Wasatch Weather Weenies

Changes are afoot that will result in a shift in the weather for Utah and a significant rainfall event in the eastern United States. The pattern currently developing over North America will give weather forecasters headaches from coast to coast.  It features multiple interactions between upper-level closed lows and high-amplitude ridges, with a tropical cyclone thrown in just for good measure.  The interactions between these features are notoriously difficult to nail down and this leads to considerable forecast uncertainty. The low hanging fruit is in Utah.  Our run of well-above-average temperatures will come to an end on Friday as an upper-level trough from the Pacific swings into the Intermountain West, bringing cooler air and showery weather. After that, it's tough to say.  The models have been all over the place dealing with the interaction of Friday's trough with another upper-level trough dropping down from British Columbia over the weekend (such an i...

We've had a remarkable period of sustained warmth over the past week in Salt Lake City.  Not only have we set two maximum temperature records (93ºF on Sep 25 and 90ºF on Sep 26), the average temperature for the past week (Sep 21–27) of 74.1ºF is the highest on record, easily eclipsing the 72.9ºF observed in 2001. A look at the time series above suggests that this past week is indeed quite an outlier and one of only 5 such September periods going back to 1874 with a mean temperature above 70ºF (note that the records above are a composite of observations collected in the Salt Lake Area as the airport didn't exist back then!). An unfortunate aspect of this hot dry weather is a loss of moisture from the big rains we had from September 14–16.  As shown in the chart below for the Mill D North SNOTEL in Big Cottonwood Canyon, those big rains greatly increased the soil moisture content of the soils at both 2 and 8 inch depths. Data Source: NRCS  Similarly, soils elsew...

The Aspens were on fire today in Big Cottonwood Canyon. Some groves have dropped their leaves, others haven't turned yet.  Upper elevations are probably going to lose a lot of leaves this week, but mid elevations will probably still be good next weekend.  We hiked up Gobblers Knob and Mill A Basin is probably at peak, but the Butler Trees were still pretty green and I suspect next weekend might be quite nice (I haven't bothered to see if the weather might cooperate!).

Long-time friend to the nordic and backcountry skiing communities of Utah, Dave Hanscom, was inducted into the Intermountain Ski Hall of Fame on Thursday.  It couldn't have happened to a nicer guy. Along with Alexis Kelner, Dave is the co-author of Wasatch Tours, Volumes 1, 2, and 3, the first definitive guides to backcountry skiing in the Wasatch Range.  Volume 2, covering the northern Wasatch, including the tri-canyons, contains wonderful prose.  One of my favorites is the description for the approach to Thomas Fork. " No ski area developers have cleared the willows and oak, so considerable ingenuity and determination are required to get through the brush.  True cross country touring is, after all, a character developing and strengthening form of recreation ."  I don't know if Dave or Alexis wrote that section, but the entire book series is filled with great commentary of this type.  Dave has also contributed greatly to the nordic communi...

The American Meteorological Society Committee on Mountain Meteorology hosts a webinar series exploring various topics in mountain weather research and forecasting.  Yesterday I had the opportunity to give a webinar on the influence of mountains on lake effect, which was followed by a discussion of operational issues by Paul Sisson of the National Weather Service Forecast office in Burlington Vermont. I considered embedding the video here, but it's much better viewed in full format, which you can access by clicking here . Access to the complete seminar series, which includes a number of topics that may be of interest to readers of this blog, is also available by clicking here .

Yogi Berra leaping into Don Larsen's arms after his perfect game in the 1956 World Series encapsulates the joy of sport.  Yogi Berra passed away yesterday at the age of 90.  He was one of the greatest catchers in baseball history and participated in 21 World Series as a player or coach.  Nevertheless, for many of us who never saw him play, we know him more for his quotes.  Here are five that are relevant for the weather weenies, scientists, and academic types out there. " In theory there is no difference between theory and practice.  In practice there is. "  I'm sure that quote was baseball motivated, but substitute application for practice and you are on to something for scientists and academics.   " I wish I had an answer to that because I'm tired of answering that question. " I'll be using that one at my next lecture on global warming. " You can observe a lot just by watching ."  Damn straight, and a good line...

Last week, the August climate numbers were released by the National Centers for Environmental Information (NCEI) and not surprisingly 2015 continues to be a hot one. For the January–August period, 2015 is well ahead of any previous year on record for global average temperature and a full 0.1ºC ahead of second place 2010. Source: NCEI The numbers for August the past two years are really out there.  August 2014 was 0.09ºC warmer than second place August 2009, and then August 2015 doubled down and added another  0.09ºC. Source: NCEI These big numbers reflect the long-term global warming combined with the strong El Nino that has developed in recent months.  Similarly, 1998 was a remarkably strong El Nino and it was a real outlier in terms of temperature (see the top bar chart).  Those wishing to argue that global warming "stopped" have frequently used 1998 as the start point of their time series as it results in a relatively flat trend over the last several ...

Still a couple of storms away (ha ha) But with weather like today That's okay

Monday's flash floods contributed to the deaths of 19 individuals, with one still missing.  It's Utah's worst day for weather-related loss of life in history.  Moving forward from here, the good news is that weather forecasts, watches, and warnings have never been better and will continue to improve in the future.  The bad news is that with increasing population, development, tourism, and recreation, Utah's vulnerability to severe weather has never been higher and is only likely to increase in the future. Here are two potential disasters that have yet to occur, but concern me as a meteorologist.  We probably can't eliminate the potential risks, but there are steps that can be taken to reduce the likelihood or severity of catastrophe. Avalanches in Little Cottonwood Canyon As I discuss in chapter 6 of Secrets of the Greatest Snow on Earth , 50 avalanche paths intersect SR-210 and other roads and parking lots in Little Cottonwood Canyon. Source: Secrets of t...

A critical question pertaining to the meteorology of the Hildale flood is how unusual was the storm that triggered it. I'm going to provide some preliminary analysis here based on radar precipitation estimates.  I want to emphasize preliminary because there are a host of issues regarding radar precipitation estimates that will ultimately need to be explored in the coming weeks. The image below shows the estimated storm-total precipitation in the Hildale area for the period ending at 2301 UTC (5:01 PM MDT).  All but about 0.1" of this total was produced during the flood period from 2000–2300 UTC (2–5 PM MDT).  The black square is located in the upper reaches of Maxwell Canyon along the axis of maximum precipitation and just north of Hildale.  The greatest estimated precipitation accumulation is actually southwest of Hildale.  Amounts in the area generating the flood are around 1.5 inches. The bar chart below shows the storm-total estimated precipitation...

Pretty nifty loop below showing the very persistent triggering of convection over the central Wasatch as the main precipitation band approached from the west.  Note how radar echoes extend downstream all the way to the UT-WY border.

In terms of loss of life, the Hildale Flash Flood was the worst weather-related disaster in recent decades, but was it the worst in Utah history? It depends. Tragically, 12 are confirmed dead in the Hildale Flash Flood, with one missing.  Records of weather disasters are better in recent decades but than in the distant past, but there is evidence of at least one weather-related disaster in Utah history that was worse.  On February 13, 1885, avalanches killed 15 in what was then the mining community of Alta, Utah.  This is documented in an article by Mark Kalitowski entitled The Avalanche History of Alta , which appeared in the December 1, 1988 issue of The Avalanche Review. C. R. Savage photo of Alta, UT on July 3, 1885 following a winter in which avalanches nearly destroyed the town However, late yesterday we learned of another tragic flash flood catastrophe that occurred on Monday in Zion National Park's Keyhole Canyon.  Four are confirmed dead, with thre...

A quick post on today's storm, which moved slowly through the Salt Lake and Utah Valleys and produced some urban flooding.  Being a mountain meteorologist, however, my thoughts are always on the high terrain and one thing that impressed me is how the convective line moved across the Wasatch Range, especially the imposing bulk of Mt. Timpanogos, like nothing was there.  We're talking a barrier that is over 2000 m high. It would not have been pleasant to be on Mt. Timpanogos when that went through.  Lightning, heavy precipitation, and probably some snow, hail, and graupel thrown in for good measure.

A terrible tragedy struck Hildale, UT yesterday afternoon.   Reports on ksl.com this morning suggest that at least 16 people were caught in a flash flood just north of the city, with eight confirmed dead and five still missing. The topo map below provides some perspective on the local terrain.  According to KSL, the vehicles had stopped in Maxwell Canyon, which extends northwest from the thumbnail and were swept into Short Creek, the main drainage that runs past Hildale and ultimately southwest to Arizona highway 389 south of the map.   KUTV reports that the cars were swept away near the crossing of Canyon Street and Williams Avenue.  I can't find the latter on Google Maps, but the former is near the thumbnail. The time of the flood is a bit uncertain.  The KSL report says a bit before 5 PM MDT (2300 UTC).  Media reports last night suggested a bit after 4 PM (2200 UTC). The radar loop below shows two periods of heavy rainfall that may have contrib...

Shortly after 4 PM today, a thunderstorm moved over the University of Utah, providing a nice downpour of rain with some embedded small hail just to add insult to injury for anyone walking around campus. Could someone have issued a nowcast with 30 minute lead time that this storm was going to hit campus? No. The loop below shows that the storm blew up rapidly in the central Salt Lake Valley and moved northeast over the University of Utah in only 15 min.  The first echoes produced by the developing cell were observed at 2149 UTC (3:49 PM MDT), with rain beginning on campus at about 2205 UTC (4:05 PM MDT). There is no human or computer-based forecast tool available today that can reliably forecast the development of a storm cell from nothing on such short time scales.  Very-short-range forecasting, known as nowcasting , is based primarily on the linear extrapolation of the motion of existing radar echoes (there are some exceptions, but for the most part, nowcasting is ...

The past few days have been beautiful in northern Utah, but a shift in the flow late yesterday and overnight has brought a return of smoke to the Salt Lake Valley. Below is a comparison of yesterday morning (top) and this morning (bottom).  Things aren't too bad yet, but there's been a noticeable decline in visibility between the two days. The primary source of the smoke appears to be California, although we may have some from Oregon or Idaho mixed in just for good measure.  The MODIS image below shows the leading edge pushing into northern Utah late yesterday. Dealing with a little smoke is a minor inconvenience for us.  One California fire, the Butte Fire, has grown rapidly from 100 acres on Wednesday to 65,000 acres this morning with 132 structures destroyed.

September is one of my favorite months in Utah and today was simply a beautiful day.  My plans were blown out of the water this morning when I was driving down I-215 and found out that Big Cottonwood was closed.  Then I thought I'd do a hike in Mill Creek, but it was blocked by a fire!  The intermediate option was Neffs Canyon, which requires considerable pain and agony to get to the good stuff, but once you are in the upper canyon, it's simply beautiful. A rough, steep ascent of a bit over 2000 vertical feet puts you in the meadow and the start of the upper canyon.  Plenty of color today.  It seems a bit early.  Perhaps a good sign?  Let's hope so. There are many bird's-eye views to be had of Salt Lake City in upper Neffs.  This one is from near the divide with Thaynes Canyon, which drops into Mill Creek Canyon. More beautiful colors in the upper canyon along the divide between Neffs and Big Cottonwood. I ended up bagging peak 964...

Photo: Stan Honda, AP It has now been 14 years since 9/11.  We all have deeply personal feelings and views of the confusion, fear, and tragedy of that day and the days and weeks that followed. Amongst my most vivid memories are the efforts of the first responders in the days following the attack to find survivors or just bring closure for those who had lost loved ones.  It was a heroic effort in an extremely difficult environment, with exposure to smoke and dust that was emitted from the smoldering pile long after the collapse of the towers.   A team of scientists led by noted aerosol research Tom Cahill and including University of Utah Professor Kevin Perry collected and analyzed samples of particulate matter from very near the collapse site, with their results summarized in article entitled "Analysis of Aerosols from the World Trade Center Collapse Site, New York, October 2 to October 30, 2001", which appeared in the journal Aerosol Science and Technolog...

Do you feel like this has been a remarkably pleasant summer?  It didn't seem as hot as years past.  I feel the same way, but the data doesn't support that view, at least if you look at the average temperature.  For the entire summer (June, July, and August), the average temperature was 77.5ºF, making it the 8th warmest on record at the Salt Lake City International Airport.   Source: NOAA Regional Climate Centers What gives?  Well, timing is everything.  If you want to have an enjoyable summer with an overall temperature that is unusually warm, it's best to stick the warmth in June, which is a climatologically cooler month than July or August.  That's exactly what happened.  June was easily the hottest on record.   Source: NOAA Regional Climate Centers However, July, which is climatologically hotter, was instead cool relative to the recent past (i.e., since about 1998).   Source: NOAA Regional Climate Centers Simil...

Perhaps I'm just suffering from jet lag, but I could use an assist from a radar guru out there to help decipher this morning's radar loop. As shown in the loop below, things this morning start innocently enough with wide spread clear-air returns.  As the morning progresses, however, some blobs of high returns persist, in some cases generate over the Great Salt Lake, and move downstream with the large-scale flow. What are these blobs?  I doubt they are meteorological as there is nothing to be seen on satellite.  Dust or birds?  I've looked at the some of the additional fields provided by the polarimetric radar, including correlation coefficient, and nothing obvious jumped out at me, although I confess my experience examining bugs and insects with radars is limited. Any thoughts?

After a weekend of sightseeing, I'm back in the US, but not quite back to Salt Lake City.  For my students who are reading this, yes, I should be back in time to teach class.  For the rest of you, here are a few photos. Bicycles are everywhere.  The photo below was taken at the train station in Salzburg. Surprisingly, few people wear helmets.  I think that's one custom I won't adopt.   Speaking of alternate forms of transport, I'm sure this horse is grateful for the waterproof and breathable hard shell.   Austria: Where the meat is meat and the vegetables are wrapped in bacon. Schnee!  Yup, winter is coming.  Our travel to Munich followed the main corridor of refugee migration to Germany.  Mrs. Powder Professor was able to lend a hand to one extremely polite Syrian family. On the train to Munich, I saw one refugee in tears.  Heartbreaking. Our train in Munich was met by the Polizei, who segregated t...