Indian Ocean Signal is for Real

[usedtobe]

My first foray into medium range forecasting this winter is going to have a lot of fail, I see

You could always be right, I'm no long range forecaster, I just play at it and have been known to be wrong.

[usedtobe]

The initial burst of cold was forecasted to really blitz the upper plains and even get into the northeast before 11/20...but we mentioned in the pattern change thread in the NE subforum (back on the the other site) that it was likely rushing things at the time and that thinking looks like it turned out correct.

It looks like the east could be below average for a while after Turkey Day even if the EPO starts to go back toward positive...the cold is already dumped into Canada and the -NAO will help hold in whatever cold is there and potentially move it southeast. It won't be a huge frigid outbreak since the two blocking mechanisms aren't working in tandem in the ideal locations, but we should definitely see the NAO working to keep it cool for at least a while. How much moderation there is after that probably depends on just how much the GOA low and +EPO comes back and its orientation. If we keep a bit of ridging north of AK/Bering straight, then it can still deliver cold to Canada even if the EPO is positive and there is a GOA low.

That's what it looks like if the consensus of models is correct. They have been bouncing around with the pacific but all have pretty much strengthened the neg nao with the 12Z gfs now shifting the block westward where it would indeed shunt some cold air east and south once the turkey day low goes north of my back yard. I don't like seeing the mjo trending back towards phase 5 as that should eventually lead to a positive epo. However, the more strongly negative this nao is, the more likely we'll see another rebound once it slackens some which might help later in Dec even if we lose it for awhile and warm up.

[CoastalWx]

That's what it looks like if the consensus of models is correct. They have been bouncing around with the pacific but all have pretty much strengthened the neg nao with the 12Z gfs now shifting the block westward where it would indeed shunt some cold air east and south once the turkey day low goes north of my back yard. I don't like seeing the mjo trending back towards phase 5 as that should eventually lead to a positive epo. However, the more strongly negative this nao is, the more likely we'll see another rebound once it slackens some which might help later in Dec even if we lose it for awhile and warm up.

That's an interesting point too. BTW the euro ensembles continue to have a +300 or better H5 anomalies in Greenland, and it does slowly shift west and south with time.

[ORH_wxman]

That's an interesting point too. BTW the euro ensembles continue to have a +300 or better H5 anomalies in Greenland, and it does slowly shift west and south with time.

There continues to be about as a robust signal for a -NAO as you will see on an ensemble mean post-200 hours....and its even still very visible at the end of the EC ensemble run at 360 hours. Pretty impressive.

The PAC setup will limit just how cold the airmass is as it comes south and east, but it (NAO) certainly should affect the pattern. You can almost see the NAO and SE ridge battling in the latter part of the time frame as some troughiness out in the southwest is trying to bring the heights back up in the SE but the NAO certainly wants to counteract that.

[JamieO]

There continues to be about as a robust signal for a -NAO as you will see on an ensemble mean post-200 hours....and its even still very visible at the end of the EC ensemble run at 360 hours. Pretty impressive.

The PAC setup will limit just how cold the airmass is as it comes south and east, but it (NAO) certainly should affect the pattern. You can almost see the NAO and SE ridge battling in the latter part of the time frame as some troughiness out in the southwest is trying to bring the heights back up in the SE but the NAO certainly wants to counteract that.

Pardon a dumb question, but isn't that a pattern that favors overrunning?

[ORH_wxman]

Pardon a dumb question, but isn't that a pattern that favors overrunning?

Yeah that's one way to get it.

I guess anytime you have some form of lower heights in the SW with a bit of ridging in the SE and some mechanism to compress the height field in between the SE ridge and the lower heights in Canada, then it can be favorable for overrunning events. The often mentioned '93-'94 winter didn't have a -NAO to fight the SE ridging at times, but it had a mega PV in Hudson Bay/SE Canada to pick up the slack instead.

12z OP Euro is actually trying to show some overrunning potential with the initial front near or just before Thanksgiving. Still a ways out obviously, but it could be possible with some of these larger features in place. A lot of that euro solution was dependent on hanging enough energy from the western trough back so it could eject out later after the front seeped far enough south and produce a nice wave along the front.

[Gibbsfreeenergy]

is it me or is the NAO block in the models look more rex like..almost like a cutoff low underneath the high with more zonal flow as opposed to causing more meridional displacement omega style?

I feel good about the Pac setup, and why it looks like it does, now to figure out how that configured NAO look alters things...if it verifies. The Euro ens dropped heights in eastern Canada and the DS a ton vs the previous run, this after the previous run (00z) trended exactly the opposite.

[ORH_wxman]

is it me or is the NAO block in the models look more rex like..almost like a cutoff low underneath the high with more zonal flow as opposed to causing more meridional displacement omega style?

I feel good about the Pac setup, and why it looks like it does, now to figure out how that configured NAO look alters things...if it verifies. The Euro ens dropped heights in eastern Canada and the DS a ton vs the previous run, this after the previous run (00z) trended exactly the opposite.

Initially I it looks more like that I think...but it appears to try and expand W and retrograde some through the period which shoves a larger split off chunk of the PV SE into SE Canada, particularly near or after Thanksgiving. Obviously being 10+ days out, a lot can change with that prog.

The Pacific looks very ragged on the ensembles after T-day. Looks like a lot of uncertainty.

[Gibbsfreeenergy]

Initially I it looks more like that I think...but it appears to try and expand W and retrograde some through the period which shoves a larger split off chunk of the PV SE into SE Canada, particularly near or after Thanksgiving. Obviously being 10+ days out, a lot can change with that prog.

The Pacific looks very ragged on the ensembles after T-day. Looks like a lot of uncertainty.

what do you think about this image as a relatively close match to the ridge anomaly in Greenland shown in modeling? I know its not Dec yet, but figured since we will be closer to it than early November I looked at Dec matches.

[Gibbsfreeenergy]

what do you think about this image as a relatively close match to the ridge anomaly in Greenland shown in modeling? I know its not Dec yet, but figured since we will be closer to it than early November I looked at Dec matches.

[Matt Rogers]

what do you think about this image as a relatively close match to the ridge anomaly in Greenland shown in modeling? I know its not Dec yet, but figured since we will be closer to it than early November I looked at Dec matches.

Will the Greenland ridge be stronger than the Aleutians ridge?

[ORH_wxman]

what do you think about this image as a relatively close match to the ridge anomaly in Greenland shown in modeling? I know its not Dec yet, but figured since we will be closer to it than early November I looked at Dec matches.

Yeah its not a bad match. I think the EC ensembles have the anomalies a little N and W more into Greenland rather than to the south of there. Also higher anomalies into the Davis Straight later in the run. It was pretty impressive for so deep into an ensemble mean run. (post 300 hours)

The Pacific looks a lot more ambiguous. They definitely look like they want to return a GOA low in some fashion but its not overwhelmingly strong making me think that there isn't very good agreement...also the weaknesses and potential ridging still showing up N of the Bering straight.

[Gibbsfreeenergy]

Will the Greenland ridge be stronger than the Aleutians ridge?

i would guess not for what I am expecting. But I am trying to see what sort of anomaly that greendland ridge would suggest. What is really interesting is this....check out the surface pattern for those upper air matches that I posted..nino?

[tacoman25]

There will still be some impressive cold in the nrn high Plains imo. Some of that will move east in conjunction with a nice -nao. Hopefully this will last through part of December, but it may not last that long from the MA south. Who knows.

Oh, no doubt. Montana and North Dakota should be frigid in about a week. How far south/east the Arctic air spills is the question.

[tacoman25]

Will the Greenland ridge be stronger than the Aleutians ridge?

1950, 1955, 1970, and 1973 continue to pop up in the pattern analog matches over and over again. Little to no sign of more recent Ninas.

Coincidence? I doubt it.

[tacoman25]

1950, 1955, 1970, and 1973 continue to pop up in the pattern analog matches over and over again. Little to no sign of more recent Ninas.

Coincidence? I doubt it.

Here are those years rolled forward to December.

[usedtobe]

Here are those years rolled forward to December.

Yep, I showed the same in my thread.

[HM]

This sucks that we are losing the original thread, filled with tons of content. I suppose there is no way to bring it over; otherwise, it would have been done already. The pattern coming up will be awesome to witness unfold with the squeeze play from the Aleutian / Greenland highs on the polar heights. The key to sustainability will be a solid development of a Southeast Canadian / NW Atlantic PV wedged underneath a retrograding block. At some point, this high anomaly could connect with the high anomaly upstream of the GOA low and just form one big warm anomaly. This would be the period that would have a heightened risk for a snowstorm in the eastern states. Once the -NAO block is alleviated, it could be blowtorch city for a while until the GOA high brings the cold back into the northern-tier.

[Gibbsfreeenergy]

Here are those years rolled forward to December.

i wish we had your novie map saved

[tacoman25]

i wish we had your novie map saved

I have it. It will probably match the second half of November very well...pattern change probably arriving a little too late to make it look like a pretty calendar match. But the overall blocking pattern I was expecting has appeared, and the dominant +EPO October pattern has been left behind.

Wish we had a winter forecast from you.

[Gibbsfreeenergy]

I have it. It will probably match the second half of November very well...pattern change probably arriving a little too late to make it look like a pretty calendar match. But the overall blocking pattern I was expecting has appeared, and the dominant +EPO October pattern has been left behind.

Wish we had a winter forecast from you.

isnt it funny that with all this talk about how cold the early start to October was and then it torched, and now how November has torched and will turn colder in the back half, and yet...when all is said and done, if you composite the 10-15 strongest nina Oct and Nov, you would have nailed each month.

[Srain]

This sucks that we are losing the original thread, filled with tons of content. I suppose there is no way to bring it over; otherwise, it would have been done already. The pattern coming up will be awesome to witness unfold with the squeeze play from the Aleutian / Greenland highs on the polar heights. The key to sustainability will be a solid development of a Southeast Canadian / NW Atlantic PV wedged underneath a retrograding block. At some point, this high anomaly could connect with the high anomaly upstream of the GOA low and just form one big warm anomaly. This would be the period that would have a heightened risk for a snowstorm in the eastern states. Once the -NAO block is alleviated, it could be blowtorch city for a while until the GOA high brings the cold back into the northern-tier.

Good to see you finally chiming in.

[Gibbsfreeenergy]

Here are those years rolled forward to December.

backward roll says probably wont cut it:

[tacoman25]

isnt it funny that with all this talk about how cold the early start to October was and then it torched, and now how November has torched and will turn colder in the back half, and yet...when all is said and done, if you composite the 10-15 strongest nina Oct and Nov, you would have nailed each month.

Definitely too early to say that.

Regardless of how the exact anomalies play out at the end of this month, I'm happy that the general ideas from the "Oct Nina Matches" thread are working out. Big pattern change, major blocking kicking in, northern tier turning much colder. The first ten days of the month built up some big + anomalies in the northern plains that will be difficult to overcome, but that doesn't change the fact that this month has seen a major shift away from the October pattern.

[tacoman25]

backward roll says probably wont cut it:

Actually, there is a good chance that Nov 10-30 will look pretty similar to that. Is the calendar the be all end all?

[Gibbsfreeenergy]

Definitely too early to say that.

Regardless of how the exact anomalies play out at the end of this month, I'm happy that the general ideas from the "Oct Nina Matches" thread are working out. Big pattern change, major blocking kicking in, northern tier turning much colder. The first ten days of the month built up some big + anomalies in the northern plains that will be difficult to overcome, but that doesn't change the fact that this month has seen a major shift away from the October pattern.

but is this a surprise? something unexpected? Again the Nina signal would have suggested the same.

I was looking at verification thus far this month, used 10 day forecast dailies and assumed 11-15 day anoms, and it was difficult to find places that would come in at -1F or colder this November. Maybe PIT/BUF has best shot, esp. depending on how far north the 6-10 day warm up occurs? What is most amazing is Calgary going to come in around 0 after a crazy rollercoaster.

[Gibbsfreeenergy]

Actually, there is a good chance that Nov 10-30 will look pretty similar to that. Is the calendar the be all end all?

well then we can just pick different periods to verify our forecasts

[tacoman25]

but is this a surprise? something unexpected? Again the Nina signal would have suggested the same.

I was looking at verification thus far this month, used 10 day forecast dailies and assumed 11-15 day anoms, and it was difficult to find places that would come in at -1F or colder this November. Maybe PIT/BUF has best shot, esp. depending on how far north the 6-10 day warm up occurs? What is most amazing is Calgary going to come in around 0 after a crazy rollercoaster.

Wow, we are halfway through the month and you are actually posting this?

I saw no suggestions from you that we would see this kind of pattern showing up now...at least not in October. You mentioned it once it started showing up in the models.

[tacoman25]

well then we can just pick different periods to verify our forecasts

You are ignoring the ideas that were discussed behind the forecasts. Timing is everything when it comes to monthly forecast anomalies. The ideas and pattern analogs I discussed are looking very much in line with the current/developing pattern. Just compare how much 1950, 1955, 1964, and 1973 have shown up as CPC pattern analogs compared to 1998, 1999, 2007, etc. There is a lot more blocking showing up than was present those Novembers.

[JamieO]

but is this a surprise? something unexpected? Again the Nina signal would have suggested the same.

I was looking at verification thus far this month, used 10 day forecast dailies and assumed 11-15 day anoms, and it was difficult to find places that would come in at -1F or colder this November. Maybe PIT/BUF has best shot, esp. depending on how far north the 6-10 day warm up occurs? What is most amazing is Calgary going to come in around 0 after a crazy rollercoaster.

Not sure about BUF, but PIT and UNV was helped out by the unusual wildcard in the past warmup - clear dry November skies. Usually Novie warmups seem to be dirty/cloudy. In this warmup, temps were in the 60s in the pm and 20s at dawn.