The Medium Range Thread

[am19psu]

This is probably set up for failure because I'm not a good medium range forecaster and everyone seems happy in their regional subfora, but I'm going to give it a shot anyway. I'd like to try to get more activity on the main board. It's like a ghost town except for The Tropical Dudes (^TM HurricaneJosh).

The new Euro weeklies came out last night and showed the vaunted Nina SE ridge appearing after Valentine's Day with a +EPO/-PNA/+NAO signature and warmer than normal temperature anomalies everywhere east of the Rockies. I'm not buying it. Tropical convection shows no sign of stopping across the Australia Region. The MJO is currently moving into Phase 1, but will move to the middle shortly and then should head right back into Phase 6 around Valentine's Day.

Also, there have been some decent mountain torque events over the last five days, which should help to disrupt the polar vortex.

That would agree with Don S' forecast of February averaging a -AO, despite what the ensemble guidance is currently showing.

I suspect the core of the cold will shift westward to the OH Valley/MS Valley/Great Lakes the 2nd half of the month, versus the January core of the Southeast, but I'm not seeing full on warm anomalies for the Eastern 2/3s the way the Euro weeklies are showing.

Feel free to tell me why I'm an idiot and why going against the weeklies is a fool's errand.

[OKpowdah]

Nice thoughts, and I agree. I posted this in the New England forum yesterday:

This looks like one of those cases where, dependent on ridging in the north Pacific, the positive NAO could in fact be quite a cold scenario for the northern tier. I haven't taken much of a look at the pattern beyond day 7 yet, but I see that the MJO wave is projected to collapse shortly and reignite near Indonesia over the next week or so. Should this trigger a E Asia mt torque event, we could see the more negative EPO progs verifiy. That in combination with a +NAO yields cross polar flow into the western hemisphere. This could be a very cold period for much of Canada, while we might have a few days a bit above normal before a negative AO re-emerges by the third week of February and sends the north pole equatorward.

So first of all I could see a few SWF events that are well placed for moderate snowfall across New England. Given UL confluence south of the +NAO upper low, a period of moderate SE ridging and plenty of cold up north to create a tight temperature gradient right over the region, might see an overperformer or two.

Second, significant Archambault storm late February that rides the leading edge of a late season arctic outbreak that precedes a very cold and snowy beginning to March

[wxmx]

This is probably set up for failure because I'm not a good medium range forecaster and everyone seems happy in their regional subfora, but I'm going to give it a shot anyway. I'd like to try to get more activity on the main board. It's like a ghost town except for The Tropical Dudes (^TM HurricaneJosh).

The new Euro weeklies came out last night and showed the vaunted Nina SE ridge appearing after Valentine's Day with a +EPO/-PNA/+NAO signature and warmer than normal temperature anomalies everywhere east of the Rockies. I'm not buying it. Tropical convection shows no sign of stopping across the Australia Region. The MJO is currently moving into Phase 1, but will move to the middle shortly and then should head right back into Phase 6 around Valentine's Day.

Also, there have been some decent mountain torque events over the last five days, which should help to disrupt the polar vortex.

That would agree with Don S' forecast of February averaging a -AO, despite what the ensemble guidance is currently showing.

I suspect the core of the cold will shift westward to the OH Valley/MS Valley/Great Lakes the 2nd half of the month, versus the January core of the Southeast, but I'm not seeing full on warm anomalies for the Eastern 2/3s the way the Euro weeklies are showing.

Feel free to tell me why I'm an idiot and why going against the weeklies is a fool's errand.

Agree with you on all accounts.

The UKie mjo doesn't show the MJO moving back to phase 6, but looping in the circle of death. Nevertheless a retrogression of the PNA ridge is probably in the cards now, shifting everything west, but with the mean trough not really contributing to a full blown -PNA, though this index might be trending neutral. Also, the -AO will probably show itself as a new episode of an -EPO ridge, models are already hinting at that. This usually is a cold signal for the whole CONUS, and without a full blown -PNA pattern, cold would leak east of the Rockies after visiting the PNW. Rembember this time we have a strong PV on our side of the hemisphere.

Caveat of all this is that the progression of the MJO is not very Niña like, so unless we see a weakening Niña trend, MJO might surface back in phase 4 and/or 5 and that would be a kiss of death for the eastern 2/3 of the CONUS (with the probable exception of the northern plains).

[am19psu]

Agree with you on all accounts.

The UKie mjo doesn't show the MJO moving back to phase 6, but looping in the circle of death. Nevertheless a retrogression of the PNA ridge is probably in the cards now, shifting everything west, but with the mean trough not really contributing to a full blown -PNA, though this index might be trending neutral. Also, the -AO will probably show itself as a new episode of an -EPO ridge, models are already hinting at that. This usually is a cold signal for the whole CONUS, and without a full blown -PNA pattern, cold would leak east of the Rockies after visiting the PNW. Rembember this time we have a strong PV on our side of the hemisphere.

Caveat of all this is that the progression of the MJO is not very Niña like, so unless we see a weakening Niña trend, MJO might surface back in phase 4 and/or 5 and that would be a kiss of death for the eastern 2/3 of the CONUS (with the probable exception of the northern plains).

Yeah, the MJO/-OLR anomalies really are the key to my forecast. If they blow up more strongly in the IO than currently indicated in either the statistical or dynamical guidance, then the Euro weeklies could be plausible.

[gil888]

This is probably set up for failure because I'm not a good medium range forecaster and everyone seems happy in their regional subfora, but I'm going to give it a shot anyway. I'd like to try to get more activity on the main board. It's like a ghost town except for The Tropical Dudes (^TM HurricaneJosh).

The new Euro weeklies came out last night and showed the vaunted Nina SE ridge appearing after Valentine's Day with a +EPO/-PNA/+NAO signature and warmer than normal temperature anomalies everywhere east of the Rockies. I'm not buying it. Tropical convection shows no sign of stopping across the Australia Region. The MJO is currently moving into Phase 1, but will move to the middle shortly and then should head right back into Phase 6 around Valentine's Day.

<snip>

I suspect the core of the cold will shift westward to the OH Valley/MS Valley/Great Lakes the 2nd half of the month, versus the January core of the Southeast, but I'm not seeing full on warm anomalies for the Eastern 2/3s the way the Euro weeklies are showing.

Feel free to tell me why I'm an idiot and why going against the weeklies is a fool's errand.

I'm terrified right now of the long range forecast because the models are showing a completely different pattern for February than we have seen so far. In a sense, it does look like a more classical La Nina with that strong ridge and cold in the central plains. However the polar vortex is as strong as I've seen it in a couple of winters and the ensemble guidance is in really good agreement. Perhaps the limited climo on the -AO suggests we will go back to the blocking pattern, but the guidance suggests the complete opposite. Maybe it is just too much to ask for the -AO to keep driving things and that La Nina will finally gets it way for at least a few weeks.

And I totally agree-- the board stinks when everyone stays in their regional flora. I wish people would stay in the main forum until the storm is 48 hours away, then talk about the specifics for their region after that time. Until then, the model shifts affect everyone and it is too time-consuming to go every single forum and check out what the top members/mets think about a storm.

Do the weeklies ever show any hint of blocking returning for late Feb?

[gil888]

Agree with you on all accounts.

The UKie mjo doesn't show the MJO moving back to phase 6, but looping in the circle of death. Nevertheless a retrogression of the PNA ridge is probably in the cards now, shifting everything west, but with the mean trough not really contributing to a full blown -PNA, though this index might be trending neutral. Also, the -AO will probably show itself as a new episode of an -EPO ridge, models are already hinting at that. This usually is a cold signal for the whole CONUS, and without a full blown -PNA pattern, cold would leak east of the Rockies after visiting the PNW. Rembember this time we have a strong PV on our side of the hemisphere.

Caveat of all this is that the progression of the MJO is not very Niña like, so unless we see a weakening Niña trend, MJO might surface back in phase 4 and/or 5 and that would be a kiss of death for the eastern 2/3 of the CONUS (with the probable exception of the northern plains).

The east is cold for a different reason now-- e.g. the +PNA rather than the -AO pattern. With the +PNA sticking around and the crazy strong polar low dropping over NE N America, the cold will stick around for a while, but if a -PNA rears its head, it could get ugly in a hurry.

[am19psu]

Do the weeklies ever show any hint of blocking returning for late Feb?

No, in week 4 (2/21-2/27), the ridge grows stronger over the SE. There is a WPO ridge, but +EPO/-PNA and a neutral to positive NAO. In other words, opposite of everything we've seen so far.

[chim chiminey]

Is the GEFS MJO guidance more reliable than the AO guidance? I don't understand why the MJO guidance is taken seriously, but not other teleconnectors.

[am19psu]

Is the GEFS MJO guidance more reliable than the AO guidance? I don't understand why the MJO guidance is taken seriously, but not other teleconnectors.

No, it's pretty poor compared to the Euro and the UKMet, but it got the general idea across as a visual. The GEFS isn't the only thing showing the tropical convection remaining in the Australia Region.

[gil888]

No, in week 4 (2/21-2/27), the ridge grows stronger over the SE. There is a WPO ridge, but +EPO/-PNA and a neutral to positive NAO. In other words, opposite of everything we've seen so far.

:lightning:well there's always March!

[wxmx]

The east is cold for a different reason now-- e.g. the +PNA rather than the -AO pattern. With the +PNA sticking around and the crazy strong polar low dropping over NE N America, the cold will stick around for a while, but if a -PNA rears its head, it could get ugly in a hurry.

Yeah, it's a great coincidence that as the high latitude ridging began to wane, the west coast ridging started to grow. But even as it wanes, the -AO left us a present, the main PV piece on our side of the world. Now imagine if there's ridging over N Canada and it displaces the PV south? Brrrrr.... well, that's the take of the 12z Euro.

[chim chiminey]

No, it's pretty poor compared to the Euro and the UKMet, but it got the general idea across as a visual. The GEFS isn't the only thing showing the tropical convection remaining in the Australia Region.

Are you saying The MJO forecast was a consistent theme amongst the ensembles(moreso than other teleconnectors), and if so, is this why you decided to use it as the anchor of your forecast?

[am19psu]

Are you saying The MJO forecast was a consistent theme amongst the ensembles(moreso than other teleconnectors), and if so, is this why you decided to use it as the anchor of your forecast?

Kinda. I trust the tropical forcing to drive the synoptic mid-latitude pattern. So if I can get the tropical forcing correct (from both dynamical and statistical guidance), then I can decide whether I agree with the calculated index values or not, rather than just relying on the ensemble forecasts themselves. I'm not sure I'm explaining that cogently.

[wxmx]

Are you saying The MJO forecast was a consistent theme amongst the ensembles(moreso than other teleconnectors), and if so, is this why you decided to use it as the anchor of your forecast?

This current pattern is a product of a well forecasted MJO wave from all three products mentioned by am19psu (The UK, Euro and GFS). Obviously a good consensus would add confidence to the forecast. The UK and GEFS products are not that harmonius right now (happens with low amplitude waves), but they are not that diverging either...at least they are similar into hinting that the IO won't be the main tropical forcing zone (phases 4-5)... more like Indonesia to the dateline.

[wxmx]

Also, am19psu is mentioning mountain torque events, which send planetary waves that might disturb the polar vortex. A weak polar vortex means that the cold will likely not be contained in the far northern latitudes. This season we have seen many waves, which have helped loose the nightly polar jet, and currently yet another one, with origins in the aforementioned mountain torque events is in progress. This is why there's some skepticism about the Euro weeklies showing warmth for the eastern 2/3s of the CONUS.

[chim chiminey]

This current pattern is a product of a well forecasted MJO wave from all three products mentioned by am19psu (The UK, Euro and GFS). Obviously a good consensus would add confidence to the forecast. The UK and GEFS products are not that harmonius right now (happens with low amplitude waves), but they are not that diverging either...at least they are similar into hinting that the IO won't be the main tropical forcing zone (phases 4-5)... more like Indonesia to the dateline.

One of the things I'm wondering is if a MJO phase 6 consensus among 3 mediocre models would outweigh a fairly accurate +AO prediction outlier.. or is that not at all how forecasters think

[wxmx]

One of the things I'm wondering is if a MJO phase 6 consensus among 3 mediocre models would outweigh a fairly accurate +AO prediction outlier.. or is that not at all how forecasters think

One of the "mediocre" models is the base of the AO prediction guidance by NCEP. Also, one doesn't precludes the other (you can have any state of the AO in any phase of the MJO, there's no strong correlation between them). If you see signs that teleconnect to something that isn't shown by guidance, then there are reasons to question the guidance (in this case the AO forecast by the GEFS). MT, planetary waves and stratospheric warming argues against a strong cooling of the mid/upper troposphere in the high latitudes (+AO), it can happen still, but odds are that guidance will dampen the +AO forecast or even reverse it, IMHO.

[A-L-E-X]

The pattern being discussed in this thread is reminiscent of what happened in 1960-61, when winter basically ended after mid Feb.

I've seen quite a few LR outlooks that bring back a super -NAO in early March, so too soon to make that call.

[Chris L]

The pattern being discussed in this thread is reminiscent of what happened in 1960-61, when winter basically ended after mid Feb.

I've seen quite a few LR outlooks that bring back a super -NAO in early March, so too soon to make that call.

Alex, how about a March month like 1960?

[A-L-E-X]

Alex, how about a March month like 1960?

or 1956, which was an analog being used

[Chris L]

or 1956, which was an analog being used

Yeah, Tony (rainshadow likes that analog).

that would a heck of a way to end winter.

[wxmx]

So, will the MJO backtrack to phase 6 or will it loop in the circle of death before resurfacing in phases 8 or 1. Phase 6 is not that bad, but 8 or 1 is a similar pattern to which we have now, which would be colder for the eastern 2/3s of the CONUS...the latter is the take of the UK and op GFS, while the former is favored by the GEFS (though, looking at 06z GEFS members, it will probably be closer to UK's forecast tomorrow if solutions hold...some of the members are just amazingly cold)

I'm still confident the NCEP's AO guidance is just too positive, and it will dampen a lot ... another -EPO pattern is looking more likely past day 10, IMO.

[winterymix]

No, in week 4 (2/21-2/27), the ridge grows stronger over the SE. There is a WPO ridge, but +EPO/-PNA and a neutral to positive NAO. In other words, opposite of everything we've seen so far.

Please correct me if I'm wrong but this reads like a large scale transition of "The Westerlies" poleward,

i.e. "Pre-Springtime".

[am19psu]

Please correct me if I'm wrong but this reads like a large scale transition of "The Westerlies" poleward,

i.e. "Pre-Springtime".

It's really just zonal flow with a ridge over the SE US, but yeah, that's a warm pattern.

[wxmx]

It's really just zonal flow with a ridge over the SE US, but yeah, that's a warm pattern.

Latest Euro doesn't like warm.

[am19psu]

Latest Euro doesn't like warm.

Not at all, the 11-15d mean 850 temps are quite cold everywhere east of the Rockies. That was an impressive flop at 0z from where it had been all week.

[wxmx]

Not at all, the 11-15d mean 850 temps are quite cold everywhere east of the Rockies. That was an impressive flop at 0z from where it had been all week.

MJO and high latitude ridging do it once more, apparently.

[WhiteoutWX]

Not at all, the 11-15d mean 850 temps are quite cold everywhere east of the Rockies. That was an impressive flop at 0z from where it had been all week.

Prominent SE ridge shows up towards the end of the run, would look to keep the storm track along or west of the Apps for the most part.

[am19psu]

Asian mountain torques continued through the end of last week. I'm still expecting the AO to go negative sometime around Valentine's Day, despite what some of the dynamical guidance is showing right now. Even with the SE ridge in place, I don't think the Northeast, Great Lakes, or Northern Plains will see any prolonged periods of warmth. However, with little in the way of Atlantic blocking expected, I'd guess the primary storm track will be west of the Appalachians mid-month.

[wxmx]

Asian mountain torques continued through the end of last week. I'm still expecting the AO to go negative sometime around Valentine's Day, despite what some of the dynamical guidance is showing right now. Even with the SE ridge in place, I don't think the Northeast, Great Lakes, or Northern Plains will see any prolonged periods of warmth. However, with little in the way of Atlantic blocking expected, I'd guess the primary storm track will be west of the Appalachians mid-month.

As expected, guidance is showing more members going negative soon after peak.