‘Four Corners’ high helps pump hot air to the north
If this summer has felt exceedingly hot, you’re right.
July 2014 finished second on the all-time list of the hottest on record, according to the National Weather Service.
The average temperature for those 31 days during the seventh month of the year was 75.7 degrees, two-tenths of a degree behind the all-time 75.9 set in 1906.
Of the top-10 hottest Julys on record — there are 13 total including years that tied — seven of those came before 1960 and five before 1940.
Eastern Washington University meteorology professor Dr. Bob Quinn said the culprit is what he called the “Four Corners ridge of high pressure.”
The Four Corners is a geographical anomaly where the borders of the states of Arizona, Colorado, New Mexico and Utah all meet in the southwest part of the country.
“It’s a pattern aloft at 18,000 feet,” Quinn said, and is really quite normal. “Basically that dictates the West in terms of its summer weather pattern.”
It serves to funnel summer heat to the north. Quinn calls it “nice summer heat,” but there are many who would argue that. This pattern will exist for the foreseeable future,” he said.
“We have a dominance of warm water conditions in both the tropics — called the El Nino event,” Quinn said. There is also warm water north of that, in the Southwest, Southeast Pacific, Baja and a dominance of warm water across most of the North Pacific, he explained.
“Even though the normal summer weather pattern is sitting there, that tends to slightly increase a bit of the southerly flow,” Quinn said. “It pulls up the heat further north.”
While somewhat hotter, this is a pretty normal summer weather pattern. If sea surface temperatures were cooler there are more variations in the thermometer.
“If we had cold water off the coast, what happens is you get into that nice summer cycle which is you have 80s and 90s and the cooler air builds up along the coast (and) gets up to the Cascades,” Quinn said.
That tends to create a disturbance where an upper level trough passes through the area with a push of marine air. “So we get the winds, some times a bit of dust, but we get a 20-degree cool down,” Quinn explained.
That can last a few days and then the cycle begins again. “So the end result is you have your normal summer heat, the 80s rather than 90s,” Quinn said.
As long as that low sits up in the Gulf of Alaska the region’s weather is going to be influenced by the southwesterly flow aloft. Simply put, there are more 90s ahead in the coming days.
“The other thing — a very interesting thing to note — is when you look at the tropical sea surface temperatures, the Atlantic and Caribbean and Gulf of Mexico are all running a little cooler than normal,” Quinn said. “The end result is the Atlantic hurricane season, (which) so far has been almost a bust.”
“El Ninos tend to suppress the Atlantic hurricane season,” Quinn said. “So far there have been two named storms as of July 25.”
“Conversely, in the Pacific,” Quinn said, “Everyone forgets about it, but there have already been 11 storms with the formation of Julio, Aug. 4.”
Most Pacific storms form off the Mexican coast travel in the trade winds out to sea and do not run into anything. Once they encounter cooler water the storms dissipate and remain largely not newsworthy.
Looking ahead to fall and winter, the region will be influenced by a weak El Nino.
“That generally means split flow and the good old drought pattern for the winter in the Pacific Northwest,” Quinn said. “The Southwest — California included — tend to have wetter than normal winters.”
Hottest July’s on record
Source: Spokane International
Airport
Rank Year Avg. Temp
1 1906 75.9
2 2014 75.7
3 2007 75.6
4 1998 75.3
5 1960 75.0
1938 75.0
1985 75.0
8 1925 74.9
9 1926 74.3
10 1920 74.2
11 2013 73.9
1941 73.9
13 2006 73.7
Paul Delaney can be reached at pdelaney@cheneyfreepress.com.
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