Summer 2016: A Scorcher or Not?

May 23, 2016

It’s that time of year! Memorial Day Weekend is just days away; the traditional “start of summer”.  We’ve had a very warm spring (until the last few days) and endured 2 of the 3 hottest summers we’ve seen in Portland.  2015 was the warmest, followed by 2014 & 2009:

BMAC Summer Wrap

Remember last summer we had 27 days at/above 90 degrees, more than double the average number…it was a scorcher.


Will it happen for a 3rd consecutive summer?  I think that’s unlikely…


  1. Summer is June-August in weather circles…the 3 warmest months fo the year for most of the northern hemisphere
  2. It’s unlikely we have a scorching hot summer again, I don’t expect a repeat of last summer
  3. Of course we will have hot days (90+), but probably closer to the typical number, maybe 12-18 hot days.
  4. There is no evidence/modeling that implies we have a COOL summer on the way
  5. Most models & organizational forecasts are pointing to a warmer than normal summer

For the record…summers have been getting warmer since I was a kid (1970s).  This chart includes all stations in NCDC’s climate zone #2 here in Oregon (Willamette Valley):


I’ve spent some time looking over LOTS of data related to ENSO (El Nino Southern Oscillation), PDO (Pacific Decadal Oscillation), and analogs (similar weather setups in the past).  This is where we are right now:

May has been warm in the Pacific Northwest; what was looking like a record warm May has now been tempered by cooler weather that continues through the upcoming weekend:


Spring has been the warmest on record here in Portland.  A few degrees warm in March, record warmest ever in April, and still running 4 degrees above normal in May.

Sea surface temperatures remain very warm along the Pacific Coast and hundreds of miles offshore.  It shows no signs of cooling; a good chunk of this is due to El Nino effects lingering.  This is not THE BLOB that we talked about during 2013-2015, but the effect is similar along the coast…warmer than normal water offshore means warmer than normal temps as the summertime northwest wind moves over the milder water.  During the cold summers around 2010-2012 the waters were normal or cooler than normal.


El Nino is fading and models say we are headed towards at least a weak La Nina (or neutral on the cool side) Winter 2016-2017


The negative side represents La Nina.

The PDO is very much related to El Nino, but not always locked in together (warm PDO is not always right with an El Nino event).  The theory is that PDO runs in twenty or so year cycles of cool & warm.  The theory is also that we entered a cool period after 1998.



Talking to Cliff Mass about this last week at the AMS meeting, he suggested there is a line of thought (surprise!) that there is much more to the PDO than just a “15-30 year cycle”.  Basically we have a relatively short period of record and it’s possible there is no such thing as a specific cycle.  Look at what has happened right in the middle of the “cool phase”.  We are now past the two-year mark of a very warm PDO.  In fact the PDO number for April was the highest on record for that month!


We may have entered into a warm phase of the PDO, or it may be just a blip, a two-year warm period during a 30 year cool PDO.  It has happened before…in the late 1950s:


although it didn’t go on for two years.

So we have an El Nino transitioning to La Nina, Warmer than normal SST offshore, and a positive PDO.

I looked back at the last 13 El Nino years, then a closer look at the 7-8 that transitioned to La Nina the following winter.  A real mixed bag…4 of those 8 had normal or above normal number of 80 degree days (56) in Portland.  But 4 did not…roll the dice.  Not real helpful when using just that index.  I even added in warm/cold PDO.  Nothing significant sticks out.  Could be that I’m using the 80 degree threshold.

Instead I moved on to the NCDC anomaly plotting tool, first for all summers in which we were in an El Nino or finishing up an El Nino:


Then the summers when we were going from El Nino into La Nina (like this year maybe)…an average summer in the Pacific Northwest but a hot one across the USA in general:


But if we take only warm PDO years with El Nino in effect or fading…


If we take out 2015, the hottest ever, and 1983, the “summer of green tomatoes”:



Here are 3 forecasts, none expect a cool summer…NOAA’s official outlook:



The Weather Company (formerly known as WSI):


And WeatherBELL:



I can’t show these images, but some model forecasts:

CANSIPS:  Normal to above normal through August, SSTs remain above normal through December offshore

CFS:  Well above normal June, above normal July-September, above normal SST through at least fall.

JAMSTEC: Above normal temps, above normal SST continues through winter offshore

One last thought…since all models appear to be headed to at least a weak La Nina this coming winter/spring, you can get used to this cool/wet spring weather.  I have a feeling next February-April will be far different from what we have seen the past few years.  Lower snow levels and cool/wet late winter and spring are likely…

Chief Meteorologist Mark Nelsen




Oregon AMS Meeting Thursday

May 18, 2016

11pm Wednesday…

My favorite college professor will be in Portland tomorrow!  Cliff Mass is our guest for the May meeting of the Oregon American Meteorological Society chapter.  I’ll be there and hopefully lots of you can make it as well.  Pizza and drinks too!  Cliff was my favorite because he is one of the few academics up at the UW that is a “weather nerd”.  He loves the day to day stuff.  Believe it or not, there are people in atmospheric science that have little interest in daily weather, but are fascinated by cloud droplets, glaciers, or tropical latent heat flux.  You get the idea…

Details are in the meeting announcement:

We are excited to formally announce the return of Dr. Cliff Mass (University of Washington – Atmospheric Science Dept.) who has accepted an invite to return and speak to the Oregon AMS for the first time in 4 years at our final meeting of the season. No RSVP will be needed for this meeting…

Title: Gaps in Oregon’s radar coverage and a look at what’s new with WRF and NAM modeling at the Univ. of WA.

Guest Speaker:  Dr. Cliff Mass, Professor, Univ. of WA. Atmospheric Science Dept.

When: Thursday, May 19th 2016. Social hour beginning at 6pm. The formal meeting will begin at 7pm. Get there early for best seating and get your food orders in early as well.

Location: Stark Street Pizza (back meeting room) – 9234 S.E. Stark Street in Portland . Just one block off of I-205.


I haven’t been posting as much lately for a couple reasons: First is that I’m now on 5 shows an evening and I don’t have much time to blog.  It’s a somewhat temporary situation (a month or so) so this doesn’t mean I’m cutting way back on blogging.  The 2nd is that our weather is pretty slow this time of year anyway.

Chief Meteorologist Mark Nelsen



Very Warm, But Probably No 90 This Afternoon

May 13, 2016

1:30pm Friday…

I was just outside and was thinking it doesn’t have the “it’s gonna hit 90 today” feel.  I came in, checked observations and sure enough, only upper 70s to around 80 in metro area at 1pm.


Now I think a spot or two could touch 90, but I bet PDX only ends up around 87 today. That’s my 1pm armchair forecast since I didn’t work yesterday and don’t work today either.  On Wednesday I stuck with the 90 degree forecast, but mentioned on-air that was a high-end number, it could easily stay below 90.  The reasoning has been that overhead temperatures are not as warm as previous events this spring.  It was just +12 at 850mb over Salem this morning, expected to get up around +15 to +16 by afternoon.  We do have perfect offshore flow conditions

Assuming the high is 87-89, it will not be the warmest day of the season so far (that was 89) and not exactly a scorcher, even for mid-May.  Anywhere south of PDX in the valley stays in the 80s for sure as it is actually running COOLER than yesterday at this time in Aurora/Salem/Eugene.


Tomorrow is sure going to be a refreshing temperature shock with at least a 20 degree and possibly 25 degree drop in the high temperature.  That depends on how much shower action we get.

Inbetween the hot day today and cool showers tomorrow we clearly have a decent chance for seeing some overnight lightning in spots!  All models show some development (showers and thundershowers) during the night as the upper-level low spins towards the coastline.  Nice divergent flow overhead means some good lifting motion, perfect for elevated convection unrelated to marine push going on at the surface.  HRRR implies most action west of I-5 and toward the coast.  WRF-GFS says it’s even farther west and nothing happens in the north Willamette Valley.  In previous events the model placement of precip hasn’t been so hot; so don’t get depressed if you live way out east metro like me…anyone could see a thunderstorm during the night.

Chief Meteorologist Mark Nelsen


Warmest Spring On Record So Far; Early Berries On The Way!

May 10, 2016

10pm Tuesday…

The weather has been VERY slow lately with not much to talk about.  Just warm and dry.   First let’s talk about the warm part.  As of May 10th (today), we are experiencing the warmest spring on record here in Portland.


Yes I realize we are only 1/3 of the way through May, but looking at high temperatures between 80-90 the next 3 days, it appears even at the halfway point we’ll still have the warmest month on record.  We ran a story tonight about one big benefit…the strawberry season is about to begin!  The berry farmers out in Boring said this is the earliest they’ve ever started harvesting; even more so than last year.


No, not those hard, huge, half-yellow things from California.  Yes, I’m talking about the juicy local berries that melt in your mouth.  I made enough money picking strawberries as a 13 year old kid near Silverton to buy my first bicycle so I have an emotional attachment to those little red guys!  Of course that means they will be gone much earlier than normal too.  The same thing will happen with raspberries, blackberries, & blueberries too assuming there isn’t so sort of drastic change to unusually cold in the next few weeks.  Of course this IS the culmination of 26 months of unusually warm weather as mentioned in previous postings:


As for rain, it is getting very dry out there.  I was just working in the yard today.  While weeding (surprise!) blueberries & raspberries I noticed it’s as dry as late June in the ground.  We’ve had less than 1″ of rain in the past 3 weeks!  So we could use a big soaker, but as of this evening I don’t see a pattern change that would give us that soaking.  Yes, the models are all turning cooler/showery starting Saturday.  But they keep backing off on precipitation chances.  Four model forecasts of 10 day rain in Portland:


Not real encouraging, but the general pattern is definitely cooler Saturday through next week.  Take a look at the GFS meteogram


And the GFS ensembles for the next 15 days showing anomaly…warm the next few days then near normal beyond:


Alright, enjoy those early berries!


Big Hail Today; More Warm Weather Ahead

May 5, 2016

Another round of thunderstorms today across Eastern Oregon produced a couple severe thunderstorm warnings in the Grande Ronde Valley.  Here’s a pic from Jada Follett, from the Cove area just east of La Grande:


Looks like a bit larger than quarter size, maybe half-dollar.  That would be 1.25″

Tomorrow we’ll see more thunderstorms, but the action should stay farther south.  Let’s say a line from Bend to Ontario and spots to the south.  I don’t think it’ll be very active around La Grande and Pendleton.

We sure are going to warm up the next two days as high pressure noses in overhead and weak offshore flow develops at the surface.  Check out the cross-section from the WRF-GFS for the next 3.5 days.  Time goes from RIGHT to LEFT. Capture  It’s interesting that we get the weak offshore flow around 2-5,000′, but it’ll stay northerly down here at the surface.  That plus 850mb temps not going too wild (+15) means we probably won’t get much above 80.  We’ll see.  Definitely not above 85 degrees.


By Saturday evening a strong onshore flow is developing as an upper-level disturbance comes scooting down through British Columbia.  That gives us a cool/drizzly start Mother’s Day morning, then partly cloudy PM weather.  So yes, you still get some decent weather Sunday afternoon for Mom!

After that trough moves east, upper-level ridging returns for much of next work week…our endlessly warm April/May continues.  Check out the GFS meteogram from this evening’s run, looks more like July with very warm to hot temperatures for an extended period.



The 18z GEFS ensembles were a bit more reasonable, but still show above normal temperatures for at least the next 2 weeks.  Amazing…I’m going to plant my warm weather veggies…it’s time.  Very early for my foothills location where it’s cooler than down in the city.


Enjoy the warm weather the next two days!

Chief Meteorologist Mark Nelsen



A Very Early Dry Season Start?

May 2, 2016

11pm Monday…

It’s starting to get dry out there…you know that if you’re a gardener like me.  In the past 16 days Portland has seen less than 1″ of rain.  If you add in the much warmer than normal temps, soils are quickly drying out.  Feels more like June…

What’s ahead?  Unfortunately I see drier than normal or even mainly dry conditions over the next 10+ days.  That takes us to mid-May.  Why?  It’s that persistent upper-level ridging over the Western USA we’ve seen off & on this spring.  It is breaking down right now, we get some normal temps midweek along with some showers, then the ridge pops back up over us this weekend and early next week.

Take a look at the GFS rain forecast for Portland for the past 3.5 days. GFS_precip  Each horizontal line is one run of the model out to 10 days, the most recent forecast is at the bottom.  Incredibly dry isn’t it?  Looks more like July.  All models are staying with the “much drier than normal” theme through mid-month…PDX rain for the next 10 days:


Do you realize that 8 monthly record high temperatures have been tied or set in the past two years?  One of those occurred twice (both Oct 2014 & 2015):

AUG 2014
SEPT 2014
OCT 2014
MAR 2015
JUN 2015
OCT 2015
FEB 2016
APR 2016

So when you look at the all-time warmest months here in Portland, 7 of the 12 have occurred in the past two years!  That’s an amazing run of warm weather.  Wow.   A huge climate test will be this fall and winter if/when La Nina conditions take hold.  If we turn cooler than normal with abundant mountain snow that will be great.  If we get a so-so winter with just average winter temps then it’ll be a bit more clear that the warming seen around the globe is beginning to have more of an effect in the Pacific Northwest.  Deep thoughts for 11pm…enjoy the more reasonable temperatures tomorrow!

Chief Meteorologist Mark Nelsen

Record Warm April

May 1, 2016

11pm Sunday…

You just experienced the warmest April we’ve ever seen here in Western Oregon.  That’s assuming you are younger than 80-90 years old.  Here in Portland it was the warmest on record


Those records go back to around 1940.  April 1926 and 1935 were warmer in many places though so in those spots it wasn’t the warmest on record.   Regardless, we are in a 26 month warm period that shows no sign of ending; we’ll see if a possible La Nina this fall/winter puts an end to that (or not).

We broke another record last month in Portland…most days in April above 70 degrees


A strong upper-level high is just to our northeast and tomorrow we’ll be in a southeast flow overhead.  That plus some moisture and some decent instability  mean we COULD get a thunderstorm in the late afternoon or evening in western Oregon.  Models are definitely not as bullish on thunder prospects as they were with the event last week so I’m not quite as wound up about it this go around.

So…we MIGHT see something interesting in the late afternoon and evening so I’ll be watching that radar pretty closely!

Chief Meteorologist Mark Nelsen


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