Tuesday, May 3, 2016

Congrats Jim Ehleringer!

Source: SustainableUtah
This morning I learned that Jim Ehleringer, Distinguished Professor of Biology at the University of Utah and, more importantly, regular reader of this blog, has been elected to the National Academy of Sciences.

There are only 2,291 active members in the academy, making election truly significant.  Jim received his Ph.D. from Stanford and has been at the University of Utah since 1977.  HIs full bio is available here, but I'll give a brief summary.  Nearly 500 articles.  Former chair of the biology department.  Director of the SIRFER stable isotope ratio facility.  Lead honcho for IsoCamp, a summer course in stable isotope biogeochemistry and ecology with hundreds of alumni from around the world.  Former director and visionary leader of the Global Change and Sustainability Center, which has become a catalyst for environmental research on campus.  Fellow of the American Geophysical Union.  Fellow of the American Association for the Advancement of Science.  Etc. Etc.

I'm not sure when I first met Jim, but at some point several years ago I found myself going to one of his graduate courses on stable isotope ecology.  At the time, I knew nothing about isotopes.  Today, I still know practically nothing, but I'm conversant just enough to appreciate the remarkable work that Jim and others do on campus using isotopes to understand everything from paleoclimate to transpiration, and for that I thank him.

Congratulations to Jim on this well deserved election and recognition.  

Monday, May 2, 2016

Windstorm Oddities

Forecasts of easterly downslope winds in northern Utah have improved considerably in recent years due in part to improved numerical modeling, improved monitoring, and better understanding.  Nevertheless, there's always more to be learned.

Amongst the oddities of our most recent event is the duration of the easterlies.  Below are 750 mb (near crest-level for the northern Wasatch) wind analyses for 1200 UTC (0600 AM MDT) yesterday and today showing a dramatic drop off in the strength of the easterly crest-level flow.

Although this dropoff can also be seen in mountain-top and pass observations from the Wasatch Range, the corresponding dropoff in wind speed at the base of the Wasatch Mountains is weaker.  For example, at the top of the Strawberry Bowl at Snowbasin Saturday night, winds were generally around 50 mph with gusts to 70.  Meanwhile, in Farmington (US-89 at Park Lane), winds were just a bit stronger.  During the day yesterday, winds at both sites weakened commensurately.  However, last night and this morning we clearly entered a new regime.  While the flow at the top of Strawberry Bowl weakened, winds of about 30 mph with gusts to 40-50 mph persisted at Farmington.

This potentially suggests two differing regimes for flow dynamics across the Wasatch.  In the first, strong flow near the crest plunges into the lee, but experiences only a small acceleration (Saturday night and Sunday morning).  In the second, the plunging flow strongly accelerates into the lee (last night and this morning).  At least in this event, the latter does not lead to damaging winds, but that's not necessarily the case in all events.

Of course there is always the possibility that the localized nature of the Strawberry Bowl observing site makes it somewhat unrepresentative of the flow moving across the Wasatch Range immediately east of Farmington.  It's unfortunate that we don't have a wind observing site in that part of the Wasatch Range and perhaps installing one should be a high priority for the state given the severe impact these events have on the northern Wasatch Front.

It would also be helpful to have soundings taken during future events from along highway 66 south of Morgan.  My colleagues at the University of Utah have done this for a couple of events, but it would be great if we could find a way to do it regularly during events.  Combined with high-resolution modeling, we could tease out some of these oddities and potentially better predict some of their more fine-scale aspects.

Sunday, May 1, 2016

Windstorm Update

As of 8 am, wind gusts ≥ 60 mph reported to Mesowest:
  • Bountiful Bench (BBN): 61
  • Fruit Heights (AS519): 63
  • Centerville (C8948): 63
  • Kaysville (AT097): 63
  • Centerville (UP028): 65
  • Hill Field (KHIF): 67
  • Layton (AS186): 69
  • South Ogden (C5505): 70
  • Brigham City (KBMC): 74
  • Centerville (UP138): 80
  • Centerville (CEN): 81
  • Farmington (AP611): 87
  • Farmington (UTPKL): 91
Those observations are based on measurements from a variety of sensors with a variety of capabilities and limitations.  The 91 mph at Farmington is from a site operated by UDOT at US-89 and Park Lane and is likely reliable.  Overall, these observations show high winds covering nearly the entire Wasatch Front from Bountiful north to Brigham City.  

Observations from UTPKL show winds began to gust over 60 mph beginning around 1900 (7 PM) yesterday, reaching their peak from 0400–0600 (4–6 AM) this morning.  

Rocky Mountain Power reports more than 28,000 people currently without power.  

In the Salt Lake Valley, peak gusts include 58 mph at the Triad Center, 53 mph in the upper Avenues, and 53 mph at the University of Utah.  Those peak gusts occurred late yesterday or earlier in the overnight hours.  Along the east bench where winds were strongest, winds weakened in the late night hours.  

Although not as strong as overnight, downslope winds will persist this morning from Bountiful North.  The event will wind down this afternoon.  Latest forecasts at http://www.wrh.noaa.gov/slc/

Saturday, April 30, 2016

Tonight's Downslope Windstorm: Don't Be Complacent

I'm pretty blown away (pun intended) by the model forecasts for tonight and tomorrow (Sunday) morning.

The 0600 UTC NAM is generating strong easterly flow across the northern Wasatch Front with 700-mb (near crest-level) winds reaching 50 knots in places.  There is also a strong pressure gradient from Evanston to Ogden.  Coming overnight and in the early morning, these are ingredients for a strong downslope wind event.

The National Weather Service has issued a high-wind watch for the Cache Valley and northern Wasatch Front for sustained winds between 30 and 40 mph with gusts in excess of 60 and localized gusts in excess of 75 mph in some areas, especially Davis and Weber Counties.

Take the time today to secure loose outdoor items if you are in areas affected by these downslope winds and monitor forecasts at http://www.wrh.noaa.gov/slc/.

Thursday, April 28, 2016

This Is the Biggest Storm Cycle of the Season

Here's one for you.  When did we have the biggest storm cycle of the ski season?  December?  January? February?


The answer is right now, and it isn't even close. 

The chart below shows the running 5-day accumulation of water equivalent at the Snowbird SNOTEL station since October.  In terms of water equivalent, the 5-day accumulated total through today is 4.3 inches.  The next highest is December 25th with 2.8 inches.

All I can say is what an event, especially Tuesday and Tuesday night when we picked up 16 inches and about 2.25 inches of water at Alta-Collins.  Although snow was in the forecast, that was impressive.

And we got a bit more last night and will get a bit more today.  Note the inexact terms "a bit more."  I'm feeling beaten and battered by these closed lows and their whimsical precipitation patterns.

Wednesday, April 27, 2016

Winter Rises from the Dead

Source: Rankin-Bass
Just when you thought winter was over, it rises from the dead.

A whopping 16 inches at Alta-Collins in the last 24 hours has pushed the total snow depth up to 115 inches, the deepest since late March.  

That 16 inches contained 2.27 inches of water.  That's a water content of 14%.  Thick and creamy, but I bet anyone out this morning won't be complaining.

The pattern remains showery and unpredictable for the next few days, but don't wait.  The best time to get good turns this late in the spring is when it is snowing.