Model discussion highlights

[Met4Cast]

Regardless of any SSW's the outlook in terms of cold appears to be quite favourable to me. We've got the MJO moving round into a high amplitude phase 3, likely to be there for a relatively extended period of time, this should help to trigger a +ve EAMT event and resultant rise in the AAM. 

MJO phase 3 correlates to height rises to the W/NW of the UK towards Greenland. At the same time this is going on, the SPV will be weakening dramatically (major SSW or not, a weakening is likely). This in my eyes supports a period of blocking towards the middle of February when factoring in lag times etc. 

Now, it seems likely that we'll be stuck with a mid Atlantic limpet high for a while, perhaps sitting further east or further west, exact placement remains to be seen but fairly decent long-range signals that eventually that high will begin to build northwards. Yesterdays GEM did exactly this only about 2 weeks earlier than I'd have expected to see it happen. 

Favourable outlook, SSW or not.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794080

[mushymanrob]

Regarding SSWs and their actual impact on our weather ..

Looking further into this, im finding hard to identify just what cold spells following a SSW were down to the SSW . Most Winters have cold spells, some Winters have Easterlies and often they have nothing to do with a SSW, February 1986 is a classic example.

Given that not all cold spells come via a SSW and not all SSWs produce anything, im not sure we can actually identify many that do. I think our perception of SSWs has been tainted rose coloured by 2013 and 2018. These two did deliver quite spectacularly.

But so far, checking the charts post SSW, there no clear indication that a cold spell WAS down to a SSW, and sometimes the Easterlies SSWs are supposed to promote, miss the UK.  The cold spells that im doubtful about are post SSW Northerlies...

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794075

[Ali1977]

11 minutes ago, bluearmy said:

You wouldnt expect the gefs to grasp anything from the strat ahead of the eps. Looking at the gfs 00z op run, it seems that the trop pattern is imprinting upwards into the mid strat as week 2 progresses so we could have a scenario where the existing pattern (where the trop leads the dance) continues,   but the upper strat begins to flush down westerly momentum at higher latitudes. That looks very complex to me and even more reason to be overly cautious of week 2 ens output 

Something has stirred them, huge upgrade with the ENS fir some reason. Some Day 10s below 

 

The mean sending the ridge higher, and a bit further West 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794123

[Kirkcaldy Weather]

Wanted to look again at my previous outlooks, see where we are currently and the big things to focus on going forward

On 06/01/2023 at 17:53, Kirkcaldy Weather said:

Would fit in the movie San Andreas, sometimes there aren't words to describe the amazing power of mother nature

Sending prayers and positive vibes to those living in the bay areas and sierras.

I've been doing a lot of studying & research and have found very interesting stuff.

I had this saved from a great paper I read years ago about the connection of the MJO and stratospheric warming events. Fits nice with the progression of MJO phases we have had over the last month or so

I've highlighted that we entered MJO phase 7 roughly New Year's Eve 

We are beginning to see the signal emerging that the phase 7 pattern will begin to filter into the surface conditions by weeks 2-3 of Jan

 

Super interesting that pattern matches really well with the 2nd highest percentage from this paper on precursor patterns connecting with SSW events 

Just a moment...

AGUPUBS.ONLINELIBRARY.WILEY.COM

If that didn't link correctly just google search for Classifying the tropospheric precursor patterns of sudden stratospheric warmings

More on the MJO influence on stratospheric warming from a different paper

 

We see a clear connection with SSW's leading to Greenland blocking 

Which would pair with the lagged phase 7 composites from CPC

Another very interesting find from my research is something I wasn't award of, a big connection of the bomb cyclone / Atmospheric river pattern in the Pacific (the pattern we see right now) and SSW's 

"This study provides the modeling evidence that bomb cyclones in the North Pacific can modulate the onset of SSW."

Just a moment...

AGUPUBS.ONLINELIBRARY.WILEY.COM

Again search for A Critical Role of the North Pacific Bomb Cyclones in the Onset of the 2021 Sudden Stratospheric Warming

We also have a bomb cyclone in the Atlantic, whilst not in that study I'd suspect this will fit with that research and play a part in upcoming stratospheric developments 

Potential for another to develop by early next week 

And a continuation of that pattern on the Pacific side too 

A really positive longer range MJO outlook too should a secondary strat warming event be required 

And I found some more info on the dramatically below average December Iceland saw

All in all a VERY exciting period as January unfolds across multiple meteorological categories 

^ (nearly 2 weeks ago)

'We are beginning to see the signal emerging that the phase 7 pattern will begin to filter into the surface conditions by weeks 2-3 of Jan'

Excellent match up with that and the current pattern

 

'Super interesting that pattern matches really well with the 2nd highest percentage from this paper on precursor patterns connecting with SSW events'

 

Again very similar to current setup and as we progress.

'More on the MJO influence on stratospheric warming from a different paper'

 

Looks like it has linked well again with current expectations 

'We see a clear connection with SSW's leading to Greenland blocking'

I discussed this yesterday but definitely a big pattern to focus on going forward

'Which would pair with the lagged phase 7 composites from CPC'

 

Another good fit with current modelling

'Another very interesting find from my research is something I wasn't award of, a big connection of the bomb cyclone / Atmospheric river pattern in the Pacific (the pattern we see right now) and SSW's 

"This study provides the modeling evidence that bomb cyclones in the North Pacific can modulate the onset of SSW." '

Looks like this has indeed had a huge role in association with upcoming strat developments 

On 09/01/2023 at 13:56, Kirkcaldy Weather said:

Today + Tomorrow seeing the most extreme of the Atmospheric river conditions so far

Day 1 Valid 12Z Mon Jan 09 2023 - 12Z Tue Jan 10 2023 ...A MODERATE RISK OF EXCESSIVE RAINFALL CONTINUES ACROSS A LARGE PORTION OF CALIFORNIA, INCLUDING THE BAY AREA AND MUCH OF THE CENTRAL VALLEY... ...NUMEROUS FLASH FLOODING EVENTS LIKELY, SOME POSSIBLY SIGNIFICANT, ESPECIALLY OVER BURN SCARS... A more significant, elongated Atmospheric River (or AR) event is already beginning to impact much of CA ahead of a more amplified upper trough, effectively tapping into the subtropical regions of the north Pacific. Guidance continues to show PWs climbing between 1.25-1.5" (highest along the coast, and easily surpassing the max moving average per OAK and VBG sounding climatology), with southwesterly 850 mb flow peaking between 60-70 kts. Low to mid-layer moisture transport will be quite robust, as the 850-700 mb moisture flux peaks at 5 standard deviation range above normal, per the GEFS. Meanwhile, some elevated instability (at least 200-400 J/kg per the ECMWF, GFS, and HREF mean), along with the degree of deep-layer forcing and moisture, would support peak hourly rainfall rates of 0.75-1.00+ inch (especially within the Moderate Risk area). Overall, guidance consensus remains quite good with respect to the QPF, with 24 hour totals between 2-4+ inches over most areas (along with pockets of 5-8+ inches along the coast-coastal ranges and across the western slopes of the Sierra Nevada). This will be a fairly significant event as far as ARs go, with the latest deterministic QPF indicating a 5 to 10 year average recurrence interval (or ARI) within portions of the Moderate Risk area. In addition, the latest HREF 40km neighborhood probabilities of 3 hourly QPF exceeding current 3 hour FFGs climb to >50% within the Moderate Risk area after 15Z Monday. Considering how wet the soils will be ahead of this event (over the 90th percentile within the top 100 cm across the majority of the outlook areas per the latest NASA SPoRT), impacts from flash flooding or more rapid inundation will become increasingly likely -- especially across the several burn scars since 2020. Churchill/Hurley Day 2 Valid 12Z Tue Jan 10 2023 - 12Z Wed Jan 11 2023 ...THERE IS A MODERATE RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF SOUTHERN CALIFORNIA... Maintained a Moderate Risk area for excessive rainfall across portions of Southern California. Models continue to indicate a distinct southward shift in the QPF maxima on Day 2, with significant rainfall already expected to be ongoing Tuesday morning across upslope portions of the Transverse Ranges (with as much as 3-6" having already fallen on Monday and Monday night). Long duration of southwesterly flow will allow for another 2-4 inches of rainfall (locally) along the terrain on Tuesday, with precipitable water values of 1.00-1.25" and the chance for thunderstorms as low-level lapse rates steepen (and ML CAPE reaching perhaps as high as 500 J/kg). Areas along the coast and in the valleys will receive closer to an inch of additional rainfall on Tuesday, coming with an additional (final) surge of tropospheric moisture (and eventual cold front passage) in the afternoon.

We see just how much outside of the climatological norm this amount of rain and snowfall is 

Also rare severe thunderstorm Day 1 + 2 outlooks for California with tornado risks 

 

Brings my mind to this 

Ended up being an impressive bomb cyclone in the atlantic with a 51mb pressure drop in 24hrs

We continue to see the MJO phase 7 & SSW precursor pattern playing out 

 

There has been a taboo around displacement events being associated with failing in bringing cold and snowy conditions to the UK however this is misleading, interesting results from this paper

"Key Points

Little difference in the longer-term (3–4 weeks+) surface response in either free-running or thermally forced displacement and split events

Conversely, large differences are apparent between displacements and splits at shorter lags

Displacements yield stronger stratospheric temperature anomalies than splits yet still give rise to similar-magnitude tropospheric responses"

'For instance,  at 60 N and 10 hPa clearly shows a weaker vortex for the displacements than the splits'

A tonne of reading in it but an excellent study  

Just a moment...

AGUPUBS.ONLINELIBRARY.WILEY.COM

Google search - displacement stratospheric warming, its the first paper from 2021

More reason not to fear displacement events, again we see the clear link of strat warmings and Greenland blocking 

 

Images from a useful thread by James P 

Initially the current signs seem more toward a displacement (this could still see a split further down the line) taking the JMA which shows that nicely 

We currently have a bit of warming taking place 

And note how the PV gets shunted away from the Arctic southwestwards 

 

Oh did you think that was it... nah we have the next EAMT event shaping up too 

I did mention weeks 2-3 of Jan would be exciting

 

^Again for those second guessing that displacements can lead to cold setups for the UK.

also i believe the EAMT is factoring in with giving a boost to the blocking especially in the Pacific.

On 12/01/2023 at 13:56, Kirkcaldy Weather said:

Very exciting times indeed I'll get onto that shortly

The snowpacks in the sierras are above levels we'd expect to see by APRIL!  

Looking like about a week more of Atmospheric river conditions before a switch in the setup, how can we tell that switch is likely? 

Again focusing on the Pacific Jet (top of image) similar to in my previous posts its still barrelling down on California 

*Also note the northwest > southeast alignment of our branch of the jet

But as we fast forward a few days we see the buckle and orientation shift in the Jet and a retraction west 

Looking closer at the conditions for the UK as we see low pressures aligned on the NW>SE Jet combining with 528 dam air this will see wintry conditions with showers of sleet and snow plus any fronts attempting to move across the UK into that air have great potential to deliver heavy battleground snow

Focusing on our Jet stream branch, we see an active jet streak 

Entrance of Jet Streaks

WWW.WEATHER.GOV

 

The one on Saturday looks very impressive

This will bring a large zone of 50-55mph gusts through Ireland, Southern Scotland and Northern England Tonight

More detailed chart of that developing storm 

Another develops hot on its heels through tomorrow and the start of the weekend 

This is a prime example of La Ninà MJO phase 8 through January  

Some more info on the Atmospheric River pattern before the most exciting part of my post

The first ever night tornado warnings issued by the Sacremento NWS area 

Stunning satellite views

Now the reasons for my excitement..

Nice MJO progression of phases 7/8/1/2

 

Here's the other setups associated with phases 8 + 1

 

 

 

 

Positive signs for a blocking pattern to set up and focus shifting to a flow from the East & NorthEast

Using my own personal method I'd expect those MJO Phases to begin transitioning into surface conditions from 23rd of Jan >>

Given Siberia is experiencing brutally low and record cold temperatures its definitely to be watched 

 

 

(Posted a week ago)

'Here's the other setups associated with phases 8 + 1

  

 

 

 

Positive signs for a blocking pattern to set up and focus shifting to a flow from the East & NorthEast

Using my own personal method I'd expect those MJO Phases to begin transitioning into surface conditions from 23rd of Jan >>'

More nice pattern matching with current outlooks

 

Very pleased with the 23rd prediction as this looks to combine with the strat warming really cranking up

On 15/01/2023 at 15:02, Kirkcaldy Weather said:

The Jet streak yesterday was indeed impressive as it helped the storm deepen pretty rapidly with official bomb cyclone requirements measured here

Pressure began at 998.51hpa and dropped to 973.32hpa

I know there was some pretty severe conditions around Ayrshire with some damage 

Overnight and into tomorrow Looking like some snow for northern England and I wouldn't rule out the chances of the rain turning to snow in the south east (possibly into London) 

Still positive signals going forward with extensive blocking and a potential linkup with the blocking around Scandinavia and an increasingly strengthening Pacific ridge / block.

I think the EAMT event will strengthen that Pacific ridge/ block quite impressively 

 

Another tweet within that helpful thread from Eric shows February patterns associated with La Ninà, VERY intriguing composite years in there 

2021,2018,2012,2009

The first BEAST appeared on yesterday's 00z 

 

Still believe it's worth keeping a close eye on as further extreme record cold temperatures are falling in Siberia 

Another country facing extreme cold is India with what they are naming the #Coldwave

&Asia too 

 

 

Some more extremes currently playing out 

Massive record breaking snowstorm in ARIZONA, particularly Flagstaff

Big Pine Creek at +738% snowfall for this time in the season have you ever seen a crazier stat

8th biggest snowstorm in history for Denver 

On 16/01/2023 at 18:38, Kirkcaldy Weather said:

It's to be expected big swings on each run likely the strat warming trying to be implemented in combination with the MJO and EAMT as I've been posting about.

Does seem a trend currently for a retrogressing block from the NE > Greenland and the linkup with the strengthening Pacific blocking I mentioned, in turn this shifts the elongated tropospheric vortex to our NE

 

 

 

 

On 17/01/2023 at 21:53, Kirkcaldy Weather said:

Definitely one of the first focus points continues to be the block retrogression then linkup to the Pacific blocking leading to that elongated trop vortex extending in our direction from the NE 

 

 

 

 

Consistency for this pattern with blocking retrogression > linkup to Pacific blocking > tropospheric vortex elongation from the Northeast 

Even current longer range modelling the big signal is consistent blocking just a question how quick does the strat warming try to work its way down to the trop pattern though certainly could be a big aid in pumping that blocking up further.

 

 

 

 

 

 

 

 

 

 

 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794195

[Met4Cast]

2 minutes ago, northwestsnow said:

Doesn't mjo phase 3 promote an active Atlantic in a La Nina ?

In theory yes - But the rise in AAM to +ve means there will be a disconnect between the ocean & atmospheric states and the atmosphere would be behaving more Nino like vs Nina like.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794088

[bluearmy]

12 minutes ago, Ali1977 said:

There are 4/5 GEFS ENS showing this set up as early as T192 - I’m just wondering if we could see a major flip on the models in the next 24 hours as they grasp STRAT/PV changes!! 

 

The mean pressure over Greenland is also 10mb less this run, nightlight more blocking ENS in that region maybe.

 

Vs the 00z below.

You wouldnt expect the gefs to grasp anything from the strat ahead of the eps. Looking at the gfs 00z op run, it seems that the trop pattern is imprinting upwards into the mid strat as week 2 progresses so we could have a scenario where the existing pattern (where the trop leads the dance) continues,   but the upper strat begins to flush down westerly momentum at higher latitudes. That looks very complex to me and even more reason to be overly cautious of week 2 ens output 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794118

[Cold Winter Night]

32 minutes ago, Bricriu said:

I wonder how many  noteworthy cold spells in say the last 40 years happened without any warming at all in the strat?  We know February 1991 had a significant warming that January. One of the cold spells between the winters of 2009 and 2011 did not have a warming at all i believe. There was a significant cold spell here in the last week of December in 2000. There was no ssw then, but the zonal winds were weak. Also i wonder what the mjo phases were during these cold spells that fell short of a techincal SSW?

It would be interesting to study stratospheric warmings without reversals. Perhaps a warming with a reversal is even better on the ground.

There are many cold spells in the past 40 years that happened without a preceding, technical SSW.
Some serious, some more modest.

- Winter of 1986
- January 1987 (SSW happened after the famous cold spell)
- February 1991, as you mentioned with strat. warming, but no tech. SSW.
- February 1994
- Winter of 1996
- Late Dec 1996/early January 1997
- December 2008/January 2009 (SSW happened late January)
- January 2010
- December 2010
- February 2012 (the one when the UK just missed out)
- January 2017
- December 2017
- December 2022

The idea that winter is only possible after technical SSW's is therefore false.

Of course, the list depends on your exact definitions of "cold spell", and your location.
It would indeed be interesting to know the state of the stratosphere before each of them. Was there any warming/weakening zonal winds involved?

SSW's as they are defined require an actual reversal of mean zonal winds at 60N at the 10hPa level. That is of course just a subjective category to make classification easier, but if you want to look at warmings outside the technical SSW's you're confronted with the question: where do you draw the line?

The study of these stratospheric events is still in its infancy, and the very small sample size doesn't help, especially if you take ENSO, QBO and MJO states into account as well.

Now we are looking at a warming in the next few weeks, and possibly a technical SSW, but here we are, not sure if that is a good thing or not! Makes for interesting viewing.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794157

[bluearmy]

looking through the 06z gfs cross section shows that the ringed area on day 2  (50-70N in the trop) is fairly benign with the hatched area of the strat covering the stronger mobility. You can see from the other screenshots how the reversals high up have forced the mobility in the lower strat and trop into the latitudes where we don’t really want to see it as week 2 progresses (50-65N) 

whilst these charts are from the op and therefore not to be taken too literally as week 2 progresses, it has been a consistent theme of the recent gfs runs for these stronger westerly flows to be appearing between 500 and 50 hpa. hence the poor late week 2 gfs op runs we’ve seen recently.  If gfs has a handle on this then wintry output won’t present itself until we’re into feb. 

Day 2                                                             Day 7                                                       Day 11 

         

day 15

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794179

[Eagle Eye]

A brief explanation of a lot of teleconnections and charts that are useful or have good explanations elsewhere;

1) The EPO is the East Pacific Oscillation with two main phases which are important in Winter when combined with what else is happening. The two typical phases are the negative and positive phases shown below. The exact positioning of the Arctic high in the negative phase is generally how our pattern will evolve from there. If it can push the cold more central and ridging along the Eastern seaboard of North America. The positive EPO phase tends to favour the more zonal flow with the positive (+VE) NAO.

2) Pacific-North American Pattern (PNA)

Has two phases as well and though it doesn’t always affect our weather majorly, the North American patterns tend to have effects on us down the line when the pattern is well amplified. The negative phase has below average heights located over the west US/Canada and a SE US ridging pattern. With stronger positive heights towards Canada but still a –VE PNA, then that can result in a pattern favourable for cold here. Though it doesn’t tend to infuence out weather majorly. A +VE PNA is the opposite though with minor differences to the general pattern can also be really good for us. So it’s a general forecasting tool that’s mainly used with other teleconnections.

3)AAM (atmospheric angular momentum)

AMB - Angular Momentum Budget

AAM - Atmospheric Angular Momentum

MT(mountain torque)

GWT(gravity wave torque)

FT(frictional torque)

If AMB increases in the atmosphere it must have been transferred from another source since AMB is always conserved. The sources for AMB are from the Earth, the Oceans and the Atmosphere.

One major aspect in affecting AAM are torques. A torque is the rotational force in the atmosphere.

The 3 main torques affecting the atmosphere are:

Mountain torque (MT) - The turning force applied with the effect of pressure systems on mountains.

Frictional torque (FT) - Boundary layer dynamics.

Gravity wave torque (GWT) - Subgrid (local) torque, upward movement and downward movement to do with the buoyancy.

If there is a net westerly surface wind, the atmosphere speeds up the Earth's rotation and transfers angular momentum to the earth and so there is a net decrease in AAM. The reverse happens with a net easterly wind.

In the NH Winter:

Global MT anomalies are constructed by sypnotic waves that scatter energy across Asia and North America. These sypnotic waves trap the SLP anomaly and push them towards the south. Driven south and east of mountains. Sypnotic wave centres amplify aloft. MT associated with anomaly air parcel transportation in terms of momentum into latitudes its next to. More angular momentum is therefore moves to the 20-20N band. This is where the AAM anomaly appears significant. The anomaly quickly becoming equally uniform leading to a global FT that weakens the AAM anomalies. An anomalous distribution of mass accompanying the MT acting to balance the zonal winds in the 20-30N region. In the mid latitude, Eddy's are the physical link between those two torques.

 The two main torques can be shown in a lag correlation and FT "leads" MT. The relationship related as previously mentioned in the last paragraph. SLP anomalies are related to FT and the coupling with MT.

Some definitions of some words you may not understand

Synoptic is a general summary.

Waves here refers to planatery waves which are propagated by the rotational forces of the Earth and transport energy even if not doing it much themselves and they show themselves in the form of a meandering jet stream.

4) Global Wind Oscillation (GWO)

GWO Phases

Phases 4-7 associated with increasing AAM and so theoretically a higher blocking and therefore cold chance (through a -VE AO and/or a -VE NAO typically) later down the line. The rest of the phases, a decreasing AAM and theoretically a more zonal (Atlantic dominant) setup.

5)MJO (Madden-Julian Oscillation)

There are 8 different MJO phases

 Firstly, the Madden-Julian Oscillation(MJO) which is the largest intra-seasonal background influence. It’s a coupling between the circulation of the atmosphere and tropical convection and is a moving pattern. Increasing tropical convection, will increase the strength of the forcing of air up from the Tropics towards the mid to high latitudes. Which depending on the Phase and so where the air generally moves each time, will either increase or decrease our cold chances in general. It typically affects or weather 10-14 days later, though can be longer or shorter.

Phase 1 is fairly non-descript for us though I find it to usually be mild and wet may just be because that's how the 'average' part of Winter is for us.

Phases 2 and 3 tend to drive the mild and wet muck that not many people like and you can probably include phase 4 in that. As these seem to help +VE Azores region Hadley cell development and the Euro high tends to form because of this.

Phase 5 is fairly non-descript.

Phases 6 and 7 are heralded mostly by UK cold lovers because they help with warm air advection towards Greenland (known as a -VE NAO) or sometimes Scandinavia(?) and that often results in a colder pattern for the UK as air can move in from the East/Northeast.

Phase 8 drives high-latitude North American blocking

6)EAMT or East Asian Mountain Torque

A +VE EAMT event is where warm air hits the Himalayas and wave activity moves vertically up into the Stratosphere and we see the gain of AAM in the Trop-Strat this way. On the other hand we have -VE EAMT where cold hits the Himalayas and there's a loss of momentum into the Earth. A +VE EAMT extends the Pacific jet, a +VE EAMT does the opposite. An extended Pacific jet tends to retract the Atlantic jet though it depends on how North America evolves and there’s too many possibly evolutions to say all of them. Similarly, a retracted Pacific jet tends to extend the Atlantic jet (more zonal) though not always.

7) NAO (North Atlantic Oscillation)

In basics, above average heights over the Greenland region is the –VE NAO phase and the opposite for below average heights. We tend to see the –VE NAO phase linked with fairly good cold for us though not always. The ‘basing’ of the –VE NAO is important; west based (west Greenland) isn’t always good and east based (east Greenland) tends to be the best –VE NAO pattern. A +VE NAO is typically linked with the large Canada-Greenland low and a flatter/zonal pattern especially during Wintertime.

AO (Arctic Oscillation)

The –VE AO is characterised by +VE (anomalies in the case of heights) heights over the Arctic and that tends to have –VE heights over the mid-latitudes where we are. That’s when you’ve got a large –VE AO though, it normally tends to be one area of +VE heights above (I think it’s) 60N and so –VE heights in areas of the mid-latitudes but not anywhere. Similarly, the +VE AO has –VE heights over the Arctic area and that tends to be more zonal in the mid-latitudes but not necessarily anywhere.

Explanations for why and how to use certain charts (some copied with reference );

9)Tropical-Northern Hemisphere Pattern (TNH)

The TNH is the main mode of Wintertime in the Northern Hemisphere. The positive(+VE TNH) is linked with the generally accepted as zonal setup. The TNH in general shows the changes in the Pacific jet. The –VE TNH is essentially when the typical pattern that favours zonal is reversed such as in early-mid December last year/earlier this Winter.

The positive phase of the TNH;

10) Geopotential heights

Geopotential heights are an approximation of the actual height of that pressure above sea level. Since cold air is less dense than warm air, heights tend to be lower in cold air masses and higher in warmer air masses. Heights are the function of the average temperature of air below that essentially when working out the approximate level though it’s a lot more complex than that.

To quote John Holmes

“By that I am referring to the major wave pattern in the atmosphere. Around the globe, north and south, long wave patterns, sometimes referred to as Rossby waves are permanently in the atmosphere. In both hemispheres the general flow is from west to east, not so around the equator where an easterly is often the direction. Within this broad westerly flow are the ridges and troughs that largely govern how the weather is at the surface. Thus if we can get the upper wind direction and pattern near enough correct then it does give a forecaster a fighting chance of getting the weather at the surface reasonably accurate. Unlike some comments you will see during the winter about ‘short wave’ developments ‘scuppering things’ they cannot develop at the surface unless the upper air pattern allows them not the other way round. We then get into the discussion as to which comes first, surface or upper air. Hugely complex and with no easy answer but the upper air does govern the surface on MOST occasions and not the other way round. Trust me.

What are ridges and troughs?

As a VERY rough guide where the ridges are generally the weather is more settled and where the troughs are is often unsettled.

Bends in the contour charts is a very simple way, the ridge is the bend at the top, see below, and the trough is the bend at the bottom is as simple as I can make it.

Sorry if the diagram is not very clear, not very good at paint and insert! (2012 period) So I hope that shows as simply as possible what I mean.

In very simple terms the ridges and troughs are caused by differences in heating north to south in the hemispheres and the mountains chains which occur over the world surface. Do NOT get too hung up on the detailed explanation for the time being.”

Full explanation from @johnholmes

11) 850 hPa temperatures and snowfall by @snowking;

 

 

12) Thickness (Jeff Haby)

“A thickness line is the vertical distance in meters between two pressure levels. The models commonly use the 1000 to 500 millibar thickness…

Thickness will INCREASE if the average virtual temperature increases (either temperature increasing or moisture content increasing or both). Thickness will DECREASE if the average virtual temperature decreases (either temperature decreasing or moisture content decreasing or both). Thickness will increase due to WAA or diabatic warming (solar heating). Thickness will decrease due to CAA or diabatic cooling (longwave cooling, evaporational cooling, etc.). The thickness values will be higher in the lower latitudes and the thickness values will be lower in the high latitudes. The thickness lines will be packed close together where there is a large temperature gradient in the atmosphere…

The thickness lines are displayed in increments of 60 geopotential meters. The solid yellow lines guide you to interpreting the value of each thickness line. The 5,700, 5,400 and 5,100 thickness lines will be shown in solid yellow. A thickness of less than 5,100 is associated with arctic air while a thickness of 5,700 or greater is associated with tropical air. The 5,400 line generally divides polar air from mid-latitude air. The 5,400 line is also used as a guide to the rain/snow line. On this chart, the 540 (another way of expressing 5,400 gpm) runs through Mississippi (follow its path across the entire U.S.). Everywhere north of this solid line, the thickness is LESS than 5,400. The first dashed line north of the 540 line is the 534 line (remember the lines are in increments of 60 Thickness near 510 will be associated with very cold air.

The next stage is to apply your knowledge of the thickness lines. When cold air moves south, lower thickness lines will be associated with this cold air. In the example, cold air is filtering toward the south (wind speed and direction can be inferred using the blue isobars) in the eastern U.S. and this region has lower heights associated with it. CAA is associated with decreasing heights and WAA with increasing heights.”

Also a bit of input from United Kingdom weather resources;

“Can the 500-1000 hPa patterns be used to infer the snow risk? Well, yes they can, but because the layer is so deep -- some 5 km, or 17,000 ft of the lower atmosphere, its not a good indicator.

Rain and snow are equally likely when the 500-1000 hPa thickness is about 5225 gpm (or 522 dam). Rain is rare when the 500-1000 hPa thickness is less than 5190 gpm. Snow is extremely rare when the 500-1000 hPa thickness is greater than 5395 gpm.”

12)Vorticity advection and it’s relation with height change

Positive vorticity advection (PVA) promotes divergence (upper level) and this cause the average temperature related to it to decrease since rising air cools. So PVA is correlated with height falls. The opposite happens with negative vorticity advection (NVA) and so the height rises.

An example of how this works (Jeff Haby);

“The image that follows shows the likely position of vorticity maximums. Again, vorticity maximums will be located in areas where the most vorticity terms are positive and largely positive in magnitude. When looking at a vorticity plot or a 500 millibar chart you should now know the processes in the atmosphere that are causing the vorticity (shear, curvature, Coriolis vorticity (aka earth vorticity).

The strength of the wind is also very important. All else being equal, stronger winds will produce stronger vorticity in the base of a trough.”

I realise that I quoted a lot more of the explanations rather than teleconnections and that's because I'm more confident in being able to explain teleconnections versus the use of different charts.

All that being said here's my thoughts on the future;

I realise that the 12Z's are likely to be out when I post this but I'm only going to be looking at the 00Z's and 06Z's.

Development of the neutral/-NAO look fairly likely with above average heights near the area but not strongly over Greenland, more of a ridging between S Greenland - Scandi that eventually retrogresses as the exiting cycle of the -VE EPO occurs. That appears to build a more typical +TNH North American pattern eventually as the -EPO appears to show a pattern evident with how it typically evolves despite the initial pattern though this appears to keep up the -VE AO for a while. Eventually, it may retrogress and so upwards wave flux starts to fade and so a SSW would preferably occur by early February as the +TNH NH pattern appears to be favoured. Importantly though, the amount of spread makes me think that there are lots of different variations that can occur. I think the exiting -VE EPO Wave may be unavoidable however the held up -VE EAMT keeping up Alaskaward heights in the Pacific and the feeback of Indian convection may initially not be that strong. That can keep up the -VE EPO into a progressive repeating pattern and some sort of mid-high latitude +VE heights may be held up somewhere between Greenland - the Urals so it's possible that we keep up the progressive heat transfer into the Strat keeping pressure on the Vortex if we haven't got a SSW by then. So it's a diffcult but by no means impossible period to forecast you've just got to be willing to fall on your sword with a forecast. In my opinion we'll see a repeating -VE EPO pattern with normal returns over North America and by no means a zonal Atlantic. Ural heights stay relatively stable perhaps transitioning more to the East with eventual -VE heights to the West of it. The expansion of the Atlantic high pressure cell is looking fairly likely and that may mean that we end up under a fairly dry spell through considering how close we could be to the easterly low pressure we may still see a retraction of the high pressure to allow a cold/snowy spell to return though what I think is more likely is that we stay fairly dry compared to what we have been but cloudy and around average temperatures. Beyond that and the exiting Wave is likely to retrogress the high pressure and that may cause the slow progression back towards the +VE TNH pattern but at this range it's hard to tell what way that will lean in terms of the high pressure regression. The retrograde Scandi-Ural high will be an interesting one to watch for surface warmth developments over Scandinavia and the displacement of the cold as that'll affect where the cold is centred, interesting for gaining cold from different areas such as the South.

00Z EPS

00Z GEFS

06Z GEFS

Still a fair amount of confusing but the exiting initial -EPO wave seems fairly likely but beyond that will rely on how the Pacific jet acts potentially making the long-term forecasts even worse than usual. I wouldn't trust the means long-term at all either (though I used some day 10+ means that was mainly to show the confusion on the models) as there's likely to be a fairly large amount of spread.

 

 

Potential for a SSW;

Based off the Eddy's I would suggest a continued Wave-1 tropopause initiation though they can be modelled quite poorly. It's important to note that most SSW potential won't be acted in the Tropopause till around near day 10 if the strong vertical energy and mass distribution occurs quickly. In which case, the Stratosphere won't actually be modelled that well despite it normally being modelled better than the Troposphere as the Troposphere is likely to have a large difference to the distribution of Eddy's so that will be interesting to see what happens with the modelling as the supposed SSW chance comes closer to time (especially the day 10+ charts) so perhaps a SSW may not be well modelled even on the operational charts just yet. This makes disregarding a SSW almost impossible given a 20-30% chance at a guess given the range. So for the Met Office to mention it is interesting to me but does make sense given that the models do tend to be trying to show one even if still at day 10+ range and fairly unlikely to be well modelled.

So to put that all together, the mid-term forecast is fairly well forecast with the likely exiting -EPO Wave(s) and resultant amplification with extratropical interactions despite the dominant mode of AAM and MJO not really favouring large tropical-extratropical forcing because of the initial North Hemispheric Pattern. Phases 2/3 of the MJO during La Nina tend to not have as much effect as the other Phases so it's possible that the effects of that may be slightly more limited.

Strat forcing should be kept up but it's looking fairly Wave-1 for now so we're still looking long-term for the best charts. The Tropospheric eventual drivers are very important so clearly long-term signals are likely to be fairly mixed. Given that basis, it's likely to be difficult even for the Professionals and though the signal may normally be quite bad, the initial state of the Atmosphere suggests that the pattern is likely to be difficult to forecast; perhaps a knife edge setup may occur.

So overall, there is certainly a lot to discuss with the forecast and a lot of differing opinions that will have actual backing. This makes it a very interesting time period but perhaps quite difficult to forecast. I've also tried to help you all understand the basics of teleconnections but there's a lot more to know about them.

After reading all of that well done, have a pizza;

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794386

[Uncertainty]

5 minutes ago, feb1991blizzard said:

hard to tell - mean possibly but looks less members going for a reversal and certainly less going for the type of big reversals that are usually indicative of a split.

 

It also shows a euro trough at the back end. The strat stays weak throughout too. The mjo returns towards the WP in Feb. 
 

Regimes look decent. You can see the middle period where a +NAO could occur, though it’s not a certainty like last winter.

In fact, lots to like about it. I’ve been keen on mid/late Feb into March since December. 
Why?

- Mjo moving towards p6/7 

- Strat downwelling effects (or, at the least, a lack of interference from a strong strat)

- Early signs of sub seasonal modelling sniffing out the idea

Still think U.K. high —> westerlies —> -NAO is the mid winter punt. Duration of each phase will be the tough one to pin down.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794518

[Catacol]

If modelling is to be believed - and it is within reliable range now - the big strat attack starts on Monday 

 

As the swift change occurs the volatility of the models will increase. 5 days after the vortex begins to scream we have an Atlantic pattern that is poised tantalisingly - anomalously high pressure to our west and clear potential for ridging

but to deliver fully we are going to need a downwelling trop response to the warming that can weaken westerlies within the TPV. Why? Because the MJO begins to work against high lat blocking once we get through next week and we have had a recent drop in AAM down to neutral levels 

Note however that still the atmosphere is resisting slipping into late winter nightmare Nina flatness - see the mid Atlantic ridge and cold few days we have had and are still having - so tropospheric interest is not all gone - but note the IO position of the MJO, never a good position for -NAO type patterns so until MJO 6/7 reappears again I think our neutral momentum pattern is going to need a kick in order to deliver a cold pattern.

Will that kick come? The million dollar question. Even Amy Butler hedging her bets just now on Twitter. No sign yet of a decisive split and there are clear risks with a displacement. More watching and waiting!

p.s - it has just started to rain here. Unbelievable. Snow hates me

 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794482

[Cheshire Freeze]

52 minutes ago, Mike Poole said:

We just need to keep an eye on where the vortex is going post SSW - a few days ago it was pushed to the Asian side, on this one it resides tip of Greenland.  Could make a big difference if we’re expecting the strat to imprint on the trop in due course…

I suspect it'll end up somewhere around Scandinavia.

CFS has a fairly strong signal for Griceland heights and a trough NE Europe (ish) at the moment

It would serve us well come the end of Feb and into March to have a Griceland HP as a NE'ly will be colder and have more margin for error than an E'ly or SE'ly.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794679

[IDO]

Looking at current output and very strong signal remains for UK HP for the next 10-days or so; London:

So remaining dry with temps slightly below average but not cold.

From D10 we see the the GEFS mean send the tPV to our NW, so the high sinking and UK on the cooler side of things:

Hard to see anything with HLB'ing until at least last two thirds of Feb, unless we have big changes.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794706

[phil nw.]

Just looking shorter term at the latest operational runs and there is still disagreement on temperatures for next week.

It looks pretty dry for most away perhaps from the far north but any milder weather may well be hindered by the movement of the high especially further south east.

GFS and ECM want to return the cold uppers by day 6 as the high is moved far enough west as it topples to get a north easterly.We can see the ukmo run is modeling a more rounded high and holds it closer to the Uk and therefore has the less cold air around. 

it will be interesting to see if the milder westerlies even get in by week 2 as this stubborn high may hang around far enough north for longer.

In view of the uncertainties with the warming affects of the Strat. on the trop. pattern i am not taking to much stock of the later ens guidance.Looking briefly at the eps postage stamps for day 10 show the high never far away.Latitude shown is around 50n.give or take,but it's exact position and orientation is still to decided.The centre could be anywhere from mid-Atlantic to Scandinavia which has a bearing on our surface conditions.

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794785

[Cold Winter Night]

4 hours ago, Eagle Eye said:

Mid February as I've been saying may offer some hope given +VE EAMT and potential movement towards MJO Phases 6/7.

A mid February MJO 6/7 would show its hand not before late February.
However, the ENSO specific composite anomalies for the preceding phases are not necessarily bad news for February.
MJO phase composite anomalies are quite different depending on ENSO.

The MJO forecast has it moving out of the COD into large amplitude phase 2-3, so we may see their effect appear in the output anomalies first.

I doubt if the current COD phase 8 will have much of an influence, but starting with MJO 2 in the next few days, given a lag of a day or ten, the January La Niña MJO 2 composite seems like a decent match with current extended ensemble output. Therefore the more zonal look late January into early February that we see in the output is not without MJO composite support.

Then, as the MJO moves into phase 3 late January/early February, things begin to improve.
For January it the composite shows height anomalies extending Northeast and also over Canada, suggesting a more meridional Atlantic pattern, maybe the jet shifting South.

We're at the turn of the month then, and the February La Niña MJO 3 composite is actually quite tasty, I’d say. Anyone interested in a Greenland High?
With a 10 day lag, we're talking about mid February here. Would be very interesting if a SSW favours a GH around that time as well.

The following MJO 4 pattern is less good, but still really not bad (more Atlantic influence, heights receding further North), and MJO 5 has mid latitude Euro blocking, but that’s all further away, and with possible Strat. Warming effects appearing that will muddy things even more.

Now, admittedly, not all these anomalies have the same confidence level, but nevertheless, there is some hope for coldies there.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4794854

[Kirkcaldy Weather]

Was going to wait until full progression of MJO phases to do my next outlook but based on how the mood in here has been going I'll do it now and I think I'll take a break for about a week which should see excitement returning with the strat warming getting impressive around then also.

I think the initial signs are starting to arrive for the models seeing the phase 2 setup. My Dates To start seeing this transition into surface synoptics from roughly February 2nd

 

Might be a slightly extended stay in phase 3 too which definitely won't be a negative

 

 

Was doing some more studying on SSWs and again the connection to Greenland blocking 

And remember the La Ninà February's I posted from Eric W 

Believe there will be lots of similar charts to this

 

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795064

[mushymanrob]

23 hours ago, mushymanrob said:

Firstly, what a cracking post @Eagle Eye one of the best ever on here...

Secondly..... the EPS is not looking good for cold/snow. IF this chart becomes reality, then the haul synoptically to a cold evolution is a very long one, and many would suggest that .. winters over? And im not sure even a SSW could alter such a strong chart.. IMHO its not looking good for cold, IF this chart is accurate.

 

After this post yesterday which seemed to cause some distain, the current EPS is even more bullish at promoting a mild start to February as the attached chart illustrates.
Now lets get one thing straight, i didnt say "winters over", i suggested that some might say "winters over? " note the question mark!
These EPS charts have consistently supported high pressure building to our near South , from the 30th until the 5th, and theres no reason to suppose this pattern wont persist.
What these charts show is a very strong TPV over Baffin/North Atlantic, which has displaced the subtropical high Eastwards away from the Azores and on these runs it just hangs about to our near South.
That suggests a mean upper flow from the Southwestern quadrant, and all mild Februaries have a mean flow from that area, and are mild months because this pattern is one that often sticks around for ages.

True, it might not. True it could change. True its only a prediction - but is actually supported by Nicks summation in his SSW blog.

Now i know a lot of you dont rate the Anoms, and thats fair enough, but lets just suppose that this chart below does become reality . It is a long way from a tropospheric pattern that would lead to cold...i mean proper widespread snowy cold (brief cold snaps are possible even in mild Februaries... Feb 2021 being a prime example) . With the strong TPV over Baffin, and given that thats highly unlikely to shift/weaken very quickly, then a Northerly cold via Greenland high/mid Atlantic ridge is out of the question, leaving only a high over Scandinavia.

This could happen, the high to our South could migrate up to Scandinavia into Febrauary, but imho thats a long shot and in unlikely. I might be wrong - Que sera sera.

Given all this, and given that once this pattern is in place and usually doesnt shift very quickly (based on experience), then a proper cold wintry spell this Winter.. ie before the end of February, via a tropospheric pattern is id suggest becoming highly unlikely.

Will a SSW rescue Winter?.. Well yesterdays post suggested not, not unless we get a strong SSW, and even if there was one its unlikely to affect us this "Winter" .... but possibly delay Spring.. I think most Spring cold spells come via a SSW as opposed to a normal tropospheric pattern. This appears to be the case in 1979, 87, 01, 09, 13, 18... possibly 1968, 70, 85, 99, 03, too although these SSWs were earlier.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795367

[Catacol]

1 hour ago, mushymanrob said:

After this post yesterday which seemed to cause some distain, the current EPS is even more bullish at promoting a mild start to February as the attached chart illustrates.
Now lets get one thing straight, i didnt say "winters over", i suggested that some might say "winters over? " note the question mark!
These EPS charts have consistently supported high pressure building to our near South , from the 30th until the 5th, and theres no reason to suppose this pattern wont persist.
What these charts show is a very strong TPV over Baffin/North Atlantic, which has displaced the subtropical high Eastwards away from the Azores and on these runs it just hangs about to our near South.
That suggests a mean upper flow from the Southwestern quadrant, and all mild Februaries have a mean flow from that area, and are mild months because this pattern is one that often sticks around for ages.

True, it might not. True it could change. True its only a prediction - but is actually supported by Nicks summation in his SSW blog.

Now i know a lot of you dont rate the Anoms, and thats fair enough, but lets just suppose that this chart below does become reality . It is a long way from a tropospheric pattern that would lead to cold...i mean proper widespread snowy cold (brief cold snaps are possible even in mild Februaries... Feb 2021 being a prime example) . With the strong TPV over Baffin, and given that thats highly unlikely to shift/weaken very quickly, then a Northerly cold via Greenland high/mid Atlantic ridge is out of the question, leaving only a high over Scandinavia.

This could happen, the high to our South could migrate up to Scandinavia into Febrauary, but imho thats a long shot and in unlikely. I might be wrong - Que sera sera.

Given all this, and given that once this pattern is in place and usually doesnt shift very quickly (based on experience), then a proper cold wintry spell this Winter.. ie before the end of February, via a tropospheric pattern is id suggest becoming highly unlikely.

Will a SSW rescue Winter?.. Well yesterdays post suggested not, not unless we get a strong SSW, and even if there was one its unlikely to affect us this "Winter" .... but possibly delay Spring.. I think most Spring cold spells come via a SSW as opposed to a normal tropospheric pattern. This appears to be the case in 1979, 87, 01, 09, 13, 18... possibly 1968, 70, 85, 99, 03, too although these SSWs were earlier.

2 things on EPS anomaly charts. Firstly - they are anomaly charts and not synoptic charts. I have been caught out more than once before in reading an anomaly as a likely guide to flow...but it doesn't always happen that way.

Secondly they vary wildly though, like many, I enjoy using them to try and pick patterns. Take the chart for a week ago on EPS for the 29 Jan at 360 given you are using very long range charts:

 

And now the EPS from last night for the same day:

Just a tad different in the atlantic.

I think EPS up to 240h is useful. Beyond that - cannon fodder. I'd rather interpret based on likely drivers and at the moment there is a fading MJO phase 7/8 signal that we are still benefitting from plus an impending SPV slowdown and stressed pattern that may impact things into February. This suggests pathways are still open for blocking, and if the MJO does manage to get back around to phase 7 on its 30-60 day cycle which currently looks to be moving on the swift side, then another blocking pathway will be open for the second half of February also.

Cold has been extended, models have not performed well this winter overall imo. Much gravy still in the pot.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795421

[Mike Poole]

2 hours ago, mushymanrob said:

Hi
to answer your  points, yes they are anomalies, but you can determine where the mean surface troughs and highs are, the flow contours illustrate that in conjunction with the surface pressure anomalies. And the Anomalies are only useful when consistent, and the EPS very often arent as you pointed out. But overall, they are saying the same thing. This is supported by the NOAA charts which i prefer, others have said they expect a period of Westerlies, a +ive NAO for this period.

So these charts may vary a little, but broadly they are on the same page and with NOAA support id suggest this pattern has some merit, with the usual caveat that nothing is certain until it happens!

We all have our "go to" preferred suite to determine what might lie ahead, its all part of the fun. Obviously im a fan of Anomaly charts, because i have never made the MJO work! I see a strong orbit an a phase, check the composite for that phase in that month...and it never seems to become reality! Ok others might argue against that, fair enough . The MJO doesnt "work" for me like the Anomalies dont "work" for others ... theres no right or wrong here, just differences in preferences and understandings.

If these predictive charts change, then so be it, but for now a +ive NAO looks likely to start February.. imho.

These charts lag behind the EPS, but are heading the same way, dropping heights to our North they showed just the other day.
 

As you say, we all have our go to products to gaze into the future.  I know that the anomaly charts have been shown to work well in some circumstances.  My take is that they work well when the ensemble members are broadly in agreement about the direction of travel, but maybe disagree about the time to get there - the fact they are averaged over time as well as ensemble members gives some protection against that, when compared to the ensemble mean at one particular time.  

They are not my preferred tool, though, for two reasons.  First, I don’t really like averaged pressure/heights or anomaly charts.  At 10 days out, an average chart is like no actual weather would actually be, so it can be difficult to interpret the highs and lows and flows.  

The second reason relates more to the 10-15 day period, which we are often looking at in winter, it seems.  This is that they really don’t work when there are big divergences in model predictions, which can be completely masked by the averaging.  It’s like trying to shoehorn the fact that multiple possibilities exist, into a single prediction, which for me, often doesn’t respect the uncertainty that exists on that timescale. 

Which is why I much prefer the cluster analysis on this timescale - if there are multiple, different options, they are shown.  And they are each illustrated not by an average, but by a single representative member, so the pressure field makes sense.  The downside is they often don’t really illuminate just one most likely path…

 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795457

[summer blizzard]

Modelling producing a relatively mobile pattern as we end the month albeit still differences in the angle of the low and how close the Azores High will be to shield us.

This is not a bad thing and to be expected IMO.

We are currently seeing a strong phase 2/3 MJO event which is not conducive to tropospheric blocking albeit it Is displacing the vortex via significant heat flux. 
The important thing here is that we then potentially a phase 6/7 strong event which may produce a second stratospheric hit and tropospheric change (weak resistance to a downwelling stratospheric wave if I understand the theory correctly).

Euro and GFS put the second high amplitude event in the first third of the month, probably peaking in the second so the mobile pattern probably doesn’t have legs.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795654

[Nick F]

Morning. Looks like the probability of a major SSW has decreased this morning looking at GEFS/GFS, on GFS op the strat PV looks to bounce back after a minor warming, as Chionomaniac / Ed mentioned on twitter recently "displacement events as a bit like pushing a finger on a balloon. Unless you can pop the balloon, when you take your finger away the balloon quickly recovers to its natural state. The upcoming displacement is a lot like this".

So we remain at the mercy of what looks like a flattening N Atlantic high and a strengthening TPV, possibly boosted by westerlies being pushed down by the warming in the polar stratosphere. However, there are hints of amplification in the extended EPS mean and clusters. So still plenty to keep any eye on and not all is lost.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795870

[bluearmy]

16 minutes ago, nick sussex said:

So the warmings in effect aren’t much use unless they finish off the PV .

They keep flushing down the mobility and so unless you get a reversal it’s long term pain for zip gain !

You really couldn’t make it up ! 

I think we have a trop that is currently very mobile at latitudes where we would want it to be blocked. The weakenings high up means that the added mobility that has been high up in the strat will find itself pushed lower down. So we end up with a weak upper strat and a mobile lower strat and trop 

4 minutes ago, KTtom said:

Yes, its nice to convince ourselves that anything can happen after day 5 but in reality I think the uncertainty of the overall pattern for our neck of the woods in currently well beyond that date. Cross model agreement that our high will sink eventually due to the TPV continuing in its relentless domination to the north. I note even the met have removed their usual caveat of 'low confidence' from their forecast which mirrors the mean charts from gfs and ecm (becoming wetter and windier from the north).  

I’d still be a little cautious ahead of later this week once the strength of the reversal high up becomes apparent and potentially until it arrives in the starting data. 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795842

[bluearmy]

8 hours ago, Don said:

Is this from the GFS?

Absolute horrific chart and can say goodbye to winter if this ends up being close to the mark!!

The strat trend is from gfs/gefs but eps are now also drifting that spv later week 2. It could be that the spread increases late on and we lose the continuity that we we usually see with ens at 10hpa. The eps strat heights for 10 hpa will be out within half an hour 

 

6 hours ago, Kirkcaldy Weather said:

Quick visit

15th Feb 2018 

Tonights GFS 18z 

 

It’s an idea to show a chart and then compare to one from yesteryear to Indicate similarities etc but surely not a gfs op at day 16 as your base ??

 

 

and this cross section at 60N from gfs op shows why we can’t get any HLB to stick away from high in the polar field. Just too much mobility which is partly due to the westerlies being pushed down/reInforced  from higher up by the reversals/weakenings 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795832

[Eagle Eye]

27 minutes ago, Nick F said:

Morning. Looks like the probability of a major SSW has decreased this morning looking at GEFS/GFS, on GFS op the strat PV looks to bounce back after a minor warming, as Chionomaniac / Ed mentioned on twitter recently "displacement events as a bit like pushing a finger on a balloon. Unless you can pop the balloon, when you take your finger away the balloon quickly recovers to its natural state.The upcoming displacement is a lot like this".

Yes that's the trouble when you've got a very strong polar-night jet, a displacement event will be fairly easily recovered from which is why I've been chasing a split even though the displacement charts were showing a reversal. The thermal dampening of the Wave-1 when you've got a still very cold displaced Vortex will allow that Vortex to push back to its initial position fairly quickly making any real Trop response fairly unlikely. I'm still waiting for now to see if a Wave-2 split comes out of nowhere but its looking increasingly unlikely in my opinion.

I suspect we'll have 1 more proper chance this Winter though, the timing of when a +VE EAMT and the MJO Phase 6/7 lag can be expected looks to time itself fairly well when looking roughly at mid to late February so if  we cannot get a major SSW that may be our last chance at getting early December style again.

Having said that I don't know the effects of the exiting -VE EPO so it's possible that that could help us closer to the end of this month but based off model outputs alone that's fairly unlikely.

Winter is most certainly not over but I dont see a Beast From The East repeat unless a split SSW happens or there's a strong response to the next MJO cycle.

I'm remaining positive though but I think beyond the response of the -VE EPO along with mid lat blocking there probably won't be much interest cropping up around early February unless we are really lucky.

I don't see it going to full zonal though, the North American Pattern is seemingly too variable right now for that to happen though another VI event may dampen that amplification as it did for late December/ early January so that needs to be watched.

A lot to keep an eye out for but not a load of interest, it's mainly so that we can get the best possible start up for the MJO Phase 6/7 to have the most effect if we can get to that before the end of Winter.

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4795904

[Cambrian]

The current modelling into week 2 looks a bit iffy. It’s no big deal if that’s what we get in any case - we have later into February and a good chunk of March still to go before the spring equinox to bring some more seasonal weather, but I’d be reticent to totally write off the chances of cold in early February just yet.

There is quite a bit of highly relevant wriggle room, typified on the day 8 ensemble mean from the 6z GFS. There’s a cross-polar flow from Alaska to Europe, thanks to the linkage of the Siberian and Scandinavian lobes of the PV, and interestingly, the Aleutian and Atlantic heights are doing just enough to prevent merging of the Canadian and Scandinavian lobes. They do merge by day 10 on the 6z GFS run, but the 0z ECM at day 10 still keeps them well apart. 

  

At day 8, a slight thickening of the lower heights through the Kara Sea, where there is a bit of spread, would straighten the cross-polar flow and elongate the Scandinavian trough. The greatest spread, however, is at either end of the Eurasian PV lobe, very much bringing the UK and Ireland into play for the Scandinavian trough with very modest changes. Around Newfoundland, the relatively weak cyclonic development spawned by the Canadian lobe is another area of doubt. This is one of the main factors preventing further retrogression of the Atlantic high. This has been a repeated feature of the spread charts over recent days. The consistent low heights in the Mediterranean also encourages the idea that a tad more retrogression might just be feasible. 

Having said that, overall it does look most likely that the centre of the high will become anchored to our southwest for a fair while, which is supported by the spreads for where the high is located too. 

However, the spreads do also suggest that there is probably a good deal more scope for further polar maritime and/or northerly incursions around its northeastern flank heading into early February than is currently being played out in the ops or ensemble-wide means. 

 

Whatever we get, it’s going to be a good deal better than looking out your window and seeing this like the inhabitants of Bursa, Turkey did a few days ago. I tell you, one look at that and I’d have been clean out of there before you could say kebab, let alone lenticular cloud. 

Original post: https://community.netweather.tv/topic/98196-model-output-discussion-new-year-and-beyond/?do=findComment&comment=4796023