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"Arctic Shots" potential more PNW focused 2014-15


richard mann

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My thinking is mainly climatological-based, while taking into account the ENSO state and some past analogue years. I don't put much stock into any of the shorter-term oscillations or long range models, which become too chaotic beyond 10 days.

 

I have observed a relationship between the strength of El Nino and the onset of arctic air, with stronger El Ninos favoring an earlier onset (mid December) and weaker ones favoring a later onset (early January). El Nino is currently classified as weak, but is very close to moderate.

 

With this in mind, I'm estimating a general pattern shift to commence shortly after Dec 20th, initially in the form of cooler troughing. A further shift to more substantive cold may commence right around Christmas, +/- a few days. I won't speculate on whether this will occur in time for Christmas snow.

 

Basically, my "window" for arctic air is Dec 20th to Jan 15th, with the critical period being roughly Dec 25th to Jan 10th. Whatever arctic air we do get, I expect to be mainly gone by Jan 15th, barring any inversion which may keep the surface artificially cold. Climatology argues strongly against arctic air persisting past mid-January during an El Nino, particularly a borderline moderate one. It could happen (and has), but I wouldn't bet on it.

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This is a perfect thread to post some of the evidence I have found of a significant cold snap in the NW in the late Dec to Mid Jan time frame.  The occurrence of significant cold snaps in winters following summers / autumns with an extremely high average temperature in the Jul - Oct period is quite profound.  When the list of years is further narrowed by choosing only years that had warmish neutral to weak El Nino the timing gets pinned down pretty firmly.  On the other hand the list of years that were very warm Jul - Oct almost all had Arctic blasts somewhere I the early Dec to mid Feb time frame regardless of ENSO.  For now I will post the list of years narrowed to warmish neutral of weak El Nino conditions.

 

1958-59 - Significant Arctic blast early Jan

1979-80 - Significant Arctic blast early Jan and late Jan.  Major widespread lowland snowstorm from blast number 1.

1990-91 - Top tier Arctic blast late December (2 waves)

2003-04 - Significant cold late December followed by a true Arctic blast in early Jan

2004-05 - Major cold and snow event in the north interior of Western WA first half of Jan.  Moderate cold Puget Sound region.  Narrowly missed historic blast.

 

Besides that you have the track record of warmish neutral / weak Nino winters that weren't preceded by a warm  Jul - Oct

 

1951-52 - Persistent cold Dec and Jan long streak of days with snow on the ground in some lowland locations

1953-54 - Major cold and snowy period which began in mid January

1976-77 - Arctic outbreak early Jan with some lowland snow

 

As you can see based on this we have a highly elevated chance of scoring some decent cold somewhere between late Dec and mid Jan.

 

I did not include 1969-70 or 1977-78 because those were second year Ninos and they ALWAYS suck.

Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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My thinking is mainly climatological-based, while taking into account the ENSO state and some past analogue years. I don't put much stock into any of the shorter-term oscillations or long range models, which become too chaotic beyond 10 days.

 

I have observed a relationship between the strength of El Nino and the onset of arctic air, with stronger El Ninos favoring an earlier onset (mid December) and weaker ones favoring a later onset (early January). El Nino is currently classified as weak, but is very close to moderate.

 

With this in mind, I'm estimating a general pattern shift to commence shortly after Dec 20th, initially in the form of cooler troughing. A further shift to more substantive cold may commence right around Christmas, +/- a few days. I won't speculate on whether this will occur in time for Christmas snow.

 

Basically, my "window" for arctic air is Dec 20th to Jan 15th, with the critical period being roughly Dec 25th to Jan 10th. Whatever arctic air we do get, I expect to be mainly gone by Jan 15th, barring any inversion which may keep the surface artificially cold. Climatology argues strongly against arctic air persisting past mid-January during an El Nino, particularly a borderline moderate one. It could happen (and has), but I wouldn't bet on it.

 

The MEI is a better measure of ENSO and it says this Nino isn't nearly as strong as the actual ENSO SSTs would indicate.  Given the current MJO state a falling back of ENSO SSTs is almost a given.  When looking at the ONI keep in mind those are tri monthly averages.

 

I think we have a high chance of a cold wave being significantly extended by a ridge moving in over the top of the cold air once it's established.  Could be a far greater extension of cold than this recent event.

Death To Warm Anomalies!

 

Winter 2023-24 stats

 

Total Snowfall = 1.0"

Day with 1" or more snow depth = 1

Total Hail = 0.0

Total Ice = 0.2

Coldest Low = 13

Lows 32 or below = 45

Highs 32 or below = 3

Lows 20 or below = 3

Highs 40 or below = 9

 

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The MEI is a better measure of ENSO and it says this Nino isn't nearly as strong as the actual ENSO SSTs would indicate.  Given the current MJO state a falling back of ENSO SSTs is almost a given.  When looking at the ONI keep in mind those are tri monthly averages.

 

I think we have a high chance of a cold wave being significantly extended by a ridge moving in over the top of the cold air once it's established.  Could be a far greater extension of cold than this recent event.

 

Fair enough... looks like the current MEI value is .712

 

Obviously I'm looking at current SST's since you can't really use a tri-monthly average for any kind of forecasting... hindsight is 20/20 of course, and this could end up just a weak Nino or even warm neutral when all is said and done.

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What's next, conjecture. ?
 
So far, and if more broad brush more basically above, we've got, ….
 
 …. perhaps connected to and following the next more significant retrograde of more primary cold West, North.
 

 .... somewhere between the 20th of Dec. and Jan. 15th.
 
 It's a start.

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Irrespective of just when a next more "Arctic Shot" of cold moves south to impact the PNW, .. I just wanted to resound here, what I'd posted within the "California Weather / Climate" thread, main "The West" section, at the end of November. .About the one just past, and what followed it more immediately.

http://theweatherforums.com/index.php/topic/177-california-weather-climate/page-16?do=findComment&comment=47379

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Relavent generally. (Posted to PNW general discussion thread.)
 

... One thing I would like to point out... is that both of our cold waves this season came with little warning in the models.  In both cases the events began as shortwaves ... shown about a week out ... that rapidly became more and more impressive as the time frame narrowed.  The first thing to pick up on the last one was the CPC analogs.  The MJO entering a favorable location was also a kind of indication.

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