Wasatch Weather Weenies

Carnac the Magnificent, as played by Johnny Carson Editor's Note: Special thanks to Jeff Massey for his contributions to this post Will this be a below average, average, or above average snow year in the Wasatch Range?  We're sure you can find someone who will give you an answer.  Here's what the Wasatch Weather Weenies have concluded: WE HAVE NO IDEA! The primary modulator of year-to-year precipitation variations over western North America is the El Nino–Southern Oscillation, commonly abbreviated to ENSO.  All indications are that this year will feature neither El Nino conditions (i.e., a warm tropical eastern Pacific) nor La Nina conditions (i.e., a cold tropical eastern Pacific).  In other words, this will likely be a neutral year. El Nino, La Nina, or neutral, it really doesn't matter.  Although El Nino or La Nina can weight the odds for snowfall relative to average in other parts of the western US, in the Cottonwoods and probably the Wasatch ...

I have a busy day today with little time to blog.  Thus, for your entertainment purposes, I provide the time lapse below of the Rim Fire in Yosemite National Park.  Courtesy National Park Service.  At the end, they provide a few clips showing generally clear skies in Yosemite Valley, presumably to encourage visitors and help keep the local economy going. In addition, a summary of the summer thus far from the Salt Lake City National Weather Service Forecast Office showing where we stand for a number of records.  

Source: http://www.telegraph.co.uk/travel/travelnews/10208379/Bland-Shire-residents-visit-village-of-Dull.html Yesterday evening's rain notwithstanding, this has been a boring summer of weather in Salt Lake City and, at least for minimum temperature, possibly the most boring summer in at least the past 50 years. We already know that this summer has been hot and that we have had very few days with a below average minimum temperature (only one day in July and August has had a below average minimum temperature, see previous post).  But did you also know that the day-to-day fluctuations in minimum temperature have also been much smaller than usual? To illustrate this, Trevor Alcott sent me the analysis below showing the average (mean) and standard deviation of minimum temperature at the Salt Lake City International Airport during the heart of summer (1 July to 15 August) since 1958.  This year not only has the highest average temperature, but by far the lowest standard dev...

With three of the past four days featuring highs only in the 80s at the Salt Lake City International Airport, you might wonder if our record setting hot summer might be in jeopardy.  Well, we've lost a bit of ground, but thanks to continued high minimum temperatures, not all that much. With just five days to go, our average temperature for summer (June, July, and August) sits at 80.8ºF, 1.5ºF warmer than the previous hottest summer (2007). Source: NCDC For the next few days, the pattern largely remains the same, with some periods of monsoon clouds and thunderstorms.  I think we will hang on for victory.  One record that we might fall short of is the number of days reaching 100ºF or more.  I believe we sit at 20, whereas the record is 21.  I don't see us pushing 100 the next few days and the latest that the airport has reached 100 is Sep 8, so time is running out.  On the other hand, we've hit 99 as late as Sep 14 and the way this year is going we pr...

Recent satellite imagery has been really fascinating.  We'll start with todays visible satellite loop, which shows: (1) the decaying cyclonic (counter clockwise) circulation of tropical storm Ivo off the coast of Baja, (2) extensive mid and high clouds streaming northward and northeastward into Utah, and the fires of Yosemite.  Apologies for blogger bleaching it out. The band of clouds (and precipitation) streaming into Utah from Ivo might be called a Predecessor Rain Event or PRE,  which often develop ahead of tropical cyclones that are moving into the midlatitudes and can contribute to heavy precipitation and flooding.   This type of a pattern is, however, a disappointment for Utah storm chasers.  The widespread cloud cover is putting a damper on the daytime surface heating and thusfar has limited thunderstorm development.  This is your classic case of too much of a good thing.  Too much moisture and too much lift.  With a bit of sur...

Today's most intense thunderstorms occurred primarily (but not exclusively) over southern Nevada and California where there was a combination of moisture, instability, and strong surface heating.  Although it rained further east, and some strong storms were observed, the widespread cloud cover appeared to limit convective intensity. Many of the cells in southern Nevada and California were slow moving, resulting in some significant accumulations in some areas.  The products issued today by the National Weather Service Las Vegas Forecast office includes a long list of flash flood warnings, severe thunderstorm warnings, storm reports, etc.  I never know whether or not to trust the radar-derived precipitation totals, but there are some big numbers reaching several inches in a few locations below.   Source: NWS The Clark County Regional Flood Control District has a nice web site that provides access to gauge-based precipitation observations and radar overl...

Monsoon moisture is resident over much of the southwest and with a upper-level trough off the coast of California and the remnants of Tropical Storm Ivo moving northward, the next few days are going to be very very interesting. The latest GFS forecast below, valid for Sunday, Monday, and Tuesday afternoons, shows the high levels of moisture over the southwest today, with the weakening circulation of Ivo near the west coast of Baja.  The remnants of Ivo then move across SoCal, the Sierra Nevada, and central Nevada. For today and through late this evening, the National Weather Service has a large portion of the lower and upper Colorado River basins under a flash flood watch.  That's the dark green shading below. Source: National Weather Service/ weather.gov The forecast discussion from the National Weather Service Forecast Office in Las Vegas pretty much tells the tale for the lower Colorado River Basin.  I've added the bold font. SHORT TERM.....

I'm like a kid in a candy shop today after a 3 month sugar withdrawl.  Check out the video below of the Foehn-like orographic cloud draped over Lone Peak and the Alpine ridge south of Little Cottonwood.  Courtesy John McMillen.

As shown in the loops below, a beautiful little vortex (i.e., circulation system) has formed in the St. George area over the past few hours (note that the loops are not time synced). The system has the look and feel of a mesoscale convective vortex (MCV),  a small scale area of cyclonic (counter clockwise rotation in the Northern Hemisphere) rotation that sometimes forms with thunderstorm complexes.  MCVs can be long lived.  We'll see if this one hangs on as it moves northward through Utah.  

I don't know about you, but I thoroughly enjoyed last night's thunderstorms.  We had a BBQ in the evening and followed by the thunderstorms as they moved across the Oquirrh Mountains and towards Salt Lake City.   A crowded porch examines the approaching thunderstorms. Photo: Trevor Alcott Wasatch Weather Weenies BBQs never disappoint in August.  We're always able to conjure up some action.  Our resident photographer snapped this photo.  Fantastic! Photo: Trevor Alcott Classes start here at the University of Utah on Monday.  Readers of this blog who are U of U students might want to consider taking Atmos 1010: Severe and Unusual Weather and learn about storms like the one above.  

Yeah, it's a dry heat, but that won't be the case on Sunday and Monday in the lower Colorado River Basin.  As shown by the GFS loop below, a major surge of moisture will push into the lower Colorado River Basin ahead of and with the remnants of a tropical cyclone that is currently forming in the tropical eastern Pacific. GFS sea level pressure (solid contours), 10-m wind, and integrated water vapor (color fill with warm colors indicating higher values) forecast loop valid 1200 UTC 22 Aug through 0000 UTC 26 Aug 2013. The water vapor content of the atmosphere is indicated by the color fill in the loop below, with warmer colors indicating higher values.  Note that the initial surge of moisture into the lower Colorado River Basin from the Gulf of California that occurs in response to enhanced south-southeasterly flow associated with a tropical cyclone currently called tropical depression NINE-E (hopefully it gets strong enough to get a better name than that!). In response...

Congratulations to photographer Tobias MacPhee and University of Utah Atmospheric Sciences Graduate Student Carolyn Stwertka for scoring the cover of the 2014 Backcountry Magazine Gear Guide.  Story available here .  Now that's what I call storm chasing Utah style.

It has been a remarkably boring stretch of weather this summer.  We've had the occasional monsoon surge and a few good rounds of thunderstorms, but nothing to really draw my interest.  That could change later this coming weekend.  The computer models are calling for a tropical cyclone to form off the west coast of Mexico later this week, with its attendant tropical moisture forecast to surge northward into the southwest U.S. and Utah during the weekend and early next week.  The loop below, which shows the GFS forecast valid from 1800 UTC (1200 MDT) Friday through 0000 UTC Tuesday (1800 MDT Monday), pretty much tells the tale.  Critical to this forecast is the interplay between the upper-level trough moving onto the west coast and the tropical cyclone remnants moving northward into the Southwest.  The tango between these two features will determine whether or not the surge comes into Utah, as forecast above, or alternatively misses us to the west or th...

Through yesterday, the average temperature for June, July, and August at the Salt Lake City Airport (KSLC) was 81.2ºF, nearly 2ºF higher than the hottest summer on record, 2007, when the June–August average temperature was 79.3ºF. Source: http://xmacis.rcc-acis.org While there is little doubt that this has been a hot summer, many of my meteorological friends have wondered if there is something odd about the temperatures at the Salt Lake City airport, which seem unusually high.  For example, at Tooele, which also has a very long temperature record, 2013 is hot, but not as anomalous as it is at the airport. Source: http://xmacis.rcc-acis.org In addition, a comparison of the temperatures at KSLC (top graph below) with those measured by a weather station less than a mile away (bottom graph below) shows that KSLC is consistently about 2ºF higher. Source: MesoWest What gives?  I personally find it difficult to draw conclusions from comparisons between surfa...

The endless persistence of ridging over the Intermountain West has finally led to writer's block, so here are some items that caught my attention the past few days. Climate Change : Count me amongst those who are skeptical that carbon capture and sequestration (CCS) will every work effectively on the massive scale needed to reduce greenhouse gas emissions.  Some reasons why are discussed by Tom Zeller Jr. in an article posted today in the Huffington Post .  The article also contains a great quote by Gavin Schmidt about carbon dioxide levels recently reaching 400 ppm: "We are a society that has inadvertently chosen the double-black diamond run without having to learn first.  It will be a bumpy ride." I wish I'd thought of that one. Chemtrails : I used to get calls a couple of times a year from people asking about chemtrails, which conspiracy theorists believe are trails left by aircraft that are laced with chemical or biological agents.  There are of course good ...

Our model serving website weather.utah.edu has returned from the dead.  It was actually back early last week, but I've made a number of changes and additions since then that should be of interest for do-it-yourself forecasters: I've retired the old 40-km NAM grid and replaced it with a full product suite from the 12-km NAM grid, which is as close as you can get to the native NAM output. I've increased the number of products available from the GFS, NAM-12km, and NAM-4km (a high resolution nest embedded in the 12-km NAM), including four panels, soundings, and time-height sections for the Great Lakes region.  Why the Great Lakes?  We're doing a field program there this winter.  Tug Hill skiers and snowmobilers should be pleased!  Wasatch skiers will still find soundings and time-height sections for Alta.  These often arrive later than the other plots.   I'm hoping to replace the current sounding and time-height section plots with higher ...

We mentioned yesterday in the previous post that clouds and smoke might make it tough to hit 100 and, although I though we might eke it out, we only hit 99.   What a waste!  99 is the worst temperature psychologically.  It's hot, but 100 sounds so much hotter and it has triple digit bragging rights.  On the cold side, there's really no equivalent, Whether it's 1, 0 or -1, it all sounds damn cold.  Fahrenheit temperatures are bogus for scientists, but there's really nothing on the celsius scale like 100.  40ºC?  Please.  That's really hot (104ºF) but it clearly lacks the cachet of 100. Further, 100 yesterday would have tied the record for days of 100 or more in a summer.  The wait continues....

Yesterdays 100ºF high at the Salt Lake City airport was day 20 of 100 or more this summer.  We now sit just one day shy of tying the record, set in 1960 and 1994. It will be interesting to see if we can reach it today.  If skies were clear, I'd say it was in the bag.  The 700-mb temperature yesterday morning was 15.2ºC and yesterday afternoon was 15.6ºC.  This morning's was even higher at 16.2ºC.  Thus, today's airmass is even warmer than yesterday's. The problem is that there's more smoke over the airport today, as well as a few clouds.  This might be worth a degree of cooling.  Yesterday we were in the clear, but areas to the west like the Skull Valley and Northern Stansbury Mountains were in a thick pall of smoke, as shown by yesterday's MODIS image below.   Source: NASA Today, some smoke has drifted over the Salt Lake Valley.  So far (through 1 PM), however, temperatures are in line with yesterday's.  I think we will eke ou...

Forecast highs for today and tomorrow are 100ºF at the Salt Lake City International Airport.  If we can meet or exceed 100 both days, we will reach 21 days of 100 or more this summer, which would tie the all time record.  Let's hope it happens.  Little point in suffering without attaining some sort of prestige. We are just about half way through August and remain well ahead of any previous year for the mean summertime temperature at the Salt Lake City Airport. Source: http://xmacis.rcc-acis.org

Fire is on the landscape of northern Utah.  The Rockport 5 fire sparked yesterday  quickly grew into a beast that destroyed 13 homes .   Wildfire behavior is strongly influenced by three components summarized in the Fire Triangle below: Fuels, Topography, and Weather. Source: Southwest Environmental Research & Education Here's a video of the  a wildfire that started on Monday afternoon in the Avenues and was quickly put out by heroic fire fighters.  It pretty much shows all three of these components in action.  In particular, note how the flame front movement and intensity increase near the end of the video as the wind (i.e., weather) pushes the flame front into fresh grass (i.e., fuels).   Movement of the flame front down the hill (i.e., topography) probably resulted in a slower fire spread than if the flame front was moving uphill.  Video courtesy of John McMillen. There are some remarkable photos of the Rockport 5 fire on ...

The images provided by the Moderate Resolution Imaging Spectrometer (MODIS) aboard NASA's Terra and Aqua satellites are always spectacular and frequently provide some great perspectives on atmospheric, land, and lake processes over northern Utah .   Yesterday's Aqua overpass below tells us quite a bit about the Great Salt Lake.  Note it's limited area, with just a thin sliver of water in Farmington Bay east of Antelope Island and no water at all in most of the Bear River Bay, with the exception of diked and reservoir areas like Willard Bay.  Extensive grey areas, indicative of playa, surround the Great Salt Lake and are consistent with it's low elevation.  You can also see a large evaporative pond just to the east of Stansbury Island and the contrast in color between the northern and southern half of the lake, which is divided by an earth railroad causeway that runs westward from Promontory Point.  With the lake at a relatively low level historically, it is...

Here at the U, we run the ragged edge on just about everything.  I wish it wasn't that way, but it is a cold reality and a budgetary necessity. Those of you who use weather.utah.edu are probably wondering what happened to it.  Well, it's been stored on antiquated equipment for some time and it finally crapped out last week when I was out of town.  I've been procrastinating for months (er, years) moving it to newer hardware and it finally caught up to me. The good news is that it appears we have a very recent backup, so we will hopefully be back online in the near future.

The Patch Springs Fire in the Skull Valley west of Salt Lake City put in a great optics display last night, creating a red hue in much of the sky and a blood red sun. The reddish hue is the result of a phenomenon known as Raleigh scattering , the scattering of light by particles that are much smaller than the wavelength of the light.  As you might recall from high school physics, Roy G. Biv (Red, Orange, Yellow, Green, Blue, Indigo, and Violet) describes the visible spectrum arranged in the order of decreasing wavelength.  Colors with shorter wavelengths at the end of the Roy G. Biv spectrum are scattered more by smoke than those with longer wavelengths at the beginning of the spectrum.  Thus, more of the longer, redder wavelengths of light survive transit through the smoke, leading to the reddish hue and the blood red sun. As the sun set, we observed the shadow of the smoke move up the Wasatch Mountains, especially near Mount Olympus.  This shadow had a d...

I've been on the road attending the American Meteorological Society Conference on Mesoscale Meteorology, so I missed yesterdays exciting weather and haven't been thinking much about climate change.  Nevertheless, I owe a post on this subject. In our previous post, we discussed a recent study by Pierce and Cayan (2013) in which they examined the uneven response of several snow measures to climate change.  These measures included: SWE: The amount of water in the snowpack on 1 April SWE/P: The fraction of cold-season (1 October - 31 March) precipitation P that remains in the snowpack on 1 April.   Snowfall (SFE): The total cold-season snowfall measured as the amount of water in the snow (abbreviated as snowfall water equivalent, SFE). SFE/P: Fraction of total water in the cold-season precipitation that falls as snow Their analysis suggested that long-term trends in these snow measures will emerge at different points in the future as the climate warms over the...

Source: American Meteorological Society David Pierce and Dan Cayan of the Scripps Institution of Oceanography recently published an interesting paper in the Journal of Climate entitled The Uneven Response of Different Snow Measures to Human-Induced Climate Warming .  The paper has important implications for the detection of climate change and the future of skiing over the western United States. Their findings are based on an analysis of climate change as represented by 13 downscaled climate models driven by two greenhouse gas and aerosol emissions scenarios known as RCP4.5 and RCP8.5.  They are considered medium and high "growth" scenarios with CO2-equivalent concentrations reaching about 800 ppm and 1300 ppm, respectively, by 2100.  We currently sit just over 400 ppm (CO2-equivalent combines the global warming potential of CO2, methane, and other human generated greenhouse gas into a single number for convenience).  In this post, we will concentrate on their c...

The past two winters provided below average and were followed by hot summers, with this June–July being the hottest in the history of Salt Lake City.  In both cases, the snowpack was decimated during summer, leaving few options for the turns all year types.  This year, the carnage looks even more complete than last year.  Note in the photos below how the patch that lingered at the base of the American Fork Twin last year is gone (the comparison below might be a bit unfair given that last year's photo is about a week earlier, but I fortuitously had it on my hard disk). AF Twin from Snowbird Tram on 26 July 2012. Source: Snowbird AF Twin from Snowbird Tram on 4 Aug 2013. Source: Snowbird With some effort, you can find just a few remaining patches along the Alpine Ridge west of Snowbird (click for full res). Last year, the Timp snowfield was nearly wiped out .  We may need to put it on a death watch this year, although I suspect a patch or two may su...