Category Archives: Drought

Cage Match: Nov-Dec 1976 vs. Nov-Dec 2017

By popular demand, we now compare Nov-Dec 2017 with the comparable start period of the "season that shalt not be named", the "drought year," or simply, 1976/1977.

The 1976/1977 season is the worst on record in the modern era (i.e., since WWII) in the Wasatch Range.  Records for Alta-Guard show a total seasonal snowfall (November through April of only 314.5 inches.  This is the second lowest on record next to 2014/15, when only 267.5" was recorded.

If 1976/77 was only the 2nd worst snow year at Alta, what makes it the worst ski season?  The lack of early season snowfall.  Nov-Dec 1976 produced only 30.5 inches of snow, 17.5 inches less than the second lowest comparable period on record, Nov-Dec 1962, and 102.5 inches less than Nov-Dec 2014.  In my book, a lack of early season snow is far worse than a lack of late season snow, mainly because you can't ski on dirt and the backcountry powder skiing is far less vulnerable to the sun during November and December than March and April. 

This season, Alta-Guard reported only 15 inches of snow in November.  I haven't seen their numbers for December, but Drew Hardesty of the Utah Avalanche Center notes in today's Salt Lake Tribune that Alta-Guard hasn't yet hit 50 inches for the season, and currently sits with the second leanest snowfall behind the 1976/77 season.  I think it will come in a shade under 50 inches.  Thus, in terms of snowfall, this season is bad, but not as bad as Nov-Dec 1976.

What about temperatures?  Nov-Dec 1976 had a mean temperature at Alta 28.8ºF, making it the 10th warmest such period on record.  This Nov-Dec it was 31.2ºF, good for fourth warmest.  One might be able to make an argument that this difference in warmth may have had some impact on melt and snowmaking.  In the case of the former, the loss of snow to melt on high-elevation north aspects is very small (or non-existent) this time of year when the sun angle is low.  Perhaps the difference in temperature has had some impact on snow losses down low during warmer periods (rain on snow, for example).  I'm going to guess that the impact is small, but stand to be corrected if someone can further than analysis with more data than I can look at in the short amount of time this morning.  I suspect that the situation on south aspects between the two seasons is a draw.  Near to nothing in both instances.  In the case of the latter, perhaps snowmaking conditions were a bit worse this Nov-Dec, but the argument is irrelevant since I don't think any resorts had snowmaking in 1976.  It would be interesting to go back and read some news reports from the 1976 holidays about what was happening at the resorts (alternatively, share your perspectives in the comments).  This Nov-Dec, we clearly have benefited from snowmaking in ways that were not possible in 1976 and, for resort skiers, that's probably a trump card surely making the start of this season better.

Now, getting to the meteorology.  If you are into El Niño and La Niña, you might be interested to know that weak El Niño conditions prevailed during Nov-Dec 1976, whereas weak La Niña conditions prevailed this Nov-Dec.  That's all I'll say about that.

The upper-level pattern during Nov and Dec 1976 was very high amplitude (i.e., wavy) across the Northern Hemisphere with a high amplitude ridge parked along the Pacific coast of North America and a deep trough over eastern North America.  This pattern kept much of the western US dry, but the eastern U.S. cold and snowy.
Source: ESRL

Source: ESRL

I was 9 years old at the time and living in upstate NY, and I still remember that as a very cold winter.  The extreme nature of the winter across the US sparked a good deal of research on climate and climate variability.  In what would have been a "rapid response" paper at the time, Henry Diaz and Robert Quayle published a paper in the October 1978 Monthly Weather Review arguing that January 1977 was probably the coldest month experienced in the eastern half of the U.S. in the last 200 years and that the 1976–77 winter set a new record for fuel demand due to the extreme cold in high population areas.

Source: Diaz and Quayle (1978)
This Nov-Dec was also characterized by a very high-amplitude pattern across the Northern Hemisphere.  However, the pattern over North America in November featured a ridge centered over the west-central U.S., rather than along the Pacific coast.

Source: ESRL
 This enabled storm activity in the Pacific Northwest, but kept the Southwest dry.  For northern Utah, the snowfall numbers for November 1976 and 2017 are nonetheless quite similar at Alta Guard, with 13.5 and 15 inches, respectively.   I haven't had a chance to dig into the water equivalent numbers to see how those compare and if there were any differences in the fraction of precipitation that fell as snow in the two years.

By December, the west coast ridge was dominant.  This is a pattern somewhat reminiscent of November and December 1976.  Alta-Guard, however, did a bit better for snow this December than in December 1976. 

Source: ESRL
It's not surprising that we see some similarities (and differences) between the two Nov-Dec periods.  Droughts in the west are frequently associated with ridging along the Pacific coast and that is a preferred area for ridge development.   Whether or not the remainder of this season evolves in a manner similar to the 1976/77 season remains to be seen, but my personal view is that analog forecasting based solely on local precipitation characteristics is not bound to be reliable over many cases.  My take is we just have to see how this will play out and hope that things shift for the better soon.

A few other thoughts:

1. The 1976/77 season was unbelievably bad in the southern Sierra Nevada.  Mammoth Mountains snowfall history (available here) shows a total seasonal snowfall of only 94" and no snowfall at all from October through December.  Four inches of that 94 fell before October.

2. Alta Ski Area's web site shows 74" in this Nov-Dec, but their observing site is higher up on the mountain.

3. I have not addressed the issue of observational representativeness and uncertainty in this post.  The Alta-Guard measurement site has changed over the years and this does affect snowfall measurements.  Similarly, I've never dug into the Alta site information to see if the location of the temperature measurements have changed, and that could affect the temperature comparison (there's a big difference depending on sun exposure, especially in December).

4. SNOTEL observations in the central Wasatch do not extend back to 1976.  It would be very interesting to utilize the manually collected snow course data to do a comparison.

Dismal Pattern Continues

The large-scale pattern has not changed.  I repeat, the large-scale pattern has not changed.

Yes, we got a couple of miracle storms prior to Christmas, but on the hemispheric scale, we are still dealing with a highly perturbed, wavy, high-amplitude pattern. 

Note, for example, the dynamic tropopause (jet-stream level) analysis from 0000 UTC 27 Dec (1700 MST Tuesday/Yesterday).  Deep trough over the eastern US.  Deep trough off the coast of Asia.  High amplitude ridge over the eastern Atlantic. 

You want snow, go to the lee of the Great Lakes or western Japan.  Both have been getting pummeled. 

And, there's no end in sight for the dry weather.  Forecasts below are from the 0000 UTC 27 December initialized ECMWF and GFS models through the end of the holiday period (0000 UTC 3 January/1700 MST 2 January).  Storm track to our north.  Dry southwest. 

There are a few members of the NAEFS that drag the moisture down south enough to give us a little more action around later in the 7-day forecast period.  Thus there is a little hope, but I'm keeping my expectations low.  Plumes below are for Alta-Collins and show a small number of ensemble members giving us some action on or after the 30th of December.  Most generate no more than 4 inches of snow.  Sad!

Is this La Niña?  I'm not ready to endorse that viewpoint.  Yes, there are aspects of this pattern that are consistent with La Niña, but there are other aspects that are not.  Mechanisms affecting the large-scale circulation are multifaceted and complex.  Maybe we'll deal with this in a future post. 

Heartbreak Ridge Provides One Blutarski of Precipitation Through Mid December

The Sunday Storm delivered at the upper end of expectations, which was great for skiers and storm chasers.  That's the good news.  The bad news is that Heartbreak Ridge is here, and maybe to stay, at least for a while.

The latest GFS dynamic tropopause (jet-stream level) forecast below ain't mobile friendly, but it tells it like it is.  A ginormous ridge is building over western North America this week, diverting the storm track into northwest Canada and Alaska.  Although that ridge eventually weakens and moves downstream, another builds behind it.

Total precipitation produced by the GFS in Utah over the next 10 days is precisely "one Blutarski."  In other words, zero-point-zero.

For those of you who don't know what a Blutarski is, watch this clip from Animal House and work harder to expand your educational horizons. 

Most medium-range ensemble members are similarly going for dry conditions over the area and nearly the entire mountain west.  Perhaps the ridge will be weaker than advertised, shift a bit westward allowing something to spill over the top, or go north enough for the southern branch of the jet to come into our area.  That's about all we can hope for.

I'm not one to extrapolate already medium-range forecasts even farther into the future.  Much can happen at long lead times.  Blocking patterns like this can be very persistent, but I'm inclined not to make forecasts for the 2nd half of December at this time. 

For Wasatch Front dwellers, now is the time to reduce driving, carpool, and take transit.  The inversion begins to develop today and the cold pool it isolates in the Salt Lake Valley and adjoining lowlands probably won't be going anywhere for a long time unless we can get some sort of dry cold front to slide down the back side of the ridge.  That's not impossible, but I wouldn't count on it.  Expect today's emissions to be tomorrow's smog.

Disastrous Heartbreak Ridge to Develop Next Week

The medium range models have been calling for the ridge from hell, which I'll officially name "Heartbreak Ridge", to develop over the western U.S. next week.

Just check out these GEFS forecasts from this morning.

Penn State E-wall
Blocking patterns don't come much uglier than that, and the ECMWF ensemble forecast (mean and standard deviation below) is no prettier.

I've been in denial about these forecasts for a few days, hoping that we might get something Sunday/Monday for storm chasing and to help the skiing some, but it hit me today that we could be hosed big time.

Let's put the situation into historical perspective. Records for the Snowbird SNOTEL cover 29 years.  Time series of snowpack water equivalent from 1 October to 1 February are provided below.  We currently sit at 3.1 inches, which I've circled below.  There are only 2 water years with less snow, 2000 and 2010.     

Source: NWS
That wouldn't be cause for panic, but that block scares the bejesus out of me. I stuck an arrow for the future on the graph, assuming we get perhaps 0.5" of water out of the Sunday/Monday storm (it could be more or less, but I lean toward less).  We would go through the first week of December near the lowest snowpack in that 29 years.  If instead we hold at the current snowpack, 3.1 inches would match the low for Dec 10 set in 2010.  

Although there is some uncertainty in the SNOTEL data, we're near the bottom of the barrel.  Note that the SNOTEL records don't go back to 1976/77, better known as the "drought year", when only 13.5" fell in November and 17" in December at Alta.  That year may have been worse.  

Bottom line: Burn skis, sacrifice a goat, or whatever else you can think of to conjure snow up Sunday/Monday.  We could be facing a really ugly start to December.  

About the only thing that keeps me going in times like these are thoughts of the 100 inch storm in November 2001.  We'll need it if this continues.  

Today’s Forecasts Even More Depressing Than Yesterday’s

Oh, how I wish there was a glimmer of hope for the start of ski season.  Each day I come in looking for a bonafide chance of a real storm, only to have my hopes dashed.  Yesterday's forecasts were depressing, but today's are even worse.  They are drier, with an even higher amplitude flow over North America for the foreseeable future.

It's a bit late for Halloween, but today's forecasts are really ghastly.  Plotted below are "postage stamps" of the 10-day, 500-mb height forecasts from the Global Ensemble Forecast Systems (GEFS).  Basically, there's barely a hint of upper-level flow anywhere over western North America except in the upper-left hand forecast where there is some modest southwesterly flow over the Pacific Northwest.

Source: Penn State E-Wall
In the Canadian ensemble, there are a couple of members that tease the Pacific Northwest, but there's not much for Utah. 

It is not uncommon for the actual pattern to verify outside the range of solutions produced by these ensembles, so it's not impossible that something sneaks through the net, but my take is that the odds of skiing in the central Wasatch through the end of next week are very low.  Although temperatures today are conducive to snowmaking, and I see some guns blowing on the Alta web cams, the pattern above is also terrible for snowmaking as temperatures in the mountains will be quite warm.

At least the mountain biking and hiking should be good.  

Just How Dry Was This Summer?

Last night I awoke with a start to drops hitting the roof and leaves rustling on the windows.  My heart raced in anticipation of rainfall.  Alas, it wasn't to be.  A few sprinkles, some gusty winds, and it was over.

Similarly, this morning teased us with an ominous sky, virga, and even some mammatus clouds.

As I walked to the bus, I briefly felt raindrops on my face and arms.  So exciting!  However, hopes were once again dashed as the system moved off to the northeast.

Just how dry has it been this summer?  Well, August 31 is in the books and we can now take a look back at all of meteorological summer (June, July, and August).  Total rainfall at the Salt Lake City airport was 0.67", making it the 11th driest all time.

To put that into perspective, the histogram below shows the amount of precipitation falling in Salt Lake City by year back to 1874 ordered from high to low (I've left the years off since there are so many).  2016 is highlighted in red.  Yes, there have been drier summers, but the amount of water in the rain bucket this year is quite low and in the 10% driest summers.

For temperature, we fell just shy of the hottest of all time (behind 2013), but ended up 2nd and a full degree warmer than the next highest summer, 2007.

Source: NOAA Regional Climate Centers
You put that combination of little precipitation and exceptional warmth together and you probably have the "driest" summer on record in Salt Lake, or at least something that is close to that, if you think about it from the perspective of precipitation minus evaporation.

In the foothills, most of the grasses turn brown during the summer, but this year one sees gamble oak and other species highly stressed with browning leaves.  Near the mouth of Dry Creek just northeast of campus, where most plants survive for the summer, everything appears to be dead.

Although we may get lucky with a shower or thunderstorm today (or unlucky if it happens during the football game), we need things to turn around quickly or we are going to be entering the cool season with a huge deficit in soil moisture.   If we have a big snow season (wouldn't that be grand), that won't be a problem, but if we have another meager year, it will cut into the runoff as the first "reservoir" to be filled when the snow starts to melt is the soil.

At least cooler weather is on the way.  Looking forward to it.


Plot of summer precipitation @KSLC chronologically by year added below at request of commenter.

How "Dry" Is This Summer?

Brown, the official color of summer
Some of you have commented about how dry it is this summer.  Let's have a look at some data, focusing on the Salt Lake City area.

In Salt Lake City, the total precipitation so far this summer (1 June – 7 August) is 0.59 inches, making it the 19th driest since 1874.

Source: NOAA Regional Climate Centers
Most of that precipitation fell in June, however.  The total precipitation since July 1 is only 0.07", good for 10th driest.

Source: NOAA Regional Climate Centers
However, "dryness" reflects not only precipitation, but also evapotranspiration.  Evapotranspiration is the transfer of water from the soil to the atmosphere through evaporation and transpiration.  Many factors effect evapotranspiration, including humidity, wind speed, and temperature.  I don't have access to historical humidity or wind records, so I'm going to ignore them here.  For temperature, however, the summer so far is the warmest on record, with an average temperature of 80.6ºF.

Source: NOAA Regional Climate Centers
Since July 1, we're in 4th place (not shown), so it has been an exceptionally hot summer too, and that is a major driver of the extreme dryness, increased irrigation demand, and stress on plants.  

Elsewhere in northern Utah, a few places may have benefited from showers and thunderstorms the past couple of days, but for the most part, it's been a dry and hot summer regionally.  

Summertime precipitation shows a great deal of variability spatially and from year-to-year.  Remember that last year was remarkably wet.  Temperature also exhibits year-to-year variations, but the trend is clearly up, with heat waves becoming stronger and more persistent.  It is because of these temperature trends that we expect summers to become increasingly arid over northern Utah in the coming decades.  

A Nearly Snow Free October

Although we will see a few snow showers today and tonight in the high country, perhaps enough to coat the ground in places, it appears that October will go into the books nearly snow free as the rest of the week through Halloween looks dry.

For those of you looking to make turns, Gunsight currently has a 0-2.5 cm base.  I'm using metric for marketing purposes.

The metric base builder can be found elsewhere in the Alta–Snowbird high country...

Most of this skiff of snow consists of large graupel, ice pellets, or small hail that fell during Tuesday's frontal passage.  I never know what to call precipitation that looks like this.  In honor of The Princess Bride, perhaps we should call it "graupel of unusual size."  This mass collected in a local pit of despair.

Elsewhere in the Wasatch, Lake Mary (left) is looking forward to a recharge this winter.  I don't know what the typical "spillway" elevation of Lake Mary is in October, but it surely can't get much lower than it is this year.  Note the dry dam at upper left.

On the plus side, unless today and tonight surprise me with more snow than expected, we should end October largely facet free.  Hopefully Mother Nature will eventually turn on the spigot in a big way so that we can avoid the deep instabilities that have plagued backcountry travel in recent years.

The Southwest Drought

The New York Times occasionally runs a series of maps and charts examining a variety of issues, including their latest, Mapping the Spread of Drought Across the U.S.

Drought severity across the U.S. on July 22, 2014.  Source: New York Times.  
 Drought is an under appreciated natural disaster.  The onset and end are not typically sudden, but the costs can be quite high.  If you scan the list of billion dollar weather disasters since 1980, drought appears 18 times, with combined loses of almost $250 billion in current dollars.

Droughts are often through to be periods of abnormally low rain, but they are actually quite multifaceted with considerable geographic variability.  There's more to the story than precipitation as the conditions that lead to low soil moisture are also affected by temperature and other weather, climate, and soil factors.  Although there are many different ways to both define and determine the severity of drought, the most widely used index is the Palmer Drought Severity Index (PDSI), which attempts to account for a variety of factors that affect soil moisture.

Plots like the one above derive from the U.S. Drought Monitor, which blends a number of drought measures and expert judgement.

The Southwest is currently in the grips of widespread drought, with drought conditions rated as exceptional over portions of California and Nevada (the "more" region above).  To the first order, this drought reflects the influence of climate variability.  As concluded by Hoerling et al. (2013) in the Assessment of Climate Change in the Southwest United States:
"It is likely that most of the recent dryness over the Southwest is associated with natural, decadal coolness in tropical Pacific sea-surface temperatures, and is mostly unrelated to influences of increased greenhouse gases and aerosols." 
In other words, more persistent La Nina conditions have played an important role in the long-term drought conditions.  This is not to say that global warming has had no influence on the drought.  It is an exacerbating factor with higher temperatures, by contributing to soil drying, increasing in drought coverage and intensity.

Thus, we should be cautious in attributing the current drought to global warming.  On the other hand, we also shouldn't assume that all is well and good in the coming century.  The evidence suggests a decline in water resources over the Southwest over the long term.  As discussed by Gershunov et al. (2013) in that same Assessment of Climate Change in the Southwest United States:
"Drought, as expressed in Colorado River flow, is projected to become more frequent, more intense, and longer lasting, resulting in water deficits not seen during the instrumented record (high confidence)" 
"In terms of soil moisture, drought is expected to generally intensify in the dry season due to warming (high confidence)"