Eagle Eye

I'm back from my semi-hibernation... Got boring without good old weather, be it warm or cold, wet or dry, it's always there . As shown by my earlier post I'm still not in the right frame of mind for anything new as it was incorrect what I said. So I'm just going to stick to what I know. My mum's just finished her surgery and it went ok according to my dad but she's still very tired from it so I'm looking towards the weather for a better outlook. Haven't really read much of the model thread but there seems to be an overall theme of anticipation and excitement but still quite a lot of downers on here. I'm not sure what they want to see from the models? This is the best I've seen this since I joined here a few years ago. The Greenland high is forecasted to be positioned very well for a strong -VE NAO... Yes things can always be better but I like to take the very British approach of could be worse. In the words of Monty Python, "Always look on the bright side of life.". Specifically looking at the NAO and it could dip into negatives not seen since the year that must not be mentioned. Don't think it'll reach the lows of that but it looks like it could get close. That's a very good signal as we go forward. I think the models have that Greenland high in the mid range modelled fairly well based off the fact that no ensembles keep the NAO in a +VE state. I find it unlikely that we'll move away from that particular solution, instead we'll have to see what happens with the Iberian low and how that affects us but the constant trend on the mean for a strong easterly flow suggests that eventually the cold should win out. But we've seen this scenario so many times before, what makes this so different? It's the consistent Nino state AAM, the lag correlating with MJO phases 6 and 7 and the weak(er) zonal wind. Its a very good initial setup for amplification towards Greenland and a -NAO. We're seeing that now. It's now about ironing out the kinks as we move forward, that high located over southern Europe ridging up and that Iberian low may become a problem but I wouldn't worry too much now. We don't take cold seriously till it comes in to 120 hour territory so why should we when it doesn't favour us (us meaning the coldies here). I'm going to have to progress my transition period till the 3rd week of December at a guess because the AAM is still showing little signs of weakening yet so if it does weaken it'll be later than forecast. That's if it does weaken at all,not really showing much signs of it as of yet but a small downwards trend may be finally coming out. Beyond that, it is difficult to tell, it looks like it should increase back to the Nino-esque AAM but for now I'm going to say that I simply don't know. As a general forecast then.. Fairly weak initial easterly perhaps bringing snow to elevated layers followed by another possible, more substantial easterly based off the models and the large -VE NAO forecasted by a fair number of ensemble members. Arctic Oscillation also trending negative all the way up to the upper Troposphere or even the lower Stratosphere and a split polar vortex in the troposphere. Things are looking good for coldies...

Update, still looking scary...

Its been said time and time again, 850's don't matter as much as they are told to be. What matters most is the surface conditions. If it's snowing that matters more than the fact that the uppers may be -4.

Not sure how that could happen as rainbows technically don't exist, unless the sun was directly overhead and I suppose the air has a load of moisture in it or there was slanted rain coming at a certain angle so that the reflection was towards you.

It's gone day 2 moderate, this is looking extremely dangerous now... We're going to see a significant advection of moisture, dewpoints to go up 20-30 F in some areas and the mid-level jet to increase rapidly, this has the ingredients. Right now... SPC forecast "Hodographs are forecast to be long and curved, suggesting the environment will be favorable for tornadic supercells. A long-track and/or significant tornadoes will be possible, with the most favorable corridor located from far northeast Louisiana northeastward across northwest Mississippi. An earlier and further southwest convective initiation would be most favorable for a tornado outbreak, which would give the storms more time to move northeastward through the most unstable air. Supercells will also have potential for wind damage and isolated large hail." Looking at the NAM Clear dewpoint advection to be large scale and even more significant than modelled yesterday... As shown on the temperature advection Strong bulk shear... Clearly very good moisture pooling causing an increase in surface CAPE and hodographs look to have their curve well pronounced within the highest SB CAPE area especially over Louisiana and eventually Mississippi. A couple soundings and hodographs showing supportive dynamics for tornado's, possibly long-tracked especially closer to the surface.

I don't see what the model thread is so downbeat about (for the coldies) with the initial easterly cooling down the 850's and could bring some alright snow sometime this week... Then we get the Greenland high clearly building again, yes there' some amplification from the south but it's barely a sliver that should sink after a few hours as the Iberian low works in our favour and pushes it back down. Nowhere near nailed on but the best chance in years to see some decent snow (sods law that it happens in the energy crisis). It's clearly a waiting game for now...

Hoping we get some snow pictures from this year that's for sure

Quick note before I return to my half hibernation. Been reading this thread occasionally and before you get worried about snowfall accumulation charts just know this... The ability for models to distinguish frontal positions is very low, I've seen fronts end up 50-100 miles away from when it was forecasted at 72 hours so dont get hung up on that. And remember that the GFS isn't a Convection allowing model (CAM) and has very low ability to show Convection getting into the troposphere as gravity waves can often be hidden inside grids (even on some CAM's it can). So that can hide quite a high amount of snowfall considering the high SST's compared to normal, as precipitation generally tends to increase as the clouds get higher in the atmosphere. This will only occur with with right setup but just wanted to remind you that at this time snowfall accumulation charts are about much use as 1 random CFS member for next April.

Very interesting few days on the models Unfortunately , hodographs are getting a lot more curved which means that strong tornado's are a genuine possibility. That classic C shaped hodo hasn't appeared fully yet so hail is unlikely to be large hail but as the SPC so "Mid-level lapse rates are also expected to be steep, which should support a hail threat with the more intense cells." What needs to be considered is the time of year, Gulf moisture is still quite high and with that advecting northward mixing in with the colder troughs, we get a large line of extremely dry air and very moist air. I don't think that over convection will be too much of a problem as over saturation isn't looking likely at the moment and there will be at least semi-discrete cells for most of the event and this is where we see similarities with previous events not to be mentioned. I don't think it'll be as bad as December 10th but the timing is similar and the moisture returns ate relatively similar. It doesn't seem as volatile of an atmosphere nor as strong of a shearing just yet but that can still change.

I know I said I wouldn't post for a long time apart from document stuff but this ties in nicely with one of my older documents that I read. If this does happen, a bottom-up split (possible future SSW) event sounds similar to the first part of PJO related to the Stratospheric thermal transport and zonal wind transfer. For there to be a Stratospheric asymmetry, there has to be movement away from the mean that causes it. A split is a very good example of that movement away from the mean and note that the atmosphere wants to be in thermodynamic equilibrium. It is clear that on this specific GFS run, there are large deviations from the mean around Greenland and as that moves towards the Arctic we get very interesting dynamics occurring. To be in thermodynamic equilibrium now, the zonal wind deviations are transferred further down and with the already weakened Tropospheric zonal wind that increases the chances of a major SSW that goes on to affect the surface. It's just one run and only occurs if the split if quick enough to cause a major SSW but it's a very good run and 1 of the possibilities. Sorry @Kasim Awan just had to do one more, that's pretty much my motto. Will take the week off to recharge (especially after my mocks which I found harder than any recent meteorology documents that I've read lol) now though, see you all either late next week or after the 2010 repeat .

I'm sorry for anyone who finds my posts (if there's anyone) interesting here just feeling a bit overwhelmed at the moment. Will still do my weekly document write-ups but probably won't post here much as I can't really keep up as we go into the best chance we've arguably had for a while in early Winter. Sorry that this is off topic mods just wanted to let the 0 people interested. I don't wish to sound egotistical, after all I'm not that well versed in meteorology it's just some people seem to find my posts interesting I guess. It's sort of a half goodbye for now, don't know when I'll be back to my normal mental state though. If I still feel overwhelmed throughout Winter, good luck to everyone. Of course, I may feel better next week I just don't know. Anyway, my thoughts for now is that if this does happen, it'll be fairly decent away from lowland areas, depending on the exact direction I suppose that North Sea snow showers can occur but whether this will be cold enough to properly cool this coasts remains unknown. I think the main benefit of this is that it could bring snow to areas away from the usual early Winter areas but again, that still remain unknown. I'm not willing to commit to anything really as of yet but the AAM forecasts suggest that we'll see a gradual weakening of the Nino Atmospheric state into next week and lag correlations would suggest the second week of December or sometime around then to be the transition period before a re-entry into the Nino state and so mid to late December, interest may arise again but it's too far away for anything solid.

Despite the constant downward trend forecasts for the AAM on the GWO it's stayed in quite a steady state. So that still makes me a little wary of the latest CFS but there's no real reason not to believe it. I've also noticed the GWO's chop and change a lot from run to run and aren't amazingly accurate considering that a small change in phases has quite a wide impact on future events. 14th November Says by now we'd be on the border between phase 7 and the weak GWO. 18th November Says by now we'd be firmly into the weak GWO (+7 etc is the amount of days) vs where we are now (green dot) So, not focusing on the forecast yet and a bit of realism, there is a lot that's at stake here and truthfully, there is no set-in stone answer for this December onwards. The MJO pattern doesn't really have a solution to it The ECM looks fairly good for moving back to phases 6 and 7 However, the CFS and GFS extended both show it curving down towards phases 1,2 and 3. Note that the GFS especially has a large spread though and so MJO wise, there's too much spread to be definite of anything yet... Going to be interesting to see what happens with this much spread, makes forecasting long-term very difficult

Totally agree with you. Caution is most definitely the game right now. Most of the teleconnection signals are too weak for proper long term forecasting so anyone who's seen my long term forecasts should know that they are essentially the best case scenario with the teleconnection signals.

Short-term is definitely looking interesting but like you I'm holding back for now. My recent posts have focused on the long-term signals because I'm very much a teleconnection person but I've had a go at breaking down the models anyway. There's going to be a lot of scepticism in this post and I've tried to balance my bias but let's see what we've got. My main bit of interest, how the first low splits (or doesn't split) 06Z vs 0Z vs 18Z yesterday Why is that of interest? Well, let's have a look at the different developments down the line... 06Z vs 00Z vs 18Z yesterday I think it's pretty clear that the evolution of the high has a lot to do with that splitting of the low and that's not even taking the ECM into account. Dynamically, this essentially has a lot to do with an area of divergence forming and splits part of the low... Here's a NOAA explanation of how it works. Now, as we can see on the streamlines, it's quite strong in terms of wind strength at 500hPa and there's some fairly strong troughing but that's just based off the latest run. The last 3 runs (a little further on) 18Z yesterday vs 00Z vs 06Z Trend seems to be towards tighter troughing but it's difficult to tell. I'll leave you all to discuss this and the future impacts just my few notes...

Welcome to Netweather. I think there should be a sign on this thread every Winter saying "Please do not take every GFS run as gospel"

Agree with @MattH further up and he puts it more elegantly than I can and looking further on, as the quoted part of my post yesterday says, the AAM does dip soon (but shouldn't affect next week) but should truth back to a proper Nino state AAM and so the consequences of that will be that we get that increased -NAO chances.

Agreed Beware : Quite a long post coming up: I also think we need to be a bit cautious when we talk about the -NAO as the nailed on 100% cold that its sometimes discussed as. You've got to give time for the cold pool to develop on the Eastern side of the Greenland high otherwise its essentially useless just might be associated with a brief cold pattern. Luckily we do have the time on our side as the AAM stays relatively stable and Nino-esque. The GWO is moving towards a phase where over the next week or so when we'll likely lose Atmospheric frictional torque and the AAM goes down . Beyond that we should enter phases of postive friction torque then southward momentum and circumglobal troughs as the AAM increases again so a brief dip then back to normal. You should also refer that there is still a lag correlation with this (not sure how long it is sorry) so keep that in note. Note that the forecast is slightly out of date. What does this all mean though? The main way to lose or gain Atmospheric Angular Momentum (AAM) is by the imparting of frictional or mountain torque to or from the earth or the oceans. Frictional torque is the rotational force imparted on the atmosphere by the friction of the surface. Mountain torque is the torque acted by having different pressure systems on either side of a mountain. The main way of gaining AAM is by having frictional torque and mountain torque (sort of) move from the surface to the atmosphere imparting eastward momentum into the atmosphere, weakening the relative wind. It is also associated with a Nino-esque AAM when the AAM anomaly is above 0. What does this do though? Weakening the relative wind increases the wave oscillations from the tropics and so we get the large scale WAA and blocking perhaps towards Greenland. Greenland blocking is where you get -VE (negative) NAO that has been discussed at length before. Whereas weakening AAM decreases the oscillations and when the AAM anomaly is below 0 it's Nina-esque. What this does is decrease the strength of oscillating tropical waves and that promotes a +VE (positive) NAO pattern and a flatter and stronger relative wind and so the Atlantic is more dominant. Positive Friction torque? Where the friction torque is coming from the earth to the atmosphere and so the AAM increases. Why is southwards momentum transport between the equator and 30N seen as a good thing when surely it dampens the wave amplification? Since a steady state atmosphere is assumed, southwards momentum results in the equal and opposite reaction in the other direction and so there is also northwards momentum transport. Interestingly, the same sort of principal but on a more dynamical basis works in Convective modes (am I getting boring yet ) so I may end up researching into that another time. What about circumglobal troughs? Couldn't find much but it sounds like it's talking about where the troughs on the other side are more of a dominant force than the peaks. So after these next 1 or 2 blocking and therefore -NAO opportunities, mid to late December is also looking interesting based on recent GWO forecasts which can change but I don't think dramatically enough to keep up the interest. Note that I wrote a lot of this twice after accidentally deleting most of what I'd already written so I may have missed out an important paragraph or two and my brain is starting to hurt so if you do ask questions I may not reply till tomorrow. Generally a decent chance of a -NAO, maybe even a few but that doesn't guarantee proper cold but with the time we've got it does increase the chance of proper cold compared to a more rushed pattern than what we have now.

Very good dewpoints stretching up into parts of Arkansas from mixing in with air from the Gulf of Mexico as you said. That dryline is looking very significant though and that may start some vigorous convection. The thing is, the GFS is too low of a resolution to properly resolve the gravity wave effect on convection and so we should start getting strong convection when the CAM's come into view of this potential setup and that's when we'll know the mode. For now, the significant tornadic potential may be fairly limited with the best hodographs being fairly stretched but it's a long time away and only a GFS sounding. I think damaging wind gusts may be quite a high risk based off this initial setup but hail not looking major (although this is subject to change I would imagine). That's supported by what the SPC are saying for now: "Intense vertical shear will overlap with this unseasonably moist boundary-layer ahead of the surging cold front, supporting conditions favorable for damaging gusts and tornadoes."

Hope I'll be included in that lol, although I do find that half the time I find myself writing a load of weather terms and results but not explaining the correlation and why between the two things. Hoping this Winter I'll have an Eagle Eye for a cold weather pattern

Long battle towards cold up for us but right now it seems a fairly likely solution but how cold it gets I imagine is quite difficult to forecast. We can look at teleconnections all we want but that's only for establishing the basic pattern in the future and now the little dynamical 'errors' taking it away from being a perfect scenario means that it's going to be difficult to forecast with chopping and changing of models. That's the beauty of forecasting though (in my opinion), as it can mean that no one person is correct but nor are they necessarily wrong, it allows more voices to be heard because there's no one definite solution. So good luck everyone and let the battle... Commence.

Going for 40 degrees by the bleak mid-Winter aren't we

Since October, the AAM has been above average and so more nino-esque and so for the last month or so we've had the chance of a -AO setup and finally after a missed opportunity or two, there are lots of ensembles showing the results of this background signal and so models aside, the blocking is very likely and the resultant cold fairly likely. A -AO is almost nailed on right now and we may see it get towards low's that we haven't seen for a while.

Very good ECM run... No complaints or complicated weather phenomenon. That's all I have to say just a very good run... Edit: Wrong GIF

Realistically, the background signals will be staying relatively steady over the next few weeks and so a major pattern flip to a sustained +VE NAO is unlikely, instead a continuing risk of that -NAO will likely be there. Initially, we may see a weakening of the AAM but a steady rise as we go into December looks probable, with one of the CFS members going for a fairly strong AAM. The main reason seems to be that we are about to enter GWO (Global Wind Oscillation) phase 8 which is associated with negative friction torque and so the AAM decreases as some of the momentum goes into the oceans and/or earth. Just beyond that and the GWO signal may be quite weak but it should re-emerge and start increasing the further we get into December. Remember that there is a lag of probably about a week between the AAM and it's correlated products. What all of this means is that I think that for now, surface components will determine how this plays out, the blocking to potential -NAO signal at the moment from the WAA is there with that Nino (positive) like AAM helping it. We then go into a state of sort of neutral where the pattern may become quite messy for mid term trends before we re-emerge in early-mid December with a similar pattern to now and a steadily improving (for someone who wants cold) GWO phase. So a return to the Nino-esque AAM is looking very likely. So for now, the next one or two setups from the MJO phase 6 and 7 recycling, probably followed by a transition period that may only last a few days before a return to the increased risk of -NAO around mid December. All in all, this is a very good setup for someone wanting cold as it means we have multiple opportunities and are in no real rush for a -NAO and can afford a slow transition.

I've been saying it for a while now, the background signals look to almost constantly be in our favour. MJO recycling through phases 6 and 7 causing the Nino AAM, trend towards a -NAO, there is very little wrong with this... Blocking seems highly likely with this sort of setup, beyond that and it's up to the strength of WAA to decide our fate, all I'm saying is that we're in with a very decent chance here. Plus Oh and above average SST's in the North Sea, lake effect snow possible in right setup, etc.. Just nobody say anything to your friends and family otherwise the net weather jinx may continue . The models will toy with our emotions of course, it just wouldn't be the GFS, ECM or any other model without any drama.