Winter 2013-2014

[HM]

Based on past performance since 1950, that would nearly guarantee another one later in the winter.

 

I'm not sure if anything major happens...probably odds are against that sort of thing this year. But a couple weeks of below normal temperatures and wintry events seems possible mid-month.

 

 

What do you look at to determine that there may a west based -nao developing? 

 

Oh, so many things! The idea is knowing the background state and if the factors closer to real-time (and means less than 30 days) will allow for the changes to occur to switch the NAO. It's a combination of tropical forcing/effects, wave behavior/breaking, stratosphere/solar and z-circulation behavior.

 

Latent heat release forces a Rossby wave train that reinforces the Aleutian Low, which causes the wave-1 response in the stratosphere, which tilts with height, causing the warming in the middle/upper stratosphere over Siberia.

 

Yep! Oh and for all of those that think this was/is a SSW...it's not.

 

HM

 

You often mention solar activity in your overall analysis of earthly weather patterns and i think associate it with the polar vortex. Do you have any thoughts on how the approaching solar maximum will affect this winter? Recently there have been some pretty violent X1.7 and X2 flares.

 

We won't know for a couple of weeks how the solar activity affected the pattern. The only two ways that have reasonable research behind them are upper stratospheric wind anomalies in the Tropics-Subtropics and ozone. It is quite possible this current active period will do nothing at all to the overall low solar  averages, long-term. It is also quite possible it brings a significantly +AO DJF but allows for a late SSW / negative AO for March or something.

 

this is what happened in 1959 desite a plus AO NAO at the time...In 1959 NYC had snowstorm on 12/21-22...It was on the ground for Christmas...After that the winter was benign until March...1961 is another neutral negative enso analog with a snowstorm just before Christmas but the AO NAO were quite negative at the time...

 

Yes, this can be a sneaky way the warmth ends up capped in December. It is a matter of seasonal wavelengths, tropical forcing and the North Pacific becoming amplified all at the right time.

 

lolz

 

if he can find himself a retractable roof court it may come in handy in early December if HM is wrong.

 

I am definitely going about mid-December, cautiously. The mean background state is an ugly one all-around and I definitely understand the LR forecasts right now for a SE ridge in Dec.

[HM]

We won't know for a couple of weeks how the solar activity affected the pattern. The only two ways that have reasonable research behind them are upper stratospheric wind anomalies in the Tropics-Subtropics and ozone. It is quite possible this current active period will do nothing at all to the overall low solar  averages, long-term. It is also quite possible it brings a significantly +AO DJF but allows for a late SSW / negative AO for March or something.

We just had another major X-flare and the proton levels have been increased for a couple of days now. The upper-level stratospheric temperatures/winds were already in the process of changing across the Tropics, due to the annual cycle, but now may be accelerating in that direction. We'll have to see over the next week or so how they respond, if at all. The stronger the westerly wind and warmer the temperatures in the equatorial regions, the more +AO-tendency.

There is a possibility this winter of hitting some exceptionally high AO numbers mid-winter. The sun won't stay active forever and we'll have to see how it leaves us once it quiets back down (in terms of long-term averages).  

[Isotherm]

We just had another major X-flare and the proton levels have been increased for a couple of days now. The upper-level stratospheric temperatures/winds were already in the process of changing across the Tropics, due to the annual cycle, but now may be accelerating in that direction. We'll have to see over the next week or so how they respond, if at all. The stronger the westerly wind and warmer the temperatures in the equatorial regions, the more +AO-tendency.

There is a possibility this winter of hitting some exceptionally high AO numbers mid-winter. The sun won't stay active forever and we'll have to see how it leaves us once it quiets back down (in terms of long-term averages).  

 

 

Reminds me of the solar flux / SSN burst of late Oct/early Nov 2011, partially aiding in the development of the strong vortex for the beginning of the cold season. Geomagnetic activity has been fairly active this month as well, though recently we've calmed down. Not particularly thrilled with solar trends over the last several weeks to be honest. There are other factors of course, but the westerly QBO, heightened solar variables, and modest SAI tends to suggest that the chances of prolonged -AO periods are low this winter, at least through February. Maybe it'll be one of those seasons where we see late season / out of season -AO from Feb through April, but just speculation on my part.

 

Also will be interesting to monitor stratospheric temp anomalies this month as that has shown to be a fairly good indicator of cold season AO phase.

[HM]

Reminds me of the solar flux / SSN burst of late Oct/early Nov 2011, partially aiding in the development of the strong vortex for the beginning of the cold season. Geomagnetic activity has been fairly active this month as well, though recently we've calmed down. Not particularly thrilled with solar trends over the last several weeks to be honest. There are other factors of course, but the westerly QBO, heightened solar variables, and modest SAI tends to suggest that the chances of prolonged -AO periods are low this winter, at least through February. Maybe it'll be one of those seasons where we see late season / out of season -AO from Feb through April, but just speculation on my part.

 

Also will be interesting to monitor stratospheric temp anomalies this month as that has shown to be a fairly good indicator of cold season AO phase.

In terms of peer-reviewed research only, the actual solar flux long-term and geomagnetic activity is still in the "negligible" range with no signal. This, however, can change if we keep up the active solar conditions, presently. The exceptional +QBO/Smax conditions leading to SSW/-AO late winter were during a time of a pretty crazy ozone loss, weakened HT effect or El Nino/+PDO. It is very hard, with the limited data, to pin-down what drives what in each winter.

The sun's effect could also be elusive, aiding in the weakening of waves and the diabatic circulation more slowly instead of causing some dramatic temperature trend.

A classic late SSW winter, without El Nino, is 1990-91 with a strong HT effect (+QBO/Smax). But again, it was at a time with different sea ice, ozone loss and PDO.

There is also the possibility of seeing the upper half of the stratosphere becoming rather warm this winter but never downwell (which is actually something typical of a +QBO) until spring. So, the warming temperatures may not actually mean anything; but, I'm sure we will hear EVERYONE say it's the next downwelling SSW on the way!!

It's going to be a long winter...

[HM]

 

I'm going to look more into the potential; but, there is chance for a west-based -NAO to develop in December. I'm not sure yet on the details. If we take that potential away, we generally are dealing with a neutral AO (epo-related) / RNA style in December, dropping the cold mostly into the western states. But, should we see this "bubble" form near Greenland/D.S., it could skew the temperatures in a 1961-fashion or something.

Despite the recent solar activity, +QBO and model predictions for strengthening polar vortex, their effects may be more felt in November. If certain things can occur then, it is possible we get a "NAO burp." I'll know more after I look into things...

 

This potential has certainly gone up over the last 5 days. Despite numerous factors suggesting a strengthening vortex (and rightfully so), I think a tropical-induced El Nino-like atmosphere throws a curve ball at us. The AO state will begin to switch mid Nov and trend downward, first with Pacific contribution. Ultimately, we could move back to a temporary PNA pattern in early December.

There is 1 serious KW / +OHC ~ 160E and this Walker Cell shift hasn't stopped. It will halt some in early November but then....????

[Isotherm]

 

 

This potential has certainly gone up over the last 5 days. Despite numerous factors suggesting a strengthening vortex (and rightfully so), I think a tropical-induced El Nino-like atmosphere throws a curve ball at us. The AO state will begin to switch mid Nov and trend downward, first with Pacific contribution. Ultimately, we could move back to a temporary PNA pattern in early December.

There is 1 serious KW / +OHC ~ 160E and this Walker Cell shift hasn't stopped. It will halt some in early November but then....????

 

 

SOI dailies have been strongly negative since October 20th and the 30-day running SOI average is now negative/sub zero for the first time in awhile. Given that it seems reasonable to expect an El Nino shake-up of the atmosphere with possible warming into the central tropical pacific. Do you think we'll see much of a response in ENSO numbers? The burst won't be strong or long enough to get us to +0.5c but I think we have a shot at warm neutral in regions 4/3.4 for the cold season, maybe up to +0.3c or so.

[Rainshadow]

I did a quick and dirty comparison of warm Octobers and above average Eurasian snow cover (enso state not taken into account) for October. This is one eclectic snow group.  Dave Tolleris FB'd me Al Martino's NAO outlooks and five of these six (including the most recent four) averaged negative NAO(s) for the winter. 

 

 

  . 

[Rainshadow]

SOI dailies have been strongly negative since October 20th and the 30-day running SOI average is now negative/sub zero for the first time in awhile. Given that it seems reasonable to expect an El Nino shake-up of the atmosphere with possible warming into the central tropical pacific. Do you think we'll see much of a response in ENSO numbers? The burst won't be strong or long enough to get us to +0.5c but I think we have a shot at warm neutral in regions 4/3.4 for the cold season, maybe up to +0.3c or so.

 

Historically enso positive neutral winters have stunk for big snow events in Philadelphia.  With all due respect to meteorologists who try, the ability to accurately forecast this (or any enso) specific category is tough. Meanwhile sandwiched around that both weak el ninos and negative enso neutral winters have been good for big snow events in Philadelphia.

[Isotherm]

Historically enso positive neutral winters have stunk for big snow events in Philadelphia.  With all due respect to meteorologists who try, the ability to accurately forecast this (or any enso) specific category is tough. Meanwhile sandwiched around that both weak el ninos and negative enso neutral winters have been good for big snow events in Philadelphia.

 

 

I'm wondering if that's more due to coincidence, as I'm not sure what physical reason would cause neutral negative to be better than neutral positive. Neutral-warm I think is snowier than neutral negative for NYC/CNJ area.

[Rainshadow]

I'm wondering if that's more due to coincidence, as I'm not sure what physical reason would cause neutral negative to be better than neutral positive. Neutral-warm I think is snowier than neutral negative for NYC/CNJ area.

 

It could be small sample, maybe they tend to be east based?  Or maybe a better PNA/NAO pattern becomes favorable in neutral negative years. Here are the number of 6" or greater events in PHL by enso state (number of years in sample in parenthesis).  Yes 1993-4 was neutral warm and quite a difference from PHL north.

 

Strong nino: 8 (6)

Mdt nino:....8 (6)

Weak nino..8 (10)

pos neutral...2 (6)

neg neutral..13 (14)

weak nina....8 (9)

mdt nina......4 (6)

stg nina.......3 (6)

[HM]

SOI dailies have been strongly negative since October 20th and the 30-day running SOI average is now negative/sub zero for the first time in awhile. Given that it seems reasonable to expect an El Nino shake-up of the atmosphere with possible warming into the central tropical pacific. Do you think we'll see much of a response in ENSO numbers? The burst won't be strong or long enough to get us to +0.5c but I think we have a shot at warm neutral in regions 4/3.4 for the cold season, maybe up to +0.3c or so.

 

It is quite possible this next oceanic KW will cause a decent response in the numbers (early numbers on it look pretty strong). The warm-neutral background, as Tony already mentioned, can actually be a bad thing for snow lovers. But, again, a lot of these years sampled were during a time of weak HT effect because of ozone loss / state of our stratosphere (e.g. 1960 is a lot different than 1990). If this push occurs for an appreciable time, it could combine with other factors like the expansive snow cover to help disturb the stratosphere more...but that still could end up not affecting the DJF NAM state.

 

There was a lot about the autumn circulation this year that usually progresses into a +AO/NAO winter. But we keep getting these bursts where it looks quite the opposite (portion of late October and late September). But, in general, the circulation  has been strongly suggesting a +AO state. That's why I'm not at all confident about this -NAO, and I'm not confident that, if it did form, it would affect the temperature departure much.

[toronto blizzard]

This potential has certainly gone up over the last 5 days. Despite numerous factors suggesting a strengthening vortex (and rightfully so), I think a tropical-induced El Nino-like atmosphere throws a curve ball at us. The AO state will begin to switch mid Nov and trend downward, first with Pacific contribution. Ultimately, we could move back to a temporary PNA pattern in early December.

There is 1 serious KW / +OHC ~ 160E and this Walker Cell shift hasn't stopped. It will halt some in early November but then....????

What effects will this walker cell have on the overall pattern going forward?

[Isotherm]

It could be small sample, maybe they tend to be east based?  Or maybe a better PNA/NAO pattern becomes favorable in neutral negative years. Here are the number of 6" or greater events in PHL by enso state (number of years in sample in parenthesis).  Yes 1993-4 was neutral warm and quite a difference from PHL north.

 

Strong nino: 8 (6)

Mdt nino:....8 (6)

Weak nino..8 (10)

pos neutral...2 (6)

neg neutral..13 (14)

weak nina....8 (9)

mdt nina......4 (6)

stg nina.......3 (6)

 

 

Tony, interesting list. Weird that moderate Nina and strong Nina are actually snowier than positive neutral.

[NJwinter23]

I'd be interested to know what type of year/regime these neg-neutral and pos-neutral seasons were following...perhaps the hangover effect from prior year regime would have a say in these differences? Other thought would simply be a coincidence due to the myriad of other global factors affecting the winter patterns in these neutral years (like Isotherm suggested).

[HM]

What effects will this walker cell have on the overall pattern going forward?

 

An El Nino-like tendency on the pattern this time of year can be pretty warm. In fact, this October has behaved similarly to El Ninos of the past that went on to produce blowtorch early winters. But, the stratosphere has NOT behaved that way so far and has been quite the opposite. What a ridiculous month this has been, especially if you are looking ahead to the winter.  

 

Mean W PAC to Dateline uplift will likely dominate a good portion of the mid Nov-mid Dec period and we will likely see the GLAAM spike late next month too. Perhaps it will build an appreciable STJ, assuming we get some coherency out of the MJO.

[toronto blizzard]

An El Nino-like tendency on the pattern this time of year can be pretty warm. In fact, this October has behaved similarly to El Ninos of the past that went on to produce blowtorch early winters. But, the stratosphere has NOT behaved that way so far and has been quite the opposite. What a ridiculous month this has been, especially if you are looking ahead to the winter.  

 

Mean W PAC to Dateline uplift will likely dominate a good portion of the mid Nov-mid Dec period and we will likely see the GLAAM spike late next month too. Perhaps it will build an appreciable STJ, assuming we get some coherency out of the MJO.

So I'm taking this as good news for snow lovers in the east?

[HM]

So I'm taking this as good news for snow lovers in the east?

 

Nope...

 

The most +NAO El Nino Decembers are: 1994, 1982, 1965, 2006, 1951, 2004 and 1986. The pattern lately has sort of resembled these but it isn't as easy as that of course (this year is obviously not an El Nino). This October also resembled years like 1993, 1995, 1989, 1978, 1975 and 1960. It has been hilarious to say the least.

[toronto blizzard]

Do you think the mid-nov - mid-dec period will be cold/below normal in the east?

[famartin]

 The pattern lately has sort of resembled these but it isn't as easy as that of course (this year is obviously not an El Nino).

Apparently not very obvious to everyone.

[Rainshadow]

Tony, interesting list. Weird that moderate Nina and strong Nina are actually snowier than positive neutral.

 

Tom,

 

This is just the relative low number of big events,  I'm kind of have my back against the wall with Aug stormdata due, staff meeting presentation coming up so sorry if I'm in/out, the six positive neutral winters are 1979-80, 1989-90, 1990-1, 1992-3,  1993-4 and 2003-4.  Overall snow (just PHL), they were not that far from normal. We had March 1993 in there too.

[blizzardof96]

In terms of peer-reviewed research only, the actual solar flux long-term and geomagnetic activity is still in the "negligible" range with no signal. This, however, can change if we keep up the active solar conditions, presently. The exceptional +QBO/Smax conditions leading to SSW/-AO late winter were during a time of a pretty crazy ozone loss, weakened HT effect or El Nino/+PDO. It is very hard, with the limited data, to pin-down what drives what in each winter.

The sun's effect could also be elusive, aiding in the weakening of waves and the diabatic circulation more slowly instead of causing some dramatic temperature trend.

A classic late SSW winter, without El Nino, is 1990-91 with a strong HT effect (+QBO/Smax). But again, it was at a time with different sea ice, ozone loss and PDO.

There is also the possibility of seeing the upper half of the stratosphere becoming rather warm this winter but never downwell (which is actually something typical of a +QBO) until spring. So, the warming temperatures may not actually mean anything; but, I'm sure we will hear EVERYONE say it's the next downwelling SSW on the way!!

It's going to be a long winter...

Thanks for the updates HM! 1985-86 is also a good example of a neutral ENSO winter, with late winter PV disruptions and what looks to be a strong HT effect. Had a downwelling +QBO, neutral ONI and low AP index that year but unfortunately had a strong +PDO from JAN to MARCH. Several upper stratospheric warnings occurred from JAN to March that year but they failed to downwell until april. Saw enhanced blocking for a time during mid winter which could have been aided by stratospheric influences. 61-62, 78-79,01-02 and 66-67 also match up pretty well with a +QBO phase, -PDO and neutral ONI state. Not sure if we saw any SSW's in those winter.

 

Question about your first paragraph... how would a weakened HT effect coupled with a decrease in ozone occur in tandem with a late winter SSW? Wouldn't these factors negate any potential disruption to the vortex? Were their other factors contributing to this SSW?

[am19psu]

Do you think the mid-nov - mid-dec period will be cold/below normal in the east?

No. Read the thread. Everything being discussed are possible disruptions to the overall +AO/warm signal.

[toronto blizzard]

No. Read the thread. Everything being discussed are possible disruptions to the overall +AO/warm signal.

Which would mean it would turn colder would it not?

[am19psu]

Which would mean it would turn colder would it not?

No. The general flavor of the early winter period is likely to be +AO/warm. HM is trying to identify periods in which the general pattern may break down.

[NaoPos]

Which would mean it would turn colder would it not?No. The general flavor of the early winter period is likely to be +AO/warm. HM is trying to identify periods in which the general pattern may break down.

[toronto blizzard]

No. The general flavor of the early winter period is likely to be +AO/warm. HM is trying to identify periods in which the general pattern may break down.

So how long does this pattern last? To me HM sounded like he was hinted toward a colder pattern towards the end of November.

[blizzardof96]

If i put aformentioned years into a noaa reanalysis composite I notice a few things. Dec starts off mild over the area despite moderate to strong west based -nao blocking. By jan the bering sea ridge propogates poleward and expands towards northwest AK. This allows the mean trough to shift a little further east over NA. By feb we see a +nao, +ao and +pna state developing.

[HM]

If i put aformentioned years into a noaa reanalysis composite I notice a few things. Dec starts off mild over the area despite moderate to strong west based -nao blocking. By jan the bering sea ridge propogates poleward and expands towards northwest AK. This allows the mean trough to shift a little further east over NA. By feb we see a +nao, +ao and +pna state developing.

image.jpg

 

 

Thanks for providing this image which outlines, beautifully, how a west based -NAO can form during a lousy Pacific (not again!!!). As Adam already suggested, this will be a temporary break-away from the mean background state.

[HM]

Apparently not very obvious to everyone.

 

I'm not sure I get your reference here; but, let me say this...I don't know if it is apparent to me anymore, lol. I mean, I've got the hard numbers which 100% say, "No El Niño." Everyone, and of course their mother, agrees with that, too. But, then I see the Walker Cell shift to 160E, 30-day average CHI over the C PAC and buoy-interpolated data go exceptionally warm across the Pacific Basin. There's another Kelvin Wave coming with the most impressive OHC / SLH anomalies yet which should transverse the Basin over the next month or so....

 

Arguably, it looks like an El Niño right now using everything else but the long-term SST averages, statistics and modeling. Quick, someone slap me back some sense!

[HM]

Thanks for the updates HM! 1985-86 is also a good example of a neutral ENSO winter, with late winter PV disruptions and what looks to be a strong HT effect. Had a downwelling +QBO, neutral ONI and low AP index that year but unfortunately had a strong +PDO from JAN to MARCH. Several upper stratospheric warnings occurred from JAN to March that year but they failed to downwell until april. Saw enhanced blocking for a time during mid winter which could have been aided by stratospheric influences. 61-62, 78-79,01-02 and 66-67 also match up pretty well with a +QBO phase, -PDO and neutral ONI state. Not sure if we saw any SSW's in those winter.

 

 

Question about your first paragraph... how would a weakened HT effect coupled with a decrease in ozone occur in tandem with a late winter SSW? Wouldn't these factors negate any potential disruption to the vortex? Were their other factors contributing to this SSW?

 

My friend, use this link for a quick reference if a particular winter had a CW, SSW and for FW timing:

http://www.geo.fu-berlin.de/en/met/ag/strat/produkte/northpole/index.html

 

While CWs are something rare these days (maybe only 1 in like the last decade), the SSW frequency has climbed. They denote a SSW by the * next to the temperature. Notice 2001-02 had multiple warmings and yet....!!!!! lol The stratosphere isn't always the answer to our sensible weather. That winter had a classic -NAO fail period, lol.

 

As for your last question, during the 1980s/1990s, the HT relationship weakened because of what we did to the ozone layer (CFCs etc.). Furthermore, the +PDO / El Niño frequency was much higher; so, a lot of the warmings tended to occur later in the season. But the ozone destruction was the reason that the typical HT relationships were not as clear cut then. We have since recovered, if not, substantially so...