Medium/Long Range thread

[Mike.Ventrice]

Thanks. I am sure I can't be the only person questioning the very basic mechanisms of this stuff!

 

I did read a lot of the old atmospheric insights stuff, but as a "looking back and learning" resource it's a tricky one. You needed to be there it seems! I have dug up old powerpoint presentations from Ed Berry, along with material on the GSDM, and scouring the internet for forum discussions (e.g. http://forum.netweather.tv/topic/52083-gwo-and-global-angular-momentum/). Apart from this, there's a precious lack of "let's start from the ground up" material. 

 

Regarding your comment about the STJ and El Nino and AAM, I can at least make sense of that. It seems reasonable. I plotted GLAAM against SOI to see how they relate:

Disclaimer: no fancy-dan statistics or filtering applied. Data grabbed. Data plotted. That's it. January only.

 

 

OK! That seems decent enough. Higher SOI's (Nina) are typically located during periods of low AAM, and vice versa, though of course there are exceptions.

 

Then I got a bit carried away. I must admit to being a bit gutted when I was plotting some composites and noticed that both January 1963 and January 1989 appeared as "low AAM years". That was somewhat dispiriting. I don't memorise seasons from the past, but I know those months were drastically different across the NH.

So I plotted AAM against NAO for Jan, and really ought not be surprised in the mess that results:

 

 

But I am surprised. If we pick a moderately high NAO value like 1.50 (ish), it seems like that can occur in both seriously high AAM periods and seriously low AAM periods. Perhaps a better approach would be to frequency bin these (or think about lag?), but the above chart is not promising, and actually is a little annoying. Surely there ought to be some sort of relationship?

 

So if I've learned anything from day in and day out forecasting is that blocking ridges, such as those that would project negatively on the NAO loading pattern, can occur regardless of the AAM state, regardless of the location of the MJO, regardless of the state of the QBO, etc. Blocking ridges (NAO/EPO/PNA, whatever EOF pattern that  is some form of indicator of high-latitude rigdging) can literally thrive in an environment created by itself and this will always lead to times where the general teleconnections we've all grown accustom to can fail. Just one of the many curveballs mother nature can toss.

[HM]

 

Do all wave trains increase AAM? 

 

Does all tropical convection increase AAM?

No and No.

 

does the increase in AAM in the region of active MJO get transported poleward, or is it completely damped by the friction so rapidly that it essentially goes nowhere? Or a little of both? 

What is the actual mechanism of poleward transport? What does it look like? Are we talking tropical sourced WCB's? The corollary is: what does equatorward transport actually look like (synoptically)?

The physical mechanism is the Hadley Cell. The surface torques in the Mid Latitudes can respond to Tropical Forcing through the Hadley Cell or perhaps a wave train (again, as an example). As discussed before, only exchange occurs at the surface. There are no simple rules with this stuff or what transports look like. With an active W-C PAC MJO, usually the transports are clean meridional mass flux processes, easily seen on a satellite. But it doesn't always happen this way. 

 

Though I'm a meteorologist this framework is entirely unfamiliar to me, so I have to do a lot of legwork. I do notice that the internet discussions can be fairly hand wavy, and you see statements like "there is currently a strong east Asian mountain torque event, and this may lead to x then y then z". I'm always thinking "slow down there". Explain step 1 to me! There is less asking of  "well, why is there a strong mountain torque right now? What is actually happening? What are the physics behind this?". e.g. with the recent event, I can only surmise that it was favored by an anticyclone over the Tibetan Plateau combined with the remnants of TC Phailin SW of the Himalaya. But is this even right? It make sense to me, but most people seem content with just ogling the torque charts and leaving it at that.

I agree that people make this stuff too simplified. The only safe statement we can say about a +MT over East Asia is that it will help increase westerly flow, over time, across the Pacific Ocean. But +MT can happen strictly by Mid Latitude-Subpolar Processes too, not just tropical waves. This is why they don't all mean the same thing. Usually, the standing waves are intensified during a +MT so that lower pressures exist to the NW of the T.P. and higher pressures SE, putting a P.G. over the mountains. This added easterly flow will cause an increase in +AAM transport from Earth to the Air.

 

If I were to treat the AAM as a diagnostic of current wind and pressure patterns (which....it surely must be?), then could a synoptic link be attained by running composites of high/low AAM months historically, to see (example below) what a high AAM November actually looks like in terms of synoptics?

Nope...

Sorry for being a right pain and derailing the thread.

lol...it's okay but come on man!

[Mike.Ventrice]

Hey guys- got a real-time analog builder using the velocity potential MJO indices retaining interannual type variability. My job is pushing for me to post more on twitter on our work account so I'll be more active on that during the week days. Anyway thought you guys might find the VPM index with ENSO (EVPM) analog surface temperature and 500 mb anomaly composites for the next 30 days: pic.twitter.com/SRtZWMhUEp

[tombo82685]

Hey guys- got a real-time analog builder using the velocity potential MJO indices retaining interannual type variability. My job is pushing for me to post more on twitter on our work account so I'll be more active on that during the week days. Anyway thought you guys might find the VPM index with ENSO (EVPM) analog surface temperature and 500 mb anomaly composites for the next 30 days: pic.twitter.com/SRtZWMhUEp

That's absolutely solid Mike, definitely will be using that. 

[NaoPos]

Wow, amazing product mike. Nice work.

[snowlurker]

You should register a copyright Mike.

[Mike.Ventrice]

You should register a copyright Mike.

 

Ah this index has been accepted for publication so in a sense it has already been copyrighted: http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-12-00327.1?prevSearch=ventrice&searchHistoryKey=

 

The analog part is what was tricky to code up and that's WSI property now I'm hoping we'll have a section on our webpage one day with this stuff on there.

[CoastalWx]

 

No and No.

 

The physical mechanism is the Hadley Cell. The surface torques in the Mid Latitudes can respond to Tropical Forcing through the Hadley Cell or perhaps a wave train (again, as an example). As discussed before, only exchange occurs at the surface. There are no simple rules with this stuff or what transports look like. With an active W-C PAC MJO, usually the transports are clean meridional mass flux processes, easily seen on a satellite. But it doesn't always happen this way. 

 

I agree that people make this stuff too simplified. The only safe statement we can say about a +MT over East Asia is that it will help increase westerly flow, over time, across the Pacific Ocean. But +MT can happen strictly by Mid Latitude-Subpolar Processes too, not just tropical waves. This is why they don't all mean the same thing. Usually, the standing waves are intensified during a +MT so that lower pressures exist to the NW of the T.P. and higher pressures SE, putting a P.G. over the mountains. This added easterly flow will cause an increase in +AAM transport from Earth to the Air.

 

Nope...

lol...it's okay but come on man!

 

This is the part where it gets a bit cloudy for me. MT helping to increase westerly flow over time which to me is +AAM( I believe), but easterly flow will cause an increase in +AAM from Earth to Air. Easterly flow to me is -AAM so is that +AAM a response I guess from friction or this added MT from easterly flow? 

[CVA]

Thanks HM for your patience  

 

This is the part where it gets a bit cloudy for me. MT helping to increase westerly flow over time which to me is +AAM( I believe), but easterly flow will cause an increase in +AAM from Earth to Air. Easterly flow to me is -AAM so is that +AAM a response I guess from friction or this added MT from easterly flow? 

 

I feel your clouds, brother. This is how I have tried to explain +MT to myself:

 

 

So the anomalous pressures produce a torque across the mountain range (yes that's part of the Himalaya in the photo). In the above case, the torque (atmosphere acting on earth) acts to try and slow down the rotation of the earth, because the earth of course rotates in a "westerly" sense (to the east).
Because we have defined our earth-atmosphere system as being closed, the only way for the earth to slow down (lose angular momentum) is for the atmosphere to speed up (gain angular momentum). Therefore, there must be a transport of angular momentum from the earth into the atmosphere, as shown by the fat blue arrow pointing upwards.

 

My understanding of the conventions in this framework (which are extremely important but sometimes people get a bit lax?): a positive torque of any flavour acts to increase atmospheric angular momentum, and hence decrease earth angular momentum. Vice versa for all negative torques.  

 

 

Right/wrong? Marks out of ten? 

[dryslotted]

Thanks HM for your patience  

 

 

I feel your clouds, brother. This is how I have tried to explain +MT to myself:

 

 

So the anomalous pressures produce a torque across the mountain range (yes that's part of the Himalaya in the photo). In the above case, the torque (atmosphere acting on earth) acts to try and slow down the rotation of the earth, because the earth of course rotates in a "westerly" sense (to the east).

Because we have defined our earth-atmosphere system as being closed, the only way for the earth to slow down (lose angular momentum) is for the atmosphere to speed up (gain angular momentum). Therefore, there must be a transport of angular momentum from the earth into the atmosphere, as shown by the fat blue arrow pointing upwards.

 

My understanding of the conventions in this framework (which are extremely important but sometimes people get a bit lax?): a positive torque of any flavour acts to increase atmospheric angular momentum, and hence decrease earth angular momentum. Vice versa for all negative torques.  

 

 

Right/wrong? Marks out of ten? 

I'm hopeful it's completely right because this clicked for me having the visual along with the narrative explanation. Thanks...

[Rainshadow]

Thanks HM for your patience

 

 

I feel your clouds, brother. This is how I have tried to explain +MT to myself:

 

 

So the anomalous pressures produce a torque across the mountain range (yes that's part of the Himalaya in the photo). In the above case, the torque (atmosphere acting on earth) acts to try and slow down the rotation of the earth, because the earth of course rotates in a "westerly" sense (to the east).

Because we have defined our earth-atmosphere system as being closed, the only way for the earth to slow down (lose angular momentum) is for the atmosphere to speed up (gain angular momentum). Therefore, there must be a transport of angular momentum from the earth into the atmosphere, as shown by the fat blue arrow pointing upwards.

 

My understanding of the conventions in this framework (which are extremely important but sometimes people get a bit lax?): a positive torque of any flavour acts to increase atmospheric angular momentum, and hence decrease earth angular momentum. Vice versa for all negative torques.  

 

 

Right/wrong? Marks out of ten? 

 

My head is spinning on this too.  So maybe I have had this all wrong? +AAM gets generated when (relative) stronger westerlies are to the lee of the Himalayas, Rockies, Andes vs approaching them from the west which would cause a net -AAM for the atmosphere? 

[CVA]

My head is spinning on this too.  So maybe I have had this all wrong? +AAM gets generated when (relative) stronger westerlies are to the lee of the Himalayas, Rockies, Andes vs approaching them from the west which would cause a net -AAM for the atmosphere? 

 

I assume that in the second case you mention, if the westerly flow approaches say the Rockies or the Andes (I will use these because the Himalaya/Karakorum massif is dog-legged and not perpendicular to the westerlies for most of its length) then the westerlies must act to "push" the mountains towards the east.

This is of course the same way as the earth's rotation, therefore the earth will speed up (gain angular momentum) and the atmosphere will slow down (lose angular momentum). Hence it must be a negative torque (+AM transport from the atmosphere into the earth). 

[NaoPos]

Wtf is the euro doing?

That's one crazy solution

[CVA]

I assume that in the second case you mention, if the westerly flow approaches say the Rockies or the Andes (I will use these because the Himalaya/Karakorum massif is dog-legged and not perpendicular to the westerlies for most of its length) then the westerlies must act to "push" the mountains towards the east.

This is of course the same way as the earth's rotation, therefore the earth will speed up (gain angular momentum) and the atmosphere will slow down (lose angular momentum). Hence it must be a negative torque (+AM transport from the atmosphere into the earth). 

 

Addressing some of the concerns I have is this paper: http://journals.ametsoc.org/doi/pdf/10.1175/2007MWR2126.1

 

"High pressure to the west of the plateau means positive torques with respect to M2 and negative ones with respect to M3. It is obvious that the passage of synoptic systems near the TP generates torques with respect to all the three components of the global angular momentum. It is, however, not clear if all baroclinic systems moving along the TP exert a substantial torque."

 

Note that M3 is the axis we usually consider when talking about atmospheric angular momentum. It's the axis pointing from pole to pole. Therefore, this confirms that high pressure to the west of the TP leads to a negative mountain torque.

 

[JamieOber]

So wtf IS the Euro doing? That's a wacky run, as irish points out.

[N. OF PIKE]

Finally, the ITCZ and warm SST have shifted back toward the Equator. Will this connection work to keep the Aleutian High more poleward?

i Was wondering if u had any new thoughts on chance for even more poleward progression of Aleutian High.

[Quakertown needs snow]

 +AO/-PNA

[Quakertown needs snow]

Wtf is the euro doing? That's one crazy solution

 

from twitter:

[Fields27]

from twitter:

 

 

Even though I know there is almost no chance for this to actually happen, I'm just happy it's the time of year that the models are starting to throw out these crazy solutions in the mid-long range.

[NaoPos]

It's gone today, but both the euro and gfs show some building heights around the Davis straights. Out in la la land, but we help temper the SE ridge.

[Quakertown needs snow]

It's gone today, but both the euro and gfs show some building heights around the Davis straights. Out in la la land, but we help temper the SE ridge.

its still there just a different location

[JamieOber]

Question for the brilliant minds in the brilliant thread here...I'm not seeing much in the way of really persistent warmth on the models yet the indices would argue for it. Why is that? Are the models out to lunch (of course I could be looking at the wrong ones)? It seems more like a roller coaster pattern, up and down, with a pretty impressive cold shot coming next week. I had told people our Monday am lows of around 20 here would be the last we see of that for a while, now I am not so sure. 

[dssbss]

JB is honking about the GFS bringing a snowstorm now too!   Ha...the facebook weather sites are getting all excited.   Is there actually a chance of some frozen precip at the end of next week or this totally out of the realm of reality?

[Quakertown needs snow]

from twit

 

[famartin]

JB is honking about the GFS bringing a snowstorm now too!   Ha...the facebook weather sites are getting all excited.   Is there actually a chance of some frozen precip at the end of next week or this totally out of the realm of reality?

[Ralph Wiggum]

Take it with a grain of salt, but a really nice setup for a storm:

 

 

Does the Euro show anything in the medium-long range?

[famartin]

or a pound

[Boch23]

Take it with a grain of salt, but a really nice setup for a storm:

 

 

Does the Euro show anything in the medium-long range?

 

It did the other night.

[atownwxwatcher]

Take it with a grain of salt, but a really nice setup for a storm:

 

 

Does the Euro show anything in the medium-long range?

Shows a cold air mass from 144-168 hrs out  , with a closed low over KY @ 180 hrs out ...However..high slips off the coast and heights start to rise by 192 hrs and we end up going warmer once again...

 

Looks like a pattern of ups and downs when it comes to the temperature department!

[Quakertown needs snow]

euro from twitter