Wednesday, August 16, 2017

Harris Hawks Hunting This AM

There was a pair of Harris Hawks hunting through the Natural Resources Park by the Rillito this morning. First time I have seen these two - they were encroaching on the territory of two Red Tails that nest in large gum tree by the Rillito pathway. Four photos of pair shown below.





Tuesday, August 15, 2017

Dry Westerlies Aloft Rest Of Week

Looks like a down week here in Tucson metro area and I'll return when the weather does.


 Another nice sunrise along the Rillito this morning - above and bottom.


Most of metro area remained dry yesterday, with the exception being some storms before midnight on the Catalinas. Plot of detected CG flashes for 24-hours ending at midnight shown above (from Atmo and Vaisala), and ALERT network rainfall for 24-hours ending at 7:00 am today is below.



The GFES forecast plumes for PW from the 06 UTC run indicate the dry-out period continuing until the weekend, when moisture returns in the model forecasts. 


Monday, August 14, 2017

Last Chance For Storms Before Dry-Out


View north yesterday at  4:00 pm MST showing the clear skies that prevailed over metro area yesterday, after the early morning rains. ALERT rainfall for 24-hours ending at 7:00 am this morning shows that only the far south parts of the network had storms and rain yesterday - much as the 15 UTC WRF-RRX forecast. There was little mixed layer CAPE over the region where the heavy rains occurred, and storms that tried to move toward the metro area from the west rapidly dissipated.



This morning (as per TWC sounding plot above) moisture remains high below 600 mb, while very dry air has moved over the state above 500 mb. Strong westerly winds in upper-half of troposphere are present, above very light westerlies below. Some CAPE remains and models forecast storms late in afternoon over eastern Pima County.


Above graphic is the composite radar forecast from the 00 UTC WRF-GFS run valid at 6:00 pm this evening (the WRF forecasts from 00 and 06 UTC are all consistent, forecasting the eastern Pima County storms). However, a slight shift toward the east would leave the metro high and dry again.

Forecast below is from same run and shows PW valid 6:00 pm. Dry air is intruding strongly at that time with a gradient of about an inch from Tucson to Yuma. The next few days will bring a dry-out as low PW air from the west prevails.


Sunday, August 13, 2017

Storm Southwest Of Salton Sea


Jim Means (Alpine, California) sent this photo of a large thunderstorm that occurred yesterday afternoon over the Anza-Borregago State Park - which is just east of the coast range and southwest of the Salton Sea.

Images below show the storm as seen by the Yuma NWS radar and the CG flash density with the storm - both very impressive.



Heavy Storms AM 13 August


View of the Catalinas at about 7:00 am MST this morning, showing stratus fractus hanging very low along the foothills, after heavy, early morning storms. We were at Santa Rita Abbey yesterday and afternoon storms between there and Tucson were quite isolated and small - we did drive through a very brief, heavy shower on Highway 83 a bit southwest of TUS Doppler radar - the exception to all this was far off to the east in Cochise County, where there heavier and somewhat organized storms..


During the early morning hours (from about 1:30 to 4:00 am) heavy storms developed over the city as several outflows collided. Rain amounts were over an inch at many ALERT sites during the 6-hours ending at 6:00 am (above) and two sites on east side had two to three inches. Here at house there was 1.16" in gauge this morning - this is fourth event of summer to produce over an inch here. 

The plot of detected CG flashes (below, from Atmo and Vaisala) shows 24 hour period ending at 4:00 am this morning.

Note that observation plot on NWS webpage has been seriously messed up for couple of weeks now - apparently due to some communication problem between TUS ASOS and MesoWest, which produces the actual plots. Don't know rainfall at TUS, but DM had 2.04" and Atmo had about 0.67".



Tropical Storm Jova apparently helped push high PW into state yesterday - with high values extending well into Arizona at 12 UTC this morning (MIMIC TPW above) However the 500 mb pattern is quite hostile (below for 12 UTC from NCAR), with westerly flow prevailing. The transition into the westerlies will dry us out and result in another down-period that may last for a week or so. Strange month so far with only one significant storm event here at house.



Two photos from Santa Rita Abbey at sunrise yesterday. Above shows Cbs off to the northeast along or near the San Pedro River; and below shows stratus hanging along top of southern portion of Santa Ritas - reason unknown since Friday afternoon was quite suppressed with storms far away to east and way down in Mexico.


Friday, August 11, 2017

Brief Look At Yesterday's Storms

Our internet connection has been down this morning until about half an hour ago. So little time to do much this morning.

Can't seem to add images - things are in disarray here.

Thunderstorm here around 4:30 pm yesterday - winds gusting from south-southeast at E60 mph. Quite a bit of damage around the city. Looked like core was going to hit here but it made a left turn - total rainfall for entire day ended up at only 0.20".

Today, PW remains high, but the upper-level IT, with dry air, is moving directly overhead. The core of this IT was devoid of storms in Mexico yesterday, and the 06 UTC WRF-GFS gets some storms going late afternoon only over the Catalinas. Looks like it will be a considerably down day wrt yesterday.

Will await Mike's discussion later this morning.


Thursday, August 10, 2017

Sonoran MCS Last Night

Mike Hardiman has sent an amazing GOES-16 IR loop of last night's huge and very cold MCS it is at:


https://media.giphy.com/media/3oEhmSsNzkG6PAeu6A/giphy.gif

Early AM Thunderstorms


Much more interesting than I expected yesterday, especially during the night last night. Top shows afternoon storms over Redington Pass area - these tried to move into the metro area but mostly fizzled. However, a band of thunderstorms with light showers moved northwestward across portions of metro between 3:00 and 5:00 am MST this morning. Received 0.10" here at house. Trailing clouds at sunrise produced a slight, morning rainbow - below.



Detected CG flashes above are for 24-hours ending at 6:30 am, from Atmo and Vaisala - yellows to pink to white show the morning storms. Below is rainfall across northern 2/3rds of ALERT network ending at 8:00 am.



There was a game-changing, huge MCS over Sonora last night - above IR image is from 0630 UTC. This system moved over northern half of GoC, producing moisture surges into Arizona. Current dewpoint at Yuma is 78 F and Doppler VAD winds below show strong, southerly winds up to 5,000 ft MSL or so.



The 12 UTC 500 mb analysis (above from NCAR)  shows the anticyclone has shifted eastward and is now centered along New Mexico - Texas border, resulting in stronger winds here from the southeast. The 12 UTC sounding plot for TWC (below) shows a typical onion sounding produced by the morning showers. This leads to question of what will conditions be like this afternoon? The wind profile is quite favorable for organized storms; however, the boundary layer will have to re-develop because of the rain-cooled low-levels. This will probably result in a sounding with CAPE but with outflows need to develop storms at low elevations. The visible image at bottom from 7:30 am seems to indicate the clouds are already thinning to our east, leaving hope for considerable heating and recovery.

Bottom line - very tough forecast situation that could be helped some by a special 18 UTC sounding for TWC.






Wednesday, August 09, 2017

Another Day Under The Anticyclone

We have been away attending to family matters in the Midwest since early Friday morning, and on our return I found an absolutely dry rain gauge. So we were away during a dismal break in thunderstorm activity and return to find a setting that may begin to improve a bit over next several days.


Pleasant and dry this morning (especially compared to last several days of high humidity in Midwest) at sunrise with a few middle clouds drifting around (above).

Plot below shows CG flash density over western U.S. for the 24-hours ending at 6:30 am MST this morning (from weather.graphics and Vaisala). Thunderstorms were confined to mountainous areas well north and east Arizona.



The morning skewT plot of TWC data (above - for 12 UTC from SPC) shows an unorganized pattern in both winds and thermal structures.  There are two layers of light and variable winds (surface to 700 mb and aloft from below 500 to about 400 mb) with southwest winds between and above. If thunderstorms develop the dominate steering might be from the southwest or indeterminant. Yesterday's old BL extends to almost 500 mb and troposphere is split into two halves by the nasty temperature inversion just below 500 mb. The moisture was well-mixed only to 700 mb. All-in-all quite a mess. The 500 mb anticyclone is a bit off to east or northeast and exhibits very warm temperatures in middle levels.

The 6 UTC WRF-GFS forecast sounding for TWC is shown below for same time as the observed above. Although PW is quite near the observed value of a bit over an inch, there are considerable differences in the thermal and wind structures below 600 mb - especially with the stronger and more organized east flow above surface. This is an important difference, since PW is higher toward El Paso - will stronger east winds develop this morning? The capping inversion near 500 mb is very much under-done in the model forecast, and this will be a formidable cap, especially for low-elevation convection.



The WRF-GFS forecast for TWC valid at 4:00 pm this afternoon (above) indicates light westerly winds in the BL, but with increased moisture in well-mixed layer. There is CAPE in the forecast, but the warm middle-levels may again be under-done. The forecast sounding, valid at same time, for Sonoita (below) indicates much more favorable conditions nearby, but at elevations of about 5,000 ft MSL.

Bottom line to all this is that there may be storms on the mountains from north to east to south of metro area. These would be producing mostly light to moderate rains and gusty winds and would have difficulty moving off the mountains. 

Increasing low-level moisture from GoC in a day or two may improve the convective situation considerably.




Thursday, August 03, 2017

Anvils Yesterday - Today Another Tough One


Virga at sunrise today - view is looking due south from Tucson at Prince (north side of city).


Yesterday was another down day for the metro area, as storms to south covered city with anvils by noon. A few spits of rain here early afternoon from thick anvil and that was it. Detected CG flashes above (from Atmo and Vaisala) and ALERT precipitation below - both 24-hours through 7:00 am MST this morning. Heaviest storms were to south and west of the city. Most intense thunderstorms were again along the lower Colorado Basin, with severe reports from Yuma to Las Vegas yesterday afternoon.



The large trough over eastern U.S. has continued to cause some shifts in the pattern over the West. The 200 mb anticyclone has shifted southward to northern Mexico - which is good. But the 500mb anticyclone remains an ambiguous mess. The height field is very flat, but winds indicate the anticyclone center remains over the Great Basin.



The morning sounding data at TWC remain very moist (PW = 1.84" - as per sounding plot above from SPC). But very light winds continue below 300 mb. Potential CAPE with heating is substantial and storms should be active again on mountains. The positive aspect of the sounding has resulted from the southward shift of the upper-level anticyclone - this has resulted in winds aloft that will push anvils back toward east-northeast. This leaves better chance for some developments at low elevations due to outflows.

The morning sounding at El Paso shows PW of only 0.93" (about half that at Tucson) and east winds in the drier air below 500 mb - so key question today will be how far into Arizona the dry air advances. The visible image (below from 7:00 am) seems to indicate that the moist air extends at least to New Mexico border. At upper-levels (above 300 mb) dry air is moving across state from the southwest - a situation of double jeopardy.

Last night's WRF-GFS forecasts indicate a very significant dry-out covers the state by the 5th. As for today, chances look improved for some storms to move into lower elevations, unless the dry air pushes in from east more quickly than WRF forecasts indicated last night. Will be watching for the 12 UTC WRF forecasts and Mike's discussion.




Wednesday, August 02, 2017

Roger Edwards - On The Road


Roger Edwards, of the Storm Prediction Center (SPC), is on a summer storm expedition out here in the Southwest. This unusual situation resulted from staff shortages in Norman, which caused him to defer his usual chase time in May until August. Now he is motoring around under the anticyclone.

Above is a photo from Monday in eastern New Mexico beneath an arcus cloud. He referred to this, in chaser jargon, as a whale's mouth arcus." 

I think he's somewhere in Arizona today; however, I doubt that August chases to the Southwest will become a habit for him. Good hunting Roger!

More On July Rainfall

Russ Scott reports on rain at the flux sites near Tombstone:


Photo of the greenness at the Kendall site. July rainfall for the sites. Kendall and Lucky Hills set monthly records (these two sites have data going back into the 1960s). The SRG site had rainfall approaching 13 inches.


Mike Luethold provided the July rainfall measured at Atmo, as per:


I get a total of 181 mm or 7.13 inches. Mike does not know whether this is a record or not. Data tracking there seems to have mostly been low priority since Cyrus Jones retired. Mike also does not know if the Atmo site is still an NWS Cooperative observation station.

Finally Sister Pam sent a plot of July rainfall measurements at Santa Rita Abbey, as per: