Mellow Midsummer Weather

July 24, 2016

9pm Sunday…

I’m back from vacation and working hard in the weather center this evening.  Well, the weather is slow so I’ve spent more time on normal/mundane “office tasks”.  Such as: catching up on emails, doing schedules, planning software upgrades etc…and I even vacuumed out the dirty area behind the green wall that’s been bothering me for months.  I think I had empty boxes and junk  thrown back there from almost two years ago.  As a result I’ve kept quite busy considering it’s almost the slowest time of the year weather-wise.  I think only September and early October are more boring for us.

HIGHLIGHTS FOR THE NEXT 7 DAYS

  1. Cooler the next two days, but temperatures just come back down to about normal
  2. A 3 day period of very warm to hot weather Wednesday-Friday
  3. This will be the first hot weather since early June.  That’s if you define 90+ as “hot weather”
  4. 95+ is unlikely, and no records will be broken
  5. Back to typical clouds/sun mix with highs 75-85 the first week of August

 

Speaking of slow weather, we are in the warmest few weeks of the year and our 7 day forecast takes us through the last day of July now (next Sunday).  So far this month has been a notch cooler than average here in Portland and right at normal in Salem and Eugene.  The Oregon coast has been warmer than normal; not sure why unless it’s the lack of strong northerly wind compared to some other summers?  You can see in general the farther north you go along the West Coast the cooler it has been compared to normal:

anomimage

Compared to California which has been normal to slightly above.  Nothing too dramatic west of the Cascades/Sierra anywhere along the coastline.  Yet east of the Cascades the cool July sticks out in Oregon, Washington, & Idaho.  I would guess no one is complaining in those typically hot areas.

Today’s 88 in Portland was the 2nd warmest of the month.  Seems strange to say we haven’t hit 90 in Portland this month…and it’s the 24th of July.

Even more strange, we’ve gone through 7 weeks in the middle of summer in Portland without hitting 90 degrees!  That’s a huge contrast to the past 3 Julys.  More like 2012 which was not exceptionally cool by any means but 90+ held off until early August.  Clearly something “switched” after the first week of June this year as mentioned in a previous posting.  We went from a crazy warm spring again to just about normal now for the past 7 weeks.

Looking ahead, we have a weak marine push tonight and then a bit more tomorrow night.  The result is a few more patches of morning clouds and slightly cooler temps each day.  Then Wednesday through Friday we get 3 days of very warm to hot temperatures.  Right now I’m going with 88-92-95.  Hardly record-breaking hot weather (records 100-107) in this upcoming period) but the warmest we’ve seen since early June.  The reason is weak and “flat” upper-level ridging developing along the West Coast.

Take a look at the 500mb pattern for Friday morning, the peak of the warming overhead:

500vty_f120_bg_NA

You can see an upper-level disturbance dropping out of Alaska and it’s headed right into the Pacific Northwest next weekend.  Thus a very quick cooldown next Saturday/Sunday…could even bring a spot of drizzle inland next Sunday AM.  This is in stark contrast to what models were showing 2-4 days ago.  At that time models were giving us a big heat wave with temperatures well above 100 degrees.  This graphic tells the story, although it does use the typically inferior GFS model:

Capture

Let me explain.  Each HORIZONTAL line is one run of the GFS.  The latest is on the bottom.  These are 850mb temperatures, which means temperatures in celsius around 5,000′ elevation.  Go UP the chart to go back in time for the forecast for any particular date which is VERTICAL.  Focus on the circled areas; next Friday-Sunday.  See that 72 hours ago up to 48 hours ago the GFS was giving us +25 to even a +28 temperature.  That’s up in the 103-107 range with any sort of offshore flow.  I’m sure some of your automated apps showed 100+ weather during that period.  Since 48 hours ago models have continued to gradually back off on temperatures AND cut off the end of the heat wave.  So we no longer really have a heatwave forecast.  It’ll be plenty hot late week, but nothing unusual for late July.  I think most of us would agree that’s a good thing!

Looking farther ahead, we return to average temperatures for the first week of August.  Other than the drizzle possibility, no rain is in sight.  Keep watering!

Chief Meteorologist Mark Nelsen