Medium/Long Range thread

[HM]

 

you lost me on the poleward stratospheric u=0 line, but otherwise, I got it.

 

Oh, this is not too bad. Notice the 0-line is extending well into the Subtropics, if not Mid Latitudes between 50-20 hpa:

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=all&var=u&lng=eng

We can infer heightened wave reflection back to the polar latitudes here from the disturbances that upwell. Because we are still forming the vortex, this first wave 1 high up there won't be as impacting to the NAM state. But it did offset the development of the PV at these heights (both the zero-wind line and wave together contributed to the displaced/weakened vortex between 70-30 hpa) and allowed a significant amount of ozone to pour into the polar regions.

Usually, the zero-wind line oscillates between 20-30 N. When you see this line more in the northern Subtropics instead of southern Subtropics, you can usually infer the wave dynamics I mentioned above.

[ravensrule]

I actually understood 90% of that.

 

Lol I was thinking I understood 1% of it and I was a genius.

[CoastalWx]

So let me just try to grasp this. Say you have a strong low coming into the pacific coast. The Rockies, which run longitudinally, and you have a high dropping down in the plains or over the great lakes, this would cause an acceleration in momentum source? Is their a bottom line where a low pressure has to be this strong or in this spot or a high pressure has to be this strong for acceleration to start? Or is it just any low pressure west of a mtn chain and high pressure east of a mtn chain will cause acceleration?

 

Tombo are you trying to infer why mets cheer +AAM surges for cold and jeer (except Adam) -AAM surges which can signal warmth for the East Coast sometimes? Basically are you wondering from an operational standpoint why we care?

[CoastalWx]

 

 

Oh, this is not too bad. Notice the 0-line is extending well into the Subtropics, if not Mid Latitudes between 50-20 hpa:

http://users.met.fu-berlin.de/~Aktuell/strat-www/wdiag/eczm.php?alert=1&forecast=all&var=u&lng=eng

We can infer heightened wave reflection back to the polar latitudes here from the disturbances that upwell. Because we are still forming the vortex, this first wave 1 high up there won't be as impacting to the NAM state. But it did offset the development of the PV at these heights (both the zero-wind line and wave together contributed to the displaced/weakened vortex between 70-30 hpa) and allowed a significant amount of ozone to pour into the polar regions.

Usually, the zero-wind line oscillates between 20-30 N. When you see this line more in the northern Subtropics instead of southern Subtropics, you can usually infer the wave dynamics I mentioned above.

 

Actually this is an interesting explanation. I take it the weakened U state right into 60N also is what you are referring to regarding ozone introduction.

[CoastalWx]

BTW HM, I wish you wouldn't care what a few weenies have to say in our subforum. It would be nice to have your thoughts as well....or anyone of you guys for that matter. Who the hell cares what they think. It shouldn't bother you.

[tombo82685]

Tombo are you trying to infer why mets cheer +AAM surges for cold and jeer (except Adam) -AAM surges which can signal warmth for the East Coast sometimes? Basically are you wondering from an operational standpoint why we care?

Scott, im just trying to grasp what you use the AAM for, and how to read it without getting into all the nitty gritty stuff.

[am19psu]

BTW HM, I wish you wouldn't care what a few weenies have to say in our subforum. It would be nice to have your thoughts as well....or anyone of you guys for that matter. Who the hell cares what they think. It shouldn't bother you.

your subforum is terrible and I wouldn't post there if I lived in Boston. Until you guys figure out that your problem is internal, there is no hope. I'm saying it here because I can but also because it's true. The old boys club has to go before you get new blood up there. Otherwise, it's going to be the same people who have posted there since 2008

[Rainshadow]

Scott, im just trying to grasp what you use the AAM for, and how to read it without getting into all the nitty gritty stuff.

 

A general way of looking at it in terms of big snow events in Philadelphia, your chances increase as the AAM anomalies increase (-1 has been the cutoff since 1958) and your chances increase further when the AAM tendency is decreasing (in others positive, but becoming less positive analogous of releasing potential energy into kinetic energy).  You're in phase 7 and 8 which are el nino phases (whether the SSTA is el nino or not).  When this insufferable shut-down is over, I will repost the position of the GWO on the day of the large events.

 

There is alot of great info here. Thank-you everyone for sharing.

[Isotherm]

In addition to the great information already posted, here's a simple explanation of the AAM and a graph of its tendencies over recent decades. AAM is essentially an index for representing the flow of the atmosphere around the equatorial tropics. The atmosphere naturally flows faster at the equator due to the width of earth, and therefore changes in the speed of this flow can have significant impacts at high latitudes in terms of the air pressure pattern. A slower AAM cycle generally coincides with La Nina / cold ENSO regimes in which the atmosphere is moving slower in the tropics. This yields a response to speed up the Earth's rotation slightly. The article I posted below explains how negative AAM / slow AAM periods tend to pile up air on the eastern side of continents, thus often creating a high pressure / drier sensible weather picture. Higher AAM / fast AAM periods which are more frequent in El Nino's, indicate a hastening of the atmosphere in the tropics and a slowing of Earth's rotation, causing air pile up / high pressure on the western side of continents, with more low pressure on the eastern side. Of course these are general rules and we've seen plenty of -AAM periods with dominant low pressure on the eastern side of continents, but it's a tendency, like most oscillations / teleconnections, that can often be overridden by other indices.

 

The cycling of the AAM is strongly correlated to ENSO variations. Like everything else, it's one tool which can be used as an aide to forecast sensible weather but should not be used by itself.

 

 

 

 

Link on AAM:

 

 

http://www.examiner.com/article/atmospheric-angular-momentum-aam-oversimplified

[Quakertown needs snow]

_{euro bringing the chill/cold next week}

[CoastalWx]

Actually that link does a pretty good explanation on AAM. I had another way of looking at it as well and tried to break it down to what it means from a forecast standpoint and why we tend to see this outcome given certain AAM tendencies. By all means if I'm missing something then correct me. Not afraid to be wrong. I can explain CSI, but sometimes not the best at this stuff so here it goes.

 

When we have an El Nino or higher AAM state these westerlies will move in the same direction as Earth. Remember AAM is conserved and these tendencies will tend to propagate poleward. Since AAM is conserved and we are sort of adding more westerly momentum, we'll tend to see more higher latitude ridging and more easterly anomalies to counteract this. Also, friction will also tend to slow these +AAM anomalies down too. Thus why we tend to see more ridging in higher latitudes along with the windward side mtn range ridging and downstream troughing. 

 

The opposite for La Nina. It's why we tend to see more of a +AO along with leeward side ridging from mtn ranges.  I hope I have this right or on the right track. 

[radarman]

Salstein and Rosen at AER authored some of the early AAM literature which is definitely worth the read. 

[Quakertown needs snow]

_{frost/freeze next week?}

[HM]

 

Actually this is an interesting explanation. I take it the weakened U state right into 60N also is what you are referring to regarding ozone introduction.

 

Yes, the zero wind line/wind minima is felt into the westerlies. Since tropospheric waves can only upwell within a westerly wind (i.e. Mid Latitudes-polar night jet region), the subtropical u=0 line acts as a "wave guide." This can determine how well waves reflect back to the pole since most of the time, as they expand when rising, they propagate equatorward.

 

BTW HM, I wish you wouldn't care what a few weenies have to say in our subforum. It would be nice to have your thoughts as well....or anyone of you guys for that matter. Who the hell cares what they think. It shouldn't bother you.

There are some great people in your subforum, some of which I have known for years. But the issue was never about 1 or 2 weenies. I have battled forum scum for years and overall I have never let it get to me. The issue was more or less on a larger-scale, the moderation etc. in combination with the catering to trolls mentality. I am just a lot happier posting on Americanwx when I'm not in your subforum. But please know, this isn't how I feel about you, radarman, etc.

[HM]

In addition to the great information already posted, here's a simple explanation of the AAM and a graph of its tendencies over recent decades. AAM is essentially an index for representing the flow of the atmosphere around the equatorial tropics. The atmosphere naturally flows faster at the equator due to the width of earth, and therefore changes in the speed of this flow can have significant impacts at high latitudes in terms of the air pressure pattern. A slower AAM cycle generally coincides with La Nina / cold ENSO regimes in which the atmosphere is moving slower in the tropics. This yields a response to speed up the Earth's rotation slightly. The article I posted below explains how negative AAM / slow AAM periods tend to pile up air on the eastern side of continents, thus often creating a high pressure / drier sensible weather picture. Higher AAM / fast AAM periods which are more frequent in El Nino's, indicate a hastening of the atmosphere in the tropics and a slowing of Earth's rotation, causing air pile up / high pressure on the western side of continents, with more low pressure on the eastern side. Of course these are general rules and we've seen plenty of -AAM periods with dominant low pressure on the eastern side of continents, but it's a tendency, like most oscillations / teleconnections, that can often be overridden by other indices.

 

The cycling of the AAM is strongly correlated to ENSO variations. Like everything else, it's one tool which can be used as an aide to forecast sensible weather but should not be used by itself.

 

 

 

 

Link on AAM:

 

 

http://www.examiner.com/article/atmospheric-angular-momentum-aam-oversimplified

 

I think you meant momentum there, not actual speed. The Earth is constantly adding westerly momentum to the tropical / subtropical latitudes for the reasons mentioned here and in that link.

 

As for that link, I understand it is simplified but just know these general rules usually don't work out so nicely. This is especially true on subseasonal timescales when things may have not "averaged out" yet in the required amount of time (could be any length really, depending on the atmospheric variables at play like ENSO). Finally, we've seen over the last few winters the importance of regional propagation over, say, the actual GLAAM anomaly.  

[HM]

Actually that link does a pretty good explanation on AAM. I had another way of looking at it as well and tried to break it down to what it means from a forecast standpoint and why we tend to see this outcome given certain AAM tendencies. By all means if I'm missing something then correct me. Not afraid to be wrong. I can explain CSI, but sometimes not the best at this stuff so here it goes.

 

When we have an El Nino or higher AAM state these westerlies will move in the same direction as Earth. Remember AAM is conserved and these tendencies will tend to propagate poleward. Since AAM is conserved and we are sort of adding more westerly momentum, we'll tend to see more higher latitude ridging and more easterly anomalies to counteract this. Also, friction will also tend to slow these +AAM anomalies down too. Thus why we tend to see more ridging in higher latitudes along with the windward side mtn range ridging and downstream troughing. 

 

The opposite for La Nina. It's why we tend to see more of a +AO along with leeward side ridging from mtn ranges.  I hope I have this right or on the right track. 

 

In an El Nino, the amount of westerly AAM produced in the tropical-subtropical latitudes exceeds the amount of it that the friction can eat in the Mid-Latitudes. Therefore, the westerly flows extend into the Mid Latitudes, extending the Pacific Jet and anchors in the Aleutian Low. The propagation of these westerlies may look linear but it is in fact the Hadley Cell that allows for the propagation (even though the exchange of momentum happens solely at the surface). The increased westerly flows from the tropical latitudes also helps intensify the STJ and in some cases more than the PJ. This creates an environment favorable for split flow, blocking and wave breaking.  

[CoastalWx]

In an El Nino, the amount of westerly AAM produced in the tropical-subtropical latitudes exceeds the amount of it that the friction can eat in the Mid-Latitudes. Therefore, the westerly flows extend into the Mid Latitudes, extending the Pacific Jet and anchors in the Aleutian Low. The propagation of these westerlies may look linear but it is in fact the Hadley Cell that allows for the propagation (even though the exchange of momentum happens solely at the surface). The increased westerly flows from the tropical latitudes also helps intensify the STJ and in some cases more than the PJ. This creates an environment favorable for split flow, blocking and wave breaking.  

 

True, the last sentence ties it in. Obviously the opposite is true too. Thanks man...so were my thoughts on track in the earlier post?

[tombo82685]

Definitely the first real shot of a frost freeze, early next week for portions of the area outside the pocs. Some of the euro individual ens members show mid 30s for the ptw-ukt corridor.Highs on the mean only in the mid to upper 50s. Definitely a decent cool shot coming it looks for next week. 

 

The cold shot coming, which looks like the brunt is aimed at the lakes midwest, is well represented by the mjo. A pretty strong phase 8-1 wave is forecasted to emerge on the gfs which favors the cold into the center of the nation that oozes eastward. The euro isn't as robust, keeps it in the COD, with an emergence in phase 1, heading into 2. Taking that into consideration i Don't think this cool shot will last long,in terms of the propagation of the mjo heading int phases 2-3, i think it may only last a week or so.... Thoughts?

 

 

 

 

[Quakertown needs snow]

6Z GFS is on board for the cold shot followed by even colder in the extended, FWIW.

Just hope we dont get snow since that would kill real winter snow .

[radarman]

 

 

Yes, the zero wind line/wind minima is felt into the westerlies. Since tropospheric waves can only upwell within a westerly wind (i.e. Mid Latitudes-polar night jet region), the subtropical u=0 line acts as a "wave guide." This can determine how well waves reflect back to the pole since most of the time, as they expand when rising, they propagate equatorward.

 

There are some great people in your subforum, some of which I have known for years. But the issue was never about 1 or 2 weenies. I have battled forum scum for years and overall I have never let it get to me. The issue was more or less on a larger-scale, the moderation etc. in combination with the catering to trolls mentality. I am just a lot happier posting on Americanwx when I'm not in your subforum. But please know, this isn't how I feel about you, radarman, etc.

 

Sorry to hear but understood.  Awesome stuff as usual HM. 

[NaoPos]

I'd be cautious of seeing any extreme negative departures in the long range verify. The models this time of year tend to over due the push of the cold air, especially as it leaks in from the midwest. The airmass tends to modify. We can get negative departures, and the teleconnectors point to it, i just wouldn't be surprised to see the models back off the extent of how cool we get.

Tombo, i wonder if the recurbing typhoon out by japan is having ffedback on the gfs' MJO outlook?

[tombo82685]

6Z GFS is on board for the cold shot followed by even colder in the extended, FWIW.

Just hope we dont get snow since that would kill real winter snow .

I only have the euro ens to go off of, but the reason why the gfs is prob so cold is because of it's mjo forecast.

[tombo82685]

I'd be cautious of seeing any extreme negative departures in the long range verify. The models this time of year tend to over due the push of the cold air, especially as it leaks in from the midwest. The airmass tends to modify. We can get negative departures, and the teleconnectors point to it, i just wouldn't be surprised to see the models back off the extent of how cool we get.

Tombo, i wonder if the recurbing typhoon out by japan is having ffedback on the gfs' MJO outlook?

It's very possible, because its the outlier right now with how strong of a wave it has in phase 8-1 of all the models

 

[tombo82685]

some pretty decent analog years on that list...

 

[Quakertown needs snow]

12Z GFS, next week, 1st snow in east for some,  brrr.

[dssbss]

Who are the "some" in the east...

 

 

12Z GFS, next week, 1st snow in east for some,  brrr.

[tombo82685]

Who are the "some" in the east...

For this area majority of it is rain, warm bl temps but the gfs does show it possibly could change to snow before it ends. If how it is shown pans out. The pocs would be a different story. They would prob start off as rain, but would have any chance if this would materialize as it stands now.

[ptb127]

For this area majority of it is rain, warm bl temps but the gfs does show it possibly could change to snow before it ends. If how it is shown pans out. The pocs would be a different story. They would prob start off as rain, but would have any chance if this would materialize as it stands now.

 

Finally some exciting weather to track! 

[tombo82685]

Euro bringing some pretty chilly air for this time of the year. Highs could be in upper 40s to low 50s for highs in the 7-10 day period. Good shot of first frost and freeze in that time frame to.

[dssbss]

Bring it on!