Thursday, October 8, 2015

Still on Track for Strong El Nino

The Climate Prediction Center issued its monthly ENSO diagnostic discussion today and not surprisingly continues to go for a 95% chance of El Nino continuing through winter.  As we've seen for some time, sea surface temperature anomalies show a well-developed El Nino signature with a tongue of anomalously warm water extending across the eastern and tropical Pacific.

Source: CPC
The International Research Institute for Climate and Society at Columbia University has a nice simple graphic summarizing the El Nino predictions showing a very high likelihood of El Nino conditions persisting through winter before the likelihood of a decline in strength increases in the spring.

As we've discussed previously, I don't consider the existence of El Nino to have a strong influence on the snowfall odds for this coming ski season in the central Wasatch (see Wasatch Weather Weenies Survival Guide for El Nino).  However, since I'm desperate for material, I thought I'd show another perspective today, albeit one based on a very small sample size.  

In the graph below, I've taken the Nov-Apr snowfall at Alta Guard and have ordered it from high to low, identifying the top 1/3 of years in blue, middle 1/3 in green, and bottom 1/3 in yellow.

Then I've identified the four strongest El Nino winters (1957–58, 1972–73, 1982–83, 1997–98) in red and the next four strongest El Nino winters in purple (1965–66, 1986–87, 1991–1992, 2009–10) based on the December to February El Nino Index.  For those of you who aren't concerned about a small sample size, you'll be glad to know that the four strongest El Ninos fall in the upper half of the distribution (Note that the 1972–73 winter may have been missing November, unless the lack of data for that month in the dataset I grabbed indicates zero).  On the other hand, the next four strongest El Nino winters are in the bottom half of the distribution.

One view of this is that a strong El Nino might be associated with a good snow year.  The other view is that the sample size here is small and that adding more cases yields a distribution that shows little correlation (note that we only have Alta snow data since WWII, so to add even more cases requires using wimpy El Ninos).  CPC has added a few more cases in the plot below by looking at strong El Ninos back to 1915 and the precipitation produced in climate zones.  Their definition of strong is a bit lower than mine and includes a couple of the moderate events that I used above.  In any event, it shows northern Utah to be sitting on the transition zone or having a slight tendency for drier winters.

Source: CPC
So, we have a small sample and imperfect data, but my read continues to be that the dice simply are not loaded very strongly for this coming winter.  However, if it will make you happy, you can cherry pick the Alta bar graph above and assume a big winter is ensured.

Tuesday, October 6, 2015

Eastern Utah Is So Weird!

As noted by David, who commented on the previous post, the valleys and lowlands of eastern Utah are just plain weird climatologically.

If one classifies the precipitation climate over the southwest U.S., there are four major regimes.  The first (row a in the image below), covering most of California, northern Nevada, and the upper elevations of northern Utah and western Colorado, features a pronounced winter maximum.  The second (row b), covering much of Arizona and portions of southern Utah, New Mexico, and southwest Colorado, features a pronounced maximum during the monsoon.  The third (row c), covering the plains of eastern Colorado and New Mexico, is somewhat related and has a maximum in the summer with less precipitation in the winter.  Finally, there is a fourth regime (row d) in the lower elevations of portions of Nevada, Utah, and western Colorado where precipitation peaks in the spring.  This includes the Salt Lake Valley.

Source: Steenburgh et al. (2013)
If you look carefully at those plots, however, you can find a region that is not included and that is the valleys and lowlands of eastern Utah, including places like Vernal and Moab.  The climate there has a maximum occurring in October.

Why October?  I can speculate, but it really deserves some investigation.  As suggested by David, there could be a magic point as the monsoon tails off and we begin to see mid-latitude storm systems coming in that enables more moisture and precipitation to move into this area.  It might also be that this area got pounded by a small number of larger storms during the past few decades, skewing the stats for October (I haven't checked to evaluate the statistical significance of the October maximum).

In any event, eastern Utah has always been a little weird and even Mother Nature likes it that way.

Monday, October 5, 2015

Stuck Between Two Regimes

Precipitation over the western United States over the next week is strongly dominated by two regimes.  The first is associated with the deep upper-level trough moving across the southwest U.S. over the next few days that will result in frequent shower and thunderstorm activity.  The second develops later this week as moist southwesterly flow penetrates into the Pacific Northwest.  

The mean precipitation produced over the next 7 days by the North American Ensemble Forecast System (NAEFS) shows these two regimes quite nicely with the largest accumulations over the Southwest and the Northwest.    
NAEFS mean precipitation 0000 UTC 5 October – 0000 UTC 12 October 2015
Northern Utah is just on the fringe of the more monsoonal regime, but misses out on the precipitation over the Northwest.  Thus, our best chance for precipitation in northern Utah is through tomorrow evening as we are brushed by the upper-level trough.  

Because we're stuck between the two regimes, we won't be seeing skiable snow for at least another week.  The NAEFS forecast plume below is for Alta and shows the precipitation through tomorrow afternoon, after which it's pretty much flatlined (i.e., dry).  It's cold enough that the higher elevations may see a dusting or light coat if there's a strong shower, but that's about it.  

No worries.  Best if it holds off for a bit longer.  

Sunday, October 4, 2015

The Mount Olympus Wilderness

It doesn't matter how long you live in Utah.  You will have days where you are just thankful for the beauty and access of the Wasatch Range.

The Mount Olympus Wilderness is a truly remarkable place.  It's right there.  It starts right on the edge of the east bench and is a remarkably wild and undeveloped place.  The vegetation is thick on north aspects and I saw plenty of deer, grouse, and woodpeckers today.

The Desolation Trail is aptly named.  Plenty of people take it the first couple of miles, but once you climb a couple thousand vertical feet, you'll find few people.

There's still nice color out there, particularly on this side of the range.  I was in Park City last weekend and was shocked at how grey everything was.  Many of the aspens on the Wasatch Back dropped their leaves early this year.  I've heard media reports that a fungus is responsible.  Apparently it's a one-and-done thing and not a long term detriment to tree health.  Let's hope so.

Gobblers Knob showed a bit of fall plumage today.  There's still some aspens that haven't gone over completely yet.  Maybe there will be some color remaining next weekend.

I wonder how many wilderness areas in the United States are so close to a metropolitan area of this size.  We are so fortunate.

The Broads Fork Twin got a nice dusting late yesterday.  It won't be long now.

Saturday, October 3, 2015

Fundraiser for Brian

I couldn't find this with a Google search when preparing the previous post about Brian McKenna, but if you are interested in donating to help with his medical expenses, there is a fundraiser at gofundme that you can access here.

Friday, October 2, 2015

A Remarkable Story of Courage and Inspiration

There's plenty to talk about meteorologically today from coast to coast, but instead I want to share a remarkable story of courage and inspiration.

Brian McKenna is a long-time follower of this blog.  We've shared a number of e-mail exchanges and I had the great opportunity to meet him briefly at the 2014 Utah Snow and Avalanche Workshop.

Via social media, I saw some reports that Brian was in an accident over the summer.  I didn't hear much more than that and I foolishly assumed that it was perhaps not all that significant.

Yesterday I learned that Brian's accident was instead quite serious.  He had been paralyzed in a mountain biking crash.  His story, which speaks strongly to the quality of his character, was covered yesterday by the Ellen Degeneres Show and can be viewed in the two clips below.

Brian – my thoughts are with you.  Continue to keep an eye on the weather and those e-mails coming.