Wednesday, October 30, 2019

Hell Has Frozen Over

Here are two things that have never been observed before in Salt Lake City in October.

First is yesterday afternoon's sounding, with a 700-mb (10,000 ft) temperature of -18.5˚C, more than 3˚C colder than the previous record of -15.3˚C.

Source: SPC
If you are wondering, temperatures aloft have already started to increase, so this morning's 700-mb temperature is -15.7˚C.  That's not as cold, but it is the 2nd lowest on record.

Second is the overnight minimum temperature of 14˚F, which is the lowest temperature recorded in the month of October in Salt Lake City with records going back to 1874.

Beyond Salt Lake, it was cold everywhere, but as usual, Peter Sink, a sinkhole in the Bear River Range known for extremely low temperatures, takes the cake.  Looks like a minimum temperature of -43.6˚F based on data available in MesoWest.  

Logan meteorologist Timothy Wright tweeted this morning that the minimum was -45.5˚F and that would be a national October record.  The lower temperature he reports could reflect that he has access to another station or data between the obs times reported to MesoWest.  I'm sure he'll get to the "bottom" of this eventually. 
I would rate this event as one of the most remarkable since I moved here in 1995, up there with the 1999 Salt Lake City Tornado and Thanksgiving 2001 Hundred Inch Storm at Alta.  Extreme cold surges are rare events in northern Utah.  This is why, when one looks at the record daily minimum temperature records for Salt Lake City (light blue line below), there are a small number of truly exceptional minimum temperature records with a spike-like appearance.  Examples include February 9-10, 1933, November 3, 1936, and November 15-16, 1955.  There is another period in December during which cold surges in 1932 and 1972 set extreme minimum records from December 9-16.
Such cold surges are the meteorological equivalent of drawing a royal flush in five-card draw.  A magic sequence of events must come together to get such extremely low temperatures.  This is especially true given the warming global climate and urban heat island effects.

An alternative perspective on the extreme nature of the event is provided by the analysis below, which is a map of departures of current surface temperatures from the 1979-2000 average for each location (referred to as anomalies).  The coldest anomalies are in western North America, centered over Wyoming.  However, the global average is 0.7˚C warmer than the 1979–2000 average, so global warming is still a thing.  Additionally, patterns that cause cold surgest into the western and central U.S. are often associated with anomalously warm temperatures in Alaska, and you can see that below.  In fact, the high temperature in Anchorage yesterday was 54˚F.

If you don't like the cold weather, then you should simply plan on going up to upper Big or Little Cottonwood Canyon tomorrow.  The warming in the mountains over the next 24 hours is going to be remarkable.  At 8am this morning it is -6˚F on the summit of Mt. Baldy (11,000 ft).  By tomorrow it will be close to freezing.  The models are showing more than a 30˚F increase in temperature in the mountains from this morning to tomorrow afternoon.


  1. - MesoWest just reports the 15-minute averages, but Timothy Wright was referring to the 15-minute minimum between 215 and 230 am.

  2. This morning in Eden on the bench it was -1 deg F at 8:30 am. At the bottom of Ogden Valley -4 F.
    Previous record for October was 11 deg F??

  3. I wonder what the temperature of the Great Salt Lake is now? I see the shoreline stations only had to reach the upper 20s F to get a lake breeze started today, so I am thinking that it is a little cold for that swim I had planned on. ( :

  4. The February 1933 cold outbreak seems ridiculous and I can't even imagine something below -10 in Salt Lake, let alone -30. If the cold surge we just had had occurred in February, would we have even come close to that? Or would cold of that magnitude require something that's pretty much impossible now due to climate change?

    1. Probably the urban heat island is a bigger factor in not getting that low. These are by there very definition extremely rare events. I'm not going to rule it out yet, but it is increasingly unlikely.