Friday: Back to Back 100 Degree Days

July 31, 2015

7pm Friday…

Another scorcher today, we hit 101 in Portland today.


That’s the first time we’ve had two consecutive 100 degree days since July 2009.


Everyone in the metro area was just a few notches cooler, and we’ll be another 4-5 degrees cooler on Saturday.  So this heat wave will just gradually wane.  By Sunday high temps should be down to around 90 degrees.  Hard to believe a high of 90 will be 13 degrees COOLER than the high Thursday!

All models are in very good agreement that a marine push arrives Sunday night for a continuing cooldown.  An upper-level trough lingering nearby late in the week means high temps likely stay in the 70s…a bit below normal.

By the way, as of today we’ve seen 21 days at/above 90 degrees this summer.  Pretty amazing to have that occur by July 31st.  In a typical (average) summer we average 5-6 the rest of the season, so it looks quite likely we’ll break the all-time record of 24 days set back in 2009.  It would be a very strange turn of events if we DON’T see any more 90+ highs after Sunday.

July was also the 2nd warmest in Portland’s history…1985 just barely beat us.  The two cool periods in the middle of the month kept the average high temperature a little lower than you might have thought.

Chief Meteorologist Mark Nelsen

Thursday: Hottest Day In 6 Years

July 30, 2015

What a scorcher today; textbook “extreme heat” here in the lower elevations of southwest Washington and northwest Oregon.  Easterly wind through the Gorge and some over the Cascades gave us the extra heating to pop temperatures into the 100-105 range in the western valleys.



The numbers at Hillsboro, McMinnville, Salem & Eugene were record highs for the day.  Check out those coastal temps too; not hot but nice and warm.

Here in Portland it was the first 100 degree day since August 2012, and the hottest day since the 106 during the heat wave in 2009.


Unfortunately, if you don’t have air conditioning, it’s going to be a warm night.  At 10pm it is still 87 in Portland, which is 4 degrees warmer than last night at this time.  We’re going for a low of 66 which would once again tie a record-warm low temperature; we did that last night at 63 degrees.

What changes tomorrow?  The atmosphere overhead doesn’t cool at all, but we lose the offshore flow.  In fact a 10-20 mph westerly wind returns to the Gorge in the afternoon.  The loss of the offshore flow (but no onshore flow) should drop our temperatures 3-4 degrees.  So…probably still a high of 100 degrees once again.  We haven’t seen back to back 100 degree days in 6 years either.

After that, a gradual cooldown over the weekend and then all models put us back into refreshing onshore flow and the hot ridge goes away next week.  Back to normal temps (around 80) or maybe even a bit cooler at times.

Chief Meteorologist Mark Nelsen

Hunker Down in a Cool Spot…100+ Likely Today!

July 30, 2015

9am Thursday…

Today should be our hottest day in 3 years in Portland.  The airmass overhead has warmed a few degrees, we actually have an easterly wind blowing through the Gorge, and it’ll be sunny the entire day.  By 5pm we can expect to see widespread 99-103 degree temperatures through the Willamette Valley and Portland metro area.  The last time we hit 100 was in August 2012.  Regardless of the final temp, it’ll be the warmest of summer so far.  Notice no one in the metro area has moved above 99 so far this season:


Tomorrow will be a scorcher as well, but probably not 100 degrees.  Then we slowly cool closer to 90 Saturday and Sunday.

Believe it or not, we won’t have a record high in Portland today since this is one of three days we’ve hit 107 degrees; our all-time high.  It happened on July 30, 1965 and then again TWICE during the great 1981 heat wave.  We were 107, then 105, then 107 again over a three day period.  That was August 8-10th, 1981.


Chief Meteorologist Mark Nelsen

The Brookings Effect Today: 101 Degrees!

July 28, 2015

A coastal city was the hottest place in Oregon today.


Yep, the temperature hit 101 degrees at Brookings way down on the south coast.

How does that happen???

It’s called the Brookings Effect, or sometimes the Chetco Effect.  With the right wind direction, air rushes down the Siskiyou Mountains, compressing and warming the airmass.  As a result, a localized area around Brookings can see temperatures soar ANY month of the year. Cliff Mass did a nice write-up about it a couple of year ago.

You know you’ve made it “big time” if you have a Wikipedia entry right? Sure enough, you can find an entry for the Brookings Effect here.

As soon as the wind direction changes the temperature drops rapidly.  It’s quite possible to have a high in the 90s one day and then be foggy and 58 the next as the air comes off the chilly Pacific Ocean.  You can see some of that up/down on a chart of the past 13 days:


The most extreme heat wave in the Brookings area occurred in July 2008.  That was a crazy few days, I can’t imagine what it was like for folks who most likely didn’t have air conditioning!  The 108 was the all-time record high for that location.  Note the low of 85 degrees the following night as the warm north wind continued to blow.


Speaking of a warm night, I see it is still 89 degrees in Brookings at 11pm with a northeast wind gusting to 16 mph.

Here in our area the heat begins tomorrow (Wednesday) and continues through at least Monday.  Models seem to be pointing towards significant cooling beginning Tuesday.

Stay cool!

Chief Meteorologist Mark Nelsen

Ahead: 2nd Long Heat Wave This Summer

July 27, 2015

9pm Monday…

This weekend was sure refreshing…showers, clouds, and comfortably cool temperatures.  Of course if you had camping reservations for “the driest weekend of the year” you were probably a bit disappointed.


As I mentioned would happen a couple of weeks ago, the last three weeks of July have been significantly cooler than the first week or so.  The average high temperature in Portland the past 18 days has been a very “normal” 81.3 degrees.  Yet in the 18 days before that, the average high was 90.6 degrees!  Quite a swing over the past 5 weeks.

Well now it appears the large/hot upper-level ridge of high pressure is going to nudge back up into the Pacific Northwest from its current position over the offshore waters of California.  This setup causes two significant changes:  First, the atmosphere overhead warms dramatically.  At 5,000′ over our heads, the temperature warms from around 45 degrees earlier today to the lower 70s Wednesday/Thursday afternoons…an almost 30 degree warming.  Then with a strong ridge overhead, the cool marine layer is suppressed to right along the coastline.  The flow overhead turns light east or northeast; we lose ALL marine influence Wednesday-Friday.


How hot?  The setup is almost exactly like what we’ve seen the past few times we’ve been close to 100 degrees this month.  Models would have us believe it’ll be only around 92-95, but all summer the effects of warmer than normal ocean water offshore seem to be showing up in a “model cool bias” during hot spells.  Due to that I went with 96-99-97 for Wednesday-Friday.  Once again this time, it does not appear to be an extreme heat setup.  I would want to see stronger offshore flow for that.

By the way, check out those sea surface temps!


Widespread 62-65 degree water temperatures all along the central/north Oregon Coast.  Wayne Garcia just told me the past few days camping at Yachats they were able to get in the water for a significant amount of time before it felt too icy cold.  Not like the normal 55 degree ice-cream headache cold stuff we are used to.

If we actually stay above 90 through next Monday for high temps, we will tie the all-time record for 90 degree days at Portland Airport.  That record is 24 days in 2009.

I don’t think this will be a LONG heat wave like the bizarre 14 day event early in the summer.  Models are trying to return some sort of weak upper-level troughing later next week.  Take a look at the ECMWF ensemble height anomaly from last night’s run.  First this week:


Then Week #2, just slightly above normal heights.


Week #3, about normal conditions, maybe slightly cooler than normal?  The actual operational run shows much hotter conditions than this.  Remember these maps represent an average of all the ensemble members.


And the last week, Week #4, which takes us into the last week of August


Seems to indicate near normal or slightly above normal conditions.

So August starts scorching hot, then seems to return to closer to normal as we head into the latter part of next week.

Chief Meteorologist Mark Nelsen

Vacation Time

July 19, 2015

I’ll be on vacation through Sunday, the 26th, so likely no postings during that time.  Mainly camping and painting my house.  Lots of family time too!

Chief Meteorologist Mark Nelsen

ECMWF Monthly Maps & Warm Nights

July 16, 2015

7:30pm Thursday…

I just took a look at last night’s monthly run of the ECMWF.  It is run twice a week and as you know I regularly post the maps in the wintertime.  Not so much in the summer because anomalies aren’t as great and patterns don’t stick out as well.  That said, this time it seems we can pick out some useful info.  Remember it’s only one model though.

Here are the 4 weekly maps; 500mb height anomaly averaged for each week

Week 1:  Cool troughing next week, especially Wednesday and beyond.  After brief hot weather this weekend temps should return to normal or a bit below through the weekend of the 26th


Week 2:  More troughing, although not as intense through the first day or two of August


Week 3:  As August begins, quite a change.  It’s not so obvious on these maps, but heights are a bit above normal.  More on that in a minute


Week 4:  Ridging returns to it’s preferred spot the past 18 months or so…looks hot.


Now these maps are the ensemble average, not the actual control run.  I took a look at the operational run and it’s quite cool right through about the 2nd of August.  Here’s a look at late next week.  Of course a week or so ago it looked like this for THIS COMING WEEKEND.  Obviously the trough was forecast too far west and ended up well inland instead.

ecmwf_next weekend

Take a look at the operational run for a few days into August.  Looks familiar doesn’t it?


This operational run has hot ridging (heights 588 dm or above) through the entire first half of August (after the 2nd).  That plus the ensembles looking much warmer than normal imply that, after a mild 2nd half of July, the first half of August could be very warm.

Again, remember it’s one model only.  But something to watch.  I am pretty confident the last 10 days of July will be real reasonable around here with no heat wave in sight!

Last night was our 25th night at/above 60 degrees in Portland this year.  Technically it is the 25th calendar day in which the low temperature didn’t drop below 60, but you get the idea.

That means we are already, on the 16th of July, halfway to last year’s “warm nights” record.


Here’s a look at the progression of 60+ nights since the Airport weather station was established around 1940…we’re heading into unprecedented territory this summer, especially if we get that hot weather in August:


I did a posting about this last September, you can find it here.

It sure does appear that the warmer than normal east Pacific (the blob) is having its way with our overnight temperatures again this summer.  Cliff Mass up at the UW just blogged about this yesterday in another excellent article.

Chief Meteorologist Mark Nelsen