounding from TWC/TUS (above) shows increased middle-level moisture, but the layer below 650 mb remains quite dry, with PW a bit below an inch. The sounding has only a hint of CAPE, and low level moisture will have to increase considerably to support widespread thunderstorm activity this afternoon. The 06 UTC GEFS plumes for CAPE (below) indicate only slight CAPE this afternoon and tonight.

Forecasts here from the 06 UTC run of the WRF-GFS (above) and from the 12 UTC WRF-RR (below). The WRF-RR forecasts considerably lighter amounts across eastern Arizona than does the earlier WRF-GFS. Based on the morning sounding, I would tend toward the WRF-RR and expect light showers across eastern Pima County, with limited thunderstorm activity this afternoon.

Current NWS morning weather story is second below, and is more similar to the WRF-GFS forecast for eastern Arizona. It's a tough forecast today and the weather outcome will depend on how much CAPE actually develops - really hurts not to have a morning Guaymas sounding!

Showers Tomorrow?

Nice morning here in Tucson with a bit of cloudiness to the east and northeast.

Storm activity stayed east of the metro area yesterday, as per the plot of detected CG flashes (below - from Atmo and Vaisala) through 0803 UTC early this morning. The WRF precipitation forecast shown in yesterday's post verified quite well, even picking up the activity activity at the south end of the Rincons. Precipitation reports were mostly in Cochise County. There were two ALERT sites with 0.04" in the southeast corner of the network. Most precipitation reported, that I found, was at Safford with 0.31".

This morning's TWC sounding plot (above) shows dry low-levels and no CAPE. However, models are forecasting increased moisture and PW moving northward into southeast Arizona late today into tomorrow. Precipitation forecasts from the 1200 UTC run of the WRF-RR indicate some rainfall today - mostly east to south of our area (below).

However, tomorrow a weak short-wave at 500 mb is forecast to move northward across Arizona - forecast above valid at 5:00 pm MST tomorrow afternoon is from the 06 UTC run of the GFS. The short-wave helps spread the forecast rainfall to the west, covering almost all of Pima county by midnight tomorrow (below from same WRF-RR run at Atmo run).

Ground here is bone dry and I have to water every other day to keep plants going. Really hoping for a meaningful rainfall soon.

Showers Parts Of Metro

Clouds over the Catalinas this Father's Day morning at a bit after 7:00 pm MST. View at bottom is from yesterday afternoon, when showers and storms were developing over northern parts of metro area. Plot of detected CG flashes yesterday (below from Atmo and Vaisala through 0133 am CST last night) indicates an active storm day over much of eastern Arizona and New Mexico..

Rain amounts (second below, from ALERT ending at 7:00 am this morning) were generally light, except for several sites on and near the Catalinas that reported over half an inch.

Here at house there was rain in the gauge - finally, but amount was only 0.02".

This mornings 500 mb analysis (above) shows the West coast trough inching closer, with the large, central US anticyclone centered over Iowa/Missouri.

The morning sounding from TWC/TUS (above) continues to indicate at least a sliver of CAPE, with southwesterly winds aloft. There will be a battle between dry air to our west and more moist air to the east today. This morning's 12 UTC WRF-RR forecast from Atmo indicates that showers will stay mostly to the east of the metro area this afternoon and tonight (below).

Showers Possible

Middle clouds over the metro area at about 7:30 am MST this morning.

The current 500 mb analysis (below) shows Arizona in the zone between the large anticyclone over US and a strong trough over the west coast.

This morning's TWC/TUS sounding plot (above) shows low levels remaining dry and a lack of CAPE. Thus, if storms are to develop this afternoon and evening, there needs to be a considerable increase in low-level moisture. The forecast sounding (below - from the 06 UTC run of the WRF-GFS at Atmo) indicates a significant increase (surface dewpoint increasing from around 32 F to the middle 50s F), along with development of some CAPE.

Plumes from the 06 UTC GEFS forecasts (above PW at airport and below QPF at airport) show a strong increase in PW during the day today, with showers through much of tonight and Saturday.

Forecast radar echoes above from the WRF run cover most of the metro area at 7:00 pm this evening.

Below is the morning forecast from the NWS Forecast Office - putting the most significant POPs for the airport during the day Saturday, as per the various model forecasts shown above.  Hoping to see the first rain in the gauge after nearly three, totally dry months.

Little Change

Clear skies just before sunrise this morning at about 5:15 am MST.

The 500 mb pattern at 12 UTC this morning (below) is quite chaotic because of weak height gradients. There is basically a large ridge which extends from the Carolinas westward to Arizona. There appear to be anticyclone circulation centers over Arkansas and the Carolinas.

As Hurricane Blas moves westward south of 20 N, low-level moisture pushes slowly northward into southeastern Arizona. The PW plots here are from the 06 UTC WRF-GFS valid at 06 UTC this morning (above) and at 06 UTC on the 19th (below).

The increased moisture leads to thunderstorm activity by the weekend, particularly on Saturday. The two forecasts shown here are for total precipitation from now through 11:00 PM Sunday night. The forecasts are similar, but with the GFS (above) indicating a bit more rainfall in eastern Pima County than does the WRF (below). 

Showers By Weekend?

Skies this morning (above), while not pristine, are considerably cleaner than they were yesterday afternoon (bottom).

While PW is VERY low this morning, the 06 UTC GEFS forecasts a very rapid increase beginning tonight - see forecast plumes above. The models plumes for precipitation indicate precipitation at the airport,  mainly on Saturday - note the very large range of amounts forecast by the ensemble members.

In contrast, the 06 UTC WRF-GFS forecast above (valid through noon on Sunday) keeps the band of rainfall east of us, with no rain at the airport. So, considerable variance among the forecasts. This morning's forecast for the airport, from the NWS, is shown below.

Further south, Tropical Storm Blas is off the southwestern coast of Mexico. The NHC forecasts Blas to become a hurricane this morning, and to move away from land toward the west-northwest.

Hot And Isolated Storms

Copper skies last evening at 7:15 pm MST.

Storms were more widespread yesterday than I expected, given the marginal morning sounding and model forecasts - of course, storms mostly avoided the metro area. Plot of detected CG flashes (above - for 24 hours ending at 2:00 am early this morning) indicates considerable thunderstorm activity from our north to east to southwest. The Atmo movie for yesterday shows some frequent lightning flashes northeast of the Catalinas - worth a look.

This morning's 500 mb analysis (above) shows that the 500 mb anticyclone has shifted to eastern New Mexico, putting our area in weak, southerly flow at that level. The 12 UTC sounding plot for TWC/TUS (below) shows some slosh-around increase of moisture in low-levels, variable winds, and a sliver of CAPE. The 06 UTC WRF-GFS forecasts isolated storms this afternoon over the far southeast corner of the state - but, given yesterday's activity, I'd be hesitant to rule out storms over the nearby mountains.

Current morning forecast for the airport (above) - clicking around the metro area, I see that many spots have a forecast high today of 110 F.

The five day outlook from NHC (below) indicates that tropical storm development off southwestern coast of Mexico is likely during next few days.