Friday, July 29, 2016

July Is Good for Vacation

I've been taking a peek at the weather in Salt Lake and remembering why I prefer to go on vacation in July.  It looks miserably hot there.

I'm back in the Adirondacks for a few days for a celebration of my Dad's life.  Yesterday we did a hike in his honor up Gothics, an iconic peak on the Great Range.  As is typical of Adirondack trails, the route was merciless and direct, involving ladders, rock scrambling, and "vegetable belays."

Don't let people tell you that there aren't avalanches in New York.  They happen and they have resulted in fatalities.  The path below comes off the shoulder of Gothics.  

Gothics' name comes from the various rock faces and slides that surround the summit, which resemble Gothic architecture.  Although I think the west side is more scenic, we approached the summit from the east.

Nearing the summit.

On the summit, we got a view of Mt. Marcy, the highest peak in New York, but, as seems to be the case whenever I hike in the Adirondack high peaks, immediately heard a clap of thunder as a storm approached from the west (right side of photo).  If only Adirondack storms would conform to the 1 PM rule, I would have far more time to enjoy summit views.

Down we went!  There's no easy descent of Gothics.  We elected to go down over what is known as the Pyramid as the route got us off the ridge as quickly as possible.  The Pyramid is a small false summit known for outstanding views.  As we crossed, I snapped a quick photo of the storm pushing over the Great Range and Gothics.  

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.

Saturday, July 16, 2016

First Half of Summer Tied for Hottest Ever in Salt Lake

We are now half way through meteorological summer and the average temperature for June 1 – July 15 is tied with the same periods in 2013 and 2015 as the hottest ever in the Salt Lake City area with an average temperature of 78.1ºF.

Source: NOAA Regional Climate Centers
Both the average minimum and average maximum temperatures were well above the long-term average for the period, although it is the minimum temperatures that have really stood out compared to past summers.

Source: NOAA Regional Climate Centers
Source: NOAA Regional Climate Centers
The traces above are based on records from Salt Lake Area stations, but exclusively records from the Salt Lake City airport beginning in 1928.  The impact of the station shift is very clearly illustrated by the abrupt drop in minimum temperature from 1927 to 1928. The airport is one of the coldest places in the Salt Lake Valley at night and shifting to that location yielded much lower minimum temperatures compared to the previous observing site.

The climb in minimum temperature since then likely reflects several factors.  One is global warming as minimum temperatures are rising faster than maximum temperatures on a global scale.  It is also likely that urbanization of the Salt Lake Valley is having an effect, especially since the flow at night is typically southeasterly at the Airport and originates in developed areas. These effects are most apparent in the summer, especially from late June through July, when the day-to-day weather variability in northern Utah is the smallest (on average) of the year.  It is during this period that the long-term warming trend is most apparent.

The growth in minimum temperatures has important implications for human health and comfort.  Imagine living in the Salt Lake Valley in the 1940s and 1950s.  For the June 1 through July 15 period, the average minimum temperature during that era was about 55ºF.  That's pretty comfortable and allowed for efficient natural cooling of your home.  Over the past 10 years, its about 60ºF and over the past 2 summers its 65ºF.  In urban areas, you can expect it to be warmer at night than that.

Welcome to Hot House Salt Lake.  Through global warming and urbanization, we are having a major impact on the climate and livability of the Salt Lake Valley.

Friday, July 15, 2016

Bikes in Wilderness Areas?

Lone Peak Wilderness Area, one of the great treasures of the central Wasatch Range
In what I thought was something from News of the Weird, Senators Mike Lee (R-UT) and Orrin Hatch (R-UT) introduced the Human-Powered Travel in Wilderness Act yesterday, which would allow local land managers to potentially allow mountain biking in wilderness areas (see Mike Lee Press Release).  My classification of this as a News of the Weird article is with all the issues that the two Senators deal with, I was quite surprised they've taken an interest in this one.

As it turns out, I took a day of vacation and climbed the Pfeifferhorn yesterday with my son.  The Pfeifferhorn lies in the Lone Peak Wilderness Area, the largest wilderness area in the Wasatch Mountains.  In addition, the terrain between the Pfeifferhorn and Lone Peak is remarkably rugged and the most difficult terrain to access in the central Wasatch.  

Looking west toward Lone Peak from the Pfeifferhorn reveals the most rugged and difficult-to-access terrain in the central Wasatch.
Mountain bikes are no threat in this area.  I suppose those with large lung capacity could ride up to Red Pine Lake or perhaps up the Dry Creek drainage (at left), but for the most part, this is tough country and hard to access by bike.  

The same can't be said, however, for other wilderness areas.  

I've been mountain biking now for more than 25 years.  If you like to laugh at those old fully rigid mountain bikes with road-frame angles, you know what my first mountain bike looked like.  I consider preservation of mountain bike access to existing trails that are open for riding to be very important.  I have lived in or regularly visit places (e.g., Seattle, Boulder) where trails have been closed to mountain bikes or where access is severely restricted.  I feel fortunate that so many trails along the Wasatch Front and Back are open for riding.  

I am, however, staunchly opposed to mountain bike access in wilderness areas.  I don't see such access as consistent with the Wilderness ethos.  I think the Wasatch Crest trail is a great mountain bike trail, but I don't particularly like hiking there due to the overwhelming number of mountain bikes.  Passage of the Human-Powered Travel in Wilderness Act opens up the possibility of mountain bike travel in, for example, the Mount Olympus Wilderness via the Desolation Trail, portions of which were originally built for motorcycles.  

Please share your thoughts.  I admit my perspective is strongly skewed by my experiences along the Wasatch Front where the mountains have a remarkably high intensity of usage.  Perhaps some arguments could be made for mountain bike access in some larger wilderness areas with lower intensity usage.  

Wednesday, July 13, 2016

Alpine Lee Cyclone Wreaking Havoc on Tour de France

Spoiler Alert: If you don't want to know what happened in today's (Wed 13 July) stage 11, read no further.

Strong winds wreaked havoc on the Tour de France today, with the Peter Sagan (stage win) and Chris Froome (putting time on rivals) taking advantage.

The weather is also expected to wreak havoc tomorrow and it has already been announced that the stage up Mt. Ventoux will stop at Chalet Reynard, about 500 vertical meters below the summit.

The culprit is a strong Alpine lee cyclone that has developed on the south side of the Alps.  The 6-hour GFS forecast valid at 1200 UTC today (around the time of Stage 11) shows the classic signature that one sees when a cold front impinges on the Alps, stalls on the north slopes due to topographic blocking, and a variety of processes contribute to cyclogenesis to the lee near or over the Gulf of Genoa.

The strong pressure gradient drives the strong Mistral (northwest) winds that affected Stage 11.

For tomorrows stage 12, the main surface low has moved off into northern Europe, but the trailing cold front remains stalled over the north slopes of the Alps and an intense lee trough remains on the south side.

Mt. Ventoux will surely be buffeted by strong winds.  It may just south enough to avoid precipitation, but I wouldn't be surprised if there was some rain.  Expect the unexpected.

It's a shame that the climb will be shortened, but it could be an interesting stage nonetheless.

Implications of an Amplified July Pattern

The large-scale circulation of the atmosphere undergoes substantial seasonal changes, especially in the Northern Hemisphere, home to a majority (68%) of our planet's land areas.

The analysis below shows the average 500-mb heights over North America in July (the flow parallels the height contours with lower heights on the left).  During July, the storm track is displaced northward compared to its wintertime position and hugs the US–Canadian border.  Upper-level ridging lies over the Atlantic Ocean near 30ºC and extends westward over central North America, centered roughly on Texas.  This leads to easterly upper-level flow in the subtropics over the Caribbean, Gulf of Mexico, Mexico, and the subtropical east Pacific.  It is the development of this easterly flow during the summer, which contrasts with the westerlies found during winter over much of this region, that is characteristics of the  North American Monsoon system and a key reason for a pronounced summer peak in rainfall over Mexico and the southwest United States.
The latest GFS forecast for 1800 UTC 16 July (Noon MDT Saturday) shows a fairly typical July pattern.  Upper-level ridging extends across the eastern Atlantic near 30ºN and central North America.  Easterlies predominate to the south over the tropics and subtropics (note the active tropical storm track in the subtropical eastern Pacific) with the midlatitude storm track perhaps just a bit south of climatology over the northern continental US.  There's also a weak trough along the west coast, similar to climatology, albeit shifted slightly inland.

That's all fine and dandy, but going out a bit further to 1200 UTC 18 July (6 AM MDT Monday) shows an amplification of the overall pattern with the west coast trough deepening and the ridging over central North America strengthening and pushing northward.

Looking further out at the gold-standard ECMWF ensemble we see a monster ridge in firm control over central North America by 0000 UTC 21 July (6 PM MDT Wednesday).

Source: ECMWF
All of this is bad news for the central US. as it will likely mean a major heat wave next week.  The CPC 6–10 day outlook pegs a > 90% chance of above average temperatures over Nebraska and Kansas.  Temperatures in and around those states are likely to be well above average.

Source: CPC
There are a host of reasons why they call the central US the fly-over states, and next week will certainly be a good time to fly over them.

You will notice that Utah is in the transition zone, making our forecast a bit tricky.  A best-case scenario for us is for the overall pattern to be shifted eastward, putting us more under the influence of the large-scale trough.  If, however, the pattern is shifted westward, with the ridge bulging over the Intermountain West, we could be seeing some heat as well, unless we can get a monsoon trajectory going to push in some moisture.  It's too soon to say for us, but the central US looks to get cooked.

Tuesday, July 12, 2016

Wasn't That Pleasant

Yesterday wasn't a record setter at the Salt Lake Airport, but it was unusually cool for a sunny day and remarkably pleasant.  As a friend commented to me last night, "isn't September wonderful in Salt Lake City."  It sure is.

For the average temperature for the day, one has to go back to 1983 to find a July 11 with a lower average temperature.

Source: NOAA Regional Climate Centers
For the maximum temperature, one has to go back to 1951 for a tie and 1936 for something lower.

Source: NOAA Regional Climate Centers
Most impressive to me is that the cool temperatures were associated with sunny skies rather than a rainy monsoon surge.  "Ah, what an airmass" as one of my former professors liked to say.

But alas, September is over.  The good news is that it really doesn't look that bad the next couple of days with highs in the upper 80s (maybe mid 80s tomorrow).  The bad news is that we will be back to more seasonable weather (i.e., highs in the 90s) later in the week, possibly for the long haul.  You can't stop July.  You can only hope to contain it.

Monday, July 11, 2016

A Few Perspectives on Our Wonderful July Cold Surge

Here are a few perspectives on the wonderful July cold surge that we are enjoying today:

1. You earned it.  The summer so far (1 June – 10 July) is the hottest on record in the Salt Lake City Area with an average temperature of 78.5ºF.  The three hottest 1 June – 10 July periods on record occurred in the last 4 years.

Source: NOAA Regional Climate Centers

2. It's an unusually cold airmass for July.  The 700-mb (10,000 ft) temperature in this morning's sounding from the Salt Lake City airport was -0.5ºF.  The all-time record low 700-mb temperature in the sounding record over northern Utah is -1.4ºF.  Although we didn't set a record, we are in rare territory as only 2 days previously in July saw a 700-mb temperature below 0ºC. 

3. The valley temperatures are blissful.  Overnight minimums at valley locations include 51ºF at the Salt Lake City airport, 50ºF at the University of Utah, 48ºF at the Ogden airport (based on 5-min observations so unofficial), and 52ºF at the Provo airport (also based on 5-min observations so unofficial).  The 51ºF at the Salt Lake City airport fell 3ºF shy of the record for the date.  Minimum temperature records are so hard to set there!

4. It was quite cold at some mountain and mountain valley locations.  Overnight minimums include 30ºF at Alta Guard, 30ºF on the Brighton Crest, 29ºF at Bald Mountain (Mirror Lake Highway, Uinta Mountains), 25ºF at Bear River (Mirror Lake Highway, Uinta Mountains), and 32ºF at Tony Grove Lake (Bear River Range).  For you Park City types, looks like the Golf Course dropped to 35ºF, and that's typically the coldest place we get data for on the Wasatch Back. Perhaps some spots in the Snyderville Basin made it down to 32ºF.

5. Is the airport running hot?  A couple of readers have contacted me wondering if the Salt Lake City airport is running hot again, as it did a few years ago.  I haven't been playing close attention, but may look into this down the road.

6. A wee bit of July snow.  Check out Big Sky base and Cody Bowl at Jackson Hole this morning.  Probably better photos out there, but I have a day job.

Source: Big Sky
Source: Jackson Hole Mountain Resort

Sunday, July 10, 2016

The Leading Edge of Cooler Air Has Arrived

Northwesterly flow developed over the Salt Lake Valley this morning as the leading edge of cooler air began to penetrate into northern Utah.  Widespread northwesterly flow was apparent in the MesoWest surface plot just after noon.

Source: MesoWest
Sometimes cold air comes in with a bang, other times with a whimper.  This is a bit of a whimper as there wasn't a gangbuster frontal passage with a dramatic drop in temperature.  Nevertheless, the total change in temperature from yesterday to Monday is going to be quite large and around 25ºF for the valley.

By tomorrow morning, forecast 700-mb temperatures (10,000 ft) are expected to be near or below 0ºC across northern Utah.

The GFS (pictured above) is going for a 700-mb temperature of -1.3ºC for 6 am tomorrow morning at the Salt Lake City airport.  As discussed in the previous post, the lowest observed 700-mb temperature in the upper-air observing record for northern Utah in July is -1.4ºC, so we are going to be in rare territory.  It's going to be a cold night in the mountains and a refreshing night in the valley.