Wasatch Weather Weenies

Through 6 AM, the overnight minimum at the Salt Lake City airport was 58˚F, with temperatures likely falling below that prior to sunrise.  At my place, it was 55˚F when I awoke, with cool air pouring through the windows.  Relief!  Simply spectacular sleeping weather. Yesterday's high at the airport reached only 89˚F.  It was the first day we did not reach 90 or higher since July 22nd.  That 38 day run is the 4th longest on record, tied with four other such periods.  #1 is a 50-day run ending on September 5, 1967.   Yesterday's low was 63 and that marked the end of a run of 51 consecutive days with a minimum of 64˚F or higher at 51, the 2nd longest all time behind a 75-day run ending on August 8, 2013.   One brute-force measure of the demand for energy to cool buildings is cooling degree days.  Through yesterday, this August sits at 566, ahead of 2013 with 554.  Source: NOAA Regional Climate Centers Thus, regardless of where we...

 There's a lot going on today.  I'll have to go into rapid-fire mode. August Temperature Record a Lock?   2020 has opened up a bit more of a lead on 2013 for the warmest August on record.  The gap is now 1.1˚F.   The max/min temps for the last days of August 2013 were 84/71, 84/67, 93/67, 97/71, 97/71, 93/72.   NWS forecast calls for 96/68*, 94/71, 93/68, 92/67, 89/67, 81/60 (*last nights minimum).   Someone can run the numbers, but I'm betting if the forecast verifies, we'll have a new record given the current 1.1˚F lead.   August Precipitation Record a Lock?    Nope.  0.10" from overnight storms.  Easy come, easy go.   Cooling Coming! I'll just put this forecast here because it calls for an actual push of cooler air into northern Utah late Sunday.  It won't feel like fall, but it will drop us a bit below averages for Monday and Tuesday.  Did I just say that? Laura Looking Very Dangerous...

Today marks the first day of classes at the University of Utah and the start of a semester like no other.  You might be surprised to learn that nobody currently at the University of Utah, including us old timers, worked at the University of Utah during the Spanish Flu pandemic.  Even still, the world has changed a lot since then, so I think it is safe to say that Fall semester will be unique and unprecedented.   I've posted frequently over the past few months about delusional administrators and their plans for reopening.  We have already seen outbreaks at other Universities that have had to shift online.  The University of Utah has adjusted its plans during the summer to a greater percentage of online classes, which I was glad to see.  I have concerns in other areas, such as testing and transparency, which seems to lag behind institutions like the University of Illinois, which is now testing thousands of people a day for free and providing information ...

After two days of cowering inside due to high PM2.5 and afternoon ozone, I was glad to get out for a hike this morning.  In the Salt Lake Valley, PM2.5 has slowsly been declining since it's peak very early Friday morning and is now sitting near the transition from low to moderate (top graph below, with green indicating low values and yellow moderate).   Additionally, although ozone peaked at unhealthy levels the last two afternoons, it appears to be leveling out at moderate levels this afternoon, although I can't rule out a spike to higher levels later.   There are two big differences between summer smoke and winter particular matter events.  The first is that, as evident in the graphs above, summer smoke can be accompanied by unhealthy ozone concentrations during the day.  Basically, it's a double whammy for bad air quality.  The second is that mixing during the summer occurs through a deep layer, so when the smoke is thick, it's usually thick ev...

If we were to name ridges like we name Hurricanes, surely the one that has gripped the western U.S. in recent days would be called Satan or Lucifer because it is straight from hell. You are already aware of the heat records.  130˚F in Death Valley, the 3rd highest temperature every recorded on this planet (and possibly the highest).  Five record highs at Salt Lake City so far this month, including two consecutive days of 105˚F on the 1st and 2nd and three straight above 100˚F this week.  Below average precipitation across much of the interior western United States, but lightning sparked fires in California.  Indeed, the Devil would be proud. Now we add poor air quality to the mix in Salt Lake City, with PM2.5 concentrations rising overnight due to smoke with values peaking at 86.1 ug/m3 (unhealthy) and remaining high at 44.3 ug/m3 (unhealthy for sensitive groups) at 6 am this morning.   Source: Utah Division of Air Quality That was high enough to cause me t...

Last night was pretty miserable.  The overnight minimum was only 78˚F.  If 78˚F were to survive through the calendar day, it would stand as the highest daily minimum ever recorded in August (the current record is 77˚F, observed several times).  The highest daily minimum on record is 81˚F on July 18, 2016.   Really, August rates pretty high on the misery scale overall.  As illustrated by the graph below, the August 1-19 period has been remarkably warm with an average temperature of 83.9˚F, which is the 2nd highest all time behind only 2013 (84.1˚F).   Source: NOAA Regional Climate Centers During the month to date, every day has had a maximum above average and a minimum at or above average (range of average temperatures in graphic below indicated by green fill).   Source: NWS In addition, 7 of the 18 days have had a maximum of 100˚F or greater and all but three have had a maximum of 95˚F or greater.   Was there any night relief?...

 Yesterday's maximum temperature at Furnace Creek in Death Valley reached 130˚F.   Source: Richard Brian/Las Vegas Review-Journal/AP It appears that this is the third highest temperature ever recorded on the face of the Earth, behind the 134˚F recorded in Death Valley on July 10, 1913 and 131˚F in Kebili, Tunisa on July 7, 1931.  Both of those early 20th century temperatures have, however, been called into question by weather historian Christopher Burt (see this Capital Weather Gang article ).    Let's have some fun and compare the 134˚F day in Death Valley to yesterday's 130˚F.  We can do this using the 20th century reanalysis, which has created global atmospheric analyses from 1835 to 2015.  The 20th century reanalysis is a product of mathematical and statistical wizardry in which surface observations, which are essentially the only observations available in the 1800s and early 1900s, are used to create an analysis.   Below I plot the ...

The forecast for the next week is ugly.  Persistently dry, hot weather of the variety that I despise.   Today will probably be the coolest day of the next week.  The GFS 700-mb (roughly 10,000 ft above sea level) temperature forecast below shows the highest temperatures over western North America moving over Utah this weekend and then remaining until at least 1200 UTC (0600 MDT) 21 August when I decided not to look any farther out.   Afternoon 700-mb temperatures are above 18˚C in northern Utah on some afternoons, such as 0000 UTC 19 August (1800 MDT Tuesday).  This is exceptional warmth for mid August.  In the upper-air sounding record for the Salt Lake City International Airport, the highest 700-mb temperature on record is 20.2˚C (measured at 0000 UTC 13 July).  After 10 August, however, the highest 700-mb temperature on record is 18.4˚C.   Consistent with the GFS forecast, the National Weather Service has issued an Excessive Heat...

News headlines related to higher education this week are dominated by articles about the postponement of the football season by the Big-10 and Pac-12, including the impacts on student athletes, athletic department budgets, and regional economies. Don't let this distract you from the reality that higher education is about to embark on a grand experiment as they attempt to reopen in various ways for the fall semester. My daughter leaves today for her junior year at Arizona State University.  She came home in March after ASU foolishly decided to reopen after spring break, only to move everything online two days after students returned.  For fall semester, their home page advertises a "safe and welcoming environment." The latter is possible, the former unclear.   At the University of Utah, where my son is a student (and I'm a faculty member), the home page makes no assertions to safety, but simply welcomes new and returning students.   Both Universities have be...

Blogging has been tough the past few weeks as the weather has been pretty monotonous.  The monsoon has largely been a nonsoon for Utah (and Arizona).   That doesn't look to change through at least Friday.  The color fill in the GFS forecast loop below is a variable known as precipitable water.  Precipitable water is a measure of the total amount of water vapor in the atmosphere, expressed as the depth of water if all that water vapor were condensed out.  This time of year, 12.5 mm might give you an isolated dry thunderstorms over the mountains.  Shower/thunderstorm and precipitation potential increase as precipitable water approaches 25 mm or an inch, when I start to pay closer attention.  I've picked a color scale below that transitions from light brown to green to blue around 20 mm.   Today, we have some weak instability and moisture with precipitable water around 15 mm.  Thus, we could see a few thunderstorms in northern Utah, bu...

 

A weak trough is pushing into northern Utah this morning, bringing in slightly cooler air and just a bit of relief from our recent run of hot weather.   MesoWest observations this morning show northwest to northerly flow across northwest Utah, especially along I-80, over the western and northern Great Salt Lake, and along the Utah-Idaho border.   Source: Mesowest Time series from milepost 29 along I-80 show a wind shift, increase in dewpoint and humidity, but virtually no drop in temperature with the trough passage. Nevertheless, there is a slight decline in temperature over the 24-hour period, so there is a very slight transition to a cooler airmass. The HRRR calls for winds in the Salt Lake Valley to shift to NW this afternoon.  This is consistent with both the approaching trough and the usual development of afternoon up-valley flow and lake-breeze effects.  The trough is so weak that it is difficult to entangle these forcing agents.  Perhaps we'll s...

Jack Hales is an alum of my department at the University of Utah with 46 years of experience in the National Weather Service, including time as a forecaster at the Storm Prediction Center, which is basically the Dream Team for US meteorologists.   He retired in 2011 to Star Valley in Wyoming and runs the Star Valley Weather Blog .  He has just posted a detailed analysis of the recent Teton Village Balloon Accident showing it was caused by a microburst.   It's worth a look and is a good reminder of the dangers of microbursts not just for airplanes, but other aviators.

You may have seen videos of the terrifying and tragic explosion in Beirut, Lebanon yesterday.  Below is one from VOA.   Note the mushroom-like veil of cloud that forms and propagates very rapidly away from the explosion.  This veil of clouds is moving much faster than the smoke generated by the explosion and quickly moves out of view.  If you watch and listen to the video carefully, you'll notice that the cloud passes out of the view of the camera before the sound of the explosion is recorded.  Thus, the cloud appears to be moving at speeds at or above the speed of sound.   Phenomena of this type are outside my normal areas of study but I suspect that the cloud is being produced by the shock or blast wave generated by the explosion.   Such a wave is characterized by a sharp increase in pressure at its leading edge followed by a decrease in pressure to sub-ambient values.  These pressure changes occur in less than a second as the wa...

The numbers are now fully in for July.  At the Salt Lake City airport, yesterday's maximum of 104˚F brought our average temperature for the month up to 81.1˚F, tied for 14th all time and behind only one 20th century year, 1960.   Source: NOAA Regional Climate Centers I've beaten this storyline like a rented mule, but here goes again.  This July was quite hot in Salt Lake City by 20th century standards, but about middle-of-the road by early 21st century standards.  In fact, it ranks 13th out of the 20 Julys since 2001.   If you want to see real heat, look at Phoenix.  The average temperature at the airport there in July was an incredible 98.9˚F, the hottest month on record at that location.   Source: NOAA Regional Climate Centers Cloud and precipitation observations indicate that the monsoon was largely a "nonsoon" for Utah, Arizona, and points west.  Outgoing long-wave radiation, commonly used for infrared satellite imagery, was ano...