Saturday, August 31, 2019

Quick Update - 31 August

NOTE - missed a week due to bad fall last Sunday and being stuck in hospital until yesterday.

View above from 6:00 pm MST yesterday with thunderstorms northeast and northwest of the Catalinas.

Plot of detected CG flashes (from Atmo and Vaisala) for 24-hours ending at 1:30 am this morning - much of eastern Pima County again storm-free yesterday afternoon.

Visible image from 7:00 am this morning above shows large area of convective debris to our southwest from several nighttime MCSs in Sonora.

The 12 UTC TWC sounding (plot below from SPC) shows high PW, decent CAPE, but with nasty cap above old BL. Significant outflow needed again today to trigger storms away from mountains. Forecast at bottom from 12 UTC WRF-RRGFS is valid at 5:30 pm this afternoon. Model forecasts severe thunderstorms over metro and also to south (note earlier runs of WRF keep severe storms to south of metro). So another maybe day.

Sunday, August 25, 2019

Another Dry Day

We've been away the last two days, but on return there were a couple of dead bugs in rain gauge and no hint of moisture. Photo above is from 5:00 pm yesterday, showing how very suppressed the afternoon was. Down at bottom is Mt. Wrightson bit after sunrise yesterday morning with tiny cap cloud. Note how green it is out at Santa Rita Abbey (5 miles north-northwest of Sonoita).

Very little thunderstorm activity yesterday except along the Rim Country.  - plot above (from Atmo and Vaisala) shows detected CG flashes for 24-hours ending at 1:00 am this morning. 

Sounding plot for TWC (above from SPC) indicates substantial CAPE with 1.83" PW, but with two nasty inversions aloft. Winds continue somewhat chaotic, but storms that would form would move westward with anvils spreading to east. Forecast sounding for 2:00 pm today, below from 12 UTC WRF-NAM, continues to indicated large CAPE but also a very shallow, well-mixed BL reaching only to about 800 mb. Note that forecast sounding has dried some, with PW at 1.50". The WRF forecasts from last night and this morning indicate only limited storm activity again today, and that remains well south and southeast of the metro area. Appears to be a situation where upper-level subsidence is dominating BL heating and CAPE.

Friday, August 23, 2019

Storms And Bit Of Rain Yesterday

View of Catalinas from campus yesterday at 6:00 pm MST.

There were thunderstorms in the metro area late yesterday afternoon - lightning and thunder here around 9:00 pm. Most storms however stayed from west to south of metro - plot of detected CG flashes above for 24-hours ending at 1:00 am this early morning from Atmo and Vaisala.

ALERT network rain measurements for 24-hours ending at 8:00 am this morning are below - top is north portion of network and second below is south part. Rain reports came mostly from south and west portions of network. Here at house we had thunder but only a Trace of rain - same for airport and DM AFB. There were only three reports of more than half an inch, but site at Arivaca had 1.61".

At 500 mb the large anticyclone continues to dominate the Southwest. However, there appear to be several embedded circulations, including a weak, inverted trough from Big Bend country west and southward to south end of GoC. Temperatures have cooled to around -8C from New Mexico across our area and northwestern Mexico.

Morning upper-air plot for TWC (below) continues to show light and variable winds below 300 mb - so no distinct steering flow and storms this afternoon will be slow moving. CAPE is present, although amounts are not very large - PW bit less than 1.50".

The 12 UTC WRF-RR forecast of composite radar echoes from Atmo (bottom valid at 6pm this evening) does indicate heavy storms in parts of the metro area. 

Tuesday, August 20, 2019

Hot And Dry In Short-term

Golden fields near Ririe, Idaho, this morning with the hay baled (Ririe is a few miles northeast of Idaho Falls).

Another hot and very suppressed day yesterday. Every day for past seven has had high temperatures over 100 F. Pleasant very early in mornings because of the low RH. Plot above shows detected CG flashes for 12-hours ending at 2:00 am MST this morning (from Atmo and Vaisala). Activity over Mexico staying mostly south of 30 

Morning 500 mb analysis (below from SPC) captures the huge anticyclone dominating much of western 2/3rds of country. There are apparently several imbedded centers of anticyclonic circulation within the large-scale feature.

This morning's upper-air sounding plot for TWC (above from SPC) indicates PW less than inch and with old BL reaching to 600 mb - no CAPE likely until low-level moisture increases. However, the GEFS ensemble plumes (below from 00 UTC on 20th) indicate an abrupt  increase in PW during the day on the 22nd. This would bring back the missing CAPE. The model increases the PW in response to a tropical disturbance forecast to be moving toward the Pacific off of southern Baja. Much of the weather late in week and over weekend will depend to some degree on how this tropical system evolves.

Saturday, August 17, 2019

Showers And Thunder Parts Of Metro Area

Another colorful sunset yesterday.

There were some showers and thunderstorms over parts of metro late yesterday until around 11:00 pm MST - purple cluster (above CG flashes from Atmo and Vaisala) for 24-hours ending at 01:00 am this morning.

Rainfall amounts (below, ALERT reports for 24-hours ending 7:00 am this morning were limited mostly to northeastern part of the city - there was one other report - Arivaca 0.08". Nothing at TUS and DM, but 0.12" at Atmo and 0.07" here at house. Showers stayed mostly at low elevations.

Morning sounding for Tucson again shows deep westerly flow; PW a bit less than an inch; and no CAPE. WRF models from last night forecast limited shower activity this afternoon in Cochise County.

Friday, August 16, 2019

Dry And Hot Continues

Clear and dry skies again this morning.  Visible satellite image below from 7:00 am MST shows large portion of all the West is also clear this morning.

Morning forecast from NWS (above) remains very dismal. The morning sounding is quite dry with only 0.74" of PW and no CAPE. 

Below is ALERT rainfall for past 30 days ending at 7:00 am this morning. Plot shows the high variability of convective rainfall - over northern 2/3rds of network one site was less than half an inch while many sites in main metro had less than an inch. Highest 30 day amount was at the Whitetail gauge in the Catalinas with over 8 inches. Here at house we've had 2.23" during the past month - actually wetter than many sites in the northwest portion of ALERT network. One site in the City had over 4 inches. In the southern third of network (not shown) Elephant Head had over 4 inches.

No significant changes to large scale pattern in sight yet. Try to stay cool.

Monday, August 12, 2019

Hot And Dry Week Ahead

Few Cu on Catalinas above at 8:16 am MST. Visible satellite image below (for 7:30 am) shows mostly clear skies across the West. Morning forecast from NWS (bottom) is for hot and dry conditions through Thursday. Not much to look for during week ahead. Keep cool.

Sunday, August 11, 2019

Heavy Rains Again Yesterday

Heavy storms in Metro area around lunch hour yesterday. Bottom - view from Atmo at sunrise this morning.

Plot below shows detected CG flashes (from Atmo and Vaisala) for 24-hours through 11:00 pm MST last night. Considerable thunderstorm activity occurred across eastern half of Pima County and over Santa Cruz County.

Alert rainfall reports for 24-hours ending 6:00 am this morning (north portion top and south portion of the network below). There were numerous reports of over half an inch to over an inch (one report in Catalinas shows over three inches). Here at house we had 0.61"; Atmo had 0.53"; TUS had 0.91" and DM reported 0.86".

Today should bring much diminished thunderstorm activity for our area.

Saturday, August 10, 2019

Increased Chances For Storms Today

Stratus hanging to west side of Kitt Peak this morning - a bit unusual for summer.

Plot of detected CG flashes (above - from Atmo and Vaisala) for 24-hours ending at 5:00 am MST this morning. Most of Pima County was suppressed wrt thunderstorms yesterday. Alert rainfall reports (below) for 24-hours ending also at 5:00 am. The rainfall occurred with the early morning showers, while rest of day had only a few sprinkles.

The morning forecast for the airport (above, from NWS) indicates 70 percent chances for measurable rainfall today and tonight, along with a flash flood watch.

The 12 UTC 500 mb chart (below) shows a weak cyclonic circulation over northern Mexico, with strong southerly winds on east side of this feature. The anticyclone center is over central Texas, somewhere south of Dallas-Ft. Worth. Temperatures remain quite warm at 500 mb over the Southwest.

The morning sounding plot for TWC (above) continues to show very moist conditions, with some CAPE, and two old BLs below 700 mb.

Radar forecast below is from the 12 UTC WRF-RR and is valid at 2:30 pm this afternoon. Heavy thunderstorms forecast to be over eastern Pima County at that time - we'll watch to see how all this evolves.

Friday, August 09, 2019

Early Morning Rain

Rain over parts of Metro area this early morning. View from campus, above, was at just a bit after 7:00 am MST. Rain was heaviest here at house between 5:00 and 6:00 am. So far, amount in gauge is at 0.64" - making this far-and-away the wettest day of summer - more later today? Atmo has measured 0.77" so far.  No walk for me this am.

Morning sounding at TWC - above, from SPC - was released (~4:00 am) a bit before the rains moved in. CAPE calculation is of no value, and current sounding is probably near saturation through much pf troposphere. Composite radar below from 5:10 am when there was moderate rain here.

Thursday, August 08, 2019


View of Catalinas at 7:28 am MST this morning shows that we had dirty air trapped over Metro area at that time.

View before sunset (bottom, from 7:00 pm yesterday) captured towering Cu over the mountains, with a orphan anvil drifting overhead.

Map of detected CGs (above, for 24-hours ending at 12:30 am this morning - from Atmo and Vaisala) indicates just a bit of thunderstorm activity over southeastern Arizona yesterday, with nothing over the Metro area. Santa Cruz County was apparently storm free, which is unusual for this time of summer.

The morning sounding plot for TWC (below from SPC) is very similar to yesterday, with bit of CAPE and hostile westerly flow through most of troposphere. The early morning WRF forecasts are even more suppressed today in some runs, while 12 UTC WRF-RR tries to get a couple of isolated storms into Metro area. Basically looks like a a similar day to yesterday.