Monday, August 19, 2019

Whither the 2019 Monsoon?

We are now deep into mid August and thus far the 2019 monsoon has been a bust for precipitation across much of the southwest U.S., including Utah.

Precipitation for the 60-day period ending 18 August is at or below average across much of Arizona, Utah, Nevada, and Southern California.  Much of Texas is similarly below average, with only New Mexico having something close to or above average. 

This past weekend we were in Phoenix helping my daughter move in for her 2nd year at Arizona State.  The high on Friday afternoon when we arrived was 111ºF, followed by 108˚F on her Saturday move-in day.  Brutally hot, with not much in sight but one thin, distant rain shaft on Friday afternoon. 

Although one might hope that in August we'd see a greater likelihood of precipitation compared to July, climate is what you expect and weather is what you get.  The challenge we are currently having in Utah is one in which the mid-latitude westerlies are just far enough south to keep us in a dry airstream, but not far enough south to get us into cooler-than-average air, as illustrated by the GFS 4-day forecast loop below.  The monsoon precipitation (green and blue color fill) remains predominantly east and south of Utah. 

Although I would not rule out the chance of a shower or thunderstorm over the mountains during this period, the coverage and intensity of precipitation is limited.  We just don't have a circulation right now that favors the transport of monsoon moisture into the state.  Hence, dry conditions will predominate through at least the work week. 

Thursday, August 15, 2019

How the Alta Snowflake Is Really Created

It may be hard to believe, but not everything you read or see on social media is true.  Often, the fallacy is cleverly hidden because it is distributed by what appears to be a reputable source.  Even experts and professional groups can be fooled or make mistakes.

Several days ago, @ZonePhysics, issued the tweet below showing how a drop of water turns into a snowflake.

That certainly looks like a convincing video and a reliable source.   Some people suggested the video showed the creation of the Alta Snowflake depicted on the Alta blue-dot logo below.

It's a wonderful story, but unfortunately it's not true.

The video above doesn't show the formation of a snowflake, it shows the melting of a snowflake.  The video is run in reverse, so it appears the water turns into a snowflake.  It's convincing, but misleading and inaccurate.

The Alta Snowflake is a rendition of a snowflake known as a stellar dendrite.  Stellar dendrites have six arms shaped like a tree (dendrite means tree like) and a star-like appearance.  Hence the name.  Ken Libbrect's great guide to snowflakes includes photos of many types of stellar dendrites.    

Snowflakes of this type do not form from water turning into ice.  When a large water droplet, say a raindrop freezes, you get a ball of ice, often referred to in the United States as sleet.  Sleet is rare in Utah, but a common feature of the so called "transition zone" between rain and snow found in the warm-frontal region of cyclones over the central and eastern United States.

Instead, stellar dendrites form primarily from water vapor condensing directly to ice through a process known as deposition. Liquid water is not involved at all.  It is possible to demonstrate the process in a cold chamber under the right conditions.  Here's an example produced by Ken in his lab.  

Ken has many more videos of snowflake growth available at  Knock yourself out.  

All of this is not to say that water turning into ice doesn't contribute to the growth of real-world snow. Most snow-producing clouds consist of a mixture of ice particles (including snowflakes) and liquid cloud droplets.  The liquid cloud droplets are colder than 0˚C (32˚F), but have not yet frozen.  Scientists call this supercooled.  Under the right conditions, these droplets collide with and freeze onto snowflakes and other ice crystals through a process known as accretion or riming.  Below are images, reproduced from my book and taken by the Electron and Confocal Microscopy Laboratory of the U. S. Department of Agriculture, of a lightly rimed ice crystal known as a plate (top right), moderately rimed dendrite that has been broken up some (center right), and a heavily rimed ice particle in which the original ice particle or snowflake is indistinguishable (lower right).  The latter is called graupel.  

Source: Secrets of the Greatest Snow on Earth
Stellar dendrites, because of their long branches and arms, typically produce low-density (i.e., dry) snow because of all the gaps and pores within the crystal structure.  Real storms are comprised of many different types of snowflakes and ice particles, but if you want blower pow, stellar dendrites are going to be abundant.  Thus, the Alta marketing people knew what they were doing.  On the other hand, the Alta skiing cognoscenti know that graupel, despite its high density, also produces amazing skiing.  It just wouldn't look that good as the basis for a logo.  

Wednesday, August 14, 2019


A little something to brighten your day today.  Although there are no freshies in Utah, the Hintereisferner in Austria received a coat of white in the past two days, although it must be thin since the snow did not survive on most of the exposed ground surrounding it. 

Yesterday I had to put a jacket on to descend City Creek Canyon on my early morning ride.  We've had minimums in the 60s five of the last six days.  Day length is decreasing noticeably now. 

It's coming!

Sunday, August 11, 2019

The Meteorology of the Salt Lake City Tornado (1999)

Today is the 20th anniversary of the Salt Lake City tornado, which I would rate as the most significant meteorological event to affect my neighborhood (The Avenues) since we moved there in 1996.

A detailed account of the tornado event is described by Dunn and Vasiloff (2001).  The tornado formed just west of downtown Salt Lake City and tracked roughly northeastward through portions of downtown, Memory Grove, and the Avenues.  It produced a path of moderate to considerable damage consistent with a rating of F2 on the old Fujita Scale (since replaced by the Enhanced Fujita Scale).  The damage path looked as if someone had sliced across the area with a surgical knife producing a narrow swath of damage with no damage in the surrounding area.

Source: Dunn and Vasiloff (1999)
The tornado touched down at 1840 UTC (1240 MDT).  I recall that we had gone with a group out to lunch and were returning to the office, commenting about the darkness of the sky and joking as Utah meteorologists do about it potentially being a "severe" day (this isn't tornado alley).  Shortly after returning to the office, someone yelled "tornado to the west", a comment that was initially met with derision, but eventually we all ran outside to watch.  The photo below was taken by our department web cam, looking west from the Browning Building on the University of Utah campus.

Source: University of Utah, Dunn and Vasiloff (1999)
It was the first and thankfully only tornado I've seen personally.  In reality, the smart thing to have done would have been to call my family and the National Weather Service immediately.

The tornado tracked within 2 or 3 blocks of our home.  My parents were in town and as the story goes, my father was eating lunch, looked out the window, and said "holy s---, a tornado."  I do not know if that is true, but it's a good story if it isn't.  He took my year-old son and my mom into the basement where they spent a tense several minutes.  We found some debris on our roof, but that wasn't anything to complain about.

In these pre-twitter days, we had no idea how bad things were until we began looking around the neighborhood that evening.  It was heartbreaking.  The Deseret News published a good review of the event two years ago that is worth a read and included the photo below, which shows the catastrophe suffered by our neighbors.

Source: Gary McKellar, Deseret News
The tornado resulted in one fatality, 80 injuries, and 300 damaged or destroyed buildings, 34 of which were uninhabitable.  Total damage was estimated at $170 million.

Dunn and Vasiloff (2001) show that the tornado formed along a convergence zone that was may have been a lake breeze front.  A strong updraft, associated with convection that formed initially over the Oquirrh Mountains, moved over this boundary and led to tornadogenesis.  The tornado was what is sometimes referred to as a non-descending or nonsupercell tornado.  Such tornadoes are typically short lived and more challenging to forecast, and indeed, the National Weather Service issued no tornado warning.

One reason for the lack of warning is poor observation of the lower atmosphere over the Salt Lake Valley by the National Weather Service Doppler Radar on Promontory Point, KMTX.  That year, however, the FAA installed a Terminal Doppler Weather Radar (TDWR) near Layton.  The TDWR was designed for detecting wind shear and other hazardous weather conditions at the Salt Lake City airport and provides higher resolution and lower altitude surveys over the Salt Lake Valley.  The data it collected was used extensively by Dunn and Vasiloff (2001) to understand the event. 

Integration of the TDWR data into National Weather Service operations, combined with improvements in KMTX scan strategies and algorithms, offer some potential that a warning would be issued for a similar tornado if it occurred today in the Salt Lake City area, although the lead time would likely be short (minutes).  Issuing warnings for this type of tornado is still very difficult and poses many challenges for contemporary forecasters.

One thing I take away from this event is that it could happen again.  Perhaps not in the same way, but the ingredients that came together on August 11, 1999 are not all that uncommon to find.  We often see convection initiating over the Oquirrhs and a convergence zone somewhere over the Salt Lake Valley as the lake-breeze front penetrates southward.  Most of the time, things don't align properly, or the convection isn't strong enough, or the the land-breeze front is sharp enough.  We also see weak tornadoes from time to time in other parts of Utah, something that has become more apparent with the proliferation of smart phones.  We should be cautious about discounting the likelihood of these events and attentive during periods of severe weather.  Know to take action by moving away from windows and exterior walls and into the basement or small interior rooms of your house (e.g., bathroom).  See for more information.

Saturday, August 10, 2019

The Joy of Solar

I did some work this past week on my chimney, which required me to get up on my roof.  While up there, I was reminded that I have a set of solar panels up there that have been doing the job now for about 2.5 years.

They are pretty stealthy.  Our roof is low pitched, so you can't see them at all from the road or from our yard.  They make no noise.  They produce no emissions.  Yet over the past 2.5 years, they've generated 23.2 megawatt hours of power.  We just pay our $9 grid-tie fee each month to Rocky Mountain Power and call it good. 

We've seen no drop off in production, despite the fact that I've done no maintenance.  July is a good month to gauge production since the weather variability is lowest during that month.  Over the past 3 Julys, we produced 1186, 1163, and 1173 kilowatt-hours of power.  That's pretty damn consistent. 

Whether or not solar makes sense for you depends on many factors.  However, I can give it a big thumbs up for our sun-exposed home. 

Friday, August 9, 2019

Downpours, Debris Flows, and Road Closures, Oh My!

Yesterday evening's storms came through with a vengeance for some areas of northern Utah, generating heavy precipitation and debris flows that forced the closure of SR-210 in Little Cottonwood Canyon, SR-6 in Spanish Fork Canyon, and the Amtrak line through Spanish Fork Canyon, as well as the evacuation of residents near Loafer Canyon.

It was only a couple of weeks ago that the Tour de France was forced to alter stages due to severe thunderstorms and debris flows in the French Alps.  At that time, I wrote that organizers of the Tour of Utah should take the opportunity to learn from that experience since they be dealing with a similar scenario (see Weather Hazards and Bike Racing).  Although I recognized this as a possibility in Utah, I wasn't anticipating that we would see such a severe event this year.  Nevertheless it has happened, and the prologue scheduled for Little Cottonwood Canyon is only three days away (Monday, August 12).  Of course, when it comes to incidents like this, there are more important issues at play than a bike race.  Thankfully, I haven't heard any reports of fatalities or injuries.

Let's take a look at what happened in Little Cottonwood late yesterday.  To begin this discussion, we should first note the conditions leading up to the event.  On August 1st, the Alta Coop Site reported 0.40 inches of precipitation.  On the 3rd, the it reported 2.11 inches of precipitation.  That event produce runoff in the upper canyon, with shallow layers of mud and rocks covering the road in the upper canyon in places (see Saturday's Cottonwoods Deluge).  The next four days leading up to yesterday's event produced 0.01, 024, 0.01, and 0.02 inches of precipitation.  Thus, the water content of soils in the canyon was likely high, limiting their ability to absorb and retain precipitation.

I suspect it rained lightly yesterday morning (although automated gauges at Collins and Alta Base show no measurable precipitation).  As that precipitation band exited, skies cleared and band of precipitation with embedded thunderstorms began to move into northern Utah.  See the tweet below for radar image at 2222 UTC/1622 MDT).  The stage was set for late day thunderstorms.

Indeed, those storms produced, with embedded cells generating locally heavy precipitation.  The radar loop below covers the period from 0102-0220 UTC/1902–2020 MDT with a black line indicating the ridgeline between Little and Big Cottonwood Canyons.  It shows a very intense cell moving across the southern Salt Lake Valley and into the central Wasatch.  Radar reflectivities above 35 dBZ and frequently above 50 dBZ, indicative of heavy precipitation, linger on the ridge for a period of about 40 minutes.

Radar estimates of precipitation have their issues and so one needs to recognize their can be large uncertainties, but the one I have access too pegs the maximum accumulated precipitation for the 1 hour period ending at 0220 UTC/2020 MDT at about 3 inches very near the Little Cottonwood-Big Cottonwood Ridgeline.  That pixel appears to be just north of Lone Peak in the upper Broads Fork/Lake Blanche area.  Although that is north of the divide, there is some uncertainty in the exact location of where precipitation falls out due to transport by the wind and other factors in and below the radar sampling volume.

The bottom line is that heavy precipitation fell in a short period of time in an area where soils were already somewhat compromised by prior precipitation.

Given that the storm came in at dusk, UDOT is just starting to send out videos of the damage.  Here's one from their Public Information Officer John Gleason.

Inevitably, I expect that we're going to hear that this was a "one in whatever year" event.  Based on the NOAA Precipitation Frequency Data Server, a three inch accumulation in 60 min has an average recurrance interval at 10,500 ft in the central Wasatch of about 500 years.  Or, better put, the odds of such an accumulation happening at any point in that area in any given year is about 500 to 1.

However, some caution is needed here.  First, I'm not sure how confident to be in the radar precipitation estimates.  That is going to require some digging.  Sadly, I don't think there is a precipitation gauge very near the area of maximum precipitation.  Alta-Collins, Alta-Base, and the Snowbird SNOTEL reported .45", .59", .7", respectively, in the 1-hour period ending at 0200 UTC/2000 MDT, but they were outside the core of heaviest precipitation.

Second, as you can infer from the 1-hour accumulation image above, thunderstorm accumulations can be very localized.  Remember that 500 to 1 is a point probability, not an area probability.  The odds of such an accumulation happening somewhere in the Wasatch Range would be greater.

Nevertheless, this was certainly an exceptional event with remarkable impacts.  It serves as a reminder of the vulnerability of mountain communities and highways, especially SR-210, to severe and hazardous weather.

Blogger's Note: The recurrence interval figure has been updated from the original post to include the legend. 

Thursday, August 8, 2019

"Perfect" Weather

If you've lived in Utah long enough, you know that a "perfect" weather day in July or August isn't sunny, but instead cloudy with rain or at least rain showers.  Today nails it as far as I'm concerned.

As of 2:30 PM MDT, we've had predominantly cloudy skies all day with some showers and some drippy rain at times.  Temperatures overnight were warm and the overnight minimum was only 69ºF, but after a warm start to the morning with temperatures in the mid 70s, rain moved in and dropped the temperatures to as low as the mid 60s at about 1 PM.  At 2:20 it was 71ºF with a dewpoint of 62ºF.  PERFECT

Source: MesoWest
Really, on the regional scale, the airmass we're presently in isn't all that cool.  Move south and you'll find an 88ºF in Milford or north for an 82˚F in Dubois.  Thank the well timed showers for the natural air conditioning today.  

And, as I like to say, things are going to get interesting later today.  The band of showers that came this morning and early afternoon is exiting to the north and a nice clear slot is opening up over northwest Utah.  Further upstream and just beginning to move across the boarder are some stronger storms. shows that the stronger cells are producing lightning.  

So, speaking like a meteorologist, if we're lucky, we'll get some action later this afternoon and this evening as the sun juices things up.  Keep your fingers crossed.

Wednesday, August 7, 2019

Secrets about Syllabi

OK, this isn't really about secrets about syllabi, but that's a catchy headline and since the Salt Lake Tribune decided to make the addition of safety information in syllabi at the University of Utah a major story (click here), I thought we could talk about it a bit today.

The University of Utah and other institutions of higher learning in the United States are facing many challenges related to campus safety and student mental health.  In the case of campus safety, I think it is safe to say that gun violence is an omnipresent concern, but there are other concerns including rape, sexual assault, harassment, etc.  In the case of student mental health, an increasing number of students at U.S. institutions of higher education, including the University of Utah, are seeking mental health services (see Under Pressure: The Growing Demand for Student Mental Health Services).

As a faculty member and a parent with two kids in college, one at the University of Utah, these issues concern me greatly.  In addition, spending time teaching at the University of Innsbruck earlier this year was a real eye opener.  First, gun violence is much less common in Austria and I can't recall ever having to do active shooter training as I have done both voluntarily and as mandated here at the University of Utah.  Second, stress amongst students is noticeably lower.  I didn't think once about adding statements about campus safety or counseling services to my syllabi there.

Here, however, I've voluntarily included a statement on counseling services in my syllabi for several semesters.  I decided to do this after visiting Penn State where, while discussing the difficulties contemporary students are having managing stress and other challenges, I learned they were requiring such a statement.  I read over their statement, decided it was a good idea, and adopted it to suit my needs.  It's not much, but at least I can mention it to students and let them know that I'm thinking of them and provide them options for professional support. 

I will add the campus safety statement, although I do have some concerns.  As noted in the Tribune article, there are some professors that are concerned that there are simply too many things being added to the syllabus.  Indeed, each semester, I consult the University of Utah Center for Teaching and Learning Excellence Syllabus Checklist, which includes a list of essential and strongly suggested content for syllabi.  It is now seven pages long.  Amongst the essential and strongly suggested content are statements or recommendations to include statements on sexual misconduct, campus safety, the academic code of conduct, student names and personal pronouns, diversity/inclusivity, undocumented student support, faculty and student responsibilities, content accommodations, syllabus changes, plagiarism software policies, official drop/withdraw date, attendance/tardy policy, wellness statement, the veterans center, learners of English as a second language, plus some additional statements concerning online and hybrid courses.

I don't wish to argue that any of these are unimportant, and I recognize that it is my option to include some of these in my syllabus, but the University needs to think much more carefully about how to prioritize this information and select what is most effectively provided via a syllabus versus other means of dissemination.  As the proverb goes, "the road to hell is paved with good intentions."  There are certainly good intentions behind these efforts, but with prioritization and pruning, we have a better chance of ensuring that our desires lead to effective outcomes.  Just because the syllabus is a convenient place to add statements, doesn't mean that it will be an effective place to provide information.  Let's make it easier for students to sip from the fountain of knowledge rather than being soaked by a firehose.

Sunday, August 4, 2019

Saturday's Cottonwoods Deluge

In late July, the last two mountain stages of the Tour de France were shortened due to hail and mudslides associated with severe convective storms of the western Alps.  As we discussed in a blog post following stage 19 (see Weather Hazards and Bike Racing), there is a very real possibility that the Tour of Utah could be affected by a similar storm.

Indeed, it is a good thing that the Tour of Utah wasn't being held in the Cottonwoods yesterday afternoon when severe thunderstorms dumped their goods in the central Wasatch, producing what the National Weather Service reported as two-inch per hour precipitation rates.  

Hail was also observed and covered the highways in both canyons per the National Weather Service.

Alta today showed plenty of evidence of heavy rainfall and associated runoff with a shallow layer of mud and rocks covering the highways and parking lots in places.  It must have been a scary experience for anyone caught out hiking, climbing, or biking during this storm. 

Let us hope we don't have a repeat for the Tour of Utah.  

Thursday, August 1, 2019

July Was Hot, but Thankfully Is in the Rearview Mirror

Yesterday was a wonderful last day of July.  Temperatures at the Salt Lake City International Airport topped out at 92˚F, but with rain moving it, it was drippy and 69˚F by 6 PM.  It was wonderful to feel the cool air and let my skin soak up the moisture.

It was my impression that July wasn't horrible.  This might reflect the fact that I lived through the European June heat wave or that we did have the occasional cool day to break up the July low-variability monotony.  However, a look at the numbers shows that the average temperature at the Salt Lake City Airport this July was still remarkably warm compared to the past.  It rates as the 9th warmest since 1874.  And, just to illustrate that you aren't living in your grandparents climate, there wasn't a single July as warm as this one until 2003.  In other words, this July was hotter than any July on record in the late 19th and 20th centuries.

Source: NOAA Regional Climate Centers
Further, the 12 warmest Julys have all occurred in the 21st century.  Brutal.

Elsewhere in July, probably the two biggest stories globally have been the extreme warmth observed in late July in Europe, during which all-time high temperatures were recorded in Belgium, Germany, Luxembourg, the Netherlands, and the United Kingdom, as well as significant melting events on the Greenland Ice Sheet.  The World Meteorological Organization (WMO) provides a summary here.  June 2019 rated as the warmest on record, and I suspect July will rate amongst the warmest if not the warmest.

Thus, it's good to have July in the rearview mirror.


Posting time series from Heber City and Tooele for comparison and to illustrate that similar trends are seen elsewhere and in less urbanized areas, although the urbanization may exacerbate things in Salt Lake.  

Wednesday, July 31, 2019

Will This Monsoon Surge Produce?

An impressive surge of monsoon moisture is currently occurring over Utah.  Below is a loop of High Resolution Rapid Refresh (HRRR) model analyses and forecasts of precipitable water for the period from 0400 UTC 31 July (2200 MDT yesterday) through 0200 UTC 1 August (2000 MDT this evening).   Precipitable water is the depth of water you would have on the ground if you were to condense out all the water vapor in an atmospheric column.  Thus, it is a measure of the total integrated water vapor in the atmosphere.  Note how high values move northward from Arizona and the lower Colorado River Basin into Utah.  Values in Salt Lake City increase from about 12 mm (0.5 inches) to about 30 mm (1.2 inches). 

Surface dewpoints overnight increased steadily with the surge, as illustrated by meteograms for St. George and Salt Lake City. 

The latest (1505 UTC/0900 MDT) satellite and radar analysis shows extensive upper-level cloud cover over Utah.  Relatively weak and spotty radar returns are evident over northern Utah, although much of that is probably not reaching the ground yet. 

Concerns for the forecast today include where will the moisture go and how will the forcing for convection and thunderstorms evolve.  The HRRR simulated reflectivity forecast does bring some showers into northern Utah, some of which may be strong enough to generate lightning and thunder.

No model today can reliably predict the timing, location, and intensity of monsoon precipitation and thunderstorms.  Be aware of the possibility of rain, which could be locally heavy, as well as the possibility of lightning and thunder.  Below is the latest summary from the National Weather Service.

Also, remember that individual storms can sometimes produce more precipitation than indicated by precipitable water values.  This is because storms process water vapor not only from the column overhead, but also from the surrounding area.  Thus, precipitable water should not be interpreted as the maximum amount of precipitation that could fall, but instead simply as a measure of how much water vapor is in the atmosphere. 

Monday, July 29, 2019

Meteorology of a Monsoon Surge

Last week, we discussed how we were in a pattern characterized by persistent upper-level ridging over the western United States, but that "critters in the woods" would modulate the monsoon moisture and shower and thunderstorm activity (see Persistent Large-Scale Pattern with Critters in the Woods). 

One of those critters gave us the relatively pleasant weather on Saturday and another will be affecting northern Utah on Wednesday. 

The setup for Wednesday illustrates how both large-scale and small-scale features play an important role during the monsoon.  The situation at 0600 UTC 30 July (0000 MDT Monday) shows a high-amplitude upper-level (500-mb) ridge centered near the 4-corners area.  Anticyclonic (clockwise) flow around this larg-e scale feature results in westerly flow to our north and easterly flow over northern Mexico as depicted below. 

However, there is also an important smaller-scale circulation feature over northern Mexico.  I have identified this feature using contours of vorticity, a quantity used by meteorologists that essentially represents the circulation density.  Vorticity helps identify areas of strong shear and curvature in the flow.  Note that there is a local maximum, denoted by an X, over northern Mexico.  Meteorologists call such a feature a vorticity maximum, and this is our critter in the woods for Wednesday.

Typically, the large-scale flow "steers" vorticity maxima, but vorticity maxima also interact with the large-scale flow and can strongly affect the weather.  In the GFS forecast panels below, which cover the period through 0600 UTC 1 Aug (0000 MDT Thursday), the vorticity maximum is coaxed northward by the circulation associated with the large-scale ridge while at the same time it intensifies, resulting in enhanced southerly flow to its east. 

Together, this pattern leads to a very pronounced northward surge of monsoon moisture into Utah, as depicted below by the loop of precipitable water.

For the forecast, however, there are some differences in where the models place the moisture.  For instance, the GFS forecast for 0000 UTC 1 Aug (1800 MDT Wednesday) has the moisture plume covering central and western Utah, whereas the NAM has the moisture plume in central and eastern Utah. 

We'll see how this all plays out, but keeping an eye on forecasts and recognizing the potential for thunderstorms and related hazards is essential for Wednesday and Wednesday night. 

Sunday, July 28, 2019

Central Wasatch Peak Bagging

I've been in Salt Lake City for nearly 25 years and in that time I've never been to the top of the American Fork Twin Peaks.  That changed today as my son and I bagged it via Gad Valley from the base of Snowbird. 

It's a really great hike, with some ridge scrambling that is fun and offers some great views. 

The photos above were taken in fairly meadowy areas.  In others, there's some rock hoping and scrambling to be had, but not difficult.  Perhaps class 3 in a few places.  In places there's a faint trail, but not much.  

Views from the Red Stack were really spectacular. 

Ditto for the views from the American Fork Twin. Timpanogos still has plenty of snow up high and the USFS was recommending ice axes/traction devices for ascending the Timp "Glacier".  

I didn't feel bad about leaving my skis at home, however, when looking down Pipeline.

I don't know where the Snowbird expansion plans are these days, but I hope that the summit of this  magnificent peak remains unspoiled.  

Friday, July 26, 2019

Weather Hazards and Bike Racing

I'm a big fan of the Tour de France, despite cycling's spotty history with performance enhancing drugs.

In recent years, Team Sky (now Team Ineos) has dominated the race, making for generally boring racing, but this year, the race has been wide open, with as many as six riders having a legitimate shot at the yellow jersey entering the final three stages.  Further, the leader entering stage 19 (of 21), Julian Alaphilipe, was not a pre-tour favorite, adding to the intrigue.  Major surprises in long stage races are few and far between.

I was hopeful that today's stage would remain dry after consulting MeteoFrance's Arome model yesterday, but it wasn't to be.  Thunderstorms laid down a major coating of hail on the end of today's stage, necessitating a halt of action while the riders were descending from the penultimate climb.  Conditions along the route to come were indeed unsafe.  Comically, overhead shots showed what looked to be a snowplow in action.

Sadly, some news reports claimed that the tour was stopped because of a snowstorm.

Hail ≠ snow.  Oh the pain and agony of it all!

There were also reports of a debris flow.
There was a time when the race would have gone on through such insanity, but they made the right decision today.

Tour of Utah organizers should take the opportunity to learn from this as "America's Toughest Stage Race" could similarly be affected by hazardous weather including but not limited to hail, flash flooding, debris flows, and lightning.

Thursday, July 25, 2019

Update on Eastern Alpine Glaciers

It was a pretty good snow year in the eastern Alps, but due to global warming, it's damn hard to have a year in which there isn't a net loss of glacier mass.

When we left Innsbruck at the end of June, the seasonal snow still covered much of the high eastern Alps, but that's changed in the past three weeks.  Seasonal snow on the Hintereisferner, Austria's best studied glacier, is disappearing rapidly, leaving grey glacier ice. 

Hintertuxer Glacier is Austria's only year-round ski area.  Here too, the deep seasonal snow cover is disappearing rapidly. 

Finally, there is the Schneeferner on Zugspitze, which is to the right of the building pictured below. It's beginning to suffer too.

I suspect at the end of summer, we'll see a net loss of mass for most of the glaciers in the eastern Alps.  Even in a good snow year, the summertime temperatures that exist today do their damage.  Additionally, the prolonged exposure of grey glacier ice results in increased absorption of solar radiation, further accelerating the loss. 

Tuesday, July 23, 2019

Persistent Large-Scale Pattern with Critters in the Woods

I'm not sure how blogger will handle it, but the loop below has been purposefully designed to run at high speed and to repeat to illustrate three key points about the GFS forecast for the next ten days. 

First, the large-scale pattern changes little with persistent upper-level ridging over the southwest U.S. and the westerly mid-latitude jet to our north.  There are variations in the strength of the ridge and the center of its circulation, but these are relatively modest.

Second, one can see precipitation "pulsing" in the lower right-hand panel, which depicts the surface forecast and includes the 3-hour accumulated precipitation.  This pulsing reflects the influence of the sun, with precipitation increasing and becoming most common later in the day and in the early evening and becoming less common over night. 

Third, as can be seen in the top two images which depict the upper-level pattern, there are some "critters in the woods" in terms of upper-level waves that are in the westerly jet to our north or moving in clockwise fashion around the upper-level ridge.  These smaller-scale features modulate the coverage, location, and intensity of the precipitation. 

Put it all together, and this is a very typical July pattern, as illustrated by the 10-day forecast. 

Personally, I'm already dreaming of September....