Wasatch Weather Weenies

With only today left, July 2013 is in a virtual dead heat with July 2007 for the hottest month in the history of Salt Lake City.  The average temperature for each month is 84.0ºF. Source: http://http://xmacis.rcc-acis.org I don't know if official records are based on the average to the nearest tenth of a degree (at some point, it's not worth slicing the onion any thinner), but let's assume that they are.  That means we need today's average temperature to be 84ºF or greater to tie or break the record. Helping a great deal is the overnight minimum, which was a balmy 75ºF.  That means we need a high of 93ºF to at least tie the record (assuming it is based on the average temperature to the nearest tenth of a degree).  The NWS forecast calls for a high of 98ºF. Of course, this all assumes that the unofficial numbers I'm using are in line with those at the NWS.  Let's hope they are.  I like seeing records happen.

After yesterday's cool afternoon, we've slipped back into a virtual tie with 2007 for the hottest July on record. Source: http://xmacis.rcc-acis.org Using this morning's minimum and the National Weather Service forecasts for maximum and minimum temperatures through tomorrow puts us just behind 2007 at the end of the month.  Don't let it slip away! Fortunately, we're still well in the lead for the hottest June–July combo.  Our suffering will not go to waste. Source: http://xmacis.rcc-acis.org I should add that data above comes from a reliable source (the NOAA Regional Climate Centers), but is unofficial.  Thus, given the narrowness of this race, we'll ultimately need to see what the National Weather Service has to say at the end of the month.  

July is nearing an end and the only question at this point is how many records will fall at the Salt Lake City Airport.  Some are going down to the wire. The record for the hottest combined June–July period (based on average temperature) looks likely to fall.  Despite the recent cooling (in terms of maximum temperatures), we are running about .75º ahead of the next closest year, 2007. Source: http://xmacis.rcc-acis.org Our string of consecutive days with above average minimum temperatures also remains intact.  The last day with a below average minimum temperature was June 23, 35 days ago.   Source: NWS I don't know what the record is for consecutive days above average—someone will need to do some sleuthing—but I think this is an impressive run.  Forecast minimum temperatures for the next few days suggest we will make it until the end of July, but one rogue thunderstorm and it's over.  I see it as likely but not a lock that we make it u...

In Colorado, where thunderstorms are pretty much a daily occurrence during the summer, the rule of thumb is to be back down to timberline by 1 PM.  Here in northern Utah, thunderstorms are not always a daily occurrence, but that rule of thumb turned out to be quite useful today. Given the forecast, I opted for a mid-morning hike up Patsey Marley.  I awoke to just a few shallow cumulus clouds over the mountains, and kept an eye on things during the ascent, which proved uneventful.  On top at about 11:45, the sky was filled with cumulus, which were growing in depth, but hadn't yet become deep enough to glaciate (i.e., develop ice crystals), which is essential for the electrification.  Rather than push it, I enjoyed lunch on top and decided to head down. Subsequently, surface heating continued to destabilize the atmosphere, resulting in increasingly deep convective clouds and eventually the development of thunderstorms over the Oquirrh Mountains and portions of t...

In the previous post ( Intricacies of Local Temperature Trends, Part I ), we showed that average summertime temperatures have increased in recent decades (since 1948), but also that minimum temperatures are increasing faster than maximum temperatures, resulting in a decrease in what meteorologists call the  diurnal (daily) temperature range (DTR). There are potentially a number of mechanisms contributing to these trends.  These mechanisms include: 1. Global warming .  It is well documented that average global surface temperatures have increased in recent decades and that this has been accompanied by a decrease in the DTR at many stations. During this period, the planet's energy balance has been modified by changes in greenhouse gas concentrations, aerosol (i.e., pollution) concentrations, and other factors.  Increasing temperatures and a decreasing DTR are consistent with what we expect from the net influence of these changes, but trends at any given location s...

As discussed in the previous post, there's a pretty good chance that the average temperature for this June and July will be the highest observed since 1948 (when I began my analysis) and very possible since the beginning of records in the Salt Lake Valley in 1874 (at least that's as far back as the National Weather Service goes). The average temperature is typically calculated by averaging the maximum and minimum temperature rather than calculating an average based on hourly observations (although not a necessity currently at the Salt Lake Airport.  Such an average, however, obscures the dramatic difference in the trends of maximum and minimum summertime temperatures over the past few decades. The graph below presents the average summertime maximum temperature at the Salt Lake City Airport each year since 1948.    There are large ups and downs from year to year, but a very gradual upward trend during the period.  The average maximum summertime temperature during ...

With meteorological summer (June, July, and August) a bit more than half over, it's worth putting our temperatures thus far into perspective.  As you might guess, they are at or beyond the outer edge of what has been observed in the instrumented record. I'm going to concentrate on data from the Salt Lake City airport since 1948, which is the beginning of records maintained by the National Climatic Data Center for the Salt Lake City Forecast Office.  The National Weather Service has data for Salt Lake City back to 1874, but I suspect that is a compendium of data from several locations. As shown below, this June was the second warmest (in terms of monthly average temperature) since 1948, topped only by 1988 (NWS records put this June as the 3rd warmest since 1874). Source: http://xmacis.rcc-acis.org Thus far, this July is the warmest since 1948, topping by just a hair 2007 and 2003. Source: http://xmacis.rcc-acis.org Putting those together, if we can maintain our...

When it is hot, it is the maximum temperatures that tend to get our attention, but the minimum temperatures are also important for health and comfort.  When afternoons are hot and uncomfortable, a good cool off overnight or from a thunderstorm can help cool off the house or apartment and make living more bearable. Unfortunately, the current heat wave has featured not only high maximum temperatures, but also high minimum temperatures.  This can be seen in the National Weather Service graphs below, which show bars of the observed temperature range (minimum to maximum temperatures) each day in June and July compared to the average (green color fill) and records (top and bottom edge of red and blue denote record maximums and minimums, respectively). Source: NWS There has not been a below average minimum temperature at the Salt Lake City airport since June 23rd.   The closest was on July 14, when we had a minimum temperature of 66ºF, compared to an average for th...

NWS forecast retrieved 7:55 AM Friday 19 July 2013 'Nuff said.

Other than a few sprinkles, the rains held off on the Alpe d'Huez today and what a race it was.  I will hold off on the discussion of results for those of you watching it this evening.

Doping or no doping, the Tour de France is one of the most grueling and punishing sporting events in the world.  Today's time trial is currently underway as I write this, but it is likely that Chris Froome will have a multi-minute lead heading into tomorrow's stage, which looks to be a real sufferfest.  The riders will navigate 172.5 km and six categorized climbs, including two "hors catégorie" (beyond category) climbs up the punishing Alpe D'Huez. Source: www.letour.fr Froome has looked unconquerable thus far, but as the saying goes, it ain't over until it's over.  A bad day or a crash can doom anyone, and there are always wildcards in cycling.  Tomorrow's wildcard could be the weather.  The Alps are presently under the influence of a weak trough, and the models call for showers and thunderstorms to develop over the region during tomorrow's stage. Wet, slick roads could make already harrowing descents even worse.  Tomorrow's stag...

Yesterday's high of 100ºF at the Salt Lake City International Airport gives us day 10 this summer of triple digits.  Yup, double digit triple digits.  We're now nearly half way through July and are running 6.2ºF above the average temperature for the month.  Oh the humanity! Forecasts for the next 7 days show very little change in the overall large-scale circulation with a long-wave ridge dominating the pattern over the western US.  Below is the forecast for 0000 UTC Sunday (6 PM MDT Saturday) showing the ridge in firm control. Source: NOAA/ESRL/PSD Subtle variations on smaller scales will give us some weather variability during this period in terms of the coverage and intensity of monsoonal convection, but that's about it.  These are the dog days of summer.  Personally, I'm hoping for as many highs as possible at or above 100.  The high 90s are such a waste.

Condensation beads on a cold beer bottle in upstate NY. Beer ~40ºF.  Dewpoint ~70ºF During the dog days of summer, it's critical to keep your drinks cold.  When the dewpoint is high, such as during monsoon surges, you either drink fast or use a beer koozy, as demonstrated above.  Here's why. During situations with high dew points, condensation will form on a cold beer (or soft drink) can or bottle.  The rate at which your beer or soft drink warms is thus affected not only by the direct flow of heat from the air to the bottle, but also condensational warming .  This warming is the result of a net flow of water molecules from vapor to liquid, which releases what meteorologists call latent heat (the converse of this is evaporative cooling, which you have certainly experienced on dry, windy days in Utah). How important is condensational warming?  This all important issue was recently explored by University of Washington Atmospheric Scientists Dale Durr...

It's been a while since we took a look at the large-scale atmospheric circulation, but it seems appropriate today. Last night, moisture moved into northern Utah, giving us some clouds and thunderstorms that were greatly appreciated after a 104ºF maximum on Wednesday.  Clouds linger this morning and we will see more showers and thunderstorms across the state today.  The National Weather Service has issued a flash flood watch from noon today through this evening for a good portion of central and southern Utah. Source: NWS The pattern producing this weather is commonly seen over the southwest United States during the summer monsoon.  As shown in yesterday morning's 1200 UTC analysis, we are under the influence of a strong upper-level ridge that is centered over the southwest US with easterlies across northern Mexico and southern Arizona turning anticyclonically and streaming northward into Utah.  This flow is confluent with a drier airstream moving into norther...

After yesterday's hot and smoky pos t where I discussed the impact of smoke on air quality, the wind shifted just enough to clear us out some, with an accompanying drop in PM2.5 (note the decline in the brown line just after noon on 7-10). In addition, although the ozone concentrations were higher than the were the previous day at noon, with the decrease in smoke, they dropped just a bit during the afternoon, resulting in a lower peak (compare blue line above on 7-9 and 7-10).  This may be evidence that the hydrocarbons accompanying the smoke were contributing to higher ozone levels. Unlike our wintertime PM2.5 pollution where we have met the enemy and it is us, the above illustrates that there are some regional-scale factors that contribute to elevated PM2.5 and ozone in the summer.  We are still our own worst enemy, but emissions from fires and other regional sources related to fossil fuel combustion play a role. BTW: Yesterday's high at the Salt Lake Airport reache...

Temperatures at the Salt Lake City Airport have reached the triple digits (100ºF as of 2 PM) and smoke has settled in over northern Utah.  The view of the Salt Lake Valley from Snowbird is not as disturbing as it is during wintertime inversions, but it isn't pristine either. Source: Snowbird The National Weather Service produced a nice graphic yesterday showing some of the primary smoke sources.  Yup, welcome to fire season in the western U.S. Source: NWS The Salt Lake Tribune reports that there's a fire on Mt. Olympus too , although I suspect that it isn't a major source of smoke for the valley (at least not yet). Smoke has a very measurable impact on air quality and contributes to both an increase in particulate matter and ozone (click here for more discussion). Trend charts from the Utah Division of Air Quality show a gradual increase in PM2.5 over the past two days.  In addition, yesterday's ozone was the highest in several days and thus far today w...

There's been some fairly exciting weather in the Salt Lake Valley the past several days, beginning with the 4th of July thunderstorms, which continued overnight leading to the closure of Little Cottonwood Canyon , and continuing through yesterday afternoon when we had another set of rumblers drop up to 0.43 inches of rain on portions of the valley. This period of thunderstorm activity is, however, slowly dwindling.  Observations of integrated precipitable water from the Salt Lake City airport show a gradual decline over the past two days, indicating a drying of the atmosphere that will lead to reduced thunderstorm activity the next couple of days.   Integrated precipitable water is the depth of water you would have if you condensed out all the water vapor in the atmospheric column above you.  As can be seen in the plot above, we were running near or above 2.5 cm (1 inch) over during the past several days, with some higher peaks (the peaks are likely associated...

Salt Lakers have been on a wild ride this year.  Remember how cold, snow covered, and polluted it was in the Salt Lake Vally during January?  During the last week of June, didn't that seem like a distant memory?  Here's a look back at the past six months in terms of mean temperature and departure from average at the Salt Lake Airport, with blue below and red above average: January: 19.4ºF (10.1ºF below average) February: 28.6ºF (5.6ºF below average) March: 44.6ºF (1.0ºF above average) April: 49.4ºF (1.2 ºF below average) May: 62.6ºF (2.8ºF above average) June: 75.3ºF (5.6ºF above average) That is one heck of a rocket ride from extreme cold to extreme heat.  As far as I'm concerned, what we experienced this year is a worst-case scenario — very cold in January to very hot in June.  If we could switch that around, life would be far more enjoyable.  A mild January is still just fine for skiing, and the colder it is in June (and July), the better. ...

A trip to southeast Alaska should be a high priority for any Wasatch Weather Weenie.  I'm presenting some commentary and photos from our recent trip below, perhaps enough to induce boredom, but if your synapses aren't stimulated along the inland passage, you lack creativity and imagination.  Further, as unearthedcomics.com/Sara Zimmerman shows below, scientists view vacations in a somewhat unique fashion. Source: unearthedcomics.com/Sara Zimmerman We begin in Juneau, where one is immediately blown away by the Mendenhall Glacier (commentary on the image below courtesy of my son). The common refrain we heard from locals is that they can't believe how much the glacier has receded in their lifetimes.  If this retreat were isolated, it might be an indicator of local climate variability, but it is consistent with what most (but not all) glaciers are doing around the world (there are a couple of glaciers in Alaska advancing, including the Taku near Juneau).  The ...

The good news is that the triple digit streak ended yesterday.  The bad news is that Little Cottonwood Canyon is closed this morning.  Yup, no first tracks today. Wait a minute.  It's July!  In this instance, the culprits for the canyon closure are rockslides produced by extremely heavy precipitation overnight .  Apparently Mother Nature wanted to put on her own fireworks show.  KSL reports that snowplows are out removing the debris. Source: ksl.com Observations from the Alta-Base observing site suggest an accumulation of 1.15 inches in the one-hour period ending at 0900 UTC (0300 MDT).  Rocks were reported on the road at about 0230 MDT. Hydrographs along Little Cottonwood Creek show a dramatic spike in streamflow during this period, with a volume exceeding that during the spring runoff. Source: NWS Impressive stuff. Thanks to Trevor Alcott for his input on this post.

It has been quite a run of triple digit temperatures in Salt Lake City.  Here's a summary thus far: June 27: 101 June 28: 105 (record for June) June 29: 105 (ditto)  June 30: 103 (record for day, longest consecutive string of triple digit days in June, June finishes with no measurable precipitation)) July 1: 104 (record for day) July 2: 102 This streak is, however, in jeopardy.  A short-wave trough is expected to sag into the Pacific Northwest by tomorrow and the ridge weakens just enough to cool us off a touch and increase the chance of thunderstorm. I think we'll eke out one more triple-digit day today, but the end of the streak could come tomorrow.  The high 90s never looked so good.

This is a guest blog from Matt Jeglum, a PhD student at the University of Utah.  Matt spent 5 years fighting wildland fires. By now most of you have probably heard about the 19 fatalities that occurred on the Yarnell Hill Fire, a wildfire about 90 miles northwest of Phoenix, AZ that has also burned at least 50 homes in the small town of Yarnell, AZ.  The 19 firefighters killed constituted nearly an entire crew and makes the Yarnell Hill Fire the most deadly wildfire in the US since the Griffith Park Fire killed 25 firefighters in 1933.  Many thanks go out to those firefighters who continue to risk their lives to save lives and property. With each major fatality wildfire, extensive investigations have led to increasing safety though improved equipment and tactics.  Some of these investigations, including the investigation of the 1990 Dude Fire in Arizona, have included improvements to the way that fire weather information is forecasted and disseminated.  Toda...