Wednesday, September 30, 2020

Will It Ever Rain Again?




At the Salt Lake City International Airport, only 0.26 inches of rain fell in July, compared to an average of 0.72.  In August, it was 0.10 compared to an average of 0.76.  September?  Only 0.19 compared to an average of 1.33.  Will it ever rain again?

Data and Methods

I looked at the Global Ensemble Forecast System (GEFS) forecasts for the next week and extrapolated them 7.6 billion years forward to when the Sun will exhaust its fuel and expand as a red giant.


No GEFS members produce precipitation at the Salt Lake City International Airport through 1200 UTC 8 October.  

Source: NCEP

Since there's no precipitation forecast for the next week, extrapolation suggests it will never rain in Salt Lake City ever again.  


It will never rain again in Salt Lake City.  This forecast, however, is contingent on a number of assumptions.  In particular, we assume that the forecast for the next week is accurate and will apply for the next 7.6 billion years. Weather variability, anthropogenic climate change, orbital variations, changes in solar luminosity, and other factors may affect this forecast.  Therefore, you should take it with a humorous grain of salt, enjoy the splendid fall weather, and hope that we see a transition to a snowy pattern in early November.  

Monday, September 28, 2020

A Busy Semester of Teaching

 Our fall semester like no other is now at the 1/3 point.  The University of Utah is now going into a two-week "circuit breaker" during which classes will be fully online.  This circuit breaker has been planned for some time, long before the most recent spike in Utah coronavirus cases began and was developed, based on modeling, to reduce COVID infections on campus and provide a pause for the Vice Presidential Debate, scheduled for October 7.

I am teaching entirely online this semester, but have gone to campus a few times, including several days of in-office working while my power was out.  With a majority of classes online, it's pretty quiet, with little of the energy and excitement that you find on a large campus during the school year. 

My online courses are taught live.  It was a major effort to retool classes that I've taught in person for 25 years.  Here's a short list:

  • I learned canvas and had to move all my course materials to that format.  
  • I revised all my assignments and exams so that they are shorter and done weekly rather than more comprehensive and done less frequently.
  • Working with our computer support staff, we found ways to enable students to remotely make use of the visualization and analysis tools that we typically use in our computer lab.
  • We completely revamped my weather discussion class to make it tractable for students to do remotely via zoom.
  • I took several online "boot camp" classes to learn what can be done with Canvas and Zoom to facilitate learning.  I've revamped my class materials and am doing polling, breakout sessions, and remote visualization.  Note that I have done all of these things previously in person, so this change is about pedagogical change and more about technological change.  It also takes time, for example, to migrate polling from one software platform to another.  Additionally, one needs to find many work arounds to do polling in zoom that involves mathematics and visualization.  

Typically on Monday, I work to get everything setup for the next week.  This involves preparing an online quiz in canvas, an online learning exercise, updating all my class notes for the online approach, preparing polls, etc.  This keeps me about a week ahead on everything.  Tuesdays and Thursdays I focus on teaching two classes and holding office hours.  I've invented a new word, canvasophobia, to describe the anxiety that accompanies teaching online with multiple apps and hoping everything actually works.  

Mostly it has.  It's difficult for me to tell so far, but I think one of my classes might be better than it was in person last year, only because of the effort put into it.  The other one I'm not sure about yet.  Ultimately, how good the class is depends on the perspectives of the students.  

My teaching load this semester also includes the development of a third course, which is brand new and called Atmos 1000: Secrets of the Greatest Snow on Earth.  The course is being designed as a general education physical and life sciences course (internal University of Utah approval is pending) and is slated to be offered for the first time in the spring.  As you might guess, this is a course specifically designed for on-the-go students with a passion for snow, winter sports, and weather.  It is fully asynchronous, meaning there are no live lectures.  Instead, each week students read a section of my book, Secrets of the Greatest Snow on Earth, view a series of short videos that expand on key material, and complete a series of scenario-based activities.  Forget boring lectures.  The class should give you an education in science that you can use for your fun and adventures.

It's difficult for me to reproduce the Canvas materials in this blog, but here's an example.  In week 5, the focus is on snow climates beyond North America, including the European Alps, New Zealand Alps, Andes, and Japan.  Students read part of a chapter of my book and then view short videos that go deeper into the snow climate of the European Alps and Japan.

They also complete a short quiz and two learning activities.  In one of the learning activities, they are planning a ski vacation to Switzerland, and use Swiss snow depth data to evaluate the natural snow-sureness at major Swiss resorts.  They are provided with a variety of web resources to do this, and I've produce high-resolution snow-depth analyses for more detailed investigation.  Below is an example for Engleberg, with snow depth overlaid on a topo map.  In this instance, I've converted to US units.  Sad, but good for better evaluations.  

I now have 10 weeks of material finished.  Below is the Canvas home page, which provides a look at the major topic areas.  I just finished off the three avalanche sections and am beginning to work on the forecasting and climate change weeks.  The content for those hasn't been finalized, and I'm thinking of possibly making some adjustments to include something on glaciology and glacial change.  

We'll talk more about this class later in the semester, when hopefully it's fully approved and I have more content produced.  We are also working on ways to offer it to those who simply want to take it for fun without being enrolled as a University of Utah student.  I should have more on that soon as well. 

Sunday, September 27, 2020

A Hot and Dry July – September

 This year's three-month July-September period is going to go down as one of the hottest and driest on record.

For the period from July 1 through September 26, 2020 is tied with 2017 for the 2nd warmest on record with an average temperature of 78.7˚F, behind only 2013 (80.1˚F). 

Source: NOAA Regional Climate Centers

With four days left, I haven't done the calculus to see where we're likely to end up, but it will be up there, although it won't be a record (we have no chance of getting 2013, which finished the full July to September period with an average temperature of 79.2˚F).

The odds of precipitation through the end of the month, however, are vanishingly small, so the 0.55" we've received since July 1 is going to be the tally.  That rates as the 8th driest such period on record.  

Source: NOAA Regional Climate Centers

The driest July to September was in 1879 with only 0.14 inches.

Looking regionally, the we see that nearly the entire southwest has been below average.  California averages paltry amounts from July to September anyway, but Arizona and Utah are well below average.  We've had a "nonsoon" this year instead of a monsoon.    

We did a leaf-peeping drive this morning.  The best we saw was on the Alpine Loop highway.  As reported by many, the aspens in Pine Canyon, Guardsman Pass, and Big Cottonwood are decimated.  It looks like mid October rather than late September.  The aspens in Big Cottonwood looked awful even during the summer.  I leave it to the ecologists to explain if this is a result of the June cold snap and/or the drought.  

It looks dry for the foreseeable future, which for me means about a week.  If you must ask, the Climate Prediction Center 8-14 day outlooks has the dice heavily loaded for above average temperatures and below average precipitation. 

I usually like a warm, dry late September and October.  Above average this time of year is comfortable and no precipitation means no snow, which is good from the standpoint that early snow, unless it comes big, typically turns into rotten snow with persistent weak layer issues as we head into winter.  However, I'm feeling moisture starved right now and would enjoy a good multi-hour soaker.  

Thursday, September 24, 2020

Changing Narratives

There is a narrative that often appears after "natural" disasters (natural in quotes since some are quite unnatural or have a strong anthropogenic component) that our society needs to change, and that is saying that the disaster was unexpected or came out of nowhere.  

An example of this is provided by the tweet below saying that 2020 has been the year of the "unexpected."

Although we have suffered a series of challenges, none of these were really unexpected.  A short list would include the pandemic, earthquake, fires/smoke, and windstorm.  Perhaps I've forgotten something as the year's been a blur.

The coronavirus pandemic isn't the first nor will it be the last.  Although the timing and details of a pandemic cannot be predicted precisely, the threat posed by them has been known for some time and the subject of significant research.  Some countries have responded well to the coronavirus threat.  The United States has not.  Why this is the case is not the subject of this post, but let's not treat the coronavirus pandemic as a surprise or a one off because it isn't.  We need the be better prepared to take effective action for the next one.  

The Magna earthquake awoke or startled many at 7:09 am MDT on March 18, with noticeable aftershocks for weeks thereafter.  


Similar to pandemics, specific earthquake prediction is not possible except in some circumstances with very short lead time of seconds to minutes.  However, scientists have been aware of the earthquake potential in our region, especially along the Wasatch fault, for decades.  Here too, there are lessons to be learned to be better prepared to take effective action for the next one, even though we don't know precisely where or when it will hit.  

The western wildfires have destroyed communities in the Pacific states and led to poor air quality at times across much of the west.  Utah has not had an easy fire season, but we've been comparatively lucky so far compared to the disasters that have ensued in California, Oregon, and Washington.  Here too, scientists have warned about wildland mangement, invasive species, development patterns, and climate change as agents for exacerbating severe wildfire behavior.  Perhaps an individual wildfire can "come out of nowhere", but the fact that we are now seeing extreme wildfire intensities and spread is not a surprise.

Finally, we have the recent windstorm.  The National Weather Service issued warnings in advance for this event as well and three days prior to the event, I commented on the potential for "strong downslope winds along the Wasatch Front on Tuesday."  An argument might be made that the impacts were more severe than anticipated, but the event was not unexpected.  

We need to change this narrative because it is one that fuels a reactionary response to natural hazards rather than one in which we more proactively build resiliency to these hazards.  Natural disasters are not acts of god and in most instances they are not unexpected, nor do they come out of nowhere. 

Our vulnerability to natural hazards today strongly reflects the choices we have made as a society and as individuals.  Our vulnerability to natural hazards in the coming decades reflects in part those choices, but also the choices we make today and in the future.  

With regards to weather and climate hazards, I often say that we are not prepared for the weather and climate of the 20th century, let alone the climate of the 21st century.   We know that the trends we see happening today: higher temperatures, more severe and prolonged drought, intensifying wildfires, and more extreme precipitation events, will continue and potentially accelerate in the future.  

We need to adapt and prepare for this coming reality, which is going to be different from the one that human civilization has experienced in the last 10,000 years.  

Fool us once, shame on you.  Fool us twice, shame on us.  In some instances, we've been fooled many times.  Let's work to build more resilient communities.  

Tuesday, September 22, 2020

What If RBG Had Been a Scientist?


"When I’m sometimes asked ‘When will there be enough (women on the Supreme Court)?’ and my answer is: ‘When there are nine.’ People are shocked. But there’d been nine men, and nobody’s ever raised a question about that.”
- Ruth Bader Ginsburg

After the passing of Ruth Bader Ginsburg on Friday, I found myself choked up.  It is the tough loss of a great woman who meant a great deal to many, including my young daughter as she has grown into a young woman.  

Ginsburg was an advocate for gender equality, an area in which the "STEM" disciplines (Science, Technology, Engineering, and Mathematics) has long lagged.  In high school, I did not have a single woman as a math or science teacher.  As an undergraduate student, I did not have a single woman as a math or science professor.  As a graduate student, I did not have a single woman as a math or science professor.  And, when I joined the faculty of the College of Mines and Earth Sciences at the University of Utah in 1995, I believe there were only two women on the tenure-line faculty.  

This is the male-dominated STEM world that Ruth Bader Ginsburg would have fought through in about 1956 when she entered graduate school, 1961 when she would have completed her Ph.D., and 1962 when she would have joined the atmospheric sciences or other STEM department at some prestigious University.  Even today, women are underrepresented throughout the STEM pipeline and account for only 18-31% of faculty in STEM fields.  

Imagine if RBG had joined the STEM world and how she would have been an agent for change.  She would have fought against gender pay inequity and sexual harassment in all of its forms.  She would have been an advocate for a more diverse faculty and the elimination of gender bias in faculty recruiting, hiring, and mentoring, as well as the classroom.  She would have rewritten the policies uses for the retention, promotion, and tenure of faculty, eliminating gender biases and rewarding faculty for their efforts to promote of feeling of belonging in STEM not just for women, but all from marginalized communities.  

RBG would have surely been a great scientist, but I think we can all be grateful that she found her passion and calling.  STEM's loss is the country's and world's gain.  However, all of us in STEM can learn from the ideals she pursued and work to achieve them in our disciplines where we still have so much work to do.  

Thursday, September 17, 2020

Time to Vent

"You can always count on Americans to do the right thing — after they've tried everything else."
– Winston Churchill

I've always liked that Winston Churchill quote and I've used it often to try and explain America to my international friends.  It usually results in a good, disarming laugh that enables us to compare and contrast cultures and political systems.

What concerns me today is whether or not we can still count on the first half of that quote: America doing the right thing.  We face many challenges in which we've either tried everything else or have failed to accept what must be done, and yet we still are not doing the right thing.  

Let's use the western wildfires as an example.  The growing and multifaceted threats of climate change, forest (mis)management, development in the urban–wildland interface, inadequate community or infrastructure preparedness, and human negligence (e.g., target shooting and other human fire starts) have been recognized for years.  No reputable scientists considers climate change the sole "cause" of the western wildfire problem, but it also cannot be ignored as an important contributor to the lengthening wildfire season, severity of drought, and intensity of wildfires in the western United States and other regions of the world (e.g., Australia).  

How many people must die and communities destroyed before we finally come to terms with the reality that climate change is real and on a trajectory that will only continue to exacerbate this problem in the coming decades?  Scientists know what is happening, why it is happening, and that it's not going to get cooler, as suggested by President Trump this week.  We also know that "cycles of burning and regrowth" are natural, as argued by Senator Mike Lee, but also that these cycles have been altered by forest management AND climate change, contributing to extreme fire behavior.  

I suppose it is a naive and pollyannish view to say I grew up in a country that invested in science and desired to utilize it to advance the general welfare of humankind.  How have we gotten so far off the tracks?  The example above is just one of many whereby scientists and scientific understanding are being dismissed and disrespected, to the detriment of our country and its citizens.  

Naomi Oreskes, a Professor of the History of Science at Harvard University, has an opinion article entitled America's Devastating Divorce from Science on  In it, she writes:

"The unfortunate reality is that our elected government is increasingly populated with many men and women who do not merely ignore scientific facts, they appear to despise them and the people who produce them. They see science as something that stands in the way of their political goals, and therefore must be pushed out of the way.

The solution to this cannot be a call for more science or the restoration of "scientific integrity," whatever that is. We have tried that and it has failed. There comes a point when maybe one simply has to accept that the dream has died and it is time for a new one. I don't know what a new social contract for science would look like, but I am pretty sure it is time to start looking for it.

She is absolutely right that we cannot fix this with more science or more efforts to better communicate science.  Climate scientists are not the only ones confronting this fact this (ask a virologist or epidemiologist).  Where we go from here, I don't know, but the road is going to be rough if we continue to deny reality, fail to utilize science as a tool, and don't recognize that we've tried everything else and that the time is now to do the right things.  

Tuesday, September 15, 2020

Cooler Weekend Ahead

Summer won't quit as we've had highs in the low 90s the past two days.  However, with the early sunset and long nights, I'll call the heat manageable as we haven't even thought of switching on the A/C as it's cooled off nicely overnight.  Last night the low at the airport was 60˚F, 32˚F lower than yesterday's high of 92˚F.  Wonderful sleeping weather.

If you can make it through this week, I'm pleased to report that the models are advertising that a cold front and upper-level trough will bring cooler air for the weekend.  The GFS forecast valid 0900 UTC 19 September (0300 MDT Saturday) shows the cold front moving through northern Utah with even a hint of rain.  

I'm not overly excited about that as most ensemble members are generating less than 0.1" and only a few members of the often too wet Canadian ensemble are generating more, but anything would be welcome.  

Really, a weekend of heavy rain would be great.  Not only could we use it, but it might keep the target shooters at home and spare us a few more human-caused fires.  

Monday, September 14, 2020

Lots of Hazards Out There

Although Utah was smacked by a severe downslope windstorm, cutting power for 170,000 (with 5,500 still powerless), we should perhaps feel fortunate as others are facing much more dire consequences.

This morning's satellite imagery is about as ominous as it gets.  Smoke from western wildfires has spread across much of the continental Unites States following both northern and southern trajectories.   We're in relatively clear air at the moment in northern Utah, although southern Utah is better.  Meanwhile, slow moving Tropical Storm Sally looms off the Gulf Coast, will likely intensify into a hurricane, and is expected to bring storm surge, flooding, and other impacts.  

Source: CIRA

Purple Air sensors show much of California, Oregon, and Washington is experiencing unhealthy air quality, with many areas hazardous.  Across the southern US, moderate air quality readings extend at least all the way to Texas due to smoke.  


I'm not going to try and summarize the direct impacts of the wildfires here.  I can't even keep up with it.  Lives have been lost.  Communities have been wiped out.  The situation is sad and tragic and my heart goes out to all affected. 

Thursday, September 10, 2020

This Was More Than a Downslope Windstorm

The windstorm of 8 September featured a remarkable coverage of strong winds both along the Wasatch Front but also westward from the base of the Wasatch Range.  Although there was certainly an important downslope wind component to the event, with the strongest winds observed at the base of the Wasatch Mountains, it's important to recognize that the event was more than just a downslope wind event.

Before looking at what happened on 8 September, lets' take a look back at another event that occurred on 1 December 2011.  You may recall this event as it produced a 101 mph gust in Centerville, Utah and quite a bit of damage in the Centerville and Farmington area.  Power outages affecting 50,000 customers occurred along the northern Wasatch Front through North Ogden, but were somewhat more limited in the Salt Lake Valley, althouth there were some in Millcreek, Murray/Holladay, and Midvale.

Power Outages from the 1 December 2011 event. Source: Salt Lake Tribune

Analyses of the event show a very typical pattern for northern Utah downslope windstorms with a developing upper-level trough in northerly flow closing off and centering in the Las Vegas area as depicted below at 700-mb (about 10,000 feet, or crest level for the Wasatch Range).  This leads to easterly flow across the Wasatch Range.  If you were to average the pattern for many Wasatch downslope windstorm events, it would look a lot like this.  

In contrast, the 8 September 2020 event produced power outages for 170,000 people with tree damage well west of the base of the Wasatch in areas such as Rose Park.  It was much more widespread.  A nice graphic produced by the Salt Lake Tribune showing peak wind gusts based on observations provided to the National Weather Service shows the strong winds along the base of the Northern Wasatch, but also remarkably strong winds in other areas including 67 mph in the northwest Salt Lake Valley, 77 mph at the Salt Lake Airport, 74 mph near East Canyon Reservoir, 61 mph at Parley's summit, and 54 mph at Kimball Junction.  

Thus, this was a regional event.  the strongest winds were at the base of the mountains in a few locations, but strong winds were observed everywhere.

A look at the 700-mb analysis for 1200 UTC (0600 MDT) 8 September shows the closed low that was found in the 1 December 2011 and other events, but note its location is near the Utah Colorado border.  Additionally, a strong gradient wraps around the low across northern Utah and over the West Desert.  A look at the water vapor imagery shows unusually high "brightness temperatures" (indicated by purple color fill) on the back side of the low.  All of this is consistent with intense upper-level front development and mid-level cyclogenesis (i.e., low pressure formation).  

That closed low developed rapidly over northern Utah.  Understanding this event and its widespread coverage requires not only thinking about mountain wave dynamics, but also the role of the developing closed low and upper-level front in producing strong regional-scale winds across northern Utah.  

At least that's my hypothesis.

I need to go and teach class, so apologies if this post is a bit uneven.  I just wanted to get this out to illustrate that the widespread nature of this event requires avoiding what I call "mountain myopia" and also considering larger-scale processes. 

Wednesday, September 9, 2020

Why This Is Such an Exceptional Event

 The events unfolding across the western United States this week are remarkable and include heavy snowfall along the Front Range of Colorado, severe downslope winds in Utah, and extreme fire behavior in the Pacific states.  We'll get to some of the details of what happened in those areas eventually, but to start, let's talk about why this is such an exceptional event.  

To do this, we must take a global perspective as everything starts with the highly anomalous large scale flow that has developed over the past few days.  A critical player in all of this appears to be Typhoon Julian, which on August 30th was near the Philippines but on track to move northward and interact with the mid-latitude jet stream (see red arrow below).  

Whenever there's a tropical cyclone recurving into the midlatitudes and interacting with the jet stream, I go on high alert.  Although this doesn't happen all the time, such interactions often lead to a rapid amplification of the jet stream flow, with the flow becoming "wavier" as the ridges amplify and the troughs strengthen.  This typically happens in domino-like fashion, with the ridge downstream of the typhoon amplifying, followed by the trough downstream of the ridge, and so on.  This is a process known as downstream development.  

By September 2nd, the seeds were sown as the decaying Julian approached the Korean Peninsula and the downstream ridge off the coast of Japan began to amplify.  This is the beginning of a period during which the jet stream pattern over the North Pacific and western North America would strongly amplify from a state that was already somewhat amplified.  

By September 5, the pattern was highly amplified with strong ridges off the coast of Asia and over western North America and the adjoining eastern Pacific and a deep trough near the dateline.  Much of the western U.S. was baking to a crisp after an already long hot, dry, summer.  

However, Mother Nature was not finished.  At low-levels beneath the upper-level trough near the dateline, a mid-latitude cyclone was developing.  

Typhoon Julian was the left jab, but this midlatitude cyclone was the right hook.  It moved northward into the Behring Sea, with warm moist air transported northward deep into Alaska and northwest Canada.  Without getting into hard-core geophysical fluid dynamics, such a pattern favors the development of a strong upper-level ridge downstream, as occurred over southeast Alaska (black 500-mb contours below), which in turn strengthened the high-pressure system at low levels over western Canada.   

At this point the door was open for further amplification of the upper-level flow and the push of an anticyclone (high pressure system) and cold air into the northern and Central Rockies.  By 1200 UTC yesterday, cold air was surging down the east side of the Rockies, stimulating an upslope snowfall event along the front range, cold air was pushing across the Wasatch at the same time an upper-level trough was forming to drive strong northeasterly flow at crest level, and strong offshore winds were developing over the Pacific Northwest (and eventually parts of California) as high pressure pushed into the Columbia and western Great Basins.  

That's an awful lot to pack into a blog post, but it often takes a series of events to drive the atmosphere into outlier mode, as has occurred over the past several days.  

That's the large-scale setup.  What has happened across the west is also dependent on the interaction of the large-scale flow with regional terrain features and variations in flow direction with height.  

Let's focus on 1200 UTC (0600 MDT) yesterday morning when we were experiencing severe downslope winds, snow was just beginning to develop in Boulder, CO.  At that time, high pressure was centered over southern Montana, but a pronounced high-pressure ridge extended southward to the east of the Colorado Rockies.  That ridge was associated with a surge of cold air along the front range, lowering snow levels. 

At the same time at 700 mb (about 10,000 feet above sea level), the flow over the northern front range was easterly and a precipitation system associated with the upper-level trough was moving into the area.  This favored snowfall in that area.  At the same time, strong easterly flow originating over southwest Wyoming was directed across the northern Wasatch, driving downslope winds along the Wasatch Front.  

So, while the large-scale setup requires a global perspective, what happens locally over the west requires a more regional perspective and consideration of not only what is happening at low levels, but also aloft.  Due to lack of time I won't get into it here, but the severity of the downslope wind storms along the Wasatch Front yesterday was probably also related to how the wind direction changed with height, which allowed for the trapping of mountain-wave energy at low levels.

I would be remiss not to also comment here about the terrible tragedy to our west as wildfires are being fanned by strong winds associated with this strong high-pressure system.  So much is happening that I'm just going to embed a satellite loop below of the incredible fires in Oregon, which spread rapidly in strong offshore winds. 

Due to lack of power and spotty cell service, I still haven't caught up on everything happening to our west, but the situation appears awful for many communities.  I consider myself fortunate to have lost only some trees from this event.  

Monday, September 7, 2020


I don't know about you, but the anticipation for colder air and some exciting weather is high today.  

And, the push of the cold front through Montana, Idaho, and Wyoming is simply fascinating.  

Let's first get a quick look at where things stand at 16:30 UTC (10:30 MDT).  As indicated by the MesoWest observations below, northerly winds and the leading edge of the cold air has surged through Montana and is now pushing through north-central Wyoming, having just reached Riverton.  Further West, northerlies have surged down the Madison Valley and other valleys in southwest Montana and are just cresting the Continental Divide.  Apologies for the ugly analysis, but it gets the job done.   Basically, the shallow, leading edge of the cold air is surrounding the high terrain in and around Yellowstone, although that region will be "submerged" eventually.  

MesoWest observations at 1030 MDT 7 Sep 2020

The 4-hour HRRR forecast valid at 1900 UTC/1100 MDT captures the observations above fairly well.  Note the front just south of the continental divide in eastern Idaho and pushing toward the Wind River Range in Wyoming.  There appears to be a slight difference in timing, but the observations above are for 30 minutes earlier and the front is moving fast, so this is a pretty good forecast.  

By 0000 UTC (1800 MDT) this afternoon, strong northerlies have spread over the eastern (upper) Snake River Plain and are approaching the I-80 corridor in Wyoming.  Basically, there are two "fronts" in this forecast, although I've connected them through the high terrain of northwest Wyoming.  The first is the one that is surging down the Snake River Plain.  The second is the one that is surging southward and westward into southwest Wyoming.  

By 0300 UTC (2100 MDT), the front that has pushed through the Snake River Valley is surging through northern Utah.  Note that the prefrontal flow over the Salt Lake Valley is northwesterly.  Thus, we will see winds from the west and northwest strengthening today ahead of the front, before we get slapped in the face by a surge of northerlies after sunset.  Meanwhile, cold air from Wyoming is beginning to surge toward Utah from the east.  This is an example of a back-door cold front.  If this forecast holds, the area around Evanston will see two cold-frontal passages later today, one from the northwest that has come through the upper Snake River Plain, followed by a second from the east, which will be even colder.  

As I like to tell my students, learn from Napoleon and remember that in war and meteorology, nothing good comes from the east, and indeed that will be the case tonight.  By 0900 UTC (0300 MDT Tuesday), cold air from the east has surged into Utah and across the Wasatch Mountains.  This will likely mark the beginning of downslope winds for the region from Parley's Canyon north to Brigham City near the base of the Wasatch Mountains.  

The NWS has issued a high wind warning for that area.  Details below.

Tomorrow you will experience a day remarkably different from today or the hell we have been through in recent weeks.  

However, if you want to see even greater change, pay attention to the Denver and Front Range area where this cold surge is expected to bring significant snow.  Check out the NWS forecast below.

Pretty incredible since they just hit 101˚F there on Saturday, the latest 100 ever recorded there.  

Sunday, September 6, 2020

Fall Colors and Wildfire Smoke

The colors are really starting to pop in lower City Creek Canyon.  Sadly, the photo below from this morning doesn't do it justice.  They seem especially pretty right now as the scrub oak begins to turn.  

Unbelievable satellite imagery this morning with thick smoke over much of California, Nevada and Oregon.  

Some of it is moving downstream into Idaho and Utah and you could see it moving in at mountain crest level from about 10 to 11:30 this morning.  Note in the photo below how the central and southern Oquirrhs around the Kennecott mine are obscured.  

My guess is that the surface heating hasn't warmed things up enough for the near-surface atmosphere to mix with the smoke layer aloft yet.  Guessing we will see that change during the day today, with PM2.5 concentrations rising in the valley as the day goes on.

The overshooting top of the Creek Fire near Fresno is very apparent in the satellite imagery above, which was taken at 15:31 UTC (0931 MDT) this morning.  That fire is an absolute beast, as is readily apparent in a satellite loop from this morning.  The Fresno Bee reports that 63 people who could not escape in time were evacuated by military helicopter from communities that include Mammoth Pool.  Apparently twenty people are in potentially critical condition after they were rescued from the Mammoth Pool Reservoir.  

I hope for the best for everyone. 

Friday, September 4, 2020

First Major Cold Surge of the Fall

 It's hard not to get excited about the first major cold surge of the season after the blistering heat we've suffered through the last several weeks.  Mother Nature is going to make us suffer this weekend, but MAJOR change is coming by Tuesday.  

The loop below shows the GFS forecast 500-mb heights (black lines) and 925-mb temperatures (colored lines) from 1200 UTC (0600 MDT) this morning through 1200 UTC (0600 MDT) Tuesday.  There are two major large-scale circulation changes that occur at upper levels.  First, the ridge from hell that has dominated our weather for so long weakens and shifts upstream.  Second, the upper-level pattern becomes much more strongly amplified, meaning that the ridges and troughs get stronger, resulting in a more wave like pattern, which by Tuesday morning features a high-amplitude ridge over the northeast Pacific and a deep trough digging into the Rocky Mountain region. 

With that trough comes one hell of an airmass change, as might be inferred from the 925-mb temperatures above.  

The ECMWF advertises a somewhat similar solution, but with a slightly stronger trough.  To illustrate the remarkable airmass change, below are ECMWF 700-mb (10,000 ft) temperature forecasts (color fill) from valid at 0000 UTC 8 September (1800 MDT Monday) and 1200 UTC 8 September (0600 MDT Tuesday).   In that 12-hour period, the 700-mb temperature drops from 15˚C to -2˚C.  

If we go six hours later to 1800 UTC 8 September (1200 MDT Tuesday), we're down to -3˚C and there are strong east winds extending from southwest Wyoming across the Wasatch Range.  Should this verify, a concern would be the potential for strong downslope winds along the Wasatch Front on Tuesday.  

Another potential issue is snow in the mountains.  The ECMWF is most productive in the Uintas.  

Ensemble forecasts for Trial Lake along the Mirror Lake Highway show most members generating an inch or two of snow, but a few members going for several inches of high-density snow.  

The bottom line is major change is coming.  Details concerning downslope winds, which are very sensitive to small changes in flow direction, or mountain snows remain less certain but warrant monitoring the forecasts and adjusting plans as needed.  

And, if you are wondering if we're going to stay cold for a while, that looks unlikely as temperatures will eventually recover during the work week.  

Tuesday, September 1, 2020

Hottest August on Record

No surprise here.  August 2020 goes down as the hottest on record with an average temperature of 83.0˚F.  Thanks to cooler weather the last two days of the month, this tops August 2013 by only 0.3˚F.  

Source: NOAA Regional Climate Centers

There have been 9 years with an average temperature at or above 80˚F, all since 2003 except for August 1994.  Prior to August 1994, there had never been an August with an average temperature above 78.5˚F.  Recent Augusts have been exceptional.

For the year to date, the average temperature was 56.7˚F, which slots in as the 7th warmest on record.  2018 produced the warmest January - August temperature at 60.1˚F.  

How do I feel about having meteorological summer behind us.  It's good to have it in the rear-view mirror.