Monday, July 25, 2016

Heat, Heat, and More Heat

The summer from hell is here.  Other than a brief cold surge earlier in July, this summer has largely been characterized by sustained warmth.  We are in a dead heat with 2013 for hottest on record.

Source: NOAA Regional Climate Centers
Temperatures this afternoon at the Salt Lake City Airport reached 100 degrees for the 8th time this year, and here's the forecast for the rest of the work week.

Looking for snow?  Good luck.  Here's the view above Big Cottonwood yesterday.  Sad.


Saturday, July 23, 2016

Antelope Island Fire

A major wildfire broke out on Antelope Island yesterday.  There were some great photos flying around on twitter of the orange glow and flame front overnight, such as these on the KUTV web site.

I took advantage of the cool weather and went out on an early morning bike ride to survey the scene.  During the day, the scene is a bit less "volcanic", but smoke obscured a good portion of the southern half of the island.  Note how the smoke is being transported southward, which reflects the northwesterly flow in the wake of a weak cold front that passed last night.

There's a sharp edge to the top of the smoke.

This is because there is an inversion in place over northern Utah behind the cold front.  The morning sounding from the Salt Lake City airport shows the inversion extending from the surface, where it was about 20ºC to 800 mb, where it was about 23ºC.

We will see smoke mixing through a deeper layer later today as intense surface heating mixes out the inversion.

Looking south over the Salt Lake Valley showed the smoke covering the western Salt Lake Valley and then over the southern valley curving eastward to near the base of Lone Peak.

The central and eastern valley were clear, but that might also change later as our usual afternoon flows and turbulence favor transport and mixing through the valley.

At least it is a little cooler today for the firefighters, who have a difficult job ahead of them.

Thursday, July 21, 2016

An Impressive Heat Wave Despite No Maximum Temperature Records

This may sound like a broken record given that I've mentioned it several times this summer already, but there's more to heat waves than maximum temperatures.  Maximum temperatures get the most press, but minimum temperatures strongly affect human comfort, animal and plant health, energy demand, and even air quality.

Bars in the graph below show the range of temperature (bottom = minimum, top = maximum) each day this month compared to average (green shading), record maximums (top of red shading), and record minimums (blue shading).  Over the past 3 days the maximum temperature has fallen short of records by a few degrees, but the extreme warmth of the period is evident in minimum temperatures that are remarkably high.

Source: NWS
The minimum temperatures the past three days were 81ºF, 77ºF, and 79ºF.  Plus, our overnight minimum last night was 79ºF.  The 81ºF is the highest minimum temperature ever observed in Salt Lake City, as summarized nicely by the graphic below from the National Weather Service.

Source: NWS
The 79ºF yesterday and the 79ºF this morning (assuming it holds as the daily minimum through midnight, which is likely), would tie for the 4th warmest.  Three days in a row of 77ºF or higher is the first on record, and it appears today will add a fourth.

Bottom line: There has never been a string of warm nights and high minimum temperatures like the one we are experiencing this week.  

The recent warm spell has also put us back in first place for hottest summer on record so far.  Through yesterday, the average temperature since June 1st was 78.9ºF, just ahead of the similar period in 2013.

Source: NOAA Regional Climate Centers
The toxic algal bloom in Utah Lake has been getting much attention in the news of late (see this Salt Lake Tribune article).  I've been avoiding touching it (figuratively and literally!), but thought I would comment on it here.

I am unaware of a long-term lake-temperature record for Utah Lake, but shallow lakes typically have temperatures that are close to the recent average atmospheric temperatures in the surrounding area.  Long-term temperature records in Utah County are spotty, but the Provo-BYU record closely mimics the Salt Lake City record above, with recent years being warmer than earlier in the century and a long-term trend over the past 4 decades.  Similar to Salt Lake City, the summer so far has been the warmest on record at Provo-BYU, although by only 0.4ºF over 2015.

Source: NOAA Regional Climate Centers
So, this summer has so far been one of unprecedented regional warmth, although the difference relative to the first part of summer last year is fairly small.  The warmth this year is probably a contributor, ultimately it must be considered with other factors (e.g., phosphorous and nitrogen loaded runoff, sunshine, etc) to understand why this year's bloom is so severe.

Wednesday, July 20, 2016

Nasty Minimum Temperatures

Although many people focus on maximum temperatures, minimum temperatures also affect heat wave severity, especially for human or animal comfort for those who do not have some sort of air cooling capabilities.

With the wind stirring things up the past three nights, overnight temperatures have not dropped below 77ºF in three days at the Salt Lake City airport. 

Overnight minimum temperatures those three days were 81ºF, 77ºF, and 77ºF.  

Maximums those three days topped out at 99ºF, 98ºF, and 99ªF.  We are on pace for something around 91–101ºF today.  I hope we hit 100.  99 is such a waste of a temperature.  If we are to be saddled with Fahrenheit temperatures as a nation, go big or go home.

Tuesday, July 19, 2016

Ski Season Is Coming!

The dog days of summer are now here.  The latter half of July is the climatologically hottest period of the year in Salt Lake.  I call it nuclear summer.  High sun angle.  High temperatures.  High-based cumulus clouds that tempt us with rain (although there were a few spots that saw drops along the Wasatch Front yesterday evening).  Brutal.

How about a few photos today to remind us that we are cresting the hill and will soon be on the "downhill slide" to ski season.

Monday, July 18, 2016

Wrong Side of the Monsoon "Dryline"?

Often during the North American Monsoon, Utah is located in a region of large-scale confluence where airstreams of different origins are drawn together between the large-scale trough along the Pacific Coast and upper-level ridging over the south-central US.  This often leads to a strong contrast in moisture and thunderstorm activity from east to west across the state.  It's a bit of a stretch, but you could call it the Monsoon "Dryline."

We have such a situation today with confluent flow over Utah leading to a strong contrast in precipitable water [a measure of the total water content of the atmosphere (color contours below with warmer colors indicating higher values)] across the state.  The dry air over western Utah and neighboring Nevada originates over the subtropical eastern Pacific and streams into the region from the southwest, whereas the moist air over eastern Utah and neighboring Colorado originates over the tropical Pacific and Gulf of California as well as the Gulf of Mexico.

Forecast precipitation by the GFS is confined to eastern and central Utah, but does nose it's way into portions of the Wasatch Front this afternoon.

This pattern will predominate over the next couple of days.  The exact location of the transition will probably vary some from day to day.  Right now, I think Salt Lake City may be just a bit too far north and west to get in on the thunderstorm action, but it's close enough that it's worth keeping an eye to the sky.  The likelihood of thunderstorms will increase as you move eastward, and that's worth keeping in mind if you are recreating in eastern Utah or the Uinta Mountains.