Heading Toward A “Warm Nights” Record; Warming Summers Too

September 18, 2014

BMAC 60 Degree Nights

The 61 degree low at PDX this morning was the 43rd morning this warm season when the temperature didn’t drop below 60 degrees.  The all-time record of 44 days was set just last summer.  If we have two more 60 degree mornings, we’ll set a new record.

It is important to point out that technically the low temperature records are for the calendar day…from midnight to midnight. For example, if it’s 62 in the morning, but then that evening cooler air pushes in with a 58 at 11:59pm, the low for the day is the 58 and it wouldn’t count in the graphic above.

And yes, Portland metro area nights are getting warmer and warmer aren’t they?  Here’s an updated look at 60 degree nights at PDX over the past 70+ years


Much of this is due to the Urban Heat Island effect…as cities grow they turn warmer.

But are our summers getting warmer? The short answer is YES.

To eliminate most of the urban heat island effects, you can average all stations in NCDC Climate Division 2 in Oregon.  That’s the Willamette Valley (and foothills) stations.  There’s a slow warming since 1950 during the 3 month period June-August. jun-augdiv2temp

Note that from the late 60s to early 80s there was a flattening or even cooling trend in there.

As I noted a year or two ago in this blog, the July-September warming is more significant (summers are hanging on longer?). In fact the only significant change in temperature in the lowlands for the past 30 years has been a cooling in the late spring and warming in the late summer.  Here is the spring chart


and the July-September chart


Winter and fall haven’t seen much of any change. In fact I noticed the Cascades have seen just about NO change in the winter months.  Keep all these numbers in mind when people argue with you one way or another over Global Warming.  Not quite as clear-cut as some would have you believe!

Chief Meteorologist Mark Nelsen

Soaking Rain Next Week

September 17, 2014

Long range models have changed a bit in the past two days.  They now show westerly flow punching through the eastern Pacific the middle of next week.  That means our first round of wet weather systems since late June.  Take a look at the ECMWF for next Wednesday.


The 18z GFS ensembles show lower than normal heights (troughing) in the eastern Pacific.  Note the strong westerly flow running right into the West Coast.


The 12z ECMWF shows a big soaking with all areas west of the Cascades in the valleys getting over an inch in the next 10 days.


You can see just about all the 50+ ensemble members of the ECMWF showing some sort of significant rain the 2nd half of next week.  The average is around 1″.


Is this the beginning of a long wet spell?  Not sure yet, especially since we’ve seen a dramatic change in the past 48 hours.

Regardless, I’m feeling more confident that we’ll get some sort of soaking starting as early as next Tuesday.  So if you have outside projects going that can’t handle getting wet…finish up this weekend!

Chief Meteorologist Mark Nelsen

Fire Smoke & Long Range Outlook

September 15, 2014

The first large forest fire close to the metro area in at least 20 years sent a lot of smoke our way the past few days.  The 36 Pit fire continues to burn just a few miles southeast of Estacada this evening; luckily winds have been light so far.

Air quality was actually surprisingly good in the Portland Metro area, in the GOOD category all day.  That’s because we had a light east and north wind in our area, sending most of the smoke south into the central and southern Willamette Valley.  Salem’s air quality was pretty bad in the afternoon; visibility was down to just over 2 miles at one point!

The good news is that a marine push (cooler ocean air) has developed this evening and the westerly wind is already pushing the smoke out of the valleys…slowly.  You can see what happened at Salem as the westerly wind kicked in…dramatic improvement in the air quality:


Tomorrow should be much better as the light westerly flow pushes just about all the smoke up into the Cascades.

This was a relatively close call for our area.  The closest we’ve seen a 1,000 acre or larger fire is way up on Mt. Hood or just east of Hood River the past 20 years.  We haven’t seen that much acreage burning within 30 miles of downtown Portland, although I have a feeling the Multnomah Falls Fire in 1991 covered a lot of ground/acres in a short period of time.  I moved to the metro area just a few weeks after that one.

The long range outlook still looks warmer than average for much of the next two weeks (the rest of September).  Here are the two ensemble charts from the 12z ECMWF:


and the 18z GFS:


Notice the ECMWF  is all over the place after next weekend’s warmup, but seems to be near/below average.  The 18z GFS is crazy warm with two more “hot spells” before we end the month.  It’s always best to follow the average of the ensembles (red line), which is still much warmer than normal.  The monthly ECMWF run last night showed ridging holding much of the next two weeks, then the ridge backing offshore into it’s preferred position over the past year and a half.  That’s out in the Gulf of Alaska.  That would cool us dramatically, but not a real wet pattern into early October.





We haven’t seen a widespread soaking in almost two months now; the last wet days were the third week of July.  And I don’t see a good soaking in the next 10 days at least.  We’ll see a few hundredths Thursday or early Friday, but that’s it and it won’t do your garden/lawn/trees any good.  Keep watering!

With today’s 90 degree temperature, we’ve now seen 20 days at/above 90 degrees this warm season, it’s been hot!

Chief Meteorologist Mark Nelsen

Strongest Wind in 6 Months Today

September 11, 2014

4:45pm Thursday…

The peak gust at PDX was 44 mph today, easily the strongest gust we’ve seen since back on March 6th.  That day we saw a 47 mph gust.  As a result, most of our neighborhood trees saw a little bit of “natural pruning”.  Lots of debris floating around yards and roadways.  MarkWind_PeakGustPDX

Luckily wind gusts didn’t get much stronger than that and power outages remained at less than 10,000 customers through the strongest wind this morning and midday.  As of 4pm it looks like still around 2,000 PGE customers are still out even though the strongest wind has passed.  Notice how widespread the easterly wind was in the metro area today, even Aurora had a 39 mph gusts…very unusual.


Plenty of small fires have popped up, and we’re lucky that most have them have been put out promptly, although at this hour one is threatening homes west of White Salmon in the Gorge.

Expect the wind to diminish to just “normal breezy” east wind tonight through Monday as a thermal trough sits overhead.  That means temperatures will warm up but no more strong gusts away from the west end of the Gorge.

Still, with very dry air overhead and hot afternoons, the NWS has extended the Red Flag Warning all the way through Sunday.

Chief Meteorologist Mark Nelsen

Unusually Strong East Wind Thursday

September 10, 2014

We’ll see a surprisingly strong east wind event here in the Portland Metro Area the next 24 hours; at least for early fall.  In fact the NWS has issued a wind advisory

MarkWarnings_High Wind

The Highlights:

  • Gusty east wind arrives in the western Gorge and foothills of the Cascades after midnight.  Those of you in those areas may wake up to trees blowing around, or your lawn furniture flying.  This includes Battle Ground, Hockinson, Sandy, Welches, Estacada, Boring etc…
  • The wind will spread across the rest of the metro area around sunrise or soon after
  • Peak gusts are likely between sunrise and 3pm
  • 55-65 mph in the western Gorge
  • 40-45 mph eastern metro area (east of I-205) and foothill locations mentioned above
  • 30-35 mph anywhere else in the orange area
  • These speeds are more typical for late fall, not the 11th of September.  So we’ll probably see scattered power outages, some fruit ripped off trees, cornstalks flattened in the windy areas, and a few trees down.
  • The rest of the lower elevations, coastline, & eastern Oregon will just be breezy, nothing too wild.


Cold high pressure is sliding south through the Rockies, bringing the first snow of the season for those areas.  The air spreading out from that high pressure is pushing northeast wind across the Pacific Northwest right now.  The easterly wind has made it into the east end of the Columbia River Gorge at 6pm.

I’m impressed by the strength of the pressure gradient and winds just above the surface tomorrow.  I don’t think I’ve ever seen a 7-8 millibar gradient through the Gorge in early September.  That’s what the UW WRF-GFS model is forecasting.

Take a look at the cross-section from the WRF-GFS:  

New Scene

You read it in reverse time-wise.  Time runs along the bottom, from this morning at 5am on the right side to Saturday afternoon at 5pm on the left side.  The bottom is here at the surface, and the 700 up top is around 10,000′ elevation.   The green colors are relative humidity above 70%.  Obviously after midday today the atmosphere was going to be quite dry…no clouds in sight through the weekend!  The wind barbs are a bit simpler, they flow with the wind direction.  Each barb is 10 kts and the triangle means 50 kts.  You can see the rapid increase in wind overhead tonight in the area I’ve circled.  By 5-8am Thursday winds are blowing 50-60 mph several thousand feet above the ground here in the metro area;  I’ve never seen the 50 knot barbs over us before Halloween!  The result is the possibility of damaging wind in spots tomorrow, especially since we don’t usually have east wind this strong while leaves are on the trees.

The real strong stuff only sticks around 10-12 hours, but then dry easterly flow (more like last week’s) continues through next Monday.  

There is one bonus…if your power goes out for a few hours when it’s sunny and 75 degrees, is that really such a big deal?  Better than when it’s icy and 25 degrees!

Chief Meteorologist Mark Nelsen

Monthly ECMWF Run…Ridge Stays Nearby

September 8, 2014

11pm Monday…

Last night’s 00z ECMWF maps…an average of all the ensembles for the next month.  It’s upper-level height anomaly (500mb) for 4 one-week periods.





 After this week’s ridge which is centered a bit to our west, it shifts directly over the West Coast through the rest of the month and into early October.  This would imply there is no start to the rainy season in the next few weeks; but there’s no reason a passing front or trough couldn’t give us 1/2″ of rain.

The 00z GFS ensemble chart (brand new this evening!) shows a peak in heights/temps around this Sunday and again the weekend of the 21st.


Easterly flow is going to be much stronger this time around later this week as strong high pressure is dropping into the Rockies.   The WRF-GFS has 30-40 kt wind barbs over the metro area from just above the surface to around 4,000′ elevation.


It’s going to get very windy on the west slopes of the Cascades on Thursday!  I also kept Thursday’s high temp at 80 degrees due to all that wind.  That’s cooler than a +15 degree 850mb temp would suggest.

Dewpoints will also plummet even lower than during the last warm spell last week.  Looks like they may even drop down into the 20s in spots west of the Cascades.

Chief Meteorologist Mark Nelsen



A September Scorcher

September 5, 2014

5pm Friday…

Whew, as expected a hot and windy (and very dry) day!  We hit 90 degrees at PDX, but the record is 101 back in 1944 so no record.  PLOT_Highs_Metro

Check out the relative humidity well down into the teens.  


I see Eugene at 4pm was down to 9%!  Definitely not a good day to flick a cigarette out the window of your car…like any day is but you know what I mean.

As expected the wind made it all the way to the beaches too.  Right around 90 on the north coast and up to 95 at Florence!  I see the wind switch at North Bend from East to WSW dropped the temperature from 91 to 66 in one hour!  That’s some natural air conditioning isn’t it?



Models say the low-level airmass warms up to 5 degrees in the western valleys tomorrow as offshore flow continues.  So we boosted the high temp to 95 degrees.

Sunday the wind will be calm in the western valleys, but residual warm air should still push temps well into the 80s.

Stay cool and enjoy this (almost) last gasp of Summer!  Fall rains can’t be too far away…

Chief Meteorologist Mark Nelsen




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