Wasatch Weather Weenies

About a month ago, there were a number of reports in the media, including this article in the Guardian , discussing a decline in U.S. CO2 emissions last year to the lowest levels since 1994.  The source of this information was a report by the Business Council for Sustainable Energy (BCSE) and Bloomberg New Energy Finance (BNEF) entitled Sustainable Energy in America 2013 Factbook . I know nothing about energy or economics, so I can't really comment on the reliability of the report, but for wonks out there who are like me and love to look at graphics and statistics, it's worth a look.  Here are a few that caught my eye. Source: Sustainable Energy in America 2013 Factbook I'll blow up Figure 2 from the top as it is most interesting.   Source: Sustainable Energy in America 2013 Factbook Those of you out there who are energy and economics wonks, feel free to add your comments and interpretation.

All observations are bad, but some are useful - Paraphrased version of George Box quote There is a tendency in meteorology to treat observations, especially those that are collected in place by weather stations, as ground truth.  Meteorology is a data starved field, which contributes to the tendency to place great value on any observations, but of course observations are not perfect and one needs to consider the possibility of error.   There are two major sources of error in meteorological observations.  The first is observational error, which is the difference between what is measured and the true value.  Such errors can by systematic, meaning that they occur regularly, or random, which means they vary from observation to observation. A good example of a systematic error is the tendency for thermometers that are not well ventilated to overheat and record a higher temperature than that in the free air when they are in the sun on days with light winds. ...

This storm simply will not quit over portions of the Wasatch Mountains.  Note on the radar below how orographic (i.e., mountain) precipitation continues to linger over the Wasatch and Oquirrh Mountains. The snow that is falling is cold smoke and comprised of lots of dendritic aggregates based on snowflake images collected by the University of Utah MultiAngle Snowflake Camera at Alta Ski Area (see Alta's  Snowflake Showcase web page ).  A sample is below. Source: http://www.alta.com/pages/snowflakeshowcase.php  Snow water contents appear to be quite low.   The last 4 inches of snow at Alta-Collins was produced by only .12 inches of water.  That's less than 4% water content!

Our paper examining the contribution of lake-effect periods to the cool season (16 September to 15 May) precipitation of the Great Salt Lake Basin was published today in the Journal of Applied Meteorology and Climatology .  The study was funded by the National Science Foundation and the paper was lead authored by Kristen Yeager, a former University of Utah graduate student, with contributions from myself and Trevor Alcott.  It can be accessed here , but for most off campus it is paywalled, so I'll hit some of the highlights here. Let's get right to the point.  How important is lake-effect?  We looked at some 700,000 radar images from the 1998-2009 cool seasons and identified 128 lake-effect periods (LEPs).  We then used a combination of radar and precipitation gauge data to determine how much precipitation (snow-water equivalent) fell during these periods.  The big winners were SNOTEL stations (Snowpack Telemetry stations that report daily precipitatio...

The large-scale pattern for the past several days has featured an active polar jet over the north Pacific and an active subtropical jet across the subtropical eastern Pacific, Mexico, and the southern tier of the U.S.  Upper-level troughs have been exiting the polar jet, digging southeastward across the western US, and then merging with the subtropical jet over the southwest US. On Saturday morning, the upper-level trough that barely missed Utah and wreaked havoc on the PGA tournament in Tucson on Thursday, was over west Texas and was being carried downstream to wreak havoc on the eastern U.S. by the subtropical jet.  The upper-level trough that produced our sublime weekend of powder skiing was over the Pacific Northwest and posed to move into Utah. This morning, it is nearly deja vu all over again.  The upper-level trough that gave us our weekend powder dug southeastward and merged with the subtropical jet over west Texas.  Another upper-level trough is ...

The pre-frontal snow never got going, but Mother Nature finally delivered the goods today with the frontal passage and post-frontal snow.  I had a day of wild adventures and misadventures, all with a strong meteorological influence. I did about a 5 hour solo ski tour out of Big Cottonwood Canyon and got to watch the front penetrating across the shoulder of Kessler Peak.  All I can say is wow.  The photos below were taken at 9:45, 9:46, and 9:47 am and illustrate the dramatic change that occurred with the cold frontal passage. Immediately following the frontal passage, there was an extended period with snow pellets or small graupel, which probably reflects the very strong rising motion at the leading edge of the front.   After a bit of a lull around noon (I could briefly see the sun through the light snow), there was an explosion of dendritic aggregates just after 1 PM, with some very high snowfall rates where I was skiing.  Dendrites are ...

We have a fascinating storm setting up for tomorrow, one that will bring some snow to the mountains and some heartburn to meteorologists. First, let's talk about the key ingredients.  Over the past few days, moist air, originating over the subtropical Pacific near China has streamed across the North Pacific and is now impinging on the Pacific Northwest.  One of my students dubbed this the "Soy Sauce Express" and it shows up as a filament of high atmospheric water vapor content (a.k.a. precipitable water) in the contours below, which are overlayed on the 1200 UTC (5 AM MST) satellite image from this morning.   1200 UTC (5 AM MST) 22 Feb 2012 IR satellite imagery and GFS Precipitable Water Analysis The water vapor content of this plume is not unusually high, but it will help fuel tomorrow's storm. Another key ingredient is the low center over the Gulf of Alaska, which has tapped into cold air originating over the high latitudes.  It is the confluence of this...

This has been a frustrating winter for me as a forecaster.  We've had some weird storms, and others that just haven't panned out as I thought.  Thus, I thought we would take a look today at how weather forecasts have improved over the past couple of decades and why the Intermountain West continues to be a black hole for weather forecasters. To do this, we will be examining the accuracy of forecasts produced by the Hydrometeorological Prediction Center (HPC), which provides precipitation forecasts and outlooks for the entire continental United States. The metric that they use to evaluate the accuracy of their forecasts is known as the equitable threat score .  Without getting into the gory details, the bottom line is the higher the equitable threat score, the more accurate the forecast. Forecasts produced by computer models (i.e., the NAM and GFS) and by the HPC forecasters show considerable progress going back to the beginning of this record in 1993 (and certainly m...

It's always disappointing when a storm decides to wreak havoc on a golf tournament in southern Arizona (i.e., the Accenture World Golf Championship near Tucson) rather than giving us deep powder, but that is the case today. The culprit is what meteorologists call a digging trough , which is a trough that is amplifying and "digging" southward rather than progressing from west to east.  The loop for the last two days shows this rather well.  Note how the upper-level (500-mb) trough (indicated by the black contours) and the surface trough and cyclone move from the northern Gulf of Alaska into the Southwest U.S. This type of storm evolution is not uncommon over the western U.S. [for you techies, there is considerable discussion of this in a recent paper by U atmospheric scientists Lareau and Horel (2012) ].  Troughs that tend to do this are typically diffluent , meaning that the flow spreads out on their downstream (eastern) side.  As is the case above, there is ...

We are awfully close to the coveted 50ºF mark this afternoon at the University of Utah campus.  If we get there, it would be the highest temperature observed thus far this calendar year on campus (eclipsing 49ºF on February 8).  Further, it's is a coveted mark for both old school (US units) and new school (metric) types since 50ºF=10ºC. Enjoy it now.  Change is a comin'.

Did you ever wonder what all the mountains around the Great Salt Lake do to lake effect?  Trevor Alcott and I have a paper on this subject that was accepted and was released today in early online format by the American Meteorological Society journal Monthly Weather Review .  You can find a summary of the article on the University of Utah web site  or, for those of you on campus or with a  subscription to the American Meteorological Society journals, the full article at http://dx.doi.org/10.1175/MWR-D-12-00328.1 .   The National Science Foundation and National Oceanic and Atmospheric Administration sponsored the research. A key finding for skiers is that we need to mow down the mountains northwest of the Great Salt Lake.  Drying and warming of northwesterly flow in the lee of those mountains makes for weaker lake-effect storms.  We'd be much better off if cold air over the Snake River Plain could penetrate directly into the Great Salt Lak...

This is probably a poorly kept secret for those of you who are constantly on the lookout for snow in the forecast, but there is going to be a major pattern shift this week that could give us one of the more active patterns of the winter.  First lets talk about what is encouraging about the forecast.  The Climate Prediction Center 6–10 day outlook has my favorite combination of colors.  Blue for below average temperatures and green for above average precipitation. Source: NOAA/CPC In addition, the GFS has three major systems coming through over the next ten days.  The first is a mid week storm, the bulk of which moves through southern Utah, but the latest computer models suggest it will give some of the goods to the north too.   This is followed by two direct hits for the weekend and early next week.  Looking at the four-panel forecasts from the GFS, you can barely tell these two storms apart.  Both feature troughs in large-scale northwest...

There are many things I love about ski touring.  Yeah, there's the powder and the endless possibilities for adventuring, but then there are all the weird things you see because of the viscoelastic properties of snow.  It helps stimulate the synapses.  On today's tour, we noticed that the snow was much deeper on the south side of these aspens than on the north side.  The slope wasn't very steep, perhaps 10 degrees.  So, my question for you snow types out there is how does this happen.  Is the tree preventing settlement on the uphill side?  Was there wind transport during the storm with snow collecting on the south side?  Inquiring minds want to know.

Presidents weekend will begin with a 10+ day tomorrow in the mountains as a high amplitude ridge builds over northern Utah.  By tomorrow afternoon, 700-mb temperatures (near crest level) are up near -2ºC. Source: http://weather.utah.edu With the sun higher in the sky, it's going to feel quite warm, but the snow should hold up well at upper-elevations on the north side of the compass.  For those of you looking for a bluebird resort day, you really can't do much better, and you should take full advantage as the weather will be changing on Sunday. I conclude today with a big congratulations to Ted Ligety who won his 3rd gold in the 2013 Alpine World Championship today.  It's the first time an individual has won 3 golds at an Alpine World Championship since Jean Claude Killy won 4 in the 1968 Olympics (which at the time also served as the world championship). Source: US Ski Team I attended the 2001 Alpine World Championships in St. Anton.  I recall riding a...

The area around campus was littered this morning with small, spongy, ball-shaped snow pellets that fell over night.  They are indeed fully recyclable. Most clouds are comprised of a mixture of ice crystals and supercooled cloud droplets.  Supercooled means that the droplets are below freezing, but remain in the liquid phase.  Graupel is a type of snow pellet that forms as an ice crystal falls and collects these supercooled cloud droplets, which freeze on contact.  This leads to the formation of a ball or lump shaped snow pellet. Source: Parkerjh, Wikipedia Commons The snow pellets that fell last night were, however, quite small.  I don't know if there is a minimum size requirement for graupel, so I'll call them "baby graupel."  The formation mechanism was probably similar to that of graupel.  Small ice crystals collected supercooled cloud droplets as they fell.  They just didn't grow to a large size. 

Big storms are overrated.  We did a dawn patrol this morning and found that the new snow wasn't too shallow and wasn't too deep, but was just right.  My partner commented that the snow was so sublime that it was almost as much fun trail breaking up as going down.  Get out and enjoy!

This is old news, but I thought I'd share the snowfall total map from last weekend's Northeast snowstorm, which was produced by Brandon Vincent at the Raleigh North Carolina National Weather Service Office. Source: http://cimmse.wordpress.com Central Connecticut is now ahead of Alta for February snowfall!  Fortunately we still have them beat in total snow depth.

I know what your thinking.  We've had a hell of a winter down here in the Salt Lake Valley.  It was more than 10ºF below average at the Salt Lake International Airport last month, we've had a deep snowpack on the ground since Christmas, and there's been that nasty inversion.  So what do I mean when I say this is a year without a winter? There are many ways to define winter.  There's astronomical winter, which runs from the winter solstice (about 21 December) to the spring equinox (about 20 March).  There's meteorological winter, which includes the months of December, January, and February.  Finally, there's Steenburgh winter . Steenburgh winter is that period during which we have the  crème de la crème of backcountry powder skiing with both a deep snowpack and a low-angle sun.  It starts when we hit 100 inches at the Alta-Collins snow-depth sensor.  Anything less is still early season conditions.  I've been amazed at what people...