Good Storm Chasing Weather?

Being a severe-weather aficionado in Utah is a bit like being a powder skier in Oklahoma.  The pickings are slim. 

However, unlike powder skiing in Oklahoma, which is essentially non-existent, there are a few days a year where something exciting might happen around here. 

The Storm Prediction Center puts parts of Utah in the marginal severe thunderstorm risk category over the next two forecast periods. 

A severe thunderstorm is one with wind gusts of 58 mph, hail at least an inch in diameter, and/or a tornado.  Marginal risk means that the storms could be spotty and limited in duration and/or intensity.  However, this is Utah and marginal is about the highest you see.

The SPC convective outlook discussion highlights that increasing moisture, strengthening wind shear, and other environmental characteristics should be favorable for isolated strong storms, potentially with strong winds and hail.  The NWS Forecast office in Salt Lake City has also issued a flash-flood watch for portions of central and eastern Utah. 

While I mentioned the storm chasing potential, the reality is that severe weather is hazardous weather.  Be careful out there and monitor forecasts, watches, and warnings.

Big Changes Are Coming

Major changes are on tap weatherwise over the next several days.

Today looks to be hot and tomorrow (Friday) even hotter as a closed low off the coast of Baja California begins to fill and lift into the southwest United States.  This leads to strong southerly flow across the Great Basin with temperature climbing and fire weather conditions deteriorating. 

NWS forecast highs for the Salt Lake City Airport are 91˚F today and 96˚F tomorrow.  Disgusting.

Saturday's forecast is crapshootish as the former closed low continues to fill and moves across Utah and a much deeper trough approaches from the west.  Right now, the GFS has the former moving across Utah in the morning and producing showers and thunderstorms producing the heaviest precipitation over central and eastern Utah.

The situation for northern Utah is pretty complicated due to the weak atmospheric stability, a front approaching from the west, and a moisture dryslot.  My guess is that there will be some decent weather on Saturday, but the threat of some showers and thunderstorms is real, so keep an eye on the radar, another on the sky, and adjust as needed. 

Right now, the GFS has the frontal band approaching Salt Lake City late Saturday and over Salt Lake City by 0300 UTC 7 June (9 PM MDT Saturday). 

That will be followed by cooler weather with periods of showers and possible some thunder as the pattern will be markedly springlike.  The NWS forecast high for Monday is 59˚F, nearly 40˚F lower than their forecast for Friday. 

If you are recreating this weekend, be aware that changes are coming and consult NWS forecasts.  Expect some evolution in forecast details (e.g., the timing of the front or periods of thunderstorms or showers), but the threats for critical fire weather conditions Friday and thunderstorms and heavy rain that could produce flash floods in southern and eastern Utah are real, as well as the overall cooling trend.  NWS flashflood information available at https://www.weather.gov/slc/flashflood.

Incredible Late May Warmth in 2003 and 2020

The numbers yesterday from the Salt Lake City airport were absolutely astounding.  With a maximum temperature of 98˚F and minimum of 76˚F, the average temperature was 87˚F, the highest ever observed in May at the airport. 

The graph below shows the highest daily average temperature observed each May in Salt Lake City based on downtown-area observations prior to 1928 and airport observations thereafter.  There are two clear outliers in this record, 2003 and 2020.  They are only Mays in the instrumented record with at least one day with an average temperature above even 80˚F. 

Source: NOAA Regional Climate Centers

Late May of 2003 was blisteringly hot on the 28th, 29th, and 30th with maximum temperatures of 99˚F, 99˚F, and 97˚F, respectively.  Minimums were 62˚F, 71˚F, and 73˚F, respectively, yielding averages of 80.5˚F, 85˚F, and 85˚F, respectively.

Late May of 2020 was blisteringly hot on the 29th and 30th with highs of 96˚F and 98˚F, but minima of 67˚F and 76˚F yielding averages of 81.5˚F and 87˚F. 

Weatherwise, yesterday was also remarkable in that it featured showers and thunderstorms that produced strong surface winds as precipitation cooled the dry low-level airmass.  Late yesterday afternoon, one could see virga and rain showers into that airmass, which in turn increased winds. 

Stations in Utah reporting gusts ≥ 60 mph to MesoWest are summarized below.  Big Indian Valley is in southeastern Utah and I haven't had a chance to examine the causes of that report.  Camel Back Mountain at Dugway Proving Ground hit 91.  Simpson Springs in the West Desert 73.  Hill Air Force Base 68. 

As if things aren't coming unglued enough, two wildfires started yesterday in northern Utah, The Tabby Canyon Fire on Stansbury Island and the 9th Street Fire near Ogden.  utahfireinfo.gov does not list the causes of these fires as I write this.  Lightning is a possibility, but I mention that not to rule out human causes, but simply to note that it can't be ruled out at this time.  There can be little doubt that their spread and behavior have been affected by the warm, dry conditions over recent weeks and the warmth, low humidity, and winds observed yesterday. 

Stay safe and vigilant.  

Yes, Masks Save Lives

As an atmospheric scientist with some background in aerosols and cloud microphysics, I've found discussions of the transmission of SARS-CoV-2 in the media to be lacking.  I've had a lot of questions about how the 6-foot rule for distancing came about and what it was based on, how such a general guideline should be adapted to differing environmental circumstances, how indoor and outdoor transmission potential differ, how masks work, etc. 

A perspective article in Science Magazine this week goes into these issues in depth.  The lead author is Kim Prather, an Atmospheric Chemist who holds multiple appointments in Atmospheric Chemistry, Chemistry, and Biochemistry at the Scripps Institution of Oceanography and UC San Diego with Coauthors from institutions in Taiwan, China, and UC San Diego. The article is entitled Reducing Transmission of SARS-CoV-2 and can be freely accessed. 

The article reviews the transmission of respiratory diseases in general and COVID-19 in particular.  The latter represents a snapshot of knowledge at present, which is still evolving.  It presents a strong case for universal mask wearing based on knowledge of aerosol physics and transport and epidemiological data.  Recognition that masks reduce transmission is not new, so the main contribution of the article is providing a good summary of the reasons why.  It also contains a nice visual illustrating mask impacts.

Source: Prather et al. (2020)

Ultimately, the battle we are fighting today is one of probability and statistics.  The authors state that countries that have most effectively reduced the spread of COVID-19 have implemented universal mask wearing.  Wearing a mask does not eliminate the potential for virus transmission, but it reduces its likelihood.  This decreases the probability that one person infects another and reduces the likelihood and size of outbreaks.  Sadly, the number of people wearing masks in the United States still seems low and it is not uncommon to see those that do wear a mask lower it when they are speaking, which is an activity that increases aerosol production. 

The question of whether or not the government should mandate mask wearing is a political one and how you answer it depends on your values and perspectives.  The questions of whether or not masks work is a scientific one and the answer to that is "yes."  They are an important tool for containing COVID-19 and rebuilding the economy. 

If you need a mask and live in Utah, the State will provide you with a free one.  The order form is here: https://coronavirus.utah.gov/mask/.

Red Sky at Morning Skiers Take Warning

This morning's sunrise

I woke up this morning, saw a red sky, and felt the warm breeze. 

My first thought was that the remnants of our snowpack are doomed.

Most Wasatch and western Uinta Snotels are now below 30% of median snow water equivalent for the date and crashing toward zero.  An exception is Snowbird, which sits at 42%, a number that is still not great.  

If only we could bend the coronavirus curve like Mother Nature is bending the snow water equivalent curve.  The crash of the spring snowpack this year has been quite remarkable and persistent since late April, with just a brief and temporary slowing last weekend and earlier this week due to a trough passage.

Over the past two days, the Snowbird SNOTEL has lost 3.5 inches of water.  With 13.3 inches remaining, the snow will be gone in four days at that rate.  That will be about 2 weeks ahead of median.  Such a shame. 

How I Can Best Teach in the Fall

Ah, the good old days.  Source: https://www.gsecclesfoundation.org/

The Salt Lake Tribune recently reported that there will be students on Utah System of Higher Education campuses this fall, including the University of Utah.  This has been discussed in numerous faculty meetings I've attended via zoom in recent weeks, so it is no surprise.  The devil is in the details, however, and those details remain murky as I've yet to see a detailed announcement from the University of Utah administration. 

In an article in today's Salt Lake Tribune, they reported that:

• Each school should prepare to monitor outbreaks, be able to contain them, and have a shutdown plan
• There won't be large auditorium classes
• Class sizes will be kept small
• Some classes will remain online for those at higher risk of infection, including both students and professors
• A few classes will be hybrid where half a class may meet in the room and half may join via video conference or half of the instruction days are in person and the other half virtual
• Desks will be spread 6 feet apart
• Each school will deep sanitize every building and space where there are students
• Universities can com up with individual plans

I continue to think about my own situation and how I can most effectively and safely teach my assigned classes in the fall.

Those classes are in Synoptic-Dynamic Meteorology and Weather Analysis and Forecasting, the latter involving student-led discussions.  These are classes that in the pre-COVID era involved a mixture of lecture, group discussions, individual active learning exercises, and computer based activities.  Often, I would look over student's shoulders or sit with them at the computer while they worked on an activity, moving around from one to another.  The class is taught in a cramped, interior computer lab with poor ventilation.  Enrollment will exceed capacity with distancing requirements.

I believe the worst-case scenario for me to teach these classes is one where the class is split between those physically in the room and those on video conference.  Such an approach can work for a traditional lecture class, but it would be very problematic for many of the activities that I lead normally.  Students at home would not have the same software as those in the computer lab, for example.  I would essentially have to prepare two separate plans and try to execute them simultaneously, which is a recipe for disaster.  

The best options for me would be either fully online or hybrid.  For fully online, I would probably teach via zoom, exploiting breakout and annotation capabilities to enable as much interaction as possible.  This would not be the same as what students could to in person, but I could design the course in a way that it would be better than trying to juggle both in-person and online instruction at the same time.

Hybrid is also attractive.  Under this scenario, I might pre-record some lectures and have the students watch them before class.  I would take my 75 minute class period and divide it into 35 minute halves with a 5 minute gap between for computer cleaning.  Half the class would attend the first period and half the last period.  Distancing would be possible, although I would probably need to use zoom with screen sharing to see what students are doing.  This will be slower than just walking around seeing how they are doing.  The one unfortunate thing about this would be that I'd have to fully separate the lecture from the learning activities, whereas I normally switch from one to the other pretty regularly.  However, this too would be better than trying to juggle both in-person and online instruction at the same time.

My hope is that the University will provide some flexibility for faculty to decide what approach is best, both for instructional quality and safety, after consultation with the enrolled students.  "In person" is going to be different than it has been in the past, and it could be that the best option for some classes this fall is to still be online or hybrid.