Tuesday, July 16, 2013

Double Digit Triple Digits

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.

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.


  1. Thanks! DO you what are the 20-century and 30-year averages for triple-digit highs? Also, these highs and the larger trend are depressing enough, but I wonder if you might be able to find and present some data on average summer lows? Anecdotal it seems to me that with climate change, nighttime lows are worsening even more than the highs ... summer nights that (should) reach the upper 50s are one of the best things about living here.

  2. The long-term average for days of 100 or greater is 5 per year, but I'm not sure what the time period is for that record. http://www.inscc.utah.edu/~reichler/6030/2006/presentations/Brian_DTR.pdf presents a summary of trends in maximum and minimum temperature and, while old and unpublished, shows the dramatic increase in minimum temperatures that have been observed at KSLC and globally the past few decades.

  3. A couple of us have noticed that the SLC airport seems a few degrees high compared to most of the surrounding area, particularly in recent months. For a while, we thought it could simply be a heat island effect due to lots of paved surfaces nearby, etc (which it might be). However, there are some situations, such as after the rain last evening, when most of the temperature reports from sites at a similar elevation are very uniform from site to site, and the airport is a few degrees higher than almost any of them. There is also a noticeably larger dew point depression in the SLC obs (8 - 10 degrees F between temperature and dew point even after a long, heavy rain with light surface winds) while other valley sites only had a few degrees F between the temperature and dew point. Putting all these factors together, it really does seems to me like maybe the obs there are too warm... is this a possibility?

    1. I've been surprised with the maximum temperatures achieved on a few days. I'm not going to say that the obs are too warm without some careful analysis, but I do think it would be interesting to do an intercomparison with a few surrounding stations over a several year period and see if there's been a drift in the bias. The cleanest option might be to compare Airport #2 to KSLC as they are fairly similar in site characteristics and it might be possible to see when calibrations and equipment changes were done by the NWS. One could throw in a couple of the DAQ sites for good measure.

      An analysis of this type was done at Sea-Tac airport and the results are quite interesting: http://cliffmass.blogspot.com/2011/07/did-sea-tacs-third-runway-change-our.html


    2. I have noticed that Airport #2 is distinctly different than SLC. It typically seems to have a cooler temperature by about 5 degrees (a couple of which could be explained by the elevation difference) and it usually seems to report a higher dew point than other stations in the area.