Winter forecast: If Seattle doesn't get a cold spell, state climatologist will 'eat a bug'
We haven't had a region-wide major lowland snow event in Seattle since January 2012, or even much of an extended cold spell, but maybe we're finally due? And if it doesn't happen again for the 5th winter, maybe we'll get a small consolation prize?
Forecasters with the Seattle office of the National Weather Service held its annual emergency managers and media workshop this week, to go into greater detail of what the winter forecasts are saying so we all know what to expect and keep you all informed.
Most of the focus was on the disappearance of La Nina from the winter forecast and the 90 day forecasts issued by NOAA a little earlier this month showing a warm autumn -- topics I've already covered here in the blog in the past couple of weeks.
The short recap: Earlier forecasts of a La Nina winter -- those are the winters that typically are cooler and wetter than normal with historically good snows -- have waned, and now we're more likely to go into a "neutral" winter of no El Nino nor La Nina.
Neutral winters are bad in the sense that they don't present any steady historical patterns of which to base a good long range forecast like El Nino (warm/dry) and La Nina (cool/wet), and thus the long range forecasts have begun to trend warmer without the cooling influence of La Nina. (Hey, I had no idea I could condense one of my rambling weather blogs into a long sentence! First time for everything...)
Jon Gottschalck with NOAA's Climate Prediction Center added neutral years thus become more sensitive to shorter-term large scale weather pattern influences such as the Madden-Julian Oscillation (MJO -- not named for John Madden, FYI), Arctic Oscillation (AO), North Atlantic Oscillation (NAO) and the Pacific/North American Pattern (PNP).
You've probably never heard of most or any of these -- this is actually fairly recent and ongoing research into discovering other regional large-scale weather patterns that occur on smaller time scales - like days to weeks instead of seasons. And we're still learning if there are ways to unlock codes depending on how all of these patterns interact inside their respective phases to expand long range forecast accuracy.
For example, the MJO is a tropical pattern in which waves of activity form in the far western Pacific, then treks west to east across the entire equatorial Pacific over a 30-60 day period. The pattern varies in intensity -- sometimes it's not there, sometimes it's weak, sometimes it's really raging. But it typically gets enhanced during neutral years with no La Nina or El Nino to get in its way. And Gottschalck says the planet gets more extreme weather -- both ends; stormy and dry -- when the MJO is more active.
Not to get too involved (this blog is stretching into two parts already) but a quick example of how the MJO can affect our weather: Researches have found 8 phases of the MJO when it's active and when it's in phase 1, it's generally cool/wet in the Pacific Northwest, while phases 1,3, and 4 usually mean very rainy weather here, and phase 8 translates to warm and dry. (You can see all 8 phases' correlation on Page 3 of this PDF file.) So they can be like little mini El Nino/La Ninas over a 5 day period. But overall, active MJO periods translate into wetter conditions around here.
RELATED | Find current MJO Forecasts at NOAA
So that can give an example of how neutral winters can really run the gamut with cold stretches, mild stretches, dry stretches, wet stretches and potentially stormy stretches. Sounds like forecasting this winter is like trying to corral a wet cat, eh?
Here's what to expect (And what was about that 'bug' thing in the headline?)
Lo and behold, even in neutral years you can get some ideas of what to expect around here with our major fall and winter headaches of flooding, windstorms, snow (mountain and lowland) and air quality. Washington State Climatologist Nick Bond gave a fantastic presentation showing how each of those events are (or are not) influenced by the large scale La Nina/El Nino patterns. For example, in neutral years, Western Washington is more prone to flooding and windstorms.
Bond provided several slides correlating our frequency of severe weather events to the La Nina/El Nino/neutral pattern. Here are the highlights:
Historically speaking, neutral years tend to bring more frequent strong flooding events.
Here's Bond's chart showing the peak flow reached on the Snoqualmie River near Carnation for each year back to 1950 -- blue dots mean La Nina, red dots mean El Nino and grey dots are neutral years.
It's quite a scatter plot but look at those higher dots and most are neutral years. (And also notice the wide range of flooding Carnation deals with each winter. You're talking a 7-8-times factor in Snoqualmie River flow between quiet years and record years.)
Their flooding forecast: "High probability of major floods" But severe events? They can't predict this far out, but just note some of greatest historical floods have occurred in neutral years.
BE PREPARED | Take Winter By Storm Flood Preparation Checklist
Neutral years have a good news/bad news relationship with windstorms. Strong wind events tend to be most frequent in La Nina years for most spots:
But neutral years have provided just about all of our greatest windstorms. If the windstorm has a name (Columbus Day, Inauguration Day, Hanukkah Eve Storm,etc... ), it happened in a neutral year. Not all neutral winters have brought historical wind storms, but if one's going to happen, it'll likely be in a neutral year such as this.
"We're poised," Bond said. "Nothing is stopping us from having an intense windstorm."
Thus their windstorm forecast: "Hard to say, but possibility of an intense storm."
BE PREPARED | Take Winter By Storm Wind Storm Preparation Checklist
OK, admit it. How many of you just scrolled to this part? (Maybe I should have saved this for the end? I still have a few more after this). While La Nina winters have decent snows and El Nino winters you can pretty much forget about needing your snowman equipment, neutral years kinda run the gamut:
Note the epic 2 week snow of December 2008 was in a similar neutral year that was on the fringe of being La Nina. (Don't ask why no data around 2000. NWS decided for 7 years not to track snowfall. Ugh)
So neutral years have some hope! We'll finally have a snow day at school?
Eh, well, there is the Blob lurking out there. It is expected to give a slight warming effect to this winter again so that's another hindrance to lowland snow.
Bond also posted this chart showing that winters in general are getting warmer in Seattle:
Note the past two winters have been quite above normal. But Bond thinks that while this upcoming winter will probably come in a little warmer than usual, he thinks it'll be cooler than the last two.
Their cold air outbreak forecast: "Better odds then last two years, but extremely low temperatures are unlikely." As specifically for lowland snow: "marginally decreased" odds is what they're going for, but then Bond might have saved the day hammering home the point that even if it's a slightly warmer winter does not kill off all odds of a cold period here and there.
"If we didn't at least have a minor (cold/snow event), I'll eat a bug!" Bond joked.
(No, we won't hold him to it!)
Just remember if we do manage to finally get a widespread snow event, it's been four years since we've had one, which means anyone who has just moved to this region in the past four years likely has no idea the freak-out factor Seattle has with snow. And what little experience Seattleites have with snow is now rusty. That... will be something to see.
Surprise! Neutral years are a bit all over the place for predicting Cascade snowpack as well. Here's the scatter chart for the past 70+ years:
Echoing the same theme as lowland snow, Bond thinks we'll end up with slightly less than the long term average, but "almost certainly" more than the record low 2014-15. That was the forecast last winter and ended up pretty spot on, and is the leading theory going into this winter. Not having El Nino will help. Again read more the Blob effects here.
The good news this year is Coastal Flooding is expected to be not as much of a danger this year because El Nino winters tend to have higher base sea levels. Bond says we were extremely lucky we didn't have any major storms during astronomical high tides last year during our record El Nino.
That doesn't mean we can't have coastal flooding, just we have more of a buffer before waters get too high.
Bond notes that we as a local society have been doing much better in using less polluting sources of heat, that our overall air quality has been on a vast improving trend, no matter the weather:
But he notes that neutral years, as much as they get stormy patterns, also tend to get extended stagnant/dry patterns which leads to inversions and burn bans. So be ready for that this year.
Putting it all together:
It looks like if you had to place odds, we'll be busy with extra flooding events this fall and winter, and be on guard for a stronger wind event. Lowland snow fans will have to cross their fingers a little; skiers should be fine. You can certainly get ahead of the game by visiting Take Winter By Storm for tips on how to be prepared.