Sunday, November 18, 2018

Snow for Thanksgiving Weekend?

Yesterday's frontal passage did little to put a dent into the November snowfall drought, generating an inch on the Alta Collins snowfall stake.  Sadly closed for uphill skiing and a close personal inspection, I suspect that there will be decent top-to-bottom skiing at Alta when they open, even if the terrain is limited, thanks to assistance from artificial snow.

Hopefully, we will also get some help from Mother Nature over Thanksgiving weekend.  For the past few days, the models have been suggesting some storm systems will move through the area during that period, but amounts have been variable.  The latest NAEFS ensemble is looking up a bit, however, with all ensemble members producing precipitation at Alta-Collins on Thanksgiving (22 November) and then periods of precipitation through the 24th (Saturday). 

For most ensemble members, the totals being produced by our downscaled NAEFS product plotted above vary from about 1.2 to 2.7 inches of water equivalent and 18 to 35 inches of snow for Alta-Collins.  The Canadian has a few very excited members, but also a couple less excited members. 

That's about the most optimistic forecast I've seen since our early October storm.  Let us hope it delivers.  Keep up the snow dances and keep an eye on the forecasts the next few days as this is an evolving forecast situation. 

Friday, November 16, 2018

Local Pollution or Smoke?

Looking toward the central Wasatch Mountains from the Avenues Foothills 3:30 PM Friday 16 November 2018
A lot of people have asked me if the haze in the valley is smoke from the fires in California.  There is probably a small amount of smoke that is in our area, but for the most part, what you are seeing in the valley is pollution of our own doing.

The vast majority of the smoke from the California fires remains over the central Valley, Bay Area, and offshore Pacific ocean, although there is some that extends eastward across the Great Basin.  This is illustrated by the HRRR-SMOKE analysis below for near-surface smoke concentrations.  Note that the HRRR estimates near-surface smoke concentrations to be 4 ug/m3 or less over northern Utah.   

Source: ESRL
I'm not sure how much to trust that estimate, but let's go with it.  PM2.5 concentrations on the University of Utah campus today have been running around 14 to 20 ug/m3, much higher than the HRRR smoke estimates.  Note that over the past two days the values have fluctuated dramatically, dropping to as low as zero overnight and then rising during the day.  This reflects the development of a down-canyon flow in Red Butte Canyon (the observing site sits at the mouth of the canyon), which brings clean air from aloft (above the smog layer evident in the picture above) at night.  This is another reason why I'm skeptical about smoke being a strong contributor to our current pollution.  We simply don't have much evidence of high smoke concentrations aloft.

Source: MesoWest
Finally, November IS part of our wintertime smog season.  The sun angle right now is plenty low and comparable to that in late January.  Further, we do have a persistent cold pool in place over the Salt Lake Valley.  Yesterday afternoon, for example, a series of stable layers just above 5000 feet prevented pollution from the valley from mixing with the atmosphere aloft.  If there were snow on the ground, we'd have a whopper of an "inversion" event. 

Source: SPC
So, as I like to say, we have met the enemy and it is us.  The good news is that the weak cold front coming through late tomorrow should stir things up.  However, we go back to ridging early next week, so consider taking the bus or alternative modes of transportation if you can do it.  

Thursday, November 15, 2018

Is Our Recent Spate of Bad Novembers "Unusual"

As far as I'm concerned, November can suck it.  I'm tired of mountain biking in the cold, wishing I was skiing.  Yeah, it's cold enough for snowmaking, but I don't live in Utah to ski fake snow.  I'd rather have some warm weather that's more enjoyable in the valley. 

It's worth taking a look at historical November snowfall at Alta Guard, where the US Forest Service and now the Utah Department of Transportation have kept records back to 1945.  The average November snowfall is 69 inches, although there is great variability (note that 1972/73 is missing in the graph below). It is also apparent that the 1980s and early 1990s were exceptional for November snowfall, with the 10-year running average (thin line below) peaking at over 100 inches in the early 1990s.  November 1994 was the ultimate with 206 inches. 

At issue is this.  Is our recent string of bad Novembers really all that unusual, or were the snowy 1980s and early 1990s the true outlier?  As far as total snowfall is concerned, recent Novembers are not all that unusual compared to the late 50s through the 1970s in terms of total snowfall.  Sadly, we don't have snowfall records going back for several hundred years to put the last 15 years or so into context. 

Note that this does not mean that the climate has not changed (it has) or that the mechanisms responsible for the recent spate of bad November snowfalls aren't different than they were in the late 1950s through 1970s.  Those are issues that would require a much more in depth analysis than I can do for a quick blog post.  However, I do believe it is worth recognizing that the 1980s and early 1990s were exceptional snow years in many ways and that they may not represent the true "average" climate of Utah, even before global warming began to accelerate. 

Tuesday, November 13, 2018

Santa Ana Air Quality Oddities

The Camp and Woolsey Fires in California, which have been fanned by Diablo and Santa Ana wins, have produced a true wildfire catastrophe.  The 7 PM 12 November incident update for the Camp Fire near Chico reports 42 civilian categories and over 7,000 structures destroyed, including 6,453 single residences.  It is now the deadliest wildfire in California history.  The incident report for the Woolsey fire near Thousand Oaks and Malibu, also updated 7 PM 12 November, reports 2 civilian fires and 435 structures destroyed, although this is an estimate.

I happened to be in the Los Angeles area this weekend.  One of the oddities of Santa Ana conditions is that in the absence of fire and smoke, they produce good air quality and visibility.  Below are a series of MODIS images for 9, 10, 11, and 12 November.  In the top image (9 November), the Woolsey fire was raging with strong Santa Ana winds blowing the smoke plume offshore.  The LA basin was smoke free.  On the 10th, however, the flow shifted and weakened, and smoke infiltrated much of the urban area.  That smoke lingered into the 11th, although it is difficult to see in the imagery.  Finally on the 12th, conditions cleared again, with smoke emissions lower.

We arrived in Los Angeles Saturday morning and drove straight to the San Gabriel Mountains and the Mt. Wilson Observatory as from the plane it appeared the visibility was good and the air clear.  Indeed we found that to be the case when we arrived at the observatory.

However, smoke was beginning to spread into the LA Basin as we left the ridge top.

On Sunday, although we had planned some hikes in the hills, the smoke was bad enough in the morning that we elected to tour art museums instead.

Monday I had a morning meeting, but afterward we made a quick stop at the Santa Monica Pier on the way to the airport.  The smoke from the Woolsey Fire was clearly subdued compared to earlier days and with the offshore flow the weather was postcard perfect.  Quintessential SoCal. 

What a paradox that the weather and air quality can be so good in one place while catastrophe is unfolding not far away.  Sadly, we still no not fully comprehend the losses from these fires as there are still many missing and the fires continue to burn.  Red Flag Warnings are currently up for the Woolsey Fire area through 5 PM this afternoon, which will mean another difficult day of firefighting conditions and the potential for rapid spread of spot fires from blowing embers or new ignitions.

Note:. Post has been updated to correct spelling of Santa Ana.

Thursday, November 8, 2018

A Realistic Pessimist

Good snowmaking weather the next few days, if you are into that sort of thing. 

Other than that, the forecast is a disaster.  The US ensemble (GEFS) gives us absolutely no love and is essentially flatlined for precip over the next week at Alta Collins.  Canadian members give us a little. 

And here's the 8-14 day outlook from the Climate Prediction Center.  A 50% chance of below average precipitation is about as strong of a loading of the dice as you will ever see from that group at such lead times. 


Wednesday, November 7, 2018

The 1963 "Goetsu" Winter

If one can't be skiing in deep powder, it's best to be thinking about big storms.  I recently learned about the 1963 "Goetsu" winter, which crippled Nagaoka and other areas of Japan.  Goetsu is Japanese for heavy snowfall.  In the 1963 Goetsu winter, the snow depth in Nagaoka, which is at an elevation of only 23 meters (75 feet) above sea level, reached 3.2 meters (125 inches).  Here is some great footage from that winter.

Notice that the snow in this footage appears to be remarkably dense.  This is common in coastal areas of central Honshu where the bulk of the snow falls at temperatures near 0˚C (32˚F).  Nagaoka is a remarkably snowy city, with a mean annual snowfall of 500 cm (236 inches), but the average temperature in January, the coldest month of the year, is 1.3˚C (34.3˚F). 

Former Powder Magazine editor Steve Casimiro once asked, "do you ever wonder what it would be like if it started snowing and never stopped?"  The residents of Nagaoka got a pretty good idea in 1963.