The Vanport Flood: 68 Years Ago Today

May 30, 2016

68 years ago today, what was once Oregon’s 2nd largest city was erased from the map in hours.  If you’ve never heard of the Vanport Flood, read on…it only happened 5 miles from downtown Portland.

( This post is a repeat from May 2011, just a few small updates)

I love weather AND history, so I find this flood fascinating, especially since it’s results echo through Portland even in 2011.

I’ll be brief, since it’s a long story.

During World War II (1940-45), huge numbers of workers were brought in to work in the shipyards here in Portland.  There was an urgent need for housing, so a city was quickly built and called VANPORT (Vancouver+Portland) on the flats north of Portland.  That’s the low area west of I-5 around Delta Park where PIR, Heron Lakes, and Delta Park West is now.  That city contained 40,000 at it’s peak, making it the 2nd largest city in the state!

After the war, lots of folks moved away, but there were still around 13,000+ residents there by the Spring of 1948, three years after the war ended.  Even a college had opened in the city for the returning GI’s…the Vanport College.

The winter of 1947-48 brought massive snowfall to the mountains of the Pacific Northwest and Rockies, along with lots of rain.  At this time there were very few dams to hold back spring floods on the Columbia and Snake Rivers…although Grand Coulee and Bonneville Dam both were operational.  The Columbia River rose throughout May 1948 and by Memorial Day Weekend was approaching the 30′ level on the Vancouver gauge.  That’s within 4′ of the all-time high in 1894.  For comparison, that 1948 level is about 14′ higher than the river is right now!  I notice the Portland Housing Authority had put out a notice in the week before saying  “REMEMBER: DIKES ARE SAFE AT PRESENT.

That didn’t happen.  On Memorial Day, May 30th, (used to be on that date instead of the last Monday of May) the railroad dike on the west side of the city (where the railroad is now) burst around 4:20pm.  A 10 foot wall of water went surging into the city.  By sunset the city was inundated and remained so for over a month.  A few factors helped keep the death toll quite low (just 15):  it was the holiday weekend with lots of people out of town and mild temps plus bright daylight kept confusion to a minimum too I suppose.  Here’s the view two weeks later from just about the same vantage point.  Note the triangular are of trees on the edge of the slough in both pictures: 

Interesting to note that the river kept rising, and peaked about the date this picture was taken…at exactly 31′ on the Vancouver gauge.  The flood was the 2nd highest on the Columbia River since record keeping began in the 1800s.

Here are the results:

1. About 1/3 of the residents were of African-American descent; largely settling into north and northeast Portland following the flood.  Lots of  good information about this online which is way out of the scope of a weather blog, but really interesting, especially considering current demographic changes in the area.

2. Vanport College was called “the college that wouldn’t die”, restarted in downtown Portland, and became Portland State University.

3. The town wasn’t rebuilt, but became a raceway, a park, golf course, and wetlands.

4. The Flood Control Act of 1950 spurred more dam building along the Columbia and it’s tributaries, due to the 1948 flood.

Chief Meteorologist Mark Nelsen

Memorial Day Weekend Forecast: Hot Weather Ahead Too

May 26, 2016

9pm Thursday…

We’ve been in a “cool” weather pattern for the past two weeks now.  By “cool” I mean the extremely warm weather that dominated April and the 1st half of May has taken a break.  It’s been replaced by the typical ups and downs we see in May.  I think we have 3 more cool days and then meteorological summer arrives right on schedule, either May 31st or June 1st (or both) we may hit 90 degrees for the first time this season.  We have hit 89 twice and 88 once, but still no 90 at PDX.

In the meantime, we have a little thing called Memorial Day Weekend to observe.  It appears to be similar to last year, maybe a bit warmer.  I expect a few scattered light showers tomorrow and possible again Saturday, otherwise the weekend should be dry south of the Columbia River.  A little better chance of showers remains up in Washington through Saturday.  The Cascades look very chilly tomorrow and Saturday (what else do you expect in May???), then a bit warmer Monday and beyond.  Here are 3 forecasts for the mountains, coast, & central Oregon…click on each for a larger view





Over the past few days models have come around to a very warm/hot pattern in the long range.  Individual model runs have been all over the place with details like which days will be hot and which are more reasonable.  Due to this I am finding ensemble forecasting more and more useful.  That’s when any one model is run with many different “perturbed” variations.  Here is one example, the ECMWF meteogram from the 12z run has a real heatwave over us next week with 4 days around/above 90 degrees.


That’s because it digs an upper-level trough offshore and keeps a hot ridge over us.  I doubted that was correct and sure enough the ECMWF ensemble chart shows that operational run is an “outlier”.


That’s the blue line which is WAY above the red; the average of all the ensembles.  Thus I did not warm temperatures up way into the 90s, but kept temps around 90 for now.  The ensemble average output numbers are far more reasonable:


The GEFS ensembles (GFS ensemble runs) are similar showing a peak temperature Tuesday or Wednesday, then a secondary peak around Sunday the 5th:


Regardless, there is excellent agreement that after 2+ weeks of the cooler weather we are headed back into a much warmer than normal pattern.  After 3 more days of cool-ish weather we’re headed into some unusually warm weather.  This time it’ll be June and it won’t be so strange, not like that 85 degree stuff almost two months ago!

By the way, May will end up a bit drier than normal and there is no big soaking on the way through at least the 5th of June.  Here’s the GFS precip forecast for each run the last 3.5 days:


Chief Meteorologist Mark Nelsen



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