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



3 Hot Days Ahead

September 4, 2014

9pm Thursday…

A classic early-fall east wind event has arrived this evening.  This is the time of year when east winds make our temperatures jump up, drop the relative humidity, and give us crystal clear skies (assuming no fires).  The view from our Skyline Camera at 1,900′ in the West Hills (recently upgraded) was stunning this afternoon.  We could easily see into the west end of the Gorge…the sandy hill on Sand Island at Rooster Rock SP showed up clearly 20 miles away!  That’s something we couldn’t do all summer with the haze/smoke filling our skies most of the time.

High pressure is centered well to our east, and a “thermal trough” of low pressure is right along the coast.  So wind flows from east to west, over the Cascades and down into the lowlands.  As a result temperatures warm quickly.  In the case of tomorrow and the first part of Saturday, that wind will make it all the way to the beaches.  Tomorrow will be one of those rare days at the Coast when temperatures soar into the 80s or even 90.


Today we hit 85 at PDX, a 12 degree jump from Wednesday.  Models seem to show 4-5 degrees warming for tomorrow, so I forecast a 90.  Then another 3-5 degrees warming on Saturday as 850mb top out around +20 to +21.  That would put us in the 93-95 degree range.  Saturday is going to be a windy scorcher!

In September last year and in 2012 we hit 95 degrees at PDX.  850mb temps were +23 and +21 degrees at Salem.  Similar offshore flow pattern so I’m pretty confident of the 94 we have in the forecast for Saturday.

What about the big picture?  Is September going to be a blowtorch month?  Two thoughts on that.

1. Yes, the first half of the month looks extremely warm.  The general pattern is the ridge/offshore flow through Sunday, a weakening trough giving us cooling Monday-Tuesday, then a return to ridging and offshore flow the 2nd half of next week. 

2. Things could change quickly the last two weeks!  We’ve seen that in the past.  Flip a coin.  A little bit of information can be gleaned from last night’s maps from the monthly run of the ECMWF. 500za_week1_bg_NA  500za_week2_bg_NA

They show the well above average upper-level heights through the 20th.  That’s a little more than 2 weeks away.  Then the following two weeks:



That last map isn’t real helpful is it?

We didn’t have measurable rain in August here in Portland (officially).  Yes, yes, I fully aware some of us had showers.  But many of us didn’t, just like PDX.  The ECMWF shows no precipitation for the next 10 days, and it would be fair to assume it shows below normal rainfall for the next 5-10 days after that.

ecmwf_10dayprecipSo keep watering…your yards/plants/trees are more stressed now than back in July/August as the soil continues to dry out.

Chief Meteorologist Mark Nelsen

September is Here

September 2, 2014

September is the month where summer fades away and fall takes over.  Much like March where winter fades away and spring gradually takes over.


Notice that last fact.  Now compare it to the following graphic


Only 1 of the last 8 summers have not seen a 90 degree temperature in PDX.  That was the cool summer of 2010.  The last two Septembers we’ve even seen a 95 degree high in the first half of the month.  It’s also interesting to note that in both cases the next day it quickly dropped to around 80 degrees.  Just as in March it’s hard to keep daytime highs cold; it’s really tough to have several days of hot weather in September. 

This weekend will be similar with a couple days near (or above) 90 degrees Friday and Saturday, then a dramatic drop either Sunday or Monday as a cool trough moves by to the north.   That turns the dry and warm east winds back to onshore and cool.

The big picture over the next 10 days or so is for a strong upper-level ridge to linger just off the West Coast, keeping us mainly or all dry.  Most likely after the cool trough early next week we’ll see another fast warm up.  

The 00z GFS has no precipitation over us for the next 16 days, and the 12z ECMWF looks quite dry as well.  Here is the 10 day precipitation accumulation. ecmwf_tprecip_nw_41  A tenth of an inch over the mountains, and just about all of that was supposed to be this evening and tonight.  So basically no rain in the lowlands through the 11th of September.

Chief Meteorologist Mark Nelsen


Warmest August In Portland & Salem History

September 1, 2014

You just survived the warmest August on record in Portland & Salem!  The average temperature was 73.096 degrees in Portland…got that?  That’s also the 3rd warmest month in Portland’s history.  After July 1985 and July 2009.


In Salem, the 72.47 degree temp was the 2nd warmest month in Salem’s history, right after July 2014!  So that means Salem just had its warmest two months on record.

It was the 2nd warmest August & month in Eugene’s history, only topped by the hot August of 1967.

As I mentioned in a previous post, the weirdest thing is that most people in the metro area probably wouldn’t say “…Whew!  that was the hottest summer I’ve ever been through here!”.   Joe Raineri & I were just talking about why.  The proof is that through this entire “2nd warmest summer on record” we didn’t have any HEATWAVE 2014 coverage in our newscasts.  Well it is true that leading up to the 99 degrees on July 1st the newsies got excited; we had to cancel that heatwave real quick when models cooled off.  But in the following two months I don’t think we ever made use of the phrase HEAT WAVE.   Basically we were consistently very warm through the last two months with almost no strong marine pushes to cool our highs into the 70s.

Coming up, it sure looks like September.  By that I mean it still looks quite dry the next 7-10 days and we have a mix of cool days and very warm (or hot) days.  East winds show up Thursday-Saturday which means very dry air…low humidity!  Ahh, warm (shorter) days and reasonably cool nights.   For some, now through mid-October is the best time of the year before the real rainy season hits in about 6-8 weeks.  I know some like the crisp/clear days of October, and so do I.  But those are often few and far between.  Cloudy days are far more common then.

I pushed the high temperatures up to right around 90 degrees both Friday and Saturday with decent offshore flow and sunshine.  ECMWF is more reliable I think with the slower arrival of a cool upper-level trough early next week so I kept temps quite warm through this coming weekend.  We get that cool trough early next week and then it’s likely ridging will nudge up against the coastline again.  You can see the Yo-Yo up/down weather the next 10 days on the ECMWF ensemble chart:  tseries_850t_000-360_Portland

This coming weekend happens to be at the high point on that chart…it’s going to be much warmer than the Labor Day Weekend was!

Chief Meteorologist Mark Nelsen




Tough Sleeping This Summer? You’re Not Alone!

August 28, 2014

It’s been a common saying in the Willamette Valley (including Portland) that you don’t need air conditioning in our climate.  I’ve been hearing that since the 1970s when I was a kid.  After the past two summers, many would disagree now.

Last summer we set a record for most nights above 60 degrees here in Portland…44!

Well here we are on August 28th, and now we’ve seen 40 such warm nights this summer so far. BMAC 60 Degree Nights  I think it’s quite likely we’ll see 5 more between now and the end of September so we’ll probably set a new record for a 2nd year.


So what’s causing this?   One thing that isn’t…plenty of these nights have been under perfectly clear skies, so it’s not as if we’ve been seeing lots more cloud cover at night.  That would sure raise overnight lows.

More likely it’s a combination of the both the urban heat island effect and our warming summers.

I can’t speak with any knowledge on the first because I haven’t check outlying areas (like Aurora, Battle Ground, Sandy etc…) to see if they have seen a similar rise in overnight temps.  Common sense would tell you that overnight temps in summer in a rapidly growing metro area should warm; although PDX isn’t exactly surrounded by concrete and buildings.  You can see the increase in warm nights since 1941


As for the warming summers…our summers have definitely been warmer, check out the June-August temps for the lower elevations of western Oregon.  timeseries_summer_willamettevalley  That’s Oregon climate zone #2.  It’s also interesting that summers seemed to cool from around 1955 to 1980, then warm again following.  With warmer summers, one would expect both warmer daytime highs and warmer nights.

Will this continue?  History would say we will be in unprecedented territory if we had a THIRD summer of 35-45 warm nights.  Looking at that chart you can see we’ve never had more than one or two summers like this before cooling a bit again.  So it’s quite possible next summer is more reasonable.  But the big picture also shows that in a slowly warming climate there will be more of this in the future…

My advice is to get at least a one-room air conditioner if you live in an urban area.  They are more efficient than they have ever been and cheaper than they were 20 years ago!

Chief Meteorologist Mark Nelsen

Is It the Warmest Summer Ever in Portland?

August 26, 2014

11pm Tuesday…

The short answer is a “no“.  But it’s one of our warmest ever recorded here, and that’s without any real heatwaves!  Let me explain how that has come to be…First, here are the official numbers from this afternoon…


And the number of 90 degree days so far this season…

BMAC July 90 degree recap


Notice Salem has seen 9 more 90 degree days than Portland, yet nowhere near a record as you can see in this graphic from the NWS.


Not sure why it says Portland averages 12 since the 1981-2010 30 year NCDC average is 13.6 days.  I’ll have to check the numbers again.

So let’s talk about this summer…I did some number crunching, finishing off the August numbers with our 7 Day forecast. Assuming that forecast is within a few degrees (one hopes), here is how the summer should rank….


Generally meteorologists consider summer in the northern hemisphere as the 3 warmest months June-August.  Of course in some places (along parts of the west coast) September is the same or warmer than June.  But for most areas it’s June-August.  Anyway, it appears August will end up the 2nd warmest in Portland.  That’s where the official records are kept at PDX back to around 1940.  It’ll also end up the 4th warmest month (of any month) in our history.  That’s after July 1985, July 2009, and August 1967.

What about Summer 2014?  We know it is the warmest since 2009.  Remember those 9-10 days above 90 and two days at 106?  That was definitely “Africa Hot”!  This summer should end up 3rd warmest behind 2009 and 2004.  That’s a hot summer…

Several things I’ve noticed about this summer…


Much of the summer we’ve seen an upper-level ridge just to our west, out in the eastern Pacific.  It’s quite similar to the pattern we’ve seen off/on for about 18 months, most likely related to the huge pool of above average ocean temps in the eastern Paciifc Ocean.  With the ridge frequently in this position the past 2 months or so, we got weak onshore flow, but rarely get a hot thermal trough west of the Cascades.  In fact only once between mid June and late August did we get gusty easterly wind in the Gorge, that was during the 99 degree event the 1st of July.

Another effect of this pattern?  It’s been consistently warm, with no prolonged periods of cooler than average temps, yet no heat waves.  We did see 5 days at the end of July and early August with high temps between 89 and 92, but that barely qualifies as a heat wave here in Portland.  Yes, I know it was hotter to our south and east, but I’m specifically talking about the Portland metro area. 

Did you notice we didn’t hit 100 this year?  A little weird since it’ll be the 3rd warmest summer.  That’s related to the lack of strong offshore flow at any point during the summer.

And did you notice what was missing much of the summer?  Morning low clouds.  I noticed how many more days started sunny this July and August compared to the past few summers (I really liked that).  The marine layer was often present, but very thin in the metro area.  Just enough to keep us out of the “real hot” range and more in the “a little hot” range.  I don’t really know what that means, but hopefully it makes sense.

It’s pretty obvious looking at 7-10day maps/models that we’re headed into a cooler than average weather pattern as we start September.  For the next week or so we’re done with the continously warmer than average weather.  Take a look at the 12z ECMWF ensemble chart



So what are YOUR thoughts about this summer?  Discuss and (nicely) argue below please…

Chief Meteorologist Mark Nelsen