A La Nina Winter Ahead…What Does It Mean?

Tuesday, November 1st

Everyone keeps asking me (as they should!) what kind of winter we are going to see.  The answer:  I don’t know.

BUT, it appears we have our first “La Nina Winter” on the way in 5 years.  That can give us a few hints, definitely not a forecast, but what direction our winter might be “weighted” toward.  I’ve spent some time looking at past La Nina episodes and what happened here in the Pacific Northwest.  I based all my graphics/research on a weak-moderate event.   Right now the Oceanic Nino Index (or ONI) is in the WEAK La Nina category, which means the average of the past three months is right on the edge of “La Nina conditions”.  Once October is added in and July subtracted in a few days, we’ll be well into WEAK category.

marklanina_thebasics

 

Model consensus says we’ll likely be in a WEAK-MODERATE category during this upcoming winter.  Here’s the latest plume of ocean/atmosphere models:

capture

Typically in these winters there are 3 effects observed to varying degrees:

  1. The north Pacific jet stream tends to be more “wavy” which means there is more of a north & south component to the jet instead of travelling straight west to east
  2. There is increased tendency for blocking somewhere in the east Pacific
  3. As a result there is sometimes more interaction of the cold Canadian air to the east and Pacific moisture with the jet stream weakening dramatically at times too.

 

Likely Effects This Winter in Our Area:

1.  Rainfall

marklanina_pacificnorthwesteffects

I think it’s unlikely that we’ll have a drought winter; but far more likely precipitation will be above average.  La Nina winters in the Pacific Northwest are dominated by a strong jet bringing frequent disturbances across the region, interspersed with sudden ridging or northerly flow.   Then it’s back to the westerly flow.  For this reason they tend to be wet.  Likely the #1 most noticeable event in these winters.

1a.  Flooding

This actually goes with the rainfall.  For obvious reasons we tend to have more flooding events in winter due to the wetter weather.

2.  Mountain Snow

marklanina_snowmthood

Lots of precipitation and cool weather systems = tons of mountain snow.  This is probably the #2 most likely event.  9 out of 14 weak-moderate La Nina winters have brought above normal snow to ALL elevations in the Cascades.  That’s opposed to last year’s warmer storms that brought okay snow up high, but terrible conditions again below 4,000′.    Note that there CAN be a bad year, but it’s quite rare…see 2000-2001 below.

marklanina_snowmthood2

3.  Foothill Snow

This happened in several of the past La Nina winters…significant snow to lower elevations (1,000′-2000′).  This MAY happen again if we get a succession of cold and wet systems coming in from the west and northwest.  Of course these are the same systems that give forecasters headaches because then snow it quite close to the Valley floor multiple times during the season.  News people get really excited about it too.  I live at 1,000′ east of Corbett and it’s pretty obvious the last 3 La Ninas were decent snow producers…highlighted in yellow

capture

For you folks that live in the western Gorge…interesting to note less freezing rain in La Nina winters isn’t it?  More on that below in the “Portland Snow” section.

4.  Wind Storm

We are overdue for a regionwide major windstorm here in the Pacific Northwest.  The last BIG one was December 1995.  That’s 21 years ago!  14 years before that we had the major November 1981 storm.  It’s interesting that all those La Ninas from 1950 to the mid 70s had a wind gust of 60+ mph at PDX each time!  Not as frequent since that time though.

5.  Extreme Cold Snap

marklanina_coldpdx

marklanina_coldpdx2

This is definitely not a guarantee, but we have a higher likelihood of a severe cold spell (arctic blast, like last December) during a La Nina winter.  That’s because we occasionally have the flow come down from the north.  BUT, the 3 most recent weak-moderate La Nina winters have NOT seen a cold blast (11-12, 07-08, 00-01).

6.  Portland Snow/Ice

marklanina_snowpdx

This one is tough.  Anyone who says a La Nina winter means lots of snow in Portland is mistaken.  Average snowfall in weak-moderate La Ninas DOES go up a bit, but not a dramatic increase.  What I find interesting is that no La Nina in the last 30 years has produced a major snowfall here in Portland.  Of course you couldn’t say the same thing about 1989 down the Valley and up into Washington, but I’m just talking about right here in the metro area.   I should point out that the “cool/wet” La Nina winters (such as the last one) often produce little freezing rain because we don’t get as many inversion episodes to our east, which means less east wind in the Gorge.  We need that for a good ice storm either in the Gorge OR in Portland.

7. Gorge Wind

Most La Nina winters tend to have less east wind through the Gorge during the winter season.  That’s because the strong easterly flow is mainly caused by stagnant high pressure sitting east of the Cascades during slow weather periods (upper-level highs overhead or split flow patterns).  During winters (like 07-08) we don’t get long periods of inversions due to frequent passage of cold fronts and low pressure centers.  I remember the winter of 98-99 (or maybe it was 99-00) was real quiet out in the Gorge too.  That said, when we DO get a big blast of cold air, we can get very strong easterly flow during the cold spell if a warm system approaches from the southwest.

ADDITIONAL THOUGHTS:

The elephant in the living room I suppose is the fact that our winters are gradually warming, and snow in Portland is definitely more rare than it used to be.  Snow each decade since the airport observations started about 1940:

snow_pdx

And downtown records that go back to the late 1800s.  The low spot in the 80s is missing some data…it should be about 15″ higher:

snow_downtown

 

We have always been in a marginal snow climate, but now warming temps are cutting off even more of the winter snow.  Every few winters we get 1 good snowstorm and we all remember that event.  Remember 2008-2009’s record snowiest December ever?  It only went on for 10 days or so, then not much happened the rest of the winter.  That’s how it works here most of the time.

We’ll see how the winter turns out…my money is on “wet” and “Cascade snow”.

Chief Meteorologist Mark Nelsen

 ADDITIONAL LINKS:


1. List of ONI values by season (Historical La Nina & El Nino Episodes)

2. Latest MEI discussion by Klaus Wolter

3. My presentation at Oct. 2016 AMS Winter Weather Conference…LOTS of graphics!

61 Responses to A La Nina Winter Ahead…What Does It Mean?

  1. Boydo3 N. Albany says:

    Last night when the election returns were just beginning to come in I switched to the Weather Channel. IT WAS GREAT!! They had on what they called “escape from the election”. It was just nice, mellow music and cool scenery. Nothing else.

  2. jim says:

    Lowering snow levels next week. Let’s get this blog going!

  3. Scooter says:

    Roland, I hope you have room for some of us rational folks that might need to emigrate to save our sanity during the next 4 years of rule under Heir Hottel!

  4. Nathan Place says:

    Record warm temps are coming today and possible Thursday. Sounds good to me.

  5. Andy says:

    How funny how so many think we will have no winter…we will see seasonal changes in the coming weeks.. this winter should be different than last. We are coming out of one of the strongest El Nino on record. Past warm periods translate into cool periods if you look at long term records. I had lows in the 30s in October here in Jefferson area…I still have hope for a more average winter.

    • It’s not worth getting worked up over other people’s inverse wishcasting (which as I already posted is itself a form of wishcasting).

      It’s also been already observed in this thread that the 08/09 season started out with a very mild November (and early December). And many a overall dry El Nino winter has started out wet. How a winter storm season starts doesn’t say much about how the season as a whole turns out.

    • Boydo3 N. Albany says:

      Right on Rube! One month’s weather is no indicator of the rest of the season.
      I remember working on a house we had bought sometime in the late 80s. Cleaning up the mess of the previous owner taking a break in the back yard on a warm and sunny early February day. Commeting on what nice weather it was…
      A week later we had 10″ of snow on the ground that stuck around under clear and cold conditions for nearly two weeks.

    • Nathan Place says:

      This just in from NOAA winter cancelled!!!!!

  6. I got 1.45″ of rain yesterday. I believe this is the fifth time this fall I have had an inch or more in 24 hours.

  7. GFS 10-16 day just caught a whiff of something a bit more seasonal.

    • Scooter says:

      OK, time will tell, you know the crystal ball gets kind of foggy this time of year.

    • That’s good- I’m getting tired of reading all about these “non-winter” predictions. My previous experience has taught me that a warmer than normal November(and the opposite) is no reliable indicator of what’s ahead.

  8. Windsday says:

    Imagine if due to various little things going on which I won’t get into cause this to be our new normal?

    First immediate effect would and likely is screwing the models around that rely on a mix of the old data sets for analogue years to forecast in the long range which will all be thrown out the window.

    Hence the no less then 45F nights however that is stretching it.

    In Demember/January we will likely see nights go to 35F or so several times even if the current pattern remains unchanged whenever it clears out of course.

    When it’s cloudy those 45 and > nights will be our new reality with constant highs around the 65-70F range dropping down to 55-60 in December and 50-55 in January?

    A lot of our record highs in December/January are in the upper 50s/low 60s.

  9. Let’s hear it for this amazing warm November weather! Temps 65-70 most places for 2 or 3 days straight. A real ‘Saint Martin’s Summer’ pattern this year 😉

  10. JJ78259 says:

    Nice looking storm heading in on the satellite picture pretty impressive.

  11. I saw a low of 41F this morning, so that ‘s below 45F. (and I was already down to 36 a couple of times last month). Look- don’t base a prediction for the winter from a mild November. Everyone remembers November 2008. It was mild. Even the first several days of December 2008. Then we know what came next.

  12. Jake-(Gresham) says:

    I will count today and tomorrow’s sunny forecast paramount for vitamin D before we go into solitary confinement. I mean a rainy season till May. I mean both. I mean we all have to pull together on this. I mean.

    I’ll just go make the hot chocolate. Shoot.

  13. Its interesting that PDX lopped off nearly 100 inches of snow on average between the 1870s and 1940s. I’m inclined to think this change was non-AGW related. I’m not discounting human affects on the atmosphere but this drastic change seems to have predated the aggregate global human impact we see today. I think something else was driving this change.

  14. Lee Wilson says:

    I here by predict a year with out a real winter.
    No Snow in any lower elevations.
    We will not fall below 45 at night and we will see temps in the 60’s as a new normal.

    better get more flea pills for you animals and lee spray, they won’t be dying anytime soon.

    This is my prediction
    lower snow packs as well.

    I hope to be wrong.
    But in this case, I am going with out science and on a pure gut instinct.

    0 chance for a white Christmas.

  15. runrain says:

    I just read that Phoenix hit 100 deg last week (Oct 27), which is the latest in the season it has ever hit 100 there. Also, Meridian, Mississippi had a record number of 90+ days this summer – 128 days! I’m sure they were humid ones too!

    • Paul D says:

      This is not the global warming you’re looking for 🙂

    • JJ78259 says:

      It was a nice warm summer in San Antonio plenty of Weather Dan Weather clear into November! Looking forward to cold winter days in the mid 70s with La Niña.

    • Paul D says:

      “cold” and “mid-70’s” don’t go together 🙂

    • runrain says:

      I wonder who the San Antonio is trying to make feel bad. More likely he is extremely remorseful about having to leave paradise for dry Texas.

    • JJ78259 says:

      Not remorseful at all Runrain. I have never been happier being able to be sitting outside in shorts and a tee shirt with the neighbors on the 3rd day of November at 9pm works for me. I really like the warmth. Won’t go back to the long cold grey winters. I was there for over 50 years I couldn’t handle a month of straight rain again let alone 5 or 6. I am glad you enjoy that.

    • runrain says:

      Eh, the rain is a tiny piece of it. Such a price to pay , that move just for some warm weather! I find an occasional sun break or two in the winter solves all that.

    • …pretty lame trolling attempt, “scooter”; i give it a d- …

  16. muxpux (Longview) says:

    When you talk about Portland snow, how much of that is skewed because of the gorge? You noted freezing rain, but I recall many events growing up, getting ready for school in Longview, 35 and raining, while all over the Portland news was how snowy it was and all the schools that were cancelled. I know those are similar to ice storm setups, but I know the gorge kinda messes with Portlands numbers.

  17. Like Rubus, I’m expecting one arctic event this winter. It could longer than a week, but no record low temperatures.

    • Nathan Place says:

      If 45 is arctic than ya i guess we might get one. Its going to be a warm boring winter.

    • W7ENK says:

      Man, and y’all though I was a Debbie Downer… Sheesh!!

      You see, folks, this right here is the difference between a realist (me) and a true pessimist:

      A realist sees a situation, takes into consideration all relevant data — regardless of which outcome they “want” — and comes up with a logical probability based on that unbiased data, leaving emotion to the side. Mark is really good at doing this, which is why he always tends to adhere to a more conservative forecasting style, he doesn’t stick his neck out there too far, and frequently chooses to “play it safe” when it comes right down to it, especially with tricky forecasts. I’d assume it’s also why Mark doesn’t like to make forecasts three or four months in advance.

      A pessimist sees a situation and automatically assumes the worst possible outcome, touts it as the God-given gospel, and stands unwavering in their dissent, regardless of any data or real possibility to the contrary. Three, four, twelve months ahead, it doesn’t matter how far out there it may be, they just spout off with reactionary pessimistic garbage without any logic, or even forethought put behind it.

      In other words, a realist keeps it real, whereas a pessimist does nothing more than talk out an ill-informed hole. I’ll let you use your imaginations to decide which hole that might be…

    • Nathan Place says:

      Easy tiger you may get a 40 degree night, my bad. Sour grapes geez.

    • Expecting no arctic blasts in an La Nada to weak La Niña year, when on average there seems to be just under 1.0 such event per winter, and on average neutral to negative years are somewhat favored for below-normal temperatures here, is indeed being illogically pessimistic.

      Now, if mid-February rolls around and there’s been no arctic blast, and there’s a Death Ridge firmly locked in place, then it’s time to throw in the towel on there being an arctic blast. But in early November? Way, way, way too early for that.

    • I’ve never seen a November where I didn’t at least get one temperature below freezing, so yes, not seeing anything below 45F this winter is unlikely in the extreme. The last few La Ninas have been disappointing as far as snow down in the city goes, but I’m still holding out hope for this winter.

    • Dave_in_Troutdale says:

      Erik, is it the dirt road hole?

    • W7ENK says:

      If that’s where your imagination led you Dave, then yes, absolutely.

  18. Scooter says:

    I predict rainy cloudy blustery days with some sunshine and a few snowflakes, no arctic blasts.

  19. W7ENK says:

    ENSO 3.4 Region is in Negative-Neutral territory, and has been for the last several weeks, though it’s finally starting to dip back down toward Weak-Niña land.

    Latest measurement this week was –0.49C, which doesn’t quite start the countdown toward an official La Niña… remember, 5 consecutive months at or below –0.50C required before it’s official.

  20. Benjamin (West Salem) says:

    I think even people who live at the 500′ elevation have a good shot at seeing lots of snow this winter. Winter of 07/08 gave about 11 inches at my Grandma’s house in South Salem. Winter of 2011/2012 she had over a foot with most of it falling in March of all months, but she also got about 3 inches in the heavy snow showers that rolled in one Tuesday morning before the big rainstorms hit in January that year. Not really making any specific point except that like with any winter, location can be everything. Imagine what PDX’s snow total could have been if the big March snowstorm of 2012 had taken place 100 miles further north???

    And thanks for the update!!! Either way, I think it should be an interesting winter.

  21. Windsday says:

    We likely used up our quota of cold weather in this warming climate during the late summer and early fall period. That was our winter which we now have to make up in + departures to balance that out.

    It wasn’t all that cool to begin with down here in the valley except maybe one or two of the cool waves we had in September.

    • What recent cold weather? Overall, there really hasn’t really been much of any, thanks largely to The Blob. For August-October in Seattle (I doubt PDX is that much different), departures in degrees F are: +2.6, -0.1, +2.0. September’s departure was so minuscule that it’s effectively a normal month. And August and October were both significantly warmer than normal, so overall we’ve still been above normal in recent months.

  22. Boydo3 N. Albany says:

    Great info! Fair and balanced 😉
    But it is noteworthy that some of our snowier winters aren’t always associated with La Nina as per three winters ago when the central and south valley scored big.
    I’m also wondering how this October’s big rainfall relates to cold winters in the past that also were preceeded by a wet Fall. I guess its time to do a little research..

  23. JohnD says:

    Thank you Mark. Excellent and detailed rendition, as always. Sad about the continued overall low elevation winter downward trends. Still–amid the odds–we can always hope for an anomalous season, given the volatility in a tropical “La Nina” winter!

  24. Maybe I’m remembering wrong. I moved here in 1976 when I was 13. I remember from then through most of the early 80’s very little snow and lots of rain. I do remember one snow event so we could build a snowman, and an ice storm in 1980/81. But other than that it was mostly warmer with a lot of rain, very little snow. Right now our winters are reminding me of those years. I don’t remember having a lot of snow until the mid-late 90’s.

  25. Anonymous says:

    Wonderful blog. I’m curious how many days per year does the heavy east wind blow through the Gorge each winter?

  26. MasterNate says:

    WOW!! You really outdid yourself on your post. Thank you for all that information you provided. Nothing is guaranteed but chances are higher for some action this winter. I’m excited and looking forward to the winter season.

    • MasterNate says:

      I’m a little frustrated by all the October Rain though!! Makes season ending farming activities much more difficult.

    • Mark Nelsen says:

      Yes, it’s been terrible. On the bright side, excellent to see 2-4″ in the desert regions of Eastern Oregon this month!

    • High Desert Mat says:

      Thanks for the post Mark. Very detailed and informative as always. And yes, it has been very wet on this of the mountains. I’m ready for a little respite before the real cold comes soon enough.

    • The central/eastern Gorge looks almost more like early spring than it does autumn, due to all the rainfall we’ve had. Normally it gets too cold and dark before there’s enough soil moisture for any kind of green growth. This year the rains came early, while there was still enough warmth and light to provoke a “second spring” into life.

    • Mark Nelsen says:

      Assuming winter and spring are somewhat normal rain-wise, I wonder if that’ll lead to an explosive wildflower season in April/May?

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