20160716

Initializations
There was an issue with the IPW correction routine for the 0Z, 6Z, and 12Z WRFRR runs and the problem has been fix for later runs.   Unfortunately, there has been a large initialization wet bias in NW Mexico recently so those runs are likely to have too much moisture.  I manually reran the WRFRR 12Z routine and it was way too wet in NW Mexico.  My guess is the uncorrected model runs, (including the NWS) are too wet.

12z RR

The 12Z NAM was also pretty bad as there was a 8mm wet bias centered on Hermosillo.  The 12Z GFS was significantly better with mainly small errors.

The morning 500mb map indicates that the high center is just to the east of Tucson and is taking it's sweet time moving into NM.  Of interest are the continued cool air with temperatures from -7 to -9C over the SW US.  Morning satellite imagery shows a weak cyclonic circulation  (MCV probably) moving out over the Gulf of California from central Sonora.  To their credit, both the RR and NAM have a weak mid level circulation in the area.

Mainly thin clouds are present over southern Arizona with somewhat thicker clouds in NW Mexico. Initializations were fine.  Overall, if it wasn't for the IPW problem in NM Mexico, all initializations would be very good.  The GFS is the best today and the NAM is OK.  The WRFRR without correction applied will probably have too much activity.

Day 1, July 16
The outflow surge did materialize and IPW is up into the low 30mm range across southern Arizona. Southerly flow continues to advect moisture into southern Arizona during the day.  Looking at the 15Z forecasts, the WRFGFS is very close to observed while the WRFNAM is somewhat too wet over SW AZ and the WRFRR is way too wet there. (due to the poor initialization in Mexico)  It is certainly nice to have all the GPSMET IPW sites working and this goes to show you the importance of the Suominet network IPW data for both model initializations, model evaluation,   Suominet will have no funding to continue past December and the NWS will be processing their own data to calculate IPW and not making it available outside of the NWS.  Weak southerly flow continues to advect moderate amounts of  moisture into Arizona by afternoon.

The outflow surge is fairly shallow as seen by the drier air out to the west, but higher 850mb Td air is present across central into southeastern Arizona.   Note the classic surge pattern of low level southerly flow up the gulf and how it curls around and flows upslope into SE Arizona.  A good set up for propagating storms (if there is some easterly mid level flow) as outflows moving to the NW will set up low level convergence.

As Bob Maddox mentioned, there isn't any mid level steering this morning and that continues into the afternoon as seen below thus large scale propagation is unlikely today and storms are likely to stick to the higher terrain.  Also, the PBL is not mixed very deeply and CAPE is only moderate at best thus it looks unlikely for any deep convection in the Tucson area.

Not until late afternoon do the  WRFNAM and WRFGFS develop storms over the higher terrain of far southern Arizona and mainly stay there throughout the evening.

Scattered activity continues across far SE Arizona into the evening hours.

Day 2, July 17
Due to the overnight activity, it's likely that widespread debris clouds will be present during the morning hours which could throw a monkey wrench into the works.  Both model runs dissipate clouds by late morning.

The thinking yesterday was that the tropical system (now Estelle) may just get close enough to get a weak surge going along the length of the Gulf of California and that continues to be the case.

In spite of continued moisture increase, CAPE isn't all that impressive as the PBL cools and mid levels warm, but enough to support deep convection over the higher terrain of eastern 1/3 of the state.

Typically, a strong surge can cause cooling in the PBL.  In spite of this one not being very strong, temperatures are only in the upper 90's at Tucson by late afternoon (morning clouds too?).  Another negative is the warming seen in the mid layers.  Lastly, mid level winds continue to be light and variable.  Thus what was looking like a quite active day for Tucson looks much less so.

The two runs are similar over the White Mountains and Rim as they both have widespread activity there during the afternoon.  Both also develop storms over SE Arizona during the late afternoon. The WRFGFS (below) has some storm development over the higher terrain of central Pima county.

By early evening, the WRFGFS moves the dissipating storms into southern Maricopa county which sends an outflow into the Phoenix area.  Also note the activity north of Phoenix.  Strong convection continues across SE Arizona with the possibility of some activity near/in the Tucson area.

There is a chance of outflow convergence over the Phoenix area during the evening and looking at the WRFGFS Skew-t, the PBL is mixed fairly deeply and some CAPE is present.  With the right combination of events, deep convection could form in and around Phoenix during the evening.

As only a single model run is forecasting this, plus the low probability of timing and locations working out, I'd not say this is very likely.  Wait and see.

20170715

Good news on the Suominet GPSMET IPW front, for once.  AZTP, Tempe is now operational and finally fills in a major gap in the coverage in south central Arizona.

The break in the monsoon continues across the state except for occasional activity along the border as the mid level high meanders around southern Arizona into Texas and keeps the monsoon moisture south.  Plenty of moisture in Mexico, as seen in the above IPW plot.  The strong (for this time of year) 500mb flow continues across the northern 1/2 of the county, causing the ridge suppression.   Additionally, the strength and position of the high is not allowing any of the many tropical systems to move close enough to the southern Gulf of California to initiate a gulf surge.

Day 2 (2016-07-16)

Over the next few days, the various model runs are now moving the high center slowly to the northeast thus allowing mid level winds to shift to southeasterly and the higher moisture in NW Mexico to advect into the southern 1/2 of Arizona.  Note the cool 500mb temperatures of around -9C over Arizona.

Overnight, what appears to be an outflow surge from thunderstorms in NW Mexico moves into southern Arizona.  The WRFGFS and WRFNAM are quite different with the amount of IPW present with the WRFGFS much wetter in SW Arizona.  I'll go with the more conservative WRFNAM.

Of course, this has a big impact on the max CAPE forecast and again, I am conservative and lean towards the WRFNAM.  Perhaps reality will be somewhere in the middle?  In any case, enough CAPE is present in the WRFNAM to support storms over much of SE Arizona tomorrow.

12Z WRFNAM

In spite of the moisture differences, the two models are very similar in developing deep convection over the higher terrain of SE Arizona during the late afternoon and early evening.

Later in the evening, the WRFGFS continues with a few storms perhaps even into Pinal county.

12Z WRFGFS

As inverted V profiles are large with the mixed layer above 700mb, there are likely to be very strong winds associated with storms and the possibility of large scale outflows and associated dust storm/haboob events.

Thunderstorms are likely to be around Tucson with possibly a few within the city.  What appears likely is a big outflow into town during the evening.

Day 3 (2016-07-17)

The tropical system, currently classified as TD Six-E, does come a little farther to the north than previous systems an may be close enough to increase the moisture over the southern Gulf of California and trigger a weak surge up the Gulf.  Moisture does increase substantially across the state by Sunday due to a combination of the gulf surge and outflow surges from previous storms.

Max CAPE forecast isn't all that great with only 500-1000 J/Kg.  Still, enough to support some deep convection.

What does look good is the wind profile as there is good low level westerly flow, that is relatively moist, plus good mid level SE steering flow and only weak SSW flow aloft to keep anvils interfering with heating.

The model runs have been inconsistent over the past few days regarding the amount of activity for Sunday.  Some runs have been very active and some with only a little thus forecast confidence is low.  In general, it is also difficult to forecast accurately this far in advance this time of year.  Saying that, both the WRFGFS and WRFNAM develop storms over southeastern AZ and up over the White Mountains and Rim by mid afternoon Sunday and are fairly similar thus there is some confidence in the forecast.

SE Arizona storms are then steered into the lower deserts with some strong storms by early evening.  Tucson looks likely to see strong storms in and around the valley.  At this point, it looks unlikely that Phoenix will see any deep convection activity.

What is possible in/around Phoenix is a big dust storm/haboob event around 8-9pm.

20160707

Previous Day
Activity was limited to the higher elevations of eastern Pima and western Cochise counties.  Some isolated spots had very heavy rain.  All the model runs were too widespread with precipitation.  The WRFGFS was the best.

 Initializations
Weak mid level flow is present over southern Arizona with perhaps a weak IT between Tucson and El Paso.  The 12Z initializations all have a weak IT just east of Tucson which looks reasonable.  Clouds aren't an issue.  RR, NAM, and GFS IPW initializations all have only minimal errors.  Model confidence is high today.

Day 1
Nearly 40mm of IPW at Tucson this morning which was more than was forecast.  Moderate low level flow continues to advect moisture into SE Arizona - more than enough for activity there today.

Impressive CAPE across SE Arizona and even up towards the White Mountains.  More than was forecast yesterday.  Goes to show you how quick the conditions can change during the monsoon season and why one shouldn't rely on the Day 2 forecasts too much.

Mid level winds continue to be very poor with a 500mb high center on top of Tucson as well as warm air with temperatures around -5C.  As usual, it's a battle between the pluses and minuses.   It looks like a repeat of yesterday with strong storms with very heavy rain locked over the higher terrain.

As predicted yesterday, CAPE is very high for the Tucson area during the afternoon.  However, multiple inversions are present thus a strong outflow is going to be needed for deep convection.  Like yesterday, maybe a storm or two can get going in/near Tucson.  They certainly are not going to move in from anywhere due to almost no mid level steering winds.

Deep convection forms by early afternoon over the higher terrain of far SE Arizona and continues to spread back to the west, similar to yesterday.  All model runs predict this, but the WRFGFS and RR have weaker storms in eastern Pima than the WRFNAM.

A few storms continue across eastern Pima/Santa Cruz into the early evening.

Day 2
Much less activity as dry air is over much of the state with only the far SE having any moisture/CAPE.  Even here, activity is limited.

It looks like after today, there will be a long period of no activity.  The WRFGFS 7 day has nothing and this break could even be longer as the ECMWF continues with various troughs over the west out to 240 hours.  It is possible that brief incursions of wet air may come in to SE Arizona from time to time from strong NW Mexico convection, but that is probably just wishful thinking.

20160706

Previous Day
For the past 48 hours or so, the WRFGFS has been forecasting a ramp up in activity in SE Arizona today due to moisture increasomg from outflow surges from earlier storms in Sonora. That did happen and storms to the south did send a big outflow through SE Arizona overnight and even into SW Arizona this morning as the Yuma Td is up to 70F with southerly winds.    I didn't write a public discussion as only the WRFGFS was forecasting this moisture increase thus confidence was low.  However, the WRFNAM did come around and had more activity beginning with the 0z run.

12Z WRFGFS 24 hour forecast

I'd like to comment briefly on the early start to the monsoon and how some equate this to us having a good monsoon season  The early start was caused by an unusually strong and northerly centered ridge due to continued El Nino atmospheric pattern and the amplified jet stream associated with it. In spite of  neutral to slightly La Nina SSTs recently, the atmosphere continues an El Nino pattern and lags the  SSTs by 6-9 months.  Hopefully this will change soon otherwise expect a continued spotty monsoon season.

Initializations
No clouds of any significance to worry about.  A MCV can be seen rotating just south of Hermosillo which to my surprise, was initialized well by all the 12Z initializations.  There is a large IT southeast of the tip of Baja that was initialized too far to the west -- not a factor for us.  The high center is over the Big Bend region with light southerly to southwesterly flow over the southern 1/2 of the state.

I've been able to contact the owners (now ADOT) of the 'AZ' GPS stations that have been down recently (Bisbee and Buckeye), and let them know.  As of last night, I do see data again from these two critical sites.  IPW was initialized somewhat too high by the NAM across most of NW Mexico and into eastern Arizona.  Not enough to cause any issues as the assimilation routine should fix those errors.  The RR and GFS have a somewhat larger wet bias in Mexico.   By the way, the new version of the RR/HRRR is again delayed, now to the end of the summer.  However, ESRL is running the developmental version more frequently and I'm going to start using it in place of the operational version as last summer showed the developmental initialization to produce quite good forecasts -- on par or better than the WRFNAM or WRFGFS.  Plus, ESRL/NOAA is running it out to 39 hours thus it can be used for day 2 forecasts.

Initializations are all quite good with no favorite

Day 1
Wet low level air (Td 12C and above) continues to advect into south central and southeastern Arizona during the morning hours, favorable for development of afternoon storms, with some being strong.

Forecast CAPE is as high as 1500 J/Kg in spite of 500mb temperatures around -5C.

12Z WRFNAM

As Bob Maddox pointed out, steering flow is generally weak and not favorable with winds light and variable by mid-day over Tucson.  However, CAPE is an impressive 1200 J/Kg+ with a well mixed PBL.  Inverted V profile is small thus large scale strong outflow boundaries are not expected and so there could be an issue kicking off deep convection in the lower elevations.

WRFNAM

Deep convection begins over the high terrain of SE Arizona by early afternoon. The model runs do not agree on the coverage or location as the WRFGFS has more storms and farther east.  Hard to say which is correct.

12Z WRFNAM

12Z WRFGFS

By late afternoon, all three model runs have scattered storms in and around Tucson.  Yesterday, the WRFGFS was predicting very strong to possibly severe storms for the Tucson area and today's run has backed off on that forecast as it has less moisture and instability.  In fact, it's the WRFNAM that has more activity for the Tucson area.  Watch the IPW to see which is more likely as the WRFNAM has 37mm by afternoon while the WRFGFS has only 32mm.  So far, the WRFGFS is doing the better job forecasting IPW as the UofA IPW is only 27mm as of 15Z.

Outflows into Pinal county are expected to be weak as the PBL is not mixed deeply and there is no strong convection in eastern Pima county.

Day 2
Another trough passes to the north of Arizona which is enough to suppress the ridge and shift mid level winds to the SW. With continued -5C mid level temperatures, conditions are not favorable for storms.

Moisture begins to decrease across southern Arizona.  Enough does remain east of Tucson for some showers and weak storms.

The WRFGFS holds on to more moisture over Tucson, but with the substance inversion, dry air above the PBL, and unfavorable winds, convection is unlikely.  Too bad as the forecast CAPE is impressive!