Wonderful July Weather Continues

I have something very exciting to show you.  High temperatures the past three days were below normal!

Source: NWS

Not only that, they were below 90ºF (89, 89, and 86).  Any day in July with a high temperature below 90 is a good day.  

And, on top of that, we have another cool, showery day on tap today, with some action in the area even this morning.  

Enjoy it while it lasts. 

Yesterday's Big Storms

Most of the Salt Lake Valley enjoyed an exciting afternoon yesterday as a series of strong thunderstorms moved through the area.

As can be seen in the loop below, we were pretty fortunate (meteorologists like myself prefer consider it fortunate to be in bad weather).  There were storms to the south and storms to the north, but in the strip from Dugway to the Salt Lake Valley, we were the most active area.

The storms generated an inch of rain in Riverton, which seems to be the big winner from this event. Here on the University of Utah campus, our weather station near the mouth of Red Butte Canyon recorded 0.37", which doesn't sound like much, but it fell in only 15 minutes, which is a pretty good rainfall rate for northern Utah.  Really most of that rain fell in about a 5-10 minute period that can be described as either heaven or hell depending on your perspective.  In addition to the heavy rain, winds gusted to 37 mph and the temperature dropped to 66ºF.

With the humidity higher than usual, the radar was able to pick up on a number of outflow boundaries produced by the thunderstorms.  These can be seen in the loop above as lines of weak reflectivity that are often arc shaped.  I've highlighted three examples from the middle of the period displayed above in the image below.

We will have to see if we are similarly lucky today, or if Mother Nature will favor other areas.

A Shift in the Pattern

The loop below shows the large-scale flow changes that have brought a pleasurable return of more seasonable temperatures to Utah and the Intermountain West.  Note in particular the westward shift of the upper-level ridge that was previously parked over northern Utah to the northeast Pacific.

Here's a closer look at the changes.  On June 29, the upper-level ridge and the highest temperatures at 700 mb (roughly 10,000 feet, color contours) were parked directly over Salt Lake City, resulting in a high temperature of 104ºF.  BTW, if you adjust that to sea level, you get a maximum of about 127ºF.

This morning, however, the upper-level ridge is thankfully over the north Pacific and our 700-mb temperatures are about 8ºC lower.

And, as a result, the National Weather Service forecast for the next few days is relatively pleasant.  

Enjoy!

It's Humid Out There!

By Salt Lake City standards, dew points don't get much higher than they are this morning.  At the Salt Lake City airport, the dew point maxed out at 67ºF at 9:50 AM and is currently sitting at a muggy 65ºF.

Nobody from the deep south will think much of this, but that's about as humid as it gets in Salt Lake City.  I don't know what the dew point records are for the Salt Lake City airport (pass them along if you know them), but I consider anything above 65ºF to be quite high and anything around 68ºF to be rare.

Although the humidity is good for the skin, it makes things far more uncomfortable and renders evaporative coolers completely ineffective.  It does, however, look like our run of >90ºF days, which sits at 20, will come to an end today.

Heat Wave Tidbits

I feel quite disoriented this morning.  I awoke yesterday in Ketchikan, Alaska on a spectacular day.  Temperatures were comfortably in the 60s as we ferried across the Tongass Narrows to the airport.

I arrived yesterday evening at the Salt Lake City airport to an apocalyptic scene.  What the hell did you do to Utah while I was gone?  Where are the green Avenues foothills?  The patches of high mountain snow?  I haven't been gone all that long, but the transformation is dramatic.  

Much has gone on in the past week or two.  We've already spoken quite a bit about the June heat, but how about the air quality?  In Utah, we tend to think about wintertime inversions, but during the summer, our ozone can also become elevated.  Below is a time series of ozone levels on the University of Utah campus over the past 30 days.  Ozone is produced photochemically by the sun's ultraviolet radiation and shows a pronounced diurnal signal with a maximum in the late afternoon and a minimum overnight, as is clearly evident below.  However, you can also see how the peaks were highest during late June during the height of the heat wave.  

Things have been hot in the western United States and Canada, but also western Europe over the past couple of days as an upper level ridge built over the region.

The Weather Channel has a good summary of the weather records here.  98.1ºF at London's Heathrow Airport, which looks to be a July record for the UK (the all-time record is 101.3ºF set in Faversham (Kent) on 10 August 2003).  103.5ºF in Paris (2nd highest all time). 103.5ºF in Madrid (June record).  These are brutal temperatures, especially in northern France and the UK.

Salt Lake City Record Recap

No surprise here.  June 2015 spanked all previous Junes at the Salt Lake City Airport with a mean temperature of 77.5ºF.  That's 1.8ºF higher than the previous record holder, June 1988 (75.7ºF).

Source: NOAA Regional Climate Centers

And, in case you are wondering, Jan–June also came in as the hottest in the instrumented record with a mean temperature of 53.0ºF, topping 1934s 52.8ºF.

Source: NOAA Regional Climate Centers

And now onto July...