Wednesday, July 31, 2019

Very Moist And Unstable This Morning

View of Catalinas this morning from campus, showing heavy cloud cover. Radar below from 7:20 am MST shows morning showers and thunderstorms near Phoenix and to southwest of metro Tucson. These are moving generally northward,

Detected CG flashes (from Atmo and Vaisala for 24-hours ending 1:00 am this morning) shows an expanded donut hole over metro area and much of eastern Pima County. Rainfall from ALERT below for 24-hours ending at 7:00 am this morning. Again, metro area with nothing reaching 0.04". There was a Trace here shortly after dark. Rainfall stayed on the mountains and to the southwest part of the network. Heaviest amounts stretched east-to-west south of Green Valley.

The morning sounding plot for TWC (above) shows high PW (near two inches) and significant CAPE (over 1000 J/Kg). Winds are southerly through the entire troposphere - which can be problematic here if there is anvil shading. However, 1330 UTC visible satellite image below shows cloud cover across all of southern Arizona, except for some clear areas along border of southern Cochise County. So heating may be lacking today, but not much will be needed for storm development. Should be an interesting day to watch the weather.

Tuesday, July 30, 2019

Scattered Storms Yesterday - Repeat Today Likely

Some nice colors at sunrise this morning.

Plot of CG flashes (above for 24-hours from Atmo and Vaisala is thru 12:30 am MST last night) indicates much thunderstorm activity over southeastern Arizona. Here in eastern Pima County storm activity over mountains east jumped parts of metro out into central parts of County.

ALERT rainfall observations (above through 7:00 am this morning) shows heavier amounts over the Rincons with not much over large part of metro area. Other amounts: TUS 0.14", DM Trace, Atmo 0.04", and here 0.06".

The NWS has issued a flash flood watch for this afternoon into the night - watch area shown below.

Little change at 500 mb (above), with anticyclone center northern New Mexico. Continue to be weak short waves over northern Mexico. Plots above and below from SPC.

The morning TWC sounding (below) is similar to yesterday's, with PW about an inch and a half and quite moist above 600 mb. There's a layer of stronger easterlies below 500 mb that could bring some downslope winds later today. Moisture somewhat lacking in low-levels - puts cloud bases around 600 mb with a sliver pf CAPE.

Radar forecast at bottom is from 12 UTC WRFRR and valid at 3:30 pm this afternoon. Models forecast increased thunderstorm activity for today.

Monday, July 29, 2019

Increased Activity Today

Phone shot by Katie of sunset colors behind the Santa Ritas last Friday evening.

There was only a bit of thunderstorm activity in far southeast Arizona yesterday afternoon, and storms pretty much were stuck on the mountains. The plot of CG flashes for 12-hours ending at 7:30 am MST (above, from Atmo and Vaisala)  shows that active flashes are still being detected with an MCS over northwestern Mexico. The IR image below from 6:30 am shows the MCS, as well as TSs Erick and Flossie far to south. These storms are expected to become hurricanes by the NHC as they move a bit north of west away North America.

The 500 mb analysis this morning (above from SPC) indicates the anticyclone - centered somewhere over northwestern New Mexico - dominates much of the West, There is perhaps a weak, inverted trough over northern Sonora. Morning sounding plot below for TWC (also from SPC) shows PW up to about an inch and a half with some CAPE. However, wind field remains very weak and disorganized.

The 06 UTC WRF-GFS forecast from Atmo (above valid at 6:00 pm this afternoon) shows some CAPE and easterly steering winds that are weak. Thus, storms may have trouble moving away from mountains again today.

The forecast of radar echoes (below, from same model run) is valid at 9:00 pm this evening with widespread thunderstorm activity over southeastern Arizona. So, perhaps some chances for additional rainfall before July comes to an end - only 1 inch of rain so far for entire month here at house.

Sunday, July 28, 2019

Quick Overview - Sunday 28 July

Above - light shower at sunrise yesterday (looking southeast from Santa Rita Abbey - 5 miles north-northwest of Sonoita - toward the Huachuca Mountains).

Very little thunderstorm activity yesterday except mountains of eastern Arizona (below, CG flashes detected for 24-hours ending at 01:00 am this morning). Forecast models are even more suppressed for today.

However, as 500 mb anticyclone shifts eastward (currently centered somewhere west of here) into New Mexico, storm activity increases considerably. Above shows GEFS plumes from 06 UTC run, for QPF at Tucson. The operational version of GFS is once again, much more moist than all the other members. The models also forecast a dramatic increase in PW for TUS during day tomorrow (below). The WRF-RR run at 12 UTC forecasts heavy thunderstorms moving into eastern Pima County by 5:30 pm MST tomorrow afternoon - bottom. Another watch and see situation.

Thursday, July 25, 2019

Last Week Of July

Buildups on Catalinas at about 2:30 m MST yesterday afternoon. 

There were storms yesterday afternoon and evening, but they mostly avoided the main metro area. The ALERT rainfall plot above is for 24-hours ending at 7:00 am this morning.Two sites near Marana had largest amounts, with just over half an inch. Shut out here as a large storm developed just off to the west. The airport had thunder with gusts to 51 mph and 0.18". Plot of detected CG flashes below (from Atmo and Vaisala) is for 24-hours ending at 1:30 am today.

At 500 mb this morning the anticyclone is centered along eastern border of Arizona, a bit to northeast of here, with generally light winds. Visible image below (for 6:30 am) shows the heaviest cloud band now extends from southern California into Utah.

The Mimic PW analysis above is for 7:00 am and shows abundant moisture across Arizona and southern California, extending northward across southern Nevada and Utah. Remnants of TS Dalila are spinning west of southern Baja. 

This morning's sounding analysis (below from SPC) continues to show over an inch and a half of PW and moderate CAPE. However, wind field continues to be disorganized, with no clear steering level winds.

The forecast of composite radar at bottom is from 06 UTC WRF-GFS and is valid at 5:00 pm. While there are some strong storms over eastern Pima County, the bulk of the activity is forecast to stay south-to-west of the metro area.

Wednesday, July 24, 2019

Tucson Donut Hole Yesterday

View north from Kitt Peak at 2:45 pm MST yesterday afternoon.

Plot of detected CG flashes (above, from Atmo and Vaisala) for 24-hours ending at 7:00 am this morning. There was a large donut hole over eastern Pima County, due mainly to the stabilizing impact of the Monday storms. Note the widespread, early morning activity across Maricopa County.

There is a wide band of clouds and storms ahead of a weak, inverted trough that is north-to-south across central Arizona. The IR image below is from 7:00 am.

This morning's TWC sounding (from SPC) is quite moist with about 1.75" of PW and moderate CAPE above 700 mb. Winds are easterly through the troposphere. The 500 mb analysis below (from SPC) shows the inverted trough to our west, as well a huge area of bad data around Flagstaff. Their sounding had very serious troubles and should never have been transmitted.

Forecast models for today range from another donut hole day to the lastest 12 UTC WRFRR, which forecasts some storms in eastern Pima County. It is a tough forecast because of the trough and early morning storm activity off to our west - a wait and see day.

Tuesday, July 23, 2019

Quick Summary 22 July

Composite radar images for 4:27 pm MST yesterday (above) and 6:45 am this morning (below). Heavy thunderstorms yesterday (much as forecast by WRF model runs at Atmo) produced local heavy rains and strong wind gusts. There were six reports of severe (greater than 50 kt) or wind damage in Pima and Santa Cruz Counties - including a gust to 66 mph at DM. Didn't see any tree damage during my morning walk.

Storms here occurred right around dusk with much thunder, lightning flashes, and light rains - estimate winds at 40 to 45 mph. 

Radar below indicates light showers in our area this early morning.

Map of detected CG flashes (above, from Atmo and Vaisala) is for 24-hours ending at  2:00 am this morning - an active day from the Rim south across our area.

Rainfall was widespread across ALERT network (below shows northern portions) - only 1 site did not measure 0.04". There were 7 sites with over an inch and 21 sites with a half inch or more.

The 12 UTC sounding plot for TWC (below) shows effects of convection yesterday below 700 mb. There is elevated CAPE from 700 to 600 mb, and this is probably feeding the morning showers. Wind profile is chopped up - strongest east winds near surface and in 400 to 200 mb layer. Layer of south winds reflect an MCS over Santa Cruz County.

The current WRF forecasts have not handled the morning convection accurately - only the 06 UTC WRF-NAM had morning showers but intensity was much too strong. Given the morning convection and convectively modified sounding, this afternoon remains to be seen. But activity usually much reduced after a round of strong storms the day before.

Monday, July 22, 2019

Looking Better - July 22

Storm over Baboquivari bit before 1:00 pm MST yesterday. Plot of detected CG flashes (from Atmo and Vaisala) below is for 12-hours ending at 3:00 am this morning. Storms over southeast Arizona stayed mostly locked to mountains yesterday. Note below that strong thunderstorms moved across the central CoG - which is good to help strong moisture push. There is heavy cloud cover this morning that is debris from activity to our south.

This morning's upper-air sounding plot (above for 12 UTC) indicates PW above 1.50 inches, with considerable afternoon CAPE. There's a bit of a cap around 600 mb, so outflows from the mountains will be needed to kick off low elevation storms. Decent vertical wind profile above 600 mb - all-in-all an interesting sounding to start the new week. The 12 UTC 500 mb analysis this morning (below, from SPC) shows the anticyclone centered near the Four Corners. Also appears to be a weak, inverted trough near the New Mexico bootheel.

Forecast of radar composite echoes from 06 UTC WRF-GFS (above valid at 5:00 pm this afternoon) indicates heavy storms crossing parts of Pima County. Wind forecast from same run indicate indicates very strong winds at 5:30 pm southwest of Tucson. Let's hope for some sunshine and heating by midday to initiate storm activity.

Friday, July 19, 2019

More Of Same - What A Dismal July So Far

Radar above from 5:41 pm MST yesterday - nice activity northeast of here, but it withered away before reaching Benson. Plot of CG flashes (from Atmo and Vaisala) for 12-hours ending at 05 UTC last night shows most activity just south of border and quite dead around Tucson. Certainly didn't call things very well yesterday, when I thought there'd be an uptick in storms for eastern Pima County.

Visible image from 6:30 am this morning (above) shows Sonora cloudiness extending well northward across western Arizona. The morning 500 mb analysis (from SPC below) shows that the center of anticyclone has shifted eastward into into Kansas and Oklahoma. Note the very warm temperatures from western California eastward across Iowa. 

The morning TWC sounding analysis (above, also from SPC) is similar to yesterday's with limited CAPE but increased PW. Wind profile continues to be chopped up. The GEFS plumes for Tucson QPF from 06 UTC (below) are also dismal. Note that the operational GFS continues to be an extreme outlier relative to other members. Only 12 days left in July - will this dry pattern break?