A Record Long Growing Season; At Least in One Spot

October 16, 2014

Have you noticed what is missing this October?  Frost!  Not here in the metro area, but elsewhere.  Only the higher parts of Central and Eastern Oregon have seen frost so far.  It hasn’t even been close west of the Cascades.  Considering we have lots more above average nights in our 7 Day Forecast, that means many areas that should have had a frost by now are seeing an unusually long growing season this year.

Tim Dearden from Trout Lake WA (north of Hood River) says there has still been no frost since April 28th at that ~2,000′ location.  He looked up the records and found that Trout Lake Ranger Station is already 15+ days ahead of its longest growing season ever!  He too noticed that nights have been much warmer than normal during the summer and early fall.  If you’ve ever been to Trout Lake, troutlake it should be obvious to you that there is no urban heat island in that location!

Tim took the numbers and plotted out the growing season length over the past 90 years.


Isn’t that interesting?  It appears the growing season IN THAT LOCATION is averaging 2-4 weeks longer than 100 years ago. I don’t have the time to research it, but I’m wondering if it’s mainly the fall dates that are changing the past 30 years at least and not the spring dates.  I was thinking it might be related to summer warmth that seems to be spreading into early fall more often.

I’d love to see how the numbers look for a few other rural locations, like maybe Corvallis, Aurora, or Hillsboro (still mainly rural at airport).  Someone get to work on some spreadsheets!

A Windy Day, And A Tornado That Never Was

October 15, 2014

The gusty southerly wind showed up as expected this morning, with peak gusts in the 25-35 mph range for most of us.  PDX hit 35 mph.  That of course prompted some scattered power outages, but those were pretty much gone by early afternoon.

Around 4pm we got an email from a viewer that thought a tornado may have gone through the part of Woodburn just west of the Outlet Stores.  So we sent a reporter down to check it out.  I assumed it probably wasn’t much, but you never know.  In the past I’ve found that unless several viewers call/email/tweet from a populated area like that, there’s a good chance that it wasn’t a tornado.  So I was surprised when I read two tweets (from other news organizations) that said there was a small tornado in Woodburn.  I said “What?”, fearing I had fallen woefully behind in the information business.  I checked the “pre-2010″ channels of National Weather Service information, which involves checking Public Weather Statements and Storm Reports…Nothing.  So then I went to the “pre-2000″ level…I called the NWS.  Of course they said “What?” too, noting they sent a team down to investigate but as of that time (5pm), there was no tornado.

Sure enough, damage pictures came in from our reporter Laura Rillos…

Woodburn Tornado 3 Woodburn Tornado 1

and showed what the NWS told us in a Tweet around 6pm…”Storm survey concludes down tree limbs on Butteville Rd (west of Woodburn Outlet Mall) was from 30-40mph straight line winds & NOT a tornado

It was just a heavy shower that sent out a strong straight-line wind.  A lot of drama for that, but it sure made two hours of TV pass quickly!

Chief Meteorologist Mark Nelsen

Spaghetti Plots…Storm Approaching Hawaii

October 14, 2014

Tropical Storm Ana is revving up and should become a hurricane within 24 hours.  This storm is forecast to end up somewhere over or quite close to the main Hawaiian Islands.  If a landfall actually happens, as far as I’m aware it will be unprecedented in historical times.  Here is a map showing all the storms that have passed within 75 miles of the main island chain…not as many as you would think:


Of course there is always error, especially 4 days out.  The official CPHC forecast looks like this right now:

MarkTropical_HurricanePacific MarkTropical_HurricanePacific2

But you might find this more interesting…a loop showing all the different model forecasts for where the center of the storm will go.  Each line is one model.

Interesting stuff eh?  Shows you why the forecast track can be so uncertain and also why it’s so important to not focus on a specific track in the middle of the “forecast cone”.  And you can also see why we call these types of charts “Spaghetti Plots”!

So as of right now it might not be a big deal, or it might be a huge storm.  For it to be a big storm, the center has to hit one of those little dots of land!

Chief Meteorologist Mark Nelsen

How Windy Tomorrow? Not a Storm, But Windy

October 14, 2014

We stayed mainly dry in the metro area today since the main rain band with a cold front has been just to our south.  We figured it would be right over us instead.  Nice way to bust a forecast though!

You may have heard rumblings of strong wind coming tonight or Wednesday.  Here’s the latest:

  • A windstorm is not on the way
  • But gusty southerly wind will develop across the western valleys of Oregon/SW Washington and the coastline late tonight and then die down after mid-morning tomorrow
  • Peak gusts 30-35 mph are likely for most of us.  About 5-10 mph stronger than last night’s gusts.
  • 40-45 mph at the Coast
  • This is strong enough for a few limbs to fall since most leaves are still on the trees, of course there will be a few scattered outages.

The NWS issued a Wind Advisory earlier this afternoon for peak wind gusts around 40 mph in the central/north Willamette Valley tomorrow morning.  I think that’s a bit much and 40 mph gusts are a bit high.  I bet PDX ends up with a peak gust 30-35 mph at best.  That said, 30-35 mph gusts in mid October will easily bring down some branches…and lots of leaves!  That means some scattered power outages are possible again like this morning.

Where is the wind coming from?  A surface low or open wave will scoot quickly north along the coastline later tonight and tomorrow morning, giving us the rush of air behind it from the south.  Models are in some disagreement on how much wind we get (lowering my confidence that anything interesting will even happen!).  The NAM has no strong wind at all, the HRRR shows no gusts over 30 mph (or even less) in the Valley:


The ECMWF gives a little more energy to the wave in the afternoon, which means no closed low and not much wind in the morning.  The WRF-GFS is alone showing wind gusts maybe 35-40 mph late tonight and early tomorrow:


Our RPM model looks like this:


That would imply gusts close to 40 mph, but our model almost always is too high…note the text output


With most wind events you can assume this text output is 5-10 mph too high on gusts, so this tells me not much is going to happen tomorrow other than the effects I noted above.

Chief Meteorologist Mark Nelsen

Last Warm & Sunny Day For Awhile

October 13, 2014

5:00pm Monday…

What a spectacular Monday afternoon!  Temperatures have jumped into the mid 70s in the metro area (where the south wind has surfaced).  That’s a good 10 degrees above average and pretty good considering some spots started foggy and chilly.

It’s not really a “storm”…more of a juicy cold front sitting just offshore with the first light rain just moving onto the coastline at this hour.  The front will gradually move inland tonight, giving us a rainy night with some southerly breeze at time.  It doesn’t appear to be a heavy rain producer, but a nice soaking again.  The HRRR model is giving most areas west of the Cascades in the valleys less than 1/2″ rainfall through sunrise.


Beyond that, the front stalls over and west of the Cascades tomorrow, which means frequent showers along with a cooler airmass.  I noticed the Lifted Index is below zero along with some CAPE tomorrow afternoon, so I threw a thunderstorm chance into the forecast.  More showers are likely Wednesday, especially early in the day.

Not so much action Thursday through Sunday with a weak system swinging through Friday night and Saturday morning…timing depends on which model you look at.

On Sunday we get a stronger upper-level high developing just to our east, putting us into a warm (and eventually moist) southwest flow in the upper atmosphere.  As a result I don’t see a setup in the next 7-10 days that would bring anything other than a brief dusting to the higher parts of Timberline and Meadows.

Big picture shows some sort of troughing in the eastern Pacific for the next few weeks, in fact last night’s run of the ECMWF out to 32 days showed off/on wet for quite awhile!





Looking Wet Next Week!

October 9, 2014

3pm Thursday…

A quick addition to yesterday’s post.  Confidence is still very high that a few days of soaking rain start Tuesday…or maybe as early as late Monday evening.  Here’s a nice graphic from the folks at WeatherBell, a great weather data subscription service…worth every penny!  It’s from the morning ECMWF (European) model, widely acknowledged as the best we’ve got on the planet right now.  It’s not always right, but is consistently better than the American models.


The blue bars across the bottom represent rainfall accumulation as we proceed through the next 10 days at PDX.  The green bars show the ENSEMBLE AVERAGE of the same thing.  That’s 51 versions of the same model run averaged together.  You get the idea…the rain gradually adds up after Tuesday.  You can see in two spots the “operational run (blue)” goes a bit higher but ends up almost exactly the same as the ensemble 10 days from now.

The upper part of the chart is pretty isn’t it?  Each row is ONE of the ensembles.  They are all stacked on top of each other.  I often don’t even look at this one except for situations where I’m wondering whether we will get rain at all at a certain time.  OR, there is snowfall version of this chart and you can see how many of the ensembles are generating snow in our area.

As I’m making my forecast this afternoon and I see this, it screams…WET!  The details have been changing, but the models have been consistently forecasting the big move towards our first real wet pattern since spring.  Turn off the sprinklers…

Chief Meteorologist Mark Nelsen

Lots of Rain Coming…Eventually

October 8, 2014

7pm Wednesday…

You can stop watering your lawns/gardens this weekend for the season; I plan to turn off my drip irrigation that goes to my raised beds at home and you can too.

Our forecast has changed a bit over the past 24 hours, mainly removing some rain from Saturday and Monday.  I don’t think a changing weekend forecast in early October is as big a deal as in May though…especially considering we have gone through 5 consecutive warm and mostly sunny weekends.  Public expectations for good weekend weather go downhill quickly in October.  Still, it’s looking like we’ll only see a few sprinkles or showers early Saturday and then dry the rest of the weekend.

Why the changes?  Our upper level ridge wants to briefly bounce back up over us Sunday and Monday between a weak system Friday night and a much wetter westerly jet for Monday night through the end of next week.  You can sure see it on the ECMWF ensemble chart… tseries_850t_000-360_Portland

Note the big (and brief!) spike in 850mb temps later Sunday through early Monday.  Also notice the chilly temps right afterwards.  It’s going to feel like late October the middle of next week!

So enjoy a “bonus” weekend with mainly dry weather.

Even with the delayed start to the rain, it IS on the way.  Take a look at the 10 day forecast from this morning’s ECMWF:


and the 8 day forecast accumulation from the midday (18z) GFS:


They both show a good soaking, at least an inch, and maybe 2 inches in the next 8-10 days.

And this time once the ground gets wet it’s not going to dry much.  I notice with the high humidity and short days this week that my lawn isn’t even close to drying at noon.  And my garden doesn’t even look dry after many days without rain.

Chief Meteorologist Mark Nelsen


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