That 18z GFS; The Massive Arctic Outbreak

That was fun eye candy…did everyone see the 18z run of the GFS?  Coldest arctic outbreak across the Pacific Northwest since maybe 1989 or 1990.  And it’s only 13 days away according to that model.  Ha!  I’ll believe that when I see it in the more believable 7-10 day range.  Here’s the 500mb chart at Day 15: 

It’s a massive, sprawling Hudson’s Bay low that shifts westward across Canada, sending cold air down across the northern 1/3 of the USA.    As I said, great eye candy, especially if you look at all the 18z ensemble runs:


Each line represents one of the 21 versions of the 18z GFS run out to 16 days. The blue line is the operational run, showing temperature, in Celsius, at about pass elevations.  For example this model claims the air temperature would be a few degrees below zero up there!  

This run (the maps we see) is out there all alone with the massive surge of cold air.  Several other runs are cooler than average, but none to this extreme. 

For kicks, here’s the 12 ECMWF ensemble plot:

It’s showing lots of runs a bit cooler than average, but none have a big arctic blast.

To wrap it up; it still appears SOMETHING will change in the 2nd half of January, we just can’t say to WHAT and WHEN and if it even involves anything other than slightly wetter and cooler.

Chief Meteorologist Mark Nelsen

71 Responses to That 18z GFS; The Massive Arctic Outbreak

  1. Cap - Hood River says:

    The question I have regarding the same model (GFS) but different times (18z, 00z, etc) is whether the algorithms are the same or not. With such widely fluctuating model results, it’s hard to believe they would be the same. Mark, any idea?

  2. Riding the model spaggeti toward the end of a run is like hanging on to the whipping end of an unsecured spraying firehose.

  3. December 2011 in Vancouver (Minnehaha)
    Highest High: 55.0, 28th
    Lowest Low: 22.4, 13th
    Highest Wind: SSE 30
    Most Precip: 0.58″, 27th

    Total Precip: 2.23″

    Avg High: 44.2
    Avg Low: 31.9
    Mean: 38.1

    2011 PRECIP: 34.35″

    My total precip is a full 10″ below that of my Battle Ground Station.

  4. PaulB/Eugene says:

    after two rounds of model riding…need to look for bodies already. Vodka handy but not yet consumed.

  5. W7ENK says:

    All gone.

    Like we didn’t see that coming, huh?

  6. TAGinGresham says:

    So with all of this flipping and flopping, is it because that is what mother nature is doing, or are the models just crappy? I don’t understand how there can be such extremes in a matter of 6 hours.

    • Mark Nelsen says:

      It’s because it’s so far out in time. You would never see a change from big cold trough to huge ridge over us just 2-3 days away. Minor upper-level changes, but nothing this dramatic.

    • TAGinGresham says:

      So, it’s really nothing to get worked up about (well regardless, weather isn’t something to get worked up about). It just stinks to see those kind of runs switch to such an extreme.

      Was the 18z and the 00z from the same model?

    • Benjamin (West Salem) says:

      It does seem like the GFS has been doing a lot of flipping around for the period of time from the 10th through the 13th. I don’t know what you guys think, but it looks kinda floppy especially for being within the180 hour time frame. Just my thoughts

    • Mark Nelsen says:

      One difference is that the GFS is run 4 times a day, the ECMWF only twice.
      Forecasting was even easier when the GFS (MRF back then) only came out once a day through much of the 1990s. I remember waiting for the 3-7 day maps around 5am each morning when I worked an overnight shift.

  7. PaulB/Eugene says:

    00z GFS has stubborn vortex over AK still at 264…arctic air not going anywhere into USA at that long as it persists….at best arctic will be delayed with this run (await ensembles)…

    • PaulB/Eugene says:

      even at 348 h…vortex over AK and broad ridge over W USA with some arctic over upper midwest..

    • stevied (North Portland) says:

      00z GFS… major flip from 18z… and thus a flop. Nothing interesting again for 384 hours. uuuugh.

  8. steveo says:

    When the next run

  9. PaulB/Eugene says:

    The key with the 18Z run I believe was that it did not form a complex hanging-back low pressure area S of aleutians around days 7 to 8…..allowing trough to progress over the top and dig S, and kept ridge from persisting over the PacNW…

    If 00Z follows suit we are golden for cold I think (at least on this run)

  10. I’ve been splitting wood all evening! I’m not going to be caught unprepared by the arctic blast!

  11. steveo says:

    Oh I hope this works out keep up post updates, love surgery High!

  12. TAGinGresham says:

    So can someone explain the difference between the operationals and the ensembles, and which is considered more accurate? I don’t know how to read the models yet, but I would at least like to understand what you all are referring to.

    Also, what are people talking about when they say thicknesses, and do you want a high number or a low number?

    Last question is, for snow and cold, do we want a trough or a ridge?

    Thanks for the help!

    • Ryan (Walnut Grove) says:

      Theoretically the operational would be the most accurate of the runs. There are 20 ensemble members that run with the GFS and as I understand are different variations of what could happen in the forecast period… the “What If’s” if you would.

      There is also a control run you can look at to determine the reliability of the operational run. If the control is an outlier you can consider the operational to be as such.

      At least this is how I’ve understood it… Someone can correct me if I’m wrong. 🙂

    • Ryan (Walnut Grove) says:

      That should have read:

      “as I understand it the ensembles are different variations of what could happen in the forecast period…”

    • For snow and cold? The position of the ridge needs to be far enough to the west but not too far. The top image of Mark’s post pretty much sums it up. Look for the ridge to our west with the upper flow coming down from the north. Then down comes those nice little lowses brings the snowes. (fantasy at its best)

    • Austin Cornelius says:

      You want a trough for snow. “troughed low” and it’s ALWAYS low numbers here. Atleast that’s what I’ve learned. A ridge is asociated with high pressure. “upper level ridge”

    • Austin cornelius says:

      I’m sorry I was wrong. Someone correctly me.

    • TAGinGresham says:

      Thanks to you both for the explanation. I want to learn these things, but at times it’s overwhelming and easier to come here and read what everyone else has to say!

  13. pdxgeologist says:

    This was on Howard Sheckter’s Mammoth Weather Dweeb page this morning (pre-18z)

    “January 4th update:

    The strato warming event in process is certainly effecting the NH polar regions with the forecasted movement of both PVs. The Dweebs are watching changes that are supported by the GFS ensemble means this morning as well as the ECMWF…

    The movement of the large upper low/polar vortex over Alaska back to Eastern Siberia allows for a significant ridge to develop over the Bering sea and Alaska in the 11-15 day period. This ridge builds into Alaska and far Western Canada and also ensures that the vortex over Eastern Siberia can not progress into Alaska. This is a significant change in the pattern to last December. Additionally, the trend in the phase of the AO and NAO is downward toward neutral by mid month. That as compared to the super positive readings of December and November.”

  14. Yeah, the 18z GFS would equal single digit temps up here. Let see if the 00z is even close to that run. Ensemble spread still pretty large… But I am satisfied that major pattern shift is imminent. Nice to reshuffle the atmospheric deck now and then.

    • Ryan (Walnut Grove) says:

      My money is on what we’ve been seeing the last couple runs with season or slightly cooler than average for 00Z.

  15. halverbk says:

    Interesting YouTube video to boot!

  16. Ryan (Walnut Grove) says:

    One thing is for sure… Both the Gulf of Alaska Low and the Hudson Bay Low are kicking into gear… Lots of cold air building up north.

    I only hope that this time it dumps west instead of east!

    • Joshua in Lake Oswego says:

      Another thing that’s for sure… we will be ice skating across the Willamatte in a couple weeks.

  17. Mark Reschke says:

    Man, I wish I had this job. Something’s coming, but what? Who knows, and it looks like change, but then it again, it may be more of the same. Pay check please.

    Okay, I am just tongue and checking this entirely!

    Mark does a great job and puts a lot of effort into the profession he loves, and he does great forecasting. I’m just sayin’ we’d all love to be able to tell our bosses, “Hey, can’t tell you much beyond next week pal.”

    Imagine if accountants could say “Hey, I was a few thousand off this quarter, but I think next time we may get it a bit closer… maybe not, can’t tell, but were trying.” ; )

    As for the long, long, ultra-long range, it does look like fun. Let’s see a few more models come into alignment in the 10-day or less range and then we can start thinking about our heating bills again.

  18. Jethro (Molalla ~320') says:

    PaulB = prophet

    Glad I took some Dramamine… everybody hold on tight for the 00z! 🙂

  19. Massive Arctic Heartbreak you mean…

  20. PaulO says:

    When Mark says “Massive Arctic Outbreak” I’m in! 🙂

  21. PaulO says:

    When Mark says “Massive Arctic Ourtbreak” I’m in! 🙂

  22. Honestly the 18z is one of the most unlikely looking model runs I’ve ever seen. Hit 59.5 up here at 1600′ today. Rain moved in and the temp is falling off quickly now. 47.8.

  23. W7ENK says:

    Yes, but it’s only one run…

  24. bgb41 says:

    Um, where is the “LIKE” button?

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