Another Round Of Seriously Hot Weather

After the record-breaking heat (three days with highs of 110 - 111 F) of the first weekend in June, it looks like a return of life-threatening heat for the the third weekend of the month.

The GFS ensemble 500 mb mean and spaghetti plot above is valid at 5:00 pm MST next Saturday, June 18th. Very little spaghetti on the plate and very strong anticyclone covering most of CONUS. The heights in the egg-shaped contour centered over New Mexico exceed 5940 m - will they reach 6000 m? Below, from the TUS NWS webpage, are charts showing record temperatures at the airport. Note in the right chart the records for June 4th and 6th last week.

It is interesting that all of the extreme records shown in the tables have occurred since 1988.

Meanwhile, this morning's outlook from NHC (above) indicates that there is medium probability that the first named tropical storm might develop in the east Pacific during the coming week. The 12 UTC blended PW analysis from CIRA at Colorado State University (below) shows high PW, subtropical air currently south of 20 degrees north, with dry air covering the Southwest. With the low humidity it was very pleasant early this morning here in north part of the City along the Rillito wash.

Brief Overview Of Friday And Saturday

We have been away to Santa Rita Abbey - left here about 5:30 pm Friday and returned late Saturday - so I'm not sure exactly what happened here at the house. There had been the slightest bit of a Trace of rain here before we left and on our return there was a definite Trace in the gauge - so not really a precipitation event right here. However, there had been a power surge, or brief power outage, so there was lightning nearby and we probably had a thunderstorm here.

Above is the 5:00 pm composite radar image from NWS TUS on Friday. The storm crossing I-10 just east of the airport location was a hail-producer. When we drove through this bit of interstate at about 6:00 pm MST there was hail drifted along the shoulders of the highway and the desert was white with melting hail - no idea how large it might have been. On Highway 83 there was a thunderstorm over the Empire Mountains and we drove through a brief period of heavy rain. 

The CG flash density plot below (from weather.graphics and Vaisala) is for the 48-hour period ending at 6:30 am MST this Sunday morning. There was definitely quite a bit of lightning and thunder over eastern Pima County - indeed more coverage by lightning than by measurable rainfall. For the 24-hour period ending 6:00 am on Saturday morning 36 ALERT sites (~40% areal coverage) measured 0.04" or more rainfall. There were 7 sites with more 1/2 an inch and 1 site in the Catalinas with more than 1 inch. Yesterday the activity was down quite a bit with only 19 sites having rainfall (~20% coverage) with the maximum amount reaching only 0.24" at two sites.

The WRF runs early Friday considerably over-forecast the coverage and intensity or the afternoon storms for Friday. However, I did notice that the ASOS site at Casa Grande had reduced visibility in blowing dust during a severe thunderstorm yesterday that produced gusts to 61 mph at the station The biggest day of the past three occurred with the very heavy storms in Cochise County and the Borderlands Thursday afternoon and night, and our unusual June event went downhill from there.

The bottom panel shows the GEFS average 500 mb forecast for next Saturday at 5:00 pm MST - quite a summer-time anticyclone for a very large part of the continental U.S. LOOKS HOT FOR LOTS OF FOLKS.

Heavy Storms Moving Into Metro Area

Heavy storms are moving northward into the Tucson metro area at 5:00 pm MST this evening - very surprising that there are no statements or advisories from NWS , other than blowing dust advisory issued this early am until 7:00 pm this evening. Very hopeful for rain in the gauge!

Big Storm Day Possible Today With Severe Winds

This morning's sounding from TWC (above) on campus is quite impressive with PW up to 1.46 inches and substantial CAPE, given some decent heating later this morning and early afternoon. Steering level winds for thunderstorms are from the northeast this morning but they will gradually be shifting toward the southeast, as a short-wave disturbance passes by to our west.

The circulation with this disturbance (located southwest of Nogales) is visible in the 8:00 am MST satellite image below. The cloud field is extensive and is perhaps the most significant wild card in today's various forecasts. There is currently more cloudiness off to our southeast than has been captured in the model forecasts - so the degree to which we get solar heating today will need to be monitored.

The WRF model from 06 UTC runs at Atmo forecasts solar IR to be intense by noon - both the WRF (above) and the GFS (below) variants of the model forecast over 1000 W/m2 of global horizontal irradiance at noon. The associated heating drives the active development of intense convection forecast by the models.

The details of storm coverage and intensity again vary between the two versions of the models, with the heaviest rains forecast  from most of Cochise County out west to central Pima County when the two forecasts are blended together. Shown here are are accumulated precipitation forecasts though 7: 00 am tomorrow morning (NAM above and GFS below). Suffice to say that a large area of southeast Arizona has the potential for strong to severe thunderstorms - quite something for June 10th.

Strong outflow winds are also different between the two WRF versions. Shown here are forecasts of 6:00 pm MST 10-m winds from the NAM (above) and GFS (below). However, both versions forecast very strong winds in the I-10 dust storm regions in Cochise County and also between Tucson and Phoenix. The GFS forecast would indicate a chance of an evening haboob impacting parts of the Phoenix metro area. Definitely a day for caution and also a threat for severe that SPC seems to have overlooked in their current outlooks.

WRF Forecasts Yesterday Very Good

The storm activity stayed mostly in Cochise and Santa Cruz Counties yesterday and last night - pretty much as forecast by the 06 UTC WRF high-resolution runs at Atmo. Above is IR image from 8:00 pm MST last evening, when heavy activity was over the Chiricahua Mountains. The CG flash density plot below (from weather.graphics and Vaisala) is for 24-hours ending 6:30 am this morning.

The 06 UTC GEFS plumes, and the NWS, were too optimistic re chances of measurable rain at TUS yesterday afternoon and last night, and I was way too optimistic about thunderstorms over our local Sky Islands. Very hard to improve on the models at times! Of course each variant was different and the best WRF forecast was a merged version of both the NAM and GFS forecasts.

As for rainfall amounts for 24 hours through 7:00 am MST this morning - the ALERT network had no rainfall recorded of 0.04" or more and the only rain report I could find in Pima County was 0.04" at the Sasbe RAWS site. The Borderland areas actually had two periods of rain and storms - one during late afternoon and evening and then another during the early morning hours. I grabbed a 24-rainfall map from MesoWest (University of Utah) but it's hard to read. Amounts of note: in Cochise County Headquarters at the Ciricahua NM had 1.53" and Rucker had 1.44", while Nogales Airport in Santa Cruz County had 0.74". I note that Mt. Hopkins RAWS (a notorously windy site when winds are from the east) reported a gust to 64 mph - this may have been a severe thunderstorm event but would require a careful look at the radar data vs timing of the strong gusts. 

Needless-to-say we continue our long run of rainless days here at the house. I did not mention it at the end of last month, but May 2016 was the first time since I started keeping weather notes in a logbook that I had NO entries for an entire month.

Look At WRF Forecasts For Today - June 9th

More things to consider today than I have time for this morning. Above graphic shows detected CG flashes for 12-hours ending at midnight last night (from Atmo and Vaisala). Most thunderstorm activity in Mexico was along and west of the Continental Divide, and the storms just south of Cochise County produced a weak outflow at Douglas. There were some thunderstorms in eastern Arizona.

This morning there is cool air at 500 mb over our region and PW values over an inch at TWC at 12 UTC. There is CAPE present this morning at low elevations, but the boundary layer (BL) has to mix out to above 600 mb and some lift is still required for BL air to reach its level of free convection. 

The main question for this afternoon and evening is whether thunderstorms will occur only over the higher elevations of Cochise and Santa Cruz Counties or will there will be some activity in eastern Pima County. The 06 UTC WRF forecasts at Atmo have fairly different outcomes.

The WRF-NAM forecast of composite radar echoes above is valid at 7:00 pm MST this evening and indicates very strong storms over parts of Cochise County but little further west. The forecast sounding from the NAM version shown below is valid at 5:00 pm for TWC. It is well-mixed to a bit above 700 mb, but would require lift to 500 mb for convection in low-levels. However, nearby mountain storms would seem possible. The steering winds are quite nice and from the east-northeast, so storms on the Catalinas and Galiuro Mountains would try to head our way. The BL mixing ratio is at about 7.5 g/kg which is high unless there is advection of more moist air into eastern Pima County.

The GFS version of the model forecasts much less activity in Cochise County and more activity in pasrt of Santa Cruz and Pima county - composite radar echoes forecast above is valid at 5:00 pm this afternoon. The PW forecast below indicates higher moisture from Sonora and also a moist outflow moving northward into the metro area - certainly more interesting forecast for Tucson than that of the NAM version. The forecast TWC sounding at bottom, however, shows that the GFS version has produced a BL mixing ratio of almost 10 g/kg - which appears very unlikely. So, watch for where the towers develop later today. I do feel that there will be more activity on the Pima County Sky Islands than either model forecasted from the 06 UTC runs. Thunderstorm bases will be very high due to depth of BL, and thus strong outflow winds and blowing dust are the main threat from today's storms.

Both versions of the model forecast a more active day for Pima County tomorrow - but when storms and outflows begin roaming around, it is often prudent to go day-by-day because of mesoscale impacts influencing the next day's forecast.

Shallow Cb Over Catalina

It did dry out as per WRF forecasts today, but there was one buildup over the Catalinas around 2:00 pm MST. Above is visible satellite image and below is photo Katie took from campus about the same time. A nice buildup, often referred to by storm chasers as a "turkey tower" because of its skinny neck and head above, with a bit of snow falling out of it. There was a more classic Cb at dusk off to the east but I wasn't able to get a decent photo. Hopefully more tomorrow.

Pocket Of High PW Air Moves In

Had a bit of a delay getting this posted this morning.

Higher Td air moved into southern Arizona last evening between 7:00 pm MST and midnight on southwest to west winds from northwestern Sonora. The dewpoint began rising here at Tucson by 10:00 PM with surface winds from the west. This morning around 7:30 am the humidity was high, with visibility way down due to haze (above), and surface dewpoints (below) were around 55 F - quite some change. 

Shown here is a quick look at the PW situation from the 06 UTC WRF-NAM - above is the initial analysis at 11:00 pm MST last evening with the higher PW covering much of Pima County. However the forecast valid at 11:00 am (just below) indicates the high PW blob moving into Maricopa County with considerable dry advection having occurred over Pima and Santa Cruz Counties. At the bottom is the dry forecast for 6:00 pm this evening. 

The WRF forecasts from 06 UTC last evening don't forecast thunderstorms for Pima County until Friday afternoon. So, just hazy skies and a bit cooler temperatures for today.

Moisture Later This Week As Per WRF-GFS

There was deep convection last evening along the highest terrain of the Sierra Madre Occidental in Mexico - IR image above from NCAR is at 03 UTC. The 06 UTC WRF-GFS analysis of PW below indicates that much of moisture feeding these storms was from the GoC. However, recycled moisture around 700 mb from the east was also supporting storm development over the mountains.

The WRF-GFS forecast for 6:00 am MST on Friday (above, on the 5.4 km grid) indicates the main push of low-level moisture for possible storms later in week will come northward up the GoC. However, the 700 mb RH forecast valid at same time (below) indicates widespread, vertical recycling of moisture. A very interesting situation evolving for  early to mid June., as shown by the WRF-GFS forecast of accumulated rainfall through 11:00 am on Friday.

Interesting Situation Developing for Early June

The GEFS plumes from 06 UTC this morning are indicating a chance for showers next Thursday into Friday. The QPF plumes above are for the airport (TUS). While amounts are light, any rainfall during the first couple of weeks in June is unusual.

The plumes for the dewpoint at TUS are shown above and indicate considerable increases in low-level moisture beginning tomorrow and peaking on Friday, with ensemble average Td going a bit above 50 F. Most of the ensemble members also forecast increasing CAPE (below) but with a large range among the various members. Currently, the operational member (blue) is one of the wetter versions of the model.

The operational GFS forecasts from 06 UTC illustrate what is leading to this unusual forecast. The forecast above is for 500 mb valid at 12 UTC on Friday morning the 10th. The trough along the west coast is interacting with the west end of a strong anticyclone over the Southeast. The 850 mb forecast (below) valid at the same time indicates moisture intruding into Arizona from the southern GoC, with values reaching over an inch. The forecast for accumulated rainfall through next Saturday morning is shown at the bottom.

Given the calendar, this would be quite some event if it all came together as per current GFS forecasts.

Hot, Smokey Skies

We have been away, up in Winslow, for several days, but it was flirting with 100 F even up there. High yesterday here in Tucson was 111 F and it was a brutal day to return from the higher elevations. Skies were smokey during our trip due to a number of active wildfires. Views here are to the north from Kitt Peak last evening (above) and also to the north this morning from campus (below). Definitely a red sky in the morning today, as the sun rose behind higher-level smoke that has been moving southward from fires in the Rim Country. Larger, active wildfire locations this morning (for Arizona and New Mexico) are shown on map that is second below. The 700 mb analysis (from NCAR) for 12 UTC this morning (bottom graphic) shows the very hot temperatures over the Great Basin and Southwest, with many upper-air observations of 15 C and higher - another day of serious heat threat for most living things here.

WRF Forecasts Quite Good Yesterday

The WRF forecasts yesterday were pretty good, keeping shower activity off to our east. The CG flash density (above from weather.graphics and Vaisala) for past 24-hours ending at 6:30 am this morning indicates no activity over southeast Arizona, with thunderstorms confined to the White Mountains.

Caution advised next few days as life-threatening heat may bring temperatures over 110 F.

Heavy Clouds And Warm Temps This AM

There were heavy clouds over much of the metro area this morning, with virga and perhaps some sprinkles off toward the Rincons. View of the Catalinas above was at 6:00 am MST, while the visible satellite image below was from 7:00 am. Heavy clouds kept temperatures very warm during the night - low temperature at TUS this morning was only 73 F versus 60 F yesterday morning.

It looks like temperatures at middle-levels are about as cool as they'll get (-14 C at 500 mb) and that warm advection will be setting in above 700 mb during the day. The 06 UTC forecasts from the WRF-NAM at Atmo seem to reflect this, with afternoon convection shifted to our east and northeast. The composite radar forecast below is valid at 5:00 pm MST this afternoon. The WRF-NAM has been a bit conservative this Spring and there may be a very slight chance for showers around our nearby Sky Islands. 

After today it looks like serious summer for a few days.