Happy Halloween! First Week of November = Calm Weather

October 31, 2018

7:30pm Wednesday…

Right now little kids are running out and about, collecting large bags of candy.  Lots of fun, but my kids are all grown up so I like to work Halloween.  Plus coworkers brought in treats!  Radar shows just about all the rain is up against the Cascade foothills and in the Cascades.  Whew…a mainly dry Halloween for lowland kids.

November arrives in just a few hours!  Typically November-February is the core of our “storm season” in the Pacific Northwest.  By that I mean that most of our windy systems, heavy rains, & all-around “busy weather days” happen during this period.  But for at least the first 10 days of this November that won’t be the case.  Why?  Take a look at the 500 millibar map for right now…an upper-level ridge just offshore.

Jet Stream Forecast 2017a

This weakens systems, allowing just lots of clouds and occasional rain into the Pacific Northwest.  The general pattern continues for at least the next week.  Here’s NEXT Wednesday

Jet Stream Forecast 2017.png

So for weather geeks like me it appears this first part of our stormy season will be a bit slow.  Interesting to note that the El Nino year of 2002-2003 was very similar.  A weak ridge kept popping up off/on through the winter.

The ECMWF ensemble forecast for rainfall the next 15 days shows a slow accumulation. Those are 24 hour totals.  A system comes through Friday morning and again Sunday.  Then maybe something more organized about a week later.


Snow has changed to rain in the Cascades as well today, Timberline and Meadows have picked up at least 1.50-2.00″ rainfall already.  I don’t see any sign of significant snow accumulation the first 10 days of the month either under this mild pattern.  October ended up snow-free at Government Camp, but that’s not unusual at all

Snow October Govt Camp 2017

To summarize:

  1. The next week will be wet at times, but plenty of dry periods too
  2. Temperatures remain near to above normal during the first week of November
  3. No sign of a stormy Pacific jet stream sending bigger weather action our way, pretty quiet weatherwise
  4. There won’t be an early opening of Cascade ski resorts this year.  At least not in the first 10 days of November

If you are a skier or snowboarder, there’s no reason to freak out.  I’ve seen LOTS of years where nothing happens early in November.  Then suddenly we get feet of snow for a week which opens up the resorts.  We’ll see how things go.

Chief Meteorologist Mark Nelsen

More Tornadoes Today; It IS “Tornado Season”

October 29, 2018

9:30pm Monday…

We had a bit less instability in the atmosphere overhead today, leading to the theory that the weather would be a bit calmer.  That more or less happened…until one, or more likely two, tornadoes briefly touched down west of the Cascades.  Once again these were very weak.  The first prompted a tornado warning about 3:40pm for far southern Marion County around Jefferson/Marion/Scio areas.  The tornado was seen on the ground briefly and we received a couple videos of the rotating funnel cloud too.  The NWS just happened to have a storm spotter class in Scio tonight, how convenient!  It turns out one sign was damaged and there was some tree damage as well.

The 2nd event was about one hour earlier.  A farmer a few miles north of Forest Grove saw a (likely) tornado’s wind touch down over his pond, pulling up water.  Then it damaged/destroyed several greenhouse structures; at that point he headed inside.  Here are some pics of that damage, the sky view is after it had moved off to the east.  Thanks to Jim Roofener for the pics:

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It was too dark for the NWS to conduct a storm survey on this one so we’ll find out if it was officially a tornado tomorrow.  UPDATE:  NWS confirmed on the morning of October 30th that it was an EF-0 tornado.

One question people ask me is why we typically don’t see these on radar?  Two reasons, one is that these “storms” are very weak.  Rotation and updrafts are nothing like we get with real tornadoes.  The other is distance from the radar site.  For example that Marion County tornado is about 70 miles from the radar site, so the lowest beam is at least 8,000′ overhead.  Much of the rotation could be below the beam and not able to be seen from that far away.

Tornado Why We Cant See Eugene

Of course the (likely but not confirmed) Forest Grove tornado was quite close to the Dixie Mountain radar site.  That said, I still didn’t see anything that stuck out.  That tells me it was very weak and even the bulk of that one may have been below the 2-3,000′ high radar beam.

Wayne Garcia came up to me and asked if this is a typical time for a tornado around here.  I’ve always know that the spring/fall seasons seem to be best.  So I pulled out the storm reports and started counting…

I checked all tornado reports in Western Oregon and 5 SW Washington counties (including Lewis County) from 1950 to this year.   I count 88 tornadoes, including the three (likely) this week.  Now check out the monthly breakdown

Tornado Season Stats

Yes, there sure is a tornado season, or maybe we should say “seasons”.  Spring and Fall.  They are rare in mid-summer and mid-winter.  October is sure a favored month isn’t it?  These are the seasons when we have the most vigorous “cold” showers and lots of mixing/instability. Interesting eh?

Now I call it “tornado season”, but those tornadoes often come in batches.  For example in Oregon, here are the last few years when we had a tornado in October:

2018, 2017, 2016, 2010, 2009, 2000.  So we can go numerous years without an October tornado; it’s not a yearly event.  But far less unusual than many of you think!

Chief Meteorologist Mark Nelsen

One Strange Tornado: EF-0 In North Portland Today

October 28, 2018

10pm Sunday…

An EF-0 tornado today brought mainly minor damage along a 1 mile or so path at 3pm.

Tornado Ground Track

Here’s the weirdest part…with every other tornado (even when out in rural areas) we get a bunch of emails/calls or social media posts to the newsroom.  This time it was only ONE.  That’s it.  Apparently no one else noticed a tornado passing overhead.  I didn’t see any media tweets or social media postings until the NWS put out the storm report just before 8pm.

First damage was observed near Portland Meadows and last damage was found along the Columbia River at Marine Drive & 6th. A viewer also sent us video of the funnel cloud still rotating over south Vancouver after crossing the Columbia River.

Tornado Today Stats

Here’s one of the semi trailers tipped over.  This is just behind the Jubitz Truck Stop area.


Thanks to Larry Miller for the pic (not the Larry that lives in Cove)

Here’s a bit more detail on the damage from the Portland National Weather Service


This is the one and only tornado in Oregon OR Washington this year.

2017 saw 5 tornadoes in the two states.  That was Bend, Aurora, and Lacomb Oregon.

2016 saw 7, including 4 in Oregon.  Those were in Wheeler & Wallowa counties, Manzanita, & Oceanside.

Other than the tornado, today’s forecast turned out just like expected.  Lots of downpours, then hail, thunder, and sunshine.  Sometimes all of them within a 5 minute period too!

Tomorrow should be a bit tamer, although we’ll still have some downpours.

Up in the mountains it’s snowing for the first time in 3 weeks.  It appears about 2″ has fallen at Timberline.  There could be another 3-6″ before it dries out tomorrow night up there.  Passes will remain clear though.

Snow MtHood Outlook

Chief Meteorologist Mark Nelsen


Thunderstorms In Metro Area

October 28, 2018

1pm Sunday…

As expected it’s turning into a wild weather day for some.  An unstable atmosphere overhead with plenty of morning sunbreaks and “heating” has allowed a few thunderstorms to pop up.  Generally they are moving from southwest to northeast.   This IS the type of pattern where we can get a funnel cloud so keep an eye to the sky…otherwise enjoy the downpours and show!

web_metroradar (1)

Chief Meteorologist Mark Nelsen


October 26, 2018
Hey folks,
It’s time again for the annual Winter Weather Forecast Conference at OMSI.  It’s coming up tomorrow at OMSI.  I’ll be presenting my usual recap of the past winter.
Mark OMSI Forecast Meeting Promo
All the details are on this media release from Oregon Chapter AMS:

26th Annual Winter Weather Forecast Conference

The Oregon Chapter of the American Meteorological Society (AMS) will host the 26th annual “Winter Weather Forecast Conference” on Saturday, October 27th @ 10 AM @ OMSI in Portland. Meteorologists from across the Pacific Northwest will once again converge on Portland to give their annual forecasts for the upcoming winter to a capacity crowd of nearly 300 attendeesWhat lies ahead this winter with the likely return of El Nino? Come hear the latest details. The Oregon AMS chapter will also be raffling off a $200 voucher to the Tolovana Inn Resort in Cannon Beach, along with a $300 Davis home weather station. This meeting is free and open to all ages of the general public.   

What: 26th Annual Winter Weather Forecast Conference
When: Saturday, October 27th 2018 @ 10 AM.
Where: Oregon Museum of Science and Industry (OMSI) main auditorium, 1945 S.E. Water Ave. in Portland.  
Meeting and parking cost: This meeting is free and open to all ages of the general public. Free parking in all OMSI parking lots.
Agenda: Meteorologists from across the Pacific Northwest will once again give their weather forecasts for the upcoming winter

Who is the Oregon AMS? The Oregon chapter of the American Meteorological Society (AMS) was founded in 1947 and is the single largest local chapter of the American Meteorological Society (AMS) in the country, with approx. 180 members. The Oregon AMS chapter normally hosts meetings from September to May that are free and open to all ages of the general public. The Oregon AMS welcomes the public to become chapter members for just $10 per year. The Oregon AMS chapter mission statement reads, “The purpose of this society shall be to advance professional ideals in the science of meteorology and to promote the development, exchange, and application of meteorological knowledge.” Our meetings are always found on our web site: http://www.ametsoc.org/chapters/oregon

Wet Season Arriving

October 25, 2018

6pm Thursday…

When I think of typical October weather, today would pretty much cover it.  Not a real soaker, but gray and rainy at times.  We’ve picked up about a quarter-inch of rain so far in much of the metro area:

Rain Metro Today Databound

I’ve been expecting a decent amount of rain during the next week, but models are a bit wetter today.  Check out the 7 Day precipitation forecast from the ECMWF, that’s through next Thursday

ECMWF Precipitation Accumulation

Pretty wet!  If this occurs, October will go down as a wet one even though we had two weeks of sunshine in the middle of the month.  This points out how things can change quickly in late October as the wet season arrives.  Notice a few spots in the Coast and Cascade ranges with 6-8″ of rain; this will provide the final soaking to finish off what was left of this fire season.

Sunday could be a particularly active weather day with frequent showers, downpours, and thunder/hail.  It’s a cool and unstable airmass moving overhead that day.  By Monday morning we’re back to that chilly airmass we saw in early October; expect snow down below Timberline Lodge but not quite sticking to the passes.  You see the dip in snow level here:

ECMWF Snow Level From 850mb Temps LONG TERM

By the middle of next week strong high pressure offshore will somewhat shut down the rainfall, or at least slow it to a trickle as we enter November.  One weak system will slide over the ridge on Halloween and that COULD give us a rare wet Halloween evening, we’ll see.  Most of the past 15 years we’ve seen dry conditions during that critical Trick-or-Treat time 5-8pm.

Halloween Weather History

Looking farther ahead, the weather pattern still looks mild and slow later next week and that first weekend of November.  You see the upper-level ridging and mild conditions on the ECMWF ensemble 500mb heights on Saturday the 3rd


There are hints of a cooler pattern just beyond that, maybe 12-14 days from now.  We’ll see, that’s a long way off.  For now I’m still confident that we don’t see a stormy pattern through the first week of November.

Chief Meteorologist Mark Nelsen

Ski Season Update, El Nino, & The Blob Returns

October 24, 2018

8pm Wednesday…

We have an easy week here at FOX12.  That’s not just due to the slow weather, but 5 nights with no early shows due to the World Series and Thursday Night Football. So what else would a weather geek do except plug some numbers into a spreadsheet and make some graphs?

2 weeks ago I posted my thoughts about this upcoming “El Nino” winter, that’s up above on the tab titled WINTER 2018-19 THOUGHTS.   Nothing has changed since that time, except that it seems to be even more a likelihood that we’re entering this kind of winter.  Note the increasing sea surface temperatures the past few weeks (right side graphs)



There is a section in there about ski area conditions during this type of winter that includes this chart


The key points?

  1. El Nino winters are rarely “ski disasters”
  4. El Nino winters are often more reasonable up above 5,000′ or so.

But tonight I wondered what happens EARLY in the ski season.

We’re talking November and December.  My conventional thinking in the past has been that many El Nino winters “begin with a bang”, like Nov/Dec 2006.  Then they often peter out to mild/dry or mild/wet after the New Year.  Apparently that’s not the case much of the time.

Let’s take the last 16 El Nino seasons.  That is my entire lifetime, back to 1969 (getting old).  I totalled November & December snow totals at Government Camp (~4,000′).

The long-term average for these two months is 87″ (35″ in November & 52″ in December)

But during El Nino seasons the average is significantly lower…just 57″, that’s the lower dashed line.  The key message is that in 10 out of 16 years, snowfall was well below average during the first two months of the wet season.

ElNino_November-December Govt Camp Snow

By the way, here’s November 19th snow depth on Mt. Hood near the bottom of Timberline’s Pucci Chairlift for the past 9 winters.  Last year was great…until a pineapple express melted much of that 34″ just before Thanksgiving.  That delayed ski area openings a bit.

Mark Mt Hood Snowpack November

On that chart above you might be wondering what the “M” refers to on some of those years?  Those were “El Nino Modoki” years, where the warm pool of water in the tropical Pacific was centered farther west.  It has been documented that these Modoki events produce different effects over the mid-latitudes than a “typical” El Nino.  Here’s a nice visual showing the difference between the two “flavors” of El Nino:

ElNino_Modoki_SST Look

And here is what we have right now


It sure looks more like a Modoki flavor of El Nino doesn’t it?  That said, I don’t see much real correlation between the early part of Modoki ski seasons and low snow totals.

Of course what really sticks out on that sea surface temp chart is the return of “THE BLOB”.  Take a look at all the “warm” water in the Eastern Pacific!  The past two months have seen a rapid development of “The Blob v2”.  You may remember that for about 18 months in 2014-15 we had a large blob of warm water offshore.  This is what it looked like in March 2015


a closer look at what we have right now…


This time the blob is slightly farther to the west, although it has moved closer to us recently…here’s one month ago


What does an El Nino winter plus tons of “warm” water to our west mean?  I don’t think anyone really knows the answer.  But I don’t think it’s good if you want a cold/wet winter with lots of mountain snowfall.  It COULD be a difficult winter ahead for the ski resorts.  Regardless, I’m going for a season pass for one family member anyway.  Except in the very few bad years, EVERY winter has decent ski conditions off/on through the season.  We’ll see how it goes.

Chief Meteorologist Mark Nelsen