Wasatch Weather Weenies

There were two different dust events today. The first occurred around 1:45pm when a strong thunderstorm went through the valley. Winds gusted to 60mph at the airport and visibility dropped to 4km, but the event only lasted about 10 minutes. The airport did report blowing dust so this will go into the books as an official event. The Radar during this time was quite impressive with dBzs greater than 50 Dust events associated with convective downdrafts are informally known as "Haboobs." They originate from local sources, do not last very long, and are quite common in Utah. The second event is going on now... This dust is not associated with a thunderstorm but rather the strong pre-frontal southerly winds. Unfortunately the concentrations are too weak and it is too late in the day to determine where the dust is coming from. Frontal passage tonight should put an end to this dusty weather.

Dust became visible yesterday afternoon a little after 5pm in the salt lake valley and it stuck around for much of the evening. Here is an image from the Olympus cove weather cam The event yesterday took place in the pre frontal environment of an approaching Intermountain Cyclone, which is very typical for spring time dust storms. The IDV analysis from 6pm yesterday clearly shows an area of low pressure over north-eastern Nevada riding along an anomalously strong pacific trough for this time of year. One of the biggest issues Jim and I have faced researching Utah dust transport is determining when a dust event takes place. Dust observations require human input making them very subjective. Unfortunately yesterday was a perfect example of why you can not always rely on human observation. When the dust came through yesterday the visibility dropped to 4 miles, but KSLC reported haze even with a 10% relative humidity! Dust detection from satellite can also be very tricky. Re...

 Mount Rainier (Photo courtesy Washington State DOT) For mountaineers and meteorologists, no mountain in the contiguous United States compares with Mount Rainier.  It has it all: massive scale, great vertical relief, extensive glaciation, ecological diversity, and incredible weather variability. Paradise Ranger Station on the south side of the mountain is one of the snowiest instrumented locations on Earth.  The National Park Service reports an average annual snowfall of 680".  As of 17 June, 907" of snow has fallen on Paradise since 1 July 2010 , which sounds like a lot, until you realize that their all-time record is 1122", set during the 1971-72 winter. Nevertheless, the SNOTEL snow-water equivalent for this year is quite impressive, peaking at just over 100" in mid May.  Remarkably, more than 80" remains today.  And this is at only 5120 feet!  Only slightly higher than Salt Lake. Source: Northwest River Forecast Center The deep snowpac...

It is quite remarkable just how much snow has melted in the Wasatch over the past week.  After nearly 8 months of incredible skiing, the snowpack is finally looking and skiing "tired', especially on south facing aspects. Grizzly Gulch, 9000 ft elevation, 26 June Over the past three days, the Snowbird SNOTEL has lost almost 9 inches of SWE and is now down to just over 30 inches (its May peak was 75).  Thus, about half the snow at this site is gone. Similarly, the Collins snow stake has dropped from 193 inches to 123".  Can we make July or perhaps the 4th with 100"?  I think the former is possible, but the latter is going to be close. Roaring torrents of water are cascading down every canyon.  Little Cottonwood Creek is a "white ribbon of hell" pulverizing everything in sight. Standing next to the creek, the ground literally shakes.  For a bit more perspective, click here for a video.     She can't take much more of this captain! De...

It is quite remarkable how much the vegetation can change in just a couple hundred meters in the Wasatch Range. Today I had a chance to experience the lush lowland oasis that is Ferguson Canyon, a minor canyon just south of Big Cottonwood Canyon.  Despite having lived in Salt Lake for more than 15 years, it was my first trip, but won't be my last! The trail starts at 5000 feet on a west facing aspect.  The vegetation here is a mix of grass, wildflowers, and sage, which is unusually lush for late June given the historically wet spring we just experienced. A short walk around the corner, however, and you enter an incredibly lush "jungle" along the stream that today was "raging" down Ferguson Canyon, which was pleasantly cool. Several factors contribute to the microclimate in Ferguson Canyon.  Although the canyon faces roughly west, it has an abrupt steep ridge immediately to its south, which reduces the net solar radiation in the canyon. Then, the strea...

As discussed in yesterday's post , I'm quite interested in looking at tropical-extratropical interactions during this monsoon season.  I'm also interested in how tropical cyclones impact weather prediction in the midlatitudes, and today we have an interesting case to examine. Over the past two days, tropical cyclone Meari has tracked north-northwestward from the maritime sub-continent toward China and is presently located between Taiwan and Japan. The Joint Typhoon Warning Center forecasts Meari to move northward, making landfall on the Korean Peninsula at around 1200 UTC 26 June. Source: Joint Typhoon Warning Center As tropical cyclones move northward and interact with the midlatitude flow, they can cause all sorts of mischief with regards to weather prediction.  In particular, they are often accompanied by heavy rainfall and related diabatic heating.  Sometimes they undergo extratropical transition and redevelop as a extratropical cyclone.  Both of these p...

As some of you know, I am going on sabbatical for the next academic year.  Contrary to conventional wisdom, sabbatical is not a one-year vacation, but release time from teaching and committee service for the purposes of professional development.  I will be writing a book (stay tuned), working on a number of research projects, and continuing my never-ending quest to be able to access meteorological data and visualize and analyze the atmosphere at "the speed of thought" so that my classes are as dynamic and exciting as possible. Along these lines, I've been using the Unidata IDV to hold the world in the palm of my hand and have a better look at tropical-extratropical interactions as we move into the monsoon season. My goal here is to be able to click a button and have a multi-day loop that allows me to look at the basics of the weather anywhere in the world.  In the above image, you are looking at a global IR image with the dynamic tropopause pressure (color filled t...

Update 1:29 PM: Blogger images are now working.  NAM figure added. Remember that long wet, cool spring?  It's over.  Summer arrived yesterday and Mother Nature is turning up the heat. By tomorrow, 700-mb temperatures over Salt Lake are forecast by the NAM model to hit +15C, which should give is a high of about 90. The heat will give us a serious pulse of runoff, including in the Cottonwood Canyons.  Little Cottonwood, for example, is expected to approach flood stage tonight (Wednesday night) and peak tomorrow night.  

You have probably seen the Subaru ads featuring the "World's Worst Weatherman."  This brutal slam of our all-important profession has really ticked off some meteorologists . I was rolling with it, but now they have really ticked me off.  They have an option on their web site to "see how much of your life you have wasted on the weather." There are two things I find deeply offensive about this.  First, one cannot waste time on the weather.  As Ben Franklin said, "Some are weather-wise, some are otherwise." Fluctuations in mercury are infinitely more interesting than fluctuations in gold.  Time spent thinking about the weather cannot be deducted from a persons life. Second, and this is the real insult, when you click on the drop down menu to select the time spent checking the weather each day, the maximum option is ONLY THREE HOURS !!! Are you kidding me? Having owned a Subaru previously, me-thinks they need to start thinking more about head...

June is typically an important transition month over southwestern North America.  It is during this month that an upper-level anticyclone develops and builds westward from over the Gulf Coast to northern Mexico, enabling relatively dry, large-scale westerly and southwesterly flow to be replaced by comparatively moist easterly and southeasterly flow over much Mexico.  This can be seen in the 10-year climatology of 500-mb height below. Mean pentad (5-day averages) 500-mb height for 1979-88. Source: Adams and Comrie (1997) This circulation change is characteristic of the so-called North American Monsoon, and it leads to a pronounced warm-season peak in precipitation across much of Mexico and portions of the American SouthWest (especially southeast Arizona and New Mexico). Seven-day mean 500-mb analyses for the first part of June show evidence of this large-scale circulation change this year.  In particular, note below the development and intensification of locally hi...

Mother Nature will not give us a break.  A well-advertised dousing is underway this morning as yet another upper-level trough moves through northern Utah.  The NAM-model analysis for 1200 UTC (0600 MST) this morning shows the uper-level trough axis just upstream of northern Utah with 700-mb temperatures of 1C over Salt Lake and less than 0C just upstream. The latest regional radar shows that the heaviest precipitation is falling over and downstream of the Great Salt Lake and over and downstream of the Salt Flats to the west. Source: NCAR/RAL More frequent and intense convection over these two areas is quite evident in the KMTX radar loop from 1237–1453 UTC. Is this simply a reflection of the larger-scale environment, or are the lake surface and salt playa contributing through locally enhanced surface heat and moisture fluxes?   In the case of the Great Salt Lake, the latest MODIS derived lake-surface temperatures from yesterday were quite balmy and in the 18-22C...

I went for a tour today in White Pine and Gad Valley and was quite disappointed to see just how "snirty" the snow has become in the past week.  All of the dust and impurities from the past winter are slowly but surely collecting on the snowpack. The "snirty" snowpack was quite evident while looking at the White Ribbon of Cruising where Snowbird groomed Regulator Johnson The snowpack is especially gross at mid elevations, such as here in Gad Valley If you know a good wax for this, give me a call Snirt means part SNow part dIRT.  Because dirty snow absorbs more solar radiation than clean snow, it results in a faster snowmelt.  We'll talk about this more in a future post.  Right now I need to get these stinky socks off and take a nap.

A recent article in the Salt Lake Tribune mentions that the Great Salt Lake is expected to rise as much as 5.7 feet thanks to this spring's runoff, which would be a one-year record.  It also suggests this may help the lake generate more lake effect snowstorms. Conventional wisdom is that a bigger lake leads to more lake-effect, but this assumes that the "weather" doesn't change.  In other words, that the frequency and characteristics of cool-season trough passages remains the same.  In reality, there are huge fluctuations in the frequency and characteristics of cool-season trough passages fro year to year. We will be unveiling some new research soon that shows that lake-effect is better correlated with the "weather" of a given winter rather than the lake size.  I'm hoping we'll see more lake-effect next winter, but I won't be counting on it.  If we have a ridge-dominated winter, a big lake makes little difference.

It's no surprise to anyone who lives in Salt Lake that this has been an incredibly cool and wet spring.  I just took a look at the climate data for May and it is impressive. For Utah as a whole, May was the 8th coldest in the 117 year period examined by the National Climatic Data Center. Source: NOAA/NCDC And the 2nd wettest. Source: NOAA/NCDC As shown in the analysis below, May was characterized by anomalous 500-mb troughing over the entire northwest United States. Source: NOAA/ESRL Persistent troughing over the northwest in May was reflective of a pattern that has dominated the entire spring (Mar–Apr–May), as shown in the 90-day 500-mb height anomaly analysis for the period from 4 Mar – 1 Jun.  Note the scale change, which makes the anomalies seem a bit more ominous than those above. Source: NOAA/ESRL And the troughs just keep coming.  The latest NAM puts a deep upper-level trough over Idaho by 1800 UTC (1200 MST) Sunday.  With 700-mb temperatur...