Wasatch Weather Weenies

Excuse the gloating, but yesterday's thunderstorms favored for once my are with the Avenues, downtown Salt Lake, and the University of Utah coming in with the highest precipitation totals in the Salt Lake Valley.  Observations for the 24-hour period ending this morning show several sites reporting accumulations of around 0.3 inches.   Source: MesoWest Multisensor precipitation estimates of 24-hour accumulated precipitation show a band of precipitation extending from West Valley City across the Salt Lake Valley and into the Avenues Foothills.  This pattern primarily reflects three thunderstorms systems that developed and intensified in the southwesterly flow as they moved across the northern Salt Lake Valley.  The heaviest precipitation was actually in the mountains northeast of Salt Lake City.   Source: https://mrms.nssl.noaa.gov/qvs/product_viewer/ The first system moved across the northern Salt Lake Valley from about 4:30 to 5:30 PM MDT, interru...

 UTA announced yesterday major cuts to ski bus service for this coming winter.  For the Cottonwoods: Route 953 up Little Cottonwood is suspended Route 972 up Big Cottonwood cut from 15-minute to 30-minute service Route 994 up Little Cottonwood cut from 15-minute to 30-minute service. A full description of cuts (or what they call "adjustments") is at  https://www.rideuta.com/Rider-Info/Ski-Service .  Below is a screenshot from that site, discussing their explanation for these service cuts.  There are a few other cuts in service on non-ski routes (see  https://www.rideuta.com/Rider-Info/Change-Day ).  In Salt Lake county, four non-ski routes will see service frequency reductions.   I hereby declare Joni Mitchell's song Big Yellow Taxi the official song of the Central Wasatch.  "Don't it always seem to go that you don't know what you've got until it's gone."

Call it Fall if you want to, but what I like to call the "bonus season" is upon us as a ridge in late September and October makes for beautiful weather, cool mornings, and sparkling afternoons.  Add the changing leaves and you have simply spectacular weather for mountain biking, hiking, or any other outdoor pursuits that don't require snow or ice.   Reds, oranges, and yellows are now dotting the Corner Canyon area and temperatures are near ideal for a steady morning climb.   It's bittersweet to ride in the Corner Canyon area knowing that expansion of trails in the Avenues foothills remains paused.  Corner Canyon has a great trail network, with a mixture of hiking trails, mixed use trails, and downhill bike flow trails.  I'm old enough to remember riding there on the old ATV and jeep trails before there was development.  Those trails have now been supplemented with better engineered single track trails, greatly expanding the riding and hiking poten...

I understand I've missed some exciting weather in northern Utah, but I have been in Steamboat Springs this week teaching an immersive course in mountain field research at Storm Peak Lab with Drs. Gannet Hallar and Sebastian Hoch.  We brought 14 graduate students here thanks to support from the National Science Foundation.   Hungry students after the long drive to Steamboat Storm Peak Lab is a mountaintop observing facility that has operated at one location or another near the top of Steamboat Springs Ski Area for more than 40 years.  The current facility was constructed in 1995.  The University of Utah recently took over operations of the lab from the Desert Research Institute.   Inside and attached to the lab are a bevy of chemical, aerosol, biological, and microphysical instruments to better understand everything from regional air quality and pollution to mountain precipitation processes.  We spent two days at the lab learning about the instrume...

Pretty exciting stuff happening right now over the north Pacific and Bering Sea where a powerful cyclone is disrupting the jet-stream level flow with implications for the weather of the western continental United States.   Understanding the event requires going back in time to 0000 UTC 14 September (6 PM MDT Wednesday 13 December).  At this time, tropical storm Merbok was moving poleward (identified below with an L) and about to interact with a trough in the mid-latitude westerlies (red dashed line).   These two features got together and decided to "go off."  With an assist from the upper-level trough, Merbok underwent what is known as extratropical transition , evolving from a tropical storm into a extratropical cyclone of the type found in the mid and high latitudes.  It also deepened explosively to remarkably low pressures.  At 0600 UTC 16 Sep (Midnight MDT last night), the cyclone was centered in the western Aleutians (L in the figure below) w...

I woke up this morning to the smell of rain, or what is known as petrichor.  The UK met office has a nice web page explaining the origins of the word and what causes the smell.  It says, " Raindrops landing on dusty or clay soils trap tiny air bubbles on the surface which then shoot upward — as in a glass of Champagne — and burst out of the drop throwing aerosols of scent into the air where they are then distributed by the wind ." Radar imagery at 1402 UTC (8:02 AM MDT) showed showers over portions of northern Utah, some likely heavy, especially in the West Desert.  I'm quite glad to see this as although we had an active monsoon for part of the summer, the last couple of weeks have been hot and bone dry.  On the other hand, there are concerns about flooding produced by heavier downpours.   The HRRR suggests that in the Salt Lake Valley we may see more isolated to scattered showers for a time today before things pick up again in the afternoon.  We'll s...

Tomorrow looks to be a day of change for northern Utah, one that might even bring....wait for it...rain!   We haven't had rain around here so far in September.  The last measurable precipitation at KSLC was on August 19th.  I've lost several perennials in this stretch.  They just seem to have given up.   Below is a test to see if blogger can deal with an animated png.  If it works, you'll see a loop of the HRRR forecast over a 48-hour period through 1200 UTC Wednesday, with shower and thunderstorm activity spreading into northern Utah.   If it doesn't, you'll see a static image for this (Monday) morning at 1200 UTC with an area of precipitation over northern Arizona and southern Nevada.  If that's the case, it also means I have some more work to do to figure out how to animate our new graphics for this blog.  

I could summarize the remarkable 7-day run of temperatures during the first week of September or the push of smoke into northern Utah to add insult to injury, but let's talk about something positive for once.   This week, I finished what I'll call phase one of upgrades to the graphics on weather.utah.edu .  This has been a heavy lift.  Many of the graphics on weather.utah.edu were produced by software I developed in 2002–2003, especially those for plotting the HRRR, NAM, and GFS.  Back then, I wasn't an old manager like I am today.  I could still code (using the languages of the time).  To do this most recent upgrade, I had to basically learn to code again, this time in Python, dealing with all of the ugliness of meteorological data formats, kludgy python functions, and multiprocessing.  As is often the case, now that I'm done, I could probably rewrite everything much more succinctly and efficiently, but it's now good enough for government work....

Placing this week's heat wave into context raises all sorts of questions concerning the veracity of weather observations, including extremes and long-term trends.  The relatively high maximum temperatures at the Salt Lake City International Airport have really cast a spotlight on this.  In fact, yesterday the National Weather Service did some measurements in the surrounding area.  They posted a complete summary thread on twitter that you can access beginning with the tweet below. We remain committed to ensuring the best quality temperature observations at our official Salt Lake City Airport climate site. Today during peak heat we visited a natural landscape location just ¼ mile south of the official site with 5 temperature sensors. A thread🧵 pic.twitter.com/Zco0vNbYS0 — NWS Salt Lake City (@NWSSaltLakeCity) September 8, 2022 The long and short of it is that the area south of the airport is a very hot place.  They found good correspondence between multiple measureme...

It's been a pretty crazy 24-hour period on the meteorological "front."  Yesterday's high at KSLC was an incredible 104˚F.  Not only is this an all-time record for September, but it is the highest temperature ever reported at KSLC after August 5th.  Some colleagues of mine pointed out that this was 4˚F warmer than reported at surrounding sites.  I have to concur that the airport highs seem jacked, whether it be instrument or siting characteristics.  Nevertheless, 100-102 would still tie or beat the all-time for September, so it remains blisteringly hot for this time of year.  I took the picture below at about 7:20 this morning while mountain biking in the Avenues foothills.  Notice anything unusual?  Ha ha.  You can't see anything unusual, but the temperatures sure were.  I woke up at 6 am and it was 80˚F at my house.  80!  Overnight downslope winds in the University of Utah area kept overnight temperatures quite elevated. Surfa...

Heat, heat, and more heat. What more can I say.  Salt Lake City easily tops records for the warmest four day stretch in the last week of August and first week of September with an average temperature of 85.9˚F.  Prior to 2022, the old record was 84.1˚F, set from 1-4 Sep 2019.  Prior to 2000, the record was 83.0˚F (26–29 Aug 1997).   If you don't like the airport obs, 1-4 September 2022 was also the warmest four-day stretch on record in the last week of August and first week of September at Bountiful Bench (complete records since 1975) with an average temperature of 82.3˚F.  The prior record was 81.9˚F from 25-28 August 1997.   Forecasts continue to advertise near or above daily-record warmth through Wednesday.  I suspect we will obliterate the average temperature for Sep 1-7 at the airport and many other stations in northern Utah.  There may be a slight retreat in temperatures after Wednesday, but they will still remain well above recent...

We are mired under a persistent upper-level ridge that is bringing record setting heat to a big portion of the west.  Yesterday's high of 102˚F at KSLC is the highest ever recorded in September.  Records are falling elsewhere as well.   High 90s and low 100s look to predominate through at least next Wednesday.  The overnight forecast for early next week from the GFS in particular caught my attention.  There's still a monster ridge over the west and 700-mb temperatures at 0000 UTC 7 September (6 PM MDT Tuesday) near 20˚C over much of Utah.   I often talk about the 20/20 rule for forecasting here.  Anything below -20˚C or above 20˚C at 700-mb (about 10,000 feet) is exceptional at KSLC.  The plot below shows statistics of 700-mb temperatures observed in upper air soundings collected at Hill Air Force Base or KSLC from 1950 to 2019.  The highest 700-mb temperature observed is 20.2˚C.  The highest for August or later is 19.4˚C....

Questions about the representativeness of the KSLC observing site notwithstanding, below are the new records for Salt Lake City based on official records from the National Weather Service.  Figures are from https://xmacis.rcc-acis.org/. 1. Highest average maximum temperature, 94.1˚F.  2. Highest average minimum temperature, 68.8˚F. 3. Highest average temperature, 81.5˚F. 4. Days with a maximum temperature ≥ 100˚F, 27. 5. Days with a minimum temperature ≥ 70˚F, 53. In an earlier post ( A Look at Max Temps @KSLC ) we took a look at temperatures at the observing site compared to site on the Bountiful Bench.  At that site, records go back to 1975 and this summer's mean maximum temperature was the 5th highest (86.5˚F, the record is 87.7˚F in 2007), the mean temperature was the third highest (76.0˚F, the record is 76.4˚F in 2021), and the mean minimum temperature was the second highest (65.5˚F, the record is 65.5˚F in 2021).  Let's also look at the top 5s for each of these...