Thursday, May 31, 2012

Utah County Pyrocu

Looks like there's a fire in Utah County.  You can see the smoke topped by a shallow pyrocumulus cloud from the Avenues.

Satellite imagery shows the smoke plume as well.  Squint at the box below and you'll see it appear at the end of the loop.

It's Over

I've been on the road so much lately that I missed an important snow-cover lowlight.  The snowpack SWE at the Snowbird SNOTEL has now officially bottomed out, bringing a pathetically early end to the snow-cover duration at that site.

In the graph above, you can compare this year to last year.  There's about a 5-6 week difference, depending on which minimum you use for the end of snow-cover duration during 2011/12.

Most of the SNOTEL sites in the southwest are now snow free.  The sites with white squares and nearly all of the red squares below have no remaining snow cover.

Those hoping to do turns-all-year will be road tripping to the Pac Northwest or working hard to find scraps in Utah and environs this summer.

Wednesday, May 30, 2012

How to Freeze in the Hot Utah Desert

Photo Credit: Gigi Thorsen
I was on a river trip the past couple of days and it was a great lesson in the power of evaporative cooling.  Temperatures in Moab reached the high 80s yesterday, and floating on a raft with a personal floatation device on was hot, if you were dry.  If you were wet, however, it was absolutely frigid and any breeze or gust of wind provided a great lesson in the power of evaporative cooling.

The temperature commonly cited in weather reports is called the dry-bulb temperature by meteorologists.  It is the temperature measured by a thermometer that is not exposed to the sun or moisture.

If wet, however, the evaporation of water can affect the temperature of an object.  The lowest temperature that an object can reach through the evaporation of water is called the wet-bulb temperature.  The wet-bulb temperature is a function of the dry-bulb temperature and the relative humidity.  In a dry airmass, the wet-bulb temperature can be much lower than dry-bulb temperature.  In a humid airmass, however, they may not differ by much (in fact, they are the same when the relative humidity is 100%).

Back in the day, the wet-bulb temperature (as well as dewpoint and relative humidity) was measured using something called a sling psychrometer.  The sling psychrometer was a thermometer with piece of fabric on it that you would wet.  You'd then "sling" the psychrometer around and the evaporation of water from the fabric would lower the temperature measured by the thermometer to the wet-bulb temperature.  This is a common experiment done in Earth science classes.

Contrary to conventional wisdom, meteorologists don't measure wet-bulb temperature (or dewpoint and relative humidity) manually anymore.  Meteorological observations are fully automated.

Nevertheless, I was the human wet-bulb thermometer the past couple of days on the Colorado River, and the observations from the USGS/National Park Service Building in Moab pretty much show what I observed.  Yesterday afternoon (29 May), for example, the dry-bulb temperature was in the high 80s yesterday (red line), but the wet-bulb temperature was in the low 50s (green line).

This difference of more than 40F reflects the remarkably dry airmass resident over the upper Colorado basin yesterday.  The dewpoint was below 20F and the relative humidity less than 10%.

Thus, there was tremendous potential for evaporative cooling.  When you were dry, it was hot in the sun, but when you were wet, your liver would quiver, especially when the wind blew hard and the energy loss to evaporation increased.

This is a common situation in Utah during the warm season and a reason why evaporative (a.k.a. swamp) coolers are quite effective for home cooling.  Of course, that effectiveness goes down quickly during monsoon surges when the dewpoint, relative humidity, and wet-bulb temperature are higher.

Sunday, May 27, 2012

Revenge of Winter

Not satisfied with its brief appearance during the ski season, winter has returned this Memorial Day Weekend.  The observations are a bit squirrelly, but the snow depth at the Alta-Collins site increased about 7 inches in the past 24 hours, with about 1.09" of snow water equivalent.

And the view from the top of Snowbird looks quite inviting.

Pity that we couldn't have gotten this snow in December when it was desperately needed.

Those of you looking for sunny day have no fear.  Tomorrow looks beautiful.

Saturday, May 26, 2012

Epic Dust Shot

Following up on the previous post, check out the coverage of dust (pink colors) over the four corners area in the Aqua-Modis image from this afternoon.

Source: Naval Research Lab
Quite an event.

Big Four Corners Dust Storm

It is nuking in the four corners area where there is an impressive dust storm underway, not to mention a smoke plume from fires in New Mexico.  The latter was clearly evident in the 17:55 UTC Terra/MODIS overpass.

It's tough to see the dust in the image above, perhaps because the event was just getting going at 1755 UTC (1155 MDT), as shown by the observations from Blanding (K4BL).  The latest report from 2055 UTC shos wind gusts to 52 mph with blowing "sand" (probably dust) reducing visibilities to 1 mile.

One can also see wide-spread dust in the four corners area in the visible satellite loop below.  Click to enlarge.

Must be fun camping in the 4 corners area today....

Addendum 5:37 PM MDT:

The Naval Research Lab dust algorithm picks up on the dust in the MODIS image above quite nicely.  The pink areas below are likely dust and clearly shows the dust that is affecting the blanding area.  

Source: NRL

Friday, May 25, 2012

Memorial Pow?

Memorial Day Weekend 2011
Last year we had perhaps as close as you can get to great powder skiing over a Memorial Day weekend.  There was a massive base, and Mother Nature brought the goods.

We don't have a great base this year, but snow does linger in the upper elevations, and I think there's a chance there might be some freshies to be had.  A deep trough is presently developing along the Pacific Coast, as illustrated in this morning's 1200 UTC (0600 MDT) 500 mb analysis.

And, the air out there is cold.  The 700-mb temperature in the heart of the trough is about -8ºC.

The GFS drags the trough through northern Utah over the next couple of days, bringing a period of cool, unsettled weather.

The airmass warms a bit before it gets here, but it is still cold enough to bring some wet, high-density snow to the higher elevations of the Wasatch Mountains Saturday night and Sunday.  How much is tough to say given the unsettled nature of the pattern and the fact that we are right on the edge of the moisture, but those in need of a fix should keep an eye to the sky and see what Mother Nature brings by Sunday.

Thursday, May 24, 2012

Hurricane Bud

Last year was a relatively quiet hurricane season in the eastern Pacific, but things have been active thusfar this year as we already have our second named storm of the year churning off the Mexican coast.  Forecasts from the National Hurricane Center suggest that Bud will meander toward the Mexican coast and then linger for a couple of days while it weakens.

Source: National Hurricane Center
I'm not sure who came up with the name Bud, but presumably you can insert a good surfer joke here.

Wednesday, May 23, 2012

A Headscratcher

There's a perplexing radar look this morning as some showers have popped up in the unstable, postfrontal, northwesterly flow over northern Utah.  

Satellite imagery shows that this area of precipitation is isolated to our area.  

I say perplexing because it is unclear what mechanisms are responsible for the showers.  Is the lake playing a role?  IT seems the flow direction isn't quite right and that the cloud band may extend to just upstream of the lake shore (see above).  How about the Oquirrh Mountains or three-dimensional terrain effects related to other mountains?  It's a head scratcher.  Any ideas out there?

Monday, May 21, 2012

A Lesson in Weather and Climate Variability

The contrast between spring 2011 and spring 2012 is mind boggling.  Can you believe that on this day last year the Wasatch had just experienced another storm cycle and the snow depth at Alta-Collins reached 197 inches?

This year?  It is at 50 inches and falling.

The Snowbird SNOTEL is down to about 4 inches of SWE, whereas last year we were sitting at about 75.
In the past two years, we have experienced pretty close to the full range of variability that exists in the Wasatch snow climate during spring.  2011 was a huge snow year, followed by a cold, snowy spring.  This year we've had "drought", followed by a warm spring.  From a best-case scenario (for skiers and runoff) to a worst-case scenario in 366 days (it a leap year after all).

Drought conditions in Utah now range from abnormally dry to severe.
What Mother Nature giveth, Mother Nature taketh away.

Sunday, May 20, 2012

Hidden Water

One of the more remarkable aspects of the Wasatch Mountains and the western United States in general is how incredibly "plumbed" the rivers and streams are.

We observed this yesterday on our hike in Neffs Canyon, which rises into the Wasatch Mountains east of Olympus Cove and just south of Mill Creek Canyon.

Neffs contains a perennial stream that is fed by snowmelt and, in the upper canyon, there's still a reservoir of scattered snow.  We even did some poor-man's skiing, here at an elevation of about 8600 ft.

Not surprisingly, there's a healthy stream fed by snowmelt and running down the upper canyon.

But here's what the stream bed looks like in the lower canyon.

It appears that the water is being captured somewhere in the canyon, perhaps just outside the wilderness area boundary, which was clearly drawn around the stream (see red line above).

The Hidden Water web site provides quite a bit of information about the major drainages above the Salt Lake Valley.  It states that the Salt Lake City Department of Public Utilities owns the water rights to four springs in the canyon, but I couldn't find anything on water extractions from the stream.  Presumably they own the rights to the stream as well and are taking all they can this year given the drought conditions.  Perhaps the water ends up, at least temporarily, in the water tank that sits along the trail just above the parking lot.

Saturday, May 19, 2012

From Russia, Tooele, or Nevada with Love?

We should be in a fairly pristine post-frontal airmass today, but the visibility is relatively poor by Utah standards.

A hazy view of downtown Salt Lake from Neff's Canyon
It appears we have some smoke in the air, but from where?  Smoke from fires in Siberia penetrated earlier this week into the central and eastern US, as discussed on "The Smog Blog."  They even posted a great MODIS image showing smoke streaming out over the Bering Sea.

Image obtained from the U.S. Air Quality Smog Blog
Perhaps some of that smoke has now found its way to Utah?

Perhaps the smoke is from less remote origin.  The Forest Service reports a few large "incidents" including a fire in Tooele County that has burned 1390 acres (fire 4 below), and one in Nevada (fire 2 below) that has scorched 17,200.

Source: USDA Forest Service
FInally, NOAA detects a fire in extreme NW Utah and a couple in eastern Oregon.

Maybe someone can dig into the satellite imagery and get a better handle on the source.  In any event, fire season is here already.

Eclipse Update

The forecast still looks good for Sunday's eclipse, with a ridge firmly in place over Utah.

Enjoy, but observe with caution!

Friday, May 18, 2012

A Great Front

The weather drought is over and interesting weather is moving into northern Utah this morning.  Most impressive was the push of a shallow cold front into the Salt Lake Valley this morning.  The time lapse imagery below faces west from Olympus Cove.  Check out the persistent orographic clouds that formed as cold air spilled over the Oquirrh Mountains and the strong shear near their tops with northwesterly flow at low levels and southerly to southwesterly flow aloft.  Such shear is very common immediately behind a surface cold front.

IR satellite imagery shows cold-topped clouds filling in the region immediately behind the surface front.

And the radar shows a broad band of precipitation beneath these clouds with some embedded thunderstorms.

The next few hours look to be quite interesting.  Batten down the hatches and enjoy the ride.

Thursday, May 17, 2012

A Big Announcement!

It is with great anticipation and excitement that I announce the return of weather to the Intermountain West after an extended absence.

Yes, there is always weather, but it is May, and we should be seeing the occasional trough passage and airmass change just to keep things interesting.  Instead, it's been slim pickins for quite a while.

That will change tonight and tomorrow.  This morning, we have an upper level trough moving into the western United States.

Today will be warm with perhaps some high-based convection with a slight chance of thunder and local gusty winds.  Late tonight and tomorrow, cooler air pushes into northern Utah, bringing showers and an increased chance of thunder.

Rain would feel oh so good.  KSLC observed .24" on May first, but since then, hasn't recorded measurable rain.  If we get a good shower, make like Tim Robbins in the Shawshank Redemption.

Tuesday, May 15, 2012

Outrageously Dry

An incredibly dry airmass has settled over northern Utah.  Currently at the Salt Lake International Airport (KSLC), the temperature is 88ºF with a dewpoint of only 3.2ºF.  Earlier, it was 90ºF with a dewpoint of -2.2ºF.  That's a relative humidity of only 3%.

I'm on the road with limited connectivity today.  Perhaps some of you can comment on the source of this incredibly dry air.

Monday, May 14, 2012

Eclipse Weather Outlook

One of our readers, Ian, has requested a weather forecast for this coming Sunday's ~7:30 PM solar eclipse.  I confess complete ignorance of astronomical matters, but do know a little something about the weather, so I may be able to help with the forecast.

The latest GFS and most of the medium-range ensemble forecasts call for a trough to be situated off the west coast with southern Utah in southwesterly flow aloft.

In such a pattern, the weather should be nice in the sense that it would be dry and quite warm, but it's impossible to say whether or not there might be some cirrus clouds floating around at the time of the eclipse.  Also, this is a fairly long projection - 150 hours, so we'll have to see how things shake out.  Keep your fingers crossed and we'll try to take a look at things in a few days.  Right now, I suggest being cautiously optimistic.

Saturday, May 12, 2012

Great Weather Songs

Desperate times call for desperate measures.  I'm out of ideas this weekend given the boring weather, so here's a post on great weather songs.  Yes, meteorologists do geek out like this.  Here are some of my favorites:
  • Like a Hurricane, Neil Young.  My personal #1, the use of hurricane here is metaphorical, but the guitar solo is one of rock's greatest and captures the essence of being in a storm, be it emotional or tropical.  
  • The Wreck of the Edmund Fitzgerald, Gordon Lightfoot.  Most meteorologists would probably call this the greatest weather song of all time.  I once had it on 45.  It was one of the first singles I owned.  Here's a snippet.  
The wind in the wires made a tattle-tale sound
And a wave broke over the railing
And every man knew, as the captain did too,
T'was the witch of November come stealin'

The dawn came late and the breakfest had to wait
When the Gales of November came slashin'
When afternoon came it was freezin' rain
In the face of a hurricane west wind
  • Subterranean Homesick Blues, Bob Dylan.  "You don't need a weatherman to know which way the wind blows." Inspired the name for another band, The Weathermen.  'Nuf said.  
  • Rock You Like a Hurricane, The Scorpions.  VH1 rated this the 18th greatest hard rock song of all time and the 4th best riff of the 80s.  The video is a classic.  Yes, I saw them live in the 80s, possibly a couple of times, but am not in this video.  
  • Thunderstruck, AC/DC.  Na na na na na, THUNDER.  Toss up with Rock You Like a Hurricane for the best heavy metal weather song.  
  • Cool Change, Pure Prairie League.  This is a stealthy weather song.  I doubt Pure Prairie League was making a connection with weather during this song, but Cool Change is a name that is sometimes used to describe the onshore surge of cool marine air in southeast Australia or a cold-frontal passage.  Put this on in July when it's 100+ in the shade.  
  • Love Reign O'er Me, The Who. Yeah, I know, Reign, not rain, but has Roger Daltry ever sounded better than when he screams LOOOOOOOOOOOOOOOOOOOVE, Reign O'er Me, O'er Me, O'er Me.  Besides, this is a weather song:
On the dry and dusty road
The nights we spent apart alone
I need to get back home to cool cool rain

The nights are hot and black as ink
I can't sleep and I lay and I think
Oh God, I need a drink of cool cool rain
  • Pop Song 89, R.E.M.  It's not easy being a meteorologist.  We don't like to make small talk by discussing the weather.  We take it too seriously.  Michael Stipe mocks it nicely for us in this song.    
Hello, I saw you, I know you, I knew you
I think I can remember your name
Hello, I'm sorry, I lost myself
I think I thought you were someone else
Should we talk about the weather?
  • Blowin' in the wind, Bob Dylan.  "The answer my friend is blowin' in the wind, the answer is blowin' in the wind." I keep waiting for a student to put that down on one of my tests when they don't know the answer.  
  • Here Comes the Sun, The Beatles.  This is a George Harrison song.  You can tell because it stirs your soul from the first note to the last.  
  • Like the Weather, 10,000 Maniacs.  The antithesis of Here Comes the Sun.  
Color of the sky as far as I can see is coal gray
Lift my head from the pillow and then fall again
Shiver in my bones just thinking about the weather
Quiver in my lip as if I might cry
  • Beyond the Edge, Dan Fogelberg.  This is more ski oriented than weather related, but I've added it because it anyway.  We aren't the Wasatch Weather Weenies for nothing.  

Feel free to add to the list, but leave these out:
  • Riders on the Storm, The Doors.  Starts good, but after the thunder and rain, I can't stand the song.  
  • Raindrops Keep Fallin' on My Head, B.J. Thomas.  Really?  Get an umbrella.  
  • Sunshine on My Shoulders, Bob Denver.  Sorry, but sunshine on my shoulders gives me sunburn.  

Friday, May 11, 2012


As we discussed on Wednesday, this cool season (Nov-Apr) was the third driest in the past 75 years based on the statewide average precipitation. We are now following up that cool season with what looks to be a very dry May.  This is not unusual in extreme southern Utah.  Climatologically, May is the second driest month of the year in St. George with an average precipitation of 0.37 inches.  At Salt Lake City, however, May is the third wettest month with an average precipitation of 1.76 inches.  Yet this year, only .24 inches has fallen thusfar this month, and there's not much hope for a good soaker in the forecast.   

Other than perhaps some very widely scattered showers today, mainly east of the Wasatch Mountains, it looks bone dry through early next week.  

A weak trough sneaks through on Tuesday and Wednesday.  Perhaps it can initiate some action, but right now it looks mainly dry.

And the long range?  It's not impossible that something sneaks in here, but most of the long-range ensembles call for this pattern to persist.  This is reflected in the Climate Prediction Center 8–14 day outlook, which shows that the dice are loaded for below average precipitation over Utah and the southwest US.

Thus, the weather word for today is parched.

Thursday, May 10, 2012

Dusty Northwest Wind

A weak cold front passed through the Salt Lake Valley early this morning, ushering in a period of stiff northwest winds of about 25 miles per hour with gusts at times into the low 30s at the Salt Lake City International Airport (KSLC).

There appears to be some dust in the post-frontal environment as the mountains are somewhat obscured compared to what one would fine with a "pristine" post-frontal airmass.

Oquirrh Mountains from the Avenues Foothills
The source of dust during these weak events is unclear.  The dust is not thick enough to detect with satellite imagery.  Is it from the playa around the Great Salt Lake?  Is it of a more remote origin?  Is the dust deposited from these weak events significant relative to major episodes during strong windstorms?  These are important questions given the role of dust in the ecology and snow hydrology of the region.

Wednesday, May 9, 2012

How Dry Was Utah This Cool Season?

The National Climatic Data Center generates statewide average temperature and precipitation analyses by month and year for the United States.  The April 2012 data has just become available, which allows us to put this past cool season's (Nov-Apr) precipitation into long-term perspective.

Based on the statewide average, it was one of the driest cool seasons in the past 75 years.  The statewide average cool-season precipitation was only 4.12 inches, the third lowest since 1937.

Source: NCDC
This cool season was nothing, however, compared to 1976–1977 when we bottomed out at 1.87".  That year remains the true outlier in the instrumented record and the gold standard for drought years on a state-wide basis.