Sunday, September 15, 2019

Damp Sunday Morning

Showers around the metro area this morning since around 3:00 am MST. View from Wyant's webcam above was at 6:53 am. Composite radar below was at 7:05 am.

Plot of detected CG flashes (from Atmo and Vaisala) for 24-hours ending at 6:00 am this morning indicates no thunderstorms at all over southeastern quarter of state. No thunder with the morning showers - ALERT map below shows rainfall of 0.04" and greater during past 6-hours. Here at house we have had only about 0.02" but appears airport has had over half an inch.There were 6 reports of more than half an inch and two reports of over an inch - significant amounts considering there no reports of thunderstorms.

The 12 UTC 500 mb analysis (above from SPC) shows the cutoff low located about halfway between Phoenix and Albuquerque. The TWC morning sounding is below (also from SPC). Quite moist with some CAPE but with nasty inversion near 500 mb and light and variable winds in the saturated layer.

Probably a good day to take an 18 UTC special sounding to see what it's like, if the showers drift away to the northeast!

Saturday, September 14, 2019

Complicated Situation Today

Above is a morning outlook statement from NWS - this is interesting since it is somewhat out-of-phase with the 06 UTC WRF-GFS forecasts (more re this below). Thunderstorms and rainfall remained mostly east of Tucson yesterday afternoon (plot of CG flashes from Atmo and Vaisala - below for 24-hours ending at midnight last night). Not much in way of rainfall amounts - three ALERT sites had rain reports of up to 0.08" in mountains; St. David had 0.42" off to east, and Nogales had 0.50" down to our south.

Visible satellite image above shows the heavy cloud cover present this morning at 7:00 am MST over much of Arizona and southwestern New Mexico. The cloud cover is associated with a weak cyclone at 500 mb (12 UTC 500 mb chart below from SPC) centered somewhere south of New Mexico bootheel.

This morning's TWC upper-air plot (above, also from SPC) shows PW of 1.24" and nice easterly steering winds, but almost no CAPE. The 06 UTC WRF-GFS forecast (all forecasts shown here are from this run) of TWC sounding for 3:30 pm this afternoon has little CAPE with two capping inversions above the well-mixed BL, as well as weakened winds around 500 mb. The 500 mb forecast (valid at 4:00 pm - second below) shows the 500 mb low centered just to our east, but with warming 500 mb temperatures.

WRF-GFS forecast of rainfall through midnight tonight (above) has huge donut hole over our area. Forecast of 10-m winds (below for 5:00 pm this afternoon) shows severe winds with storms over northeastern  Maricopa County, as well east winds around 20 kts our area.

I would like to see some rain this afternoon, but forecasts are uncertain and quite a mixed-bag!

Friday, September 13, 2019

Friday The 13th

I had the figures here ready to go at 7:00 am MST, but continuing internet troubles here have delayed me. View above from Jim Wyant's webcam at 6:30 am.

The early morning forecast from NWS (above) indicates a chance of thunderstorms every day from now through next Tuesday.

There was a large MCS last night (IR image above from 11:00 PM last evening) just east of the central GoC - and an even larger one north of Cabo Corrientes.

At 500 mb this morning a weak IT persists northern Mexico/New Mexico bootheel. This feature still forecast to become weak cutoff low and move northward.

The morning sounding from TWC (above) is very stable with PW of only 0.83" and no CAPE. The seven day time-series of PW on campus (below) shows PW decreasing steadily during past five days.

However, the 06 UTC WRF-GFS forecast above (TWC sounding valid at 2:00 PM this afternoon) indicates very substantial changes by afternoon - PW is 1.42" in the sounding, and CAPE is around 1,000 J/Kg. The switch to easterly winds below 600 mb apparently brings the increased moisture in from the east. This leads to a forecast (below from same WRF run) of considerable thunderstorm activity over eastern Pima County by 3:00 pm this afternoon. Will watch to see what happens.

Thursday, September 12, 2019

Arizona Storm-Free Yesterday

Kitt Peak north (above) just before sunrise today. Bottom is pre-dawn view of Kingman, Arizona. The low temperature here this morning was a pleasantly cool 67 F.

Yesterday was storm-free across Arizona, except for one morning storm in White Mountains (detected CG flashes above, from Atmo and Vaisala for 24-hours ending 12 UTC this morning). 

The TWC morning sounding (above from SPC) has PW of about one inch and no CAPE. Winds are light and variable below 300 mb. 

The 500 mb analysis this morning (from SPC with troughs added in blue) is quite a mess with major trough moving into Plains and several shortwaves/inverted troughs from northern Mexico east to Florida.

At 500mb the forecast above (06 UTC WRF-GFS from Atmo) valid at 8:00 pm MST tomorrow shows a weak, cutoff low over Cochise County. This feature develops over northeast Sonora and moves slowly northward. The PW increases from east tomorrow and brings increasing chances for thunderstorms southeast Arizona late tomorrow through the weekend.

Wednesday, September 11, 2019

Quick Look - AM 11 September

South view from Kitt Peak (above) shows some lingering low clouds this morning.

Plot of detected CG flashes (above from Atmo and Vaisala) is for 24-hours ending at midnight last night. Much of Arizona was totally suppressed yesterday. The II satellite image below is from 5:30 am MST this morning - shows some low clouds lingering over parts of eastern Arizona.

The MIMIC TPW analysis above (for 12 UTC today) indicates deeper moisture retreating southward, with a bit of values around an inch or bit more still holding across southern third of Arizona.

The 12 UTC 500 mb chart (above from SPC) shows the western 500 mb trough has pushed the anticyclone far south and east, with circulation centers over the Southeast and central west coast of Mexico. The morning TWC upper-air sounding (also from SPC - below) continues with moist low-levels but the potential CAPE is a bit deceiving, since the warm air aloft from 600 to 500 mb is apparently keeping a cap on deep convection (note above the -4 and -5 C temps affecting us in southern Arizona).

The 06 UTC run of the WRF-GFS forecasts (at bottom) of radar echoes at 5:30 pm this afternoon indicate another day devoid of thunderstorms, with perhaps some popcorn sprinkles around eastern Pima County.

Things have certainly gone downhill since Sunday morning here!

Tuesday, September 10, 2019

Very Suppressed Locally Yesterday

Heavy clouds again this morning. Catalinas above from campus. Visible satellite image below (for 6:45 am MST this morning) shows the cloud cover affecting much of Arizona. Second below shows Kitt Peak in the clouds this morning.

This morning's 12 UTC sounding from TWC (above) shows sounding very similar to yesterday's with moisture hanging on and considerable CAPE; main difference is the low-level southerly winds this morning. The only early morning storms occurred up in Rim Country, with no nocturnal MCS. 

Plot of CG flashes (below, for 24-hours ending at midnight last night, from Atmo and Vaisala) shows Pima County almost totally suppressed yesterday, with most thunderstorm activity over in Cochise County.

The 500 mb pattern (12 UTC above) continues to be dominated by the western trough. Not a summer monsoon pattern at all - the summer pattern seems to have ended on September 8th. The GEFS mean 500 mb forecast chart for midnight on the 17th (below) shows that westerlies continue to prevail over Arizona and northern Mexico. 

Looks like we now have to hope for some transition storms, as westerlies interact with residual moisture from GoC.

Monday, September 09, 2019

Sunday Night And Today

Heavy clouds hanging on the Catalinas this morning - above. At bottom is stratus flowing over Kitt Peak. Added Note - see some of david Blanchards summer photographs at his blog site; link to right.

ALERT 24-hour rainfall ending at 6:45 am MST this morning. Except for rains over and northwest of Catalinas, amounts reflect the morning showers at low elevations. Note the 2.91 inches report from Mt. Lemmon; however the nearby RAWS site reported less than half an inch.

During night storm developed over Catalinas and Art Rangno and Bill Cotton reported thunder and rain around Catalina before midnight. Cotton's rainfall trace (above) shows about 0.35" during the night. Plot of CG flashes (below - from Atmo and Vaisala) is for 24-hours ending about 30 minutes after midnight. Purples and whites indicate flashes a couple of hours earlier and cover the Catalinas.

This morning's 500 mb chart (above from SPC) shows the two troughs dominating the West - situation over Mexico and Texas appears chaotic and ill-defined. The MIMIC TPW (below, appears to show very dry air south and west of here.

The 12 UTC morning sounding from TWC indicates 1.34" of PW, mostly in low-levels - which are quite unstable Don't know if sounding will stay this good for thunderstorms, but steering winds remain poor, since there is little orography to force storm development to our west. Best way to monitor storm potential is to watch TWC PW time-series at Atmo page.

Morning WRF forecasts indicate scattered thunderstorms over our area during late afternoon. The forecast soundings, if they verify, indicate potential for nighttime MCS. Another interesting weather-watch day.