July Turns Cool: A Short-Term Climate Shift?

July 6, 2016

Remember the record-breaking “heat” earlier this spring with a bunch of 80s in April and May?  It’s payback time and that is the big weather news this week.  It appears we have a cool July developing for the first time in years.  

FORECAST QUESTIONS:

Will we get a big soaking this weekend?  I don’t think so, at least not in the lowlands.  Note the RPM total showing light amounts in the valleys…no models are showing more than 1/2″ rain.

RPM_RAIN_NWOREGON

Will my wedding/garden party get rained on Friday, Saturday or Sunday?  Possibly, but the pattern for Friday/Saturday is a showery one, not the “all day downpour” stuff.  Current thinking is that portions of each day will be wet but as of now we can’t time those showers.  Our RPM (not always a stellar performer) actually has most rain offshore Saturday with just a few light showers in the valleys.  That would be nice.

QUITE A CHANGE THIS JULY!

The last two Julys have been real scorchers.  2015 was the 2nd hottest on record and 2014 was the 4th hottest.  2013 was just a little above average.  This follows 3 very cool Julys:  2010-2011-2012.  Take a look at the past 30 years in the western lowlands of Oregon…this is a bunch of weather stations averaged together:

July

You can see the big swing down and then back up the past 6 years.  Also note the upward trend the past 30 years.  So yes, what goes up must come down, but over time the high points are getting higher and low points not so low as our climate very slowly warms.

But now it’s payback time since this month is actually running BELOW average already and there is no sign of above normal temps in the next 10 days!  Keep in mind the 30-year average high temperature is 80-85 in the Willamette Valley during this period.  Highs in the 70s are considered cool (although comfortable!).

Here’s the plan for the next few days:

MarkHeadlines_SummerTakesBreak

It’s because of a cold upper-level trough that’s going to settle in over the Pacific Northwest this weekend.  See the 500mb height anomaly on the ECMWF this coming Sunday AM?  Then a 2nd one on Tuesday:

Check out the GFS for Sunday the 17th…hints of ANOTHER trough trying to drop into the Pacific Northwest for the following weekend.

The natives will be getting restless if we go through TWO mid-July weekends with clouds/showers.

It’s pretty obvious to me that SOMETHING changed after the 7th of June.  Since that last of the “spring heat waves”, we haven’t seen strong upper-level ridging or unusually warm weather.  In the last month we’ve seen only two days in the upper 80s in late June; that’s it…near/below normal temps otherwise.  My gut feeling is something has switched but I don’t know what.  Sea surface temperatures are still a little above normal offshore as they have been for a few years, although a narrow near-shore cold anomaly is showing up now.  This is low-level stuff and not a reason for upper-level patterns to shift:

Capture

One more thing I’ve noticed since that last heat wave in early June too.  Models have struggled to latch on to the persistent “cool” weather.  Over and over 10+ days out warming has been showing up yet as we get closer models back off and we end up in coolish or normal temps.  Interesting that it’s a total reversal of the “oh look, a surprise warm spell has popped up again” pattern all spring long.

Another even larger question…is this the much-anticipated end of our 2+ year warm spell?  As mentioned many times in the past two years we have been in a warm period since March 2014.  We haven’t gone more than about a month with normal/below normal temps before returning to the above average stuff during this period.  IF both July and August are cool, then that will be a dramatic change and we have seen some sort of climate switch.  Only time will tell as they say…

Meanwhile, check out this beautiful but scary pic of Super-Typhoon Nepartak nearing Taiwan this evening.  That category 5 storm will hit the island nation in about 12 hours.

himawari-8_band_03_sector_04_20160707042900

Find the high-res loop here on the RAMMB site:

Chief Meteorologist Mark Nelsen