October Preliminary 2020-21 Winter Outlook

Welcome to another winter outlook update for the Northern Hemisphere, including Europe, North America and Japan. For those who prefer a simple reading/conclusion and prefer not to read the long technical analysis, scroll to the Conclusions section at the bottom.

Model Outlook

December actually shows a more -NAO-like pattern on the ECMWF model, which is shown by significant blocking around Greenland, which benefits the UK and Southern Europe in terms of more cold. We also see a strong Aleutian ridge develop, which aligns with the Nina pattern and benefits the Rockies and the PNW. With a weaker Siberian High and Aleutian Low, the Japanese snow seasons suffers.

In January, we start to see a more +NAO outlook take hold in the Atlantic, which brings European ridging and less snowfall for the continent. Troughing over British Columbia benefits snowfall over the PNW and of course BC. Ridging weakens snowfall across the rest of the North American continent, leading to a dry month. Again persistent ridging over Japan weakens snowfall there too.

February brings a clear +NAO with a Greenland low and Azores High, leading to mild and wet conditions for Western Europe, and dry conditions for Eastern Europe. Ridging shifts slightly north, but persists over Japan. Again we see a favouring of snowfall for the PNW/BC at the detriment to the rest of North America.

We see similar scenes on the wider C3S multi-model ensemble for the whole of winter, with a strong Canadian vortex, bringing cold and snowfall over Canada and the Northern US. A strong Aleutian ridge dominates the image, with ridging stretching across America to Europe. We see a +NAO pushing the jet stream into the UK/Northern Europe. And a poor ridged outlook for Japan unfortunately.

ENSO

The current ENSO state is of a Eastern Pacific and perhaps could also be considered pushing into basin wide La Niña, as recently declared by the Australian Bureau of Meteorology.

We know it could be a reasonably strong one and will continue to do so, with the forecast colder than average surface and sub-surface sea temperatures. CFS shows a deep subsurface cold underneath the ocean surface that provides a strong base for this Nina can continue across the ENSO basin.

Following on from that, last discussion I had about this in Early September, I was looking at a Central Pacific Nina. Now I have shifted my personal thoughts have shifted towards a basin wide Nina over winter. Most forecasts show that the emphasis currently upon the Eastern Pacific in the most recent observations will shift towards a more general basin wide look in the coming months, as the Nina progresses (ECMWF as an example below).

So based on the NMME multi-model forecast ensemble, we are looking at a moderate-strong La Niña in terms of looking at the strength of the event:

CFS demonstrates a forecast for a strong Nina, some of the other American models show a weaker Nina and faster recovery.

Putting together an analog for a moderate-strong Nina winters since the 1980s, based in the Eastern Pacific extending into the entire basin:

  • Troughing/low pressure in the Eastern Indian Ocean and over Maritime Continent, certainly goes with the idea of a strong tropical standing wave over Maritime Continent.
  • Strong Aleutian Ridge, supports snowfall and cold in Northern America and Canada. Less North Pacific Jet extensions, less atmospheric rivers.
  • A very weak -NAO and more obvious Scandinavian blocking, which may help support snowfall and cold in Southern Europe/UK.
  • Decent troughing of east of Japan versus strengthened Siberian blocking, which supports Japanese snowfall.

Arctic Sea Ice

Sea-ice in the Arctic is continuing the lower than average trend of the past few decades.

Some analysis of this:

However low sea ice in certain regions is of more importance to us.

NASA GMAO

The sea-ice (NASA GMAO) forecast for the Arctic is pointing to low sea ice in the Barents and Kara Seas, which leads to more blocking in the Arctic region and the proliferation of a more negative AO state that benefits for snowfall, Eastern US, Japan and UK/Southern Europe.

Slightly lower than normal ice coverage out into the Chukchi Sea in that forecast, but mostly a neutral impact from that particular region. It is worthy mentioning that ice in that region is currently very low, so a quick turnaround would be needed to get to a more neutral impact stage. The below map from LDEO shows stronger than normal sea ice in the Bering Sea for DJF (and lower sea ice in the Barents-Kara Sea), and this isn’t an outlook I am really buying, it would be a very strong turnaround of sea ice to get to that stage.

LDEO

Overall I certainly believe we will see a lower than average sea ice year through winter, which in the case of the Barents-Kara Sea, will be a positive influence for higher snowfall and more cold for Europe/UK, the Eastern US and Japan.

Snow cover

We are currently seeing lower than average Siberian snow cover as of midway through the month of October.

Judah Cohen

It is however expected that snowfall will ramp up to some extent in Siberia over the next 10 days, as seen on ECMWF below.

So upon that analysis, I am envisioning a pretty average snow cover by the end of the month, middle of the road, but I may change this prognosis in the formal regional seasonal outlooks once the month has concluded. So it’s impacts are therefore pretty neutral on the climate.

MJO

Here we have the expected tropical wave pattern for the winter ahead, that focuses on a Phase 3 (Dec) to phase 4/5/6 (Feb/March) approach to the winter, with a slow shift of focus from the Eastern Indian Ocean as the focus of tropical activity, to the Western Pacific.

To say the least, these forecasts are not overly great for most seeking out snow.

  • The US West Coast does best after an extension of the North Pacific Jetstream, allowing for atmospheric river events and higher precipitation/snowfall on the mountains. This is best done with a Phase 7/8 MJO.
  • The Eastern US receives it’s best snowfall during the MJO Phases 8/1.
  • Phase 3 + 10 days promotes a +NAO (good for Northern Alps snowfall, bad for Southern Alps/Europe and UK) and Phase 6 + 10 days promotes a -NAO (basically the reverse).
  • Japan receives the most snowfall (by the strengthening of the East Asian Winter Monsoon) around Phase 7.

Either way, the MJO’s impacts are to be unhelpful for snowfall prospects earlier in winter, and more helpful later in winter, as more westerly bursts enter the Pacific.

Sunspots

SILSO data/image, Royal Observatory of Belgium, Brussels

Same as last outlook, basically we are still in a solar minimum, which in theory helps a negative Arctic Oscillation. This would therefore assist snowfall in the Eastern US, Europe and Japan, but I don’t weigh sunspots highly as a tool in winter seasonal prediction.

QBO

The westerly/positive QBO has popped back into the seasonal outlook, after a rather malformed easterly QBO phase this year.

This is of benefit to a +AO/+NAO state, and therefore snowfall in the Western and Central US. And of less help to Europe, the UK, Eastern US and Japan, in terms of producing cold and above average snowfall (less weakening of the SPV and less correlation with a -AO).

The easterly phase on top at 10mb is present, but it won’t descend far enough to be of importance to us this winter. More information pertaining to the dynamics of the QBO is in this below quote from last year’s outlook (obviously technical):

“However it gives the false impression that the QBO is this one number index, which isn’t what it really is. It really is an Oscillation that goes from 5-10mb all the way down to 90-100mb within the equatorial region in the stratosphere, bounded by more anomalies associated with ground conditions and the Hadley cells below, and the Semi Annual Oscillation (SAO) above it. This means when the QBO is positive and descending at 30mb, it may for example be negative zonal wind anomalies below 50mb to 100mb. This shows that the effects of the QBO are not strictly linear, because of this inconsistency within the same Oscillation, creating different effects depending on the height and phase of the descending QBO. There is also the strength of the QBO to contend with, and whether the trend is for a normal QBO phase progression, or a sudden change in progression. These are all factors which play into the QBO’s effect polewardly towards the Stratospheric Polar Vortex, therefore on it’s tropospheric counterpart and then the general hemispheric circulation”

If you wanted to pick the ENSO analogs above that best fit the current QBO progression, you get this:

Obviously looks good for Northern US and Canada and even over much of Europe with a -NAO setup. Too much troughing in the East Asian region for better than average snowfall for Japan.

Stratosphere Polar Vortex

Looking at the extended range forecasts for the stratosphere, we are looking at a pretty average and normal beginning to the rise of the SPV.

EC starts with the stratospheric vortex weaker, but largely charts a pretty average course.

The bias-corrected CFS model, charts a similar course if a little weaker than the average increase through November and December. So a pretty neutral look through the first parts of the winter from the available modelling.

The only other datapoint we have in relation to SSWs and the stratosphere is to do with the transport of ozone from the SH to the NH.

Tropical upper stratosphere is currently colder than average, that indicates a stronger than normal Brewer-Dobson circulation, pushing ozone towards the NH Strat polar vortex. So again we certainly have the capacity for inducing a SSW, it’s just whether the tropospheric factors allow for it.

Another analog for the ENSO years discussed above, this time for the SPV:

So interestingly we see a capacity for the creation of SSWs in the month of February under these years, so something worth thinking about.

North Pacific

We see a very warm North Pacific. This certainly may help with precipitation a bit for the West Coast, with the Nina not helping in this aspect. But it also means ridging in the middle of the North Pacific, helping to reinforce the Nina-esque Aleutian High. So basically reinforces the focus on the Northern US for snowfall and cold.

North Atlantic

We see a clear contrast between the warm SSTAs south of the line between Newfoundland and the Iberian Peninsula, and the cool SSTAs south of Greenland. One will find the jet-stream develop along this line. The cool SSTAs south of Greenland will help to induce troughing over Greenland, or cause a +NAO setup with a strong North Atlantic jet stream. This correlates with a milder outlook for the British Isles, more snow for the Western/Northern Alps and less for the Southern Alps.

Conclusions

To summarise the factors discussed:

  • A basinwide moderate (possibly strong) La Nina this winter.
  • A positive QBO
  • Solar Minimum
  • Atlantic SSTs favourable for a +NAO
  • North Pacific SSTs favourable for a Aleutian Ridge.
  • Average growth of Stratospheric Polar Vortex into winter, potential for SSWs later.
  • Phase 3-6 MJO centred tropical base state
  • Low sea ice in Barents-Kara Sea.
  • Average snow coverage in Siberia.

To apply this to the major snowfall regions of the NH:

  1. We see a better than average season for the PNW/BC in terms of snowfall, including into the Northern Rockies (MT, ID, WY)
  2. We see an average or slightly above average winter for Utah and Colorado.
  3. We see a below average season for the Sierra Nevada (CA).
  4. A strong season for the Midwest and Northern US.
  5. A mildly above average season for New England.
  6. An average snowfall season for the Mid Atlantic to NYC.
  7. A below average snowfall season for the Southern half of the US.
  8. Moving onto Europe, we see a colder December for the UK, and a pretty average winter overall, with a weaker backend of the season.
  9. The Northern Alps should see an average season, maybe slightly better than normal.
  10. The Southern Alps (and the rest of Southern Europe) should see a slightly below average season, with the best conditions early in winter.
  11. Honshu and Hokkaido are likely to see a poor snow season this year, the latter half of the season is likely to be the better one. Possibly a bit better relative to the average for Honshu, than Hokkaido.

Thank you for reading this winter outlook! Stay tuned for the individual regional outlooks, where we look these conclusions and details in.

Early September Seasonal 2020-21 Winter Preliminary Outlook

Welcome to another seasonal forecasting season for the NH, under albeit unfortunate circumstances worldwide. Today we will take an initial look at some of the factors involved with the season ahead.

Seasonal Models

In this section, we are going to look at a selection of freshly minted seasonal model predictions.

We start December on EC Monthly, with a strong Siberian High, an Atlantic Ridge and a Aleutian High setup. This causes lower snowfall for most of the US, except perhaps the Northern Great Plains. We could see a decent early season for Japan come off, with Siberia looking the way it is. Europe looks pretty average in terms of temperatures, and potentially more precipitation for parts of the Alps.

In January, EC sees the Siberian High stick around for good snowfall potential for Japan. Europe starts to see the influence from a +NAO, which means wetter conditions for the UK, and more snow for the Northern Alps. We see the SE US/Atlantic Ridge and the Aleutian High push against a Central US trough, benefiting Colorado and the Inland PNW, as well as bringing cold to the Great Plains.

In February, EC sees a similar situation for North America, with the Nina-esque Aleutian High dictating the pattern. The +NAO strengthens, which means the impacts for the UK and Northern Europe only increase with a mild and wet outlook. This means it will be dry for other parts of Europe with a European ridge. The Japanese season slows down with a more mid-latitude belt of ridging affecting snowfall for the Japanese Alps.

March presents limited opportunity for Japan, expecting a poor late season on EC. We see a vague -AO, but still a +NAO, meaning similar effects for Western Europe, and the downstream ridging makes it warmer for the Eastern half. Northern US sees troughing and potential late snowfall, the Southern half doesn’t get to see much cold with a persistent ridge.

CFS for the entirety of the NH winter focuses on an Aleutian ridge as well with troughing for the North-Central parts of the US and Canada. It also features a +NAO meaning more snowfall for the Northern Alps, and wetter/mild conditions for the UK and Northern Europe. It features a substantial Siberian High, which would be of benefit to Japan.

CANSIPS (Canadian) focuses on a strong Northern US snowfall setup with a Canadian vortex. We also see the same +NAO effects that are seen on the other models. The ridging around Japan, rather than towards Siberia is of little benefit to Japanese snowfall, and may hamper that season. We see a very +AO, Arctic-driven outlook for the winter from it.

ENSO

If we take the model average from all of the seasonal models at play here (graphic below), we get a borderline La Niña possibly. You could argue under the definitions set by the Australian Bureau of Meteorology that it doesn’t even qualify as a Nina. One thing you could note in addition to the actual mean, is that there are outliers towards both ends, of course NASA going for a strong Nina, but a number of models including the Korean, Chinese and a few of the minor, sometimes odd American models are strong outliers for a warm neutral state or even a Nino in the first half of next year.

So if we instead take the median bunch of models around the average, we see a cooler trend towards a firmer Nina. So in practical terms, we are looking at a borderline-weak La Niña, peaking in November and December.

But of course the depth of the anomalies is only part of the story, we also must look at the location of these anomalies. We are going to take some EC modelling from last month in this instance:

We are arguably looking at a more Central Pacific or Modoki based Nina if we are going to take this for face value. There is some research backing stronger precipitation in the Japan region during the winter during a Nina Modoki. But in general we see conditions from a Nina that favour snowfall in the Northern parts of the US and Canada. And for Europe, we see a +NAO type set-up, so wet for the UK and Northern Europe, snowy for the Northern Alps, and less snowy for the Southern Alps.

I took a wide selection of Nina Modoki/Central Pacific years, and we see pretty similar themes. A strong Aleutian high, which pushes troughing into Northern and Western North America. A strong +NAO and therefore jet stream coming off the NA Continent towards the UK and Europe. And finally a +AO, indicated by the trough over the Arctic. All this points to a strong snow season for the Western and Northern US, as well as the Northern Alps.

Sunspots

SILSO data/image, Royal Observatory of Belgium, Brussels

We are at a solar minimum, which in theory helps a negative Arctic Oscillation. This would therefore assist snowfall in the Eastern US, Europe and Japan, but I don’t weigh sunspots highly as a tool in winter seasonal prediction.

Tropical Forcing

The tropical base-state over these past few months has been focused on the Indian Ocean, or around MJO Phases 1-3. The current forecast from CFS regarding tropical forcing is shifting towards a more Maritime Continent dominant tropical base-state, and suppressive of the MJO phases that traditionally benefit the Eastern US, Europe and Japan in terms of widespread cold and snowfall.

The most suitable SST region for tropical forcing over winter this season is Maritime Continent, so CFS guidance makes sense. In general, leading up to a Nina you don’t see a great deal of MJO action deep into the Pacific, but at the peak of the event (during this winter in this case), you see greater MJO amplitude. This could be of benefit to the Western US in terms of trying to break through that Aleutian High for some jetstream action (specifically referring to California here).

QBO

The westerly/positive QBO has popped back into our lives, after a rather malformed easterly QBO phase this year.

This is of benefit to a +AO/+NAO state, and therefore snowfall in the Western and Central US. And of less help to Europe, the UK, Eastern US and Japan, in terms of producing cold and above average snowfall. But the QBO is obviously a dynamic factor at play here, so best to keep track of it over the next few months, and I will clarify in the final seasonal outlooks.

Snow & Ice

Not a great deal of news on the freezing season that is useful to us in the seasonal outlook, but it is worthy of note that Arctic sea ice is at the second lowest minimum in recorded history. In general, of course there is more heat and instability in the polar region and this is just a demonstration of that. Ice cover on the Russian side is particularly low, which actually may help a more unstable -AO pattern develop later in the Spring into Winter, but it is really too soon to tell. We need data from October for this particular process.

Local SST patterns

Finally we will take a brief look at the forecast for NH SSTAs.

Both observations that can be deducted are inline with the rest of the outlook.

Warm SSTAs in the North Pacific assist with ridging in the Aleutian region, in line with a Nina climatic response.

And the Atlantic has a large warm patch of SSTAs that enhance ridging off the US Coast, and the interaction with that small patch of Colder SSTAs south of Greenland encourages a +NAO pattern.

Conclusions

These are just really rough initial conclusions to be made, these will be amended and played with over the next month or so. Stay tuned for further outlooks.

  • Good snowfall season for the Central parts of the US (Colorado, Inland PNW/Alberta, Great Plains), and for the Northern Alps.
  • Some potential, but still under the influence of a ridge (Utah, California, PNW Coast)
  • An average, perhaps early season for Japan.
  • Probably a poor snowfall season (Southwest US, Eastern US, UK, Southern Alps).

Thank you so much for reading this seasonal outlook for the Northern Hemisphere.

Seasonal outlooks tend to have bias and errors, due to the fact that these forecasts are so far out. So don’t use these outlooks to make important decisions. These outlooks are meant to be interesting information, that can help to see what the season might be like.

Thanks again for reading, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Australia on the long term 29th August

Hello all, we have the last long term outlook of the season here today, so let’s take a brief look at the state of the climate.

3rd-6th September

We have a prospect for about 10–20cm of snowfall for the Australian Alps at this point on EC for this period starting late Thursday and pushing through Friday and Saturday this coming week.

A decent sized low-pressure system that looks relatively cold, but needs a bit more moisture on the backend. Still some time for a better alignment of moisture for the Alps, rather than the precipitation that slips largely to the south.

To the contrary, GEFS needs a little more convincing with this one, quite weak:

11th-15th September

This one is per the next pass of the long wave trough, but it is looking very much like a Southwest WA peaking type of system, delivering not a lot for the Alps in the SE of Australia.


Ensembles, EPS and GEFS, concur, the latter ridging it out. EPS shows it just clipping the SE.

22nd-26th September

The next LWT as indicated by GFS looks like it is going to pass our region during the above period.

Here we refer to the node that is south of Africa at this particular forecast period.

2nd-6th October

There’s some interest that could be noted from EC Monthly about troughing in the First week of October through the Great Australian Bight through to the SE. It’s obviously very much a long shot, but worth a brief mention. And vaguely aligned to the above LWT plot as well.

MJO/Tropics

We are seeing an active MJO in the Indian Ocean weaken by the time it gets to Australia in the next week or so, which means that there is likely to be a limited impact from the MJO for us going forward. EPS concurs:

We are certainly settling back into a Niña-esque versus strong Indian Ocean pattern that we have seen most of the winter, and certainly hasn’t been delivering a great deal of results, with primarily negative tropical momentum.

AAO/Polar factors

We are currently in the midst of a general -AAO phase that helped to deliver our last big storm for the Australian Alps.

You will be able to notice some degree of weakening of the Stratosphere Polar Vortex in the upper echelons of that chart, that will help to keep us in a negative AAO for the next 10 days, but it isn’t going to be a long-term change in the stratosphere (not like the SSW that occurred in the Southern Hemisphere last year).

EC confirms the upward trend in the AAO, which isn’t going to help us in terms of snowfall for the Alps, overall in my opinion we are heading towards a pretty mundane month with a lacking in tropical/extratropical support, unless the AAO tanks negative again or we see something more long-term in the stratosphere.

Conclusions for the season

So I called for a “moderately better than average” season in autumn, this quite obviously was not so. We are currently at 167cm at Spencer’s Creek, which at the point where we are days from the average day where we see the highest point in the snowpack. This is considered pretty average, but let’s not kid ourselves. Until the storm a week back, Victoria had barely any natural snowpack in the resorts, same for lower parts in NSW. It has been a pretty poor season on the whole.

A number of reasons for this is:

  • The negative IOD forecasted for winter didn’t really happen (yet).
  • Lots of negative momentum in the tropics (lack of tropical waves and lack of MJO, not helpful).
  • And conversely not a lot of negative momentum down in the SH mid-latitudes (so it leads to a rather lacking polar setup, not a lot of troughs, more ridging).
  • This is set-up by a non-dynamic (until the last few weeks) set-up between an atmospheric Niña and an active Indian Ocean.

Either way, my seasonal forecast has not done well and this is unfortunately not an anomaly. A review will be made into it in the SH summer to hopefully improve forecasting outcomes.

For now, it is farewell. Given the current situation in the world, it is unlikely that many Australians will be able to go and ski overseas, but for those who just want to follow for the enjoyment of weather analysis or for whatever reason, one can follow my Northern Hemisphere seasonal and long term outlooks coming very soon.

Thanks again for reading this Australian snowfall outlook, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Australia on the long term 12th August

18th-22nd of August

We see a new long wave trough come through the region around this period, which shows potential for snow-bearing cold fronts. We see a proper cold trough come up on the Tuesday and Wednesday next week, as indicated by the cold air seen on the ensembles.

We see it squeezed between a ridge over NZ and the ridge SW of the trough towards Antarctic. This brings a longer trough trailing the main cold node, which brings a westerly theme to this particular system.

GEFS has a very similar setup, featuring all the same key components, with a slightly enlarged upper level cold node.

GEPS shows a zonal pattern from the Indian Ocean, with troughing anomalies stretching from WA to SE Australia, with the cold node nonetheless centred on the Southeast

Zooming in on the deterministic point of view, we have ECMWF here:

As one can see the front comes over SE Australia early on Tuesday, and pushes through to the Alps during the day.

We see stronger snowfalls associated with the cold airmass on Wednesday afternoon into Thursday morning. Then we see the main node push into the Tasman on Thursday, but we see a backdoor low coming up from the south during Thursday night into Friday, pushing up into NSW throughout Friday and bringing snow to low levels further north.

GFS shows a similar system coming down from the West on the Tues/Weds, and collapsing into the Tasman as a large-scale cold air mass. We then see the polarisation of a sharp deep low coming from the south, similar in timing to EC on Thursday night into Friday, but stronger, colder and it doesn’t shift as far north as EC.

So overall we have a great opportunity here, looking like a 30-50cm system at the moment, even more is possible with that follow-up low from the back. Certainly looks like a more traditional system, compared to some of the Tasman-based systems of recent.

Further systems

Looks like we will have potential for another cold and snow-bearing system around the 27th August to the 31st of August, per the rotation of the Long Wave Trough.

Beyond that, perhaps a possibility for a system around the 4th-9th of September, EC Monthly is willing to play ball with it.

EC Monthly is showing a stronger signal for the 17th-23rd of September as well for a cold front through SE Australia.

MJO

We are currently in the best MJO phases for snowfall (and it hasn’t delivered a lot), but we may see it’s lingering effects on our region with the system next week.

You see the strong phase over Australia/Maritime Continent, and then it weakens and skips the Western Pacific, and strengthens within two weeks over the American continent. This serves to weaken any push away from a La Niña, and generally helps to lean towards a negative AAM state in the next few weeks. This is certainly something that could potentially help our snowfall chances.

Phase 8/1 are certainly highlighted by both EC and GFS ensembles, passing up expansion into the Western Pacific phases, which would spike momentum in the tropics. While the MJO will no longer be favourable in a week or so, the base-state might be improving for us.

AAO

We are currently heading towards a -AAO state for the next week or so.

As you can see the phase is strong, but quite likely to be temporary, with some more +AAO spikes later in the month. But hopefully we can push towards a few more -AAO moments.

Also worth noting that the stratospheric polar vortex in the Antarctic remains largely stable, with only minor disturbances and relative maintenance of strength at the moment.

EC concurs with the GFS model point of view below….

Thanks again for reading this Australian long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Australia on the long term 26th July

Apologies for a lack of posts in the past weeks, life has got a little busy at the moment unfortunately. Onto the analysis….

2nd-6th August

The LWT is expected over SE Australia early in August, which means we might see a system off the backend of the larger node. There is plenty of signs that it may peak over SW WA, as has been happening with a number of systems due to stronger westerly (more convection) activity in the Indian Ocean in the past week or so. The tropical signal is forecast to move towards Australia in the first week of August, but it may not come soon enough for us to enjoy the benefits of a SE Australian peaking system.

It also increases the likelihood of a trough across the continent stretching from the SE to the NW of Australia, bringing down tropical moisture.

You can see this clearly on GEFS, but we also have a decent southern trough based off of this, that can bring decent cold and possibly snowfall.

EPS (EC ensembles) show a stronger trough from the south, but it isn’t a very deep cold front, so obviously not going to lead to maximum reward in terms of snowfall. But there is nonetheless some potential for something.

A vague cold front linked to the NW trough is to be found on GEPS, leaving all of the ensembles relatively on the same page, albeit with varying strengths. They have consolidated upon the weakfish cold front feature in the last couple of runs, prior just featuring a vague trough. It is possible it may return to this given a poor +AAO status, but there is certainly still a chance.

Overall not the most exciting setup there is, but there is certainly potential for something there, if all it is would be a clipper with 5-10cms, we will take anything at this point.

10-14th August

If we take the LWT chart at face value, we may see some potential around the LWT peak on the 10th and 11th and in the days succeeding it. But if GFS is anything to go by, it looks to be a Southwest WA peaker as well.

EC Monthly doesn’t like it very much.

20-25th August

If we continue to follow the cards indicated by the GFS LWT, we are lead to this date range.

EC Monthly indicates some activity in the Australian region during this period, and further into the last week of August, that may bring some potential for troughing in the SE of Australia.

Antarctic Oscillation

It looks strongly likely unfortunately that we are heading into a positive phase of the AAO, which is bad for Australian snowfall. As one can see from these charts, it is rather cyclical in nature which gives us some ability to predict it’s manifestations. Based upon this notion, August is likely to be largely a +AAO month, with a more negative outlook in the last third of the month being potential.

It is also important to note that the stratospheric polar vortex at it’s upper extreme here remains strong and cold, so it is unlikely to help us with any real change to the SH atmospheric circulation to help snowfall.

EC is a fan of a strong +AAO event, weakening out chances in that first week of August.

GEFS is forecasted a potential push to a -AAO reprieve from the 10th of August into the mid-month period.

MJO/AAM

On the more positive side of things, the MJO is very possibly moving into our region, at least in some capacity.

You can see the GEFS MJO forecasted tropical wave, move into the Australian region, which is beneficial to us.

Other modelling like that from ECMWF EPS is less hopeful of such a direct incursion into the Australian region, preferring to stay with the pre-existing base state that is leaving us in limbo, benefitting SW WA more than us.

This shift in momentum is leading towards a more positive AAM, as per CFS.

Although the correlation with the AAM on the data is better with a more negative outlook for snowfall, it could also possibly symbolise a little bit of a shake up in the pre-existing base state, which might get us out of this mundane pattern over the past few weeks (particularly in Victoria).

So there is still hope, but yes the numbers are not in our favour with the AAO at the moment, with some potential in the tropics. We shall wait and see.

Thanks again for reading this Australian long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Australia on the long term 21st June

Some very intriguing systems and climatic conditions to talk about, which should hopefully bring us more snowfall in the next few weeks!

But I don’t think we can go without acknowledging today’s snowfall for the Snowies, and the good potential for more snowfall over the next few days.

Taken by Charlotte Pass Snow Resort

1st-7th July

Something that was called in our last outlook a little more than 2 weeks back is becoming clearer to see now.

There are a number of schools of thoughts from the modelling about this period:

  • EPS (above) is looking for a peaking trough through the 2nd-4th of July, with this being on trend in terms of timeline from previous runs (albeit it has significantly strengthened in nature since)
  • GEFS (below) delivers us a more muted affair trying to come up over the 4th all the way through to the 7th, not as grand or strong as the EPS effort. This has been on for about two runs, succeeding a less bountiful collapsing trough to clip SE Australia, so the system is improving on trend on GEFS.
  • GEPS (not pictured) offers a more meagre scenario with a break between the ridges during the 3rd to 5th of July, being the less exciting of the models for this period. The Canadian ensemble has bucked the timeline of previous runs, pushing forward from the 1st-3rd July.

EPS is certainly the keen one and certainly has decent trend and reputation to back it. Beyond the modelling solutions, looking at the projected long wave node on GFS:

The LWT is aligned roughly around the 3rd of July. The best systems typically occur just after the long wave node, so it implies that the best possible period of favourability for the SE Australia region would be from the 3rd to the 6th. But as Deterministic GFS has appointed itself upon in the most recent run, we could always have a curtain-raiser just as the node begins to pass.

And the better main system which the first trough has cleared for gets to pass through on the 3rd-7th of July.

EC also has a massive node in the Bight, that is due to land in SE Australia’s doorstep around the 3rd of July. It is yet to be seen if this peaks over SA, or the ridge leans over it and pushes the conveyor belt right into the Australian Alps. It also might be pushed a little later as this system forecast matures, but it’s certainly the stage on what could very well be the season starter for 2020.

10th-14th July

We are looking at another potential system period in a little while, shown by the LWT south of Madagascar that should be in our region around the 10th-14th of July.

EC Monthly Control certainly agrees with a scenario that is set-up to deliver moderate-heavy snowfall for the Australian Alps. It’s certainly potentially a big fish.

20th-24th July

Should we want to go even further with the forecast, I can see the next LWT node in our region around about this time next month.

EC Monthly Control is certainly trying for it.

MJO

We are currently outside of the tropical signal, but by the end of the month and into July, we should see the tropical signal move into our region, which is beneficial for our snowfall, and should really help the 1st-7th July period come to fruition IMO.

AAO

We have a number of conflicting takes from the models on the all important long range forecast of the AAO.

EC shows a great setup for the rest of the month, as we see a strong negative decline, heading towards that potential in the first week of July. However of course it is uncertain how long it will stay like that once in July, but noting the model trend and the gravity of this switch, there is potential for it to be a while.

It’s worth discussing the GEFS, which shows a decline in the AAO now, but struggles to hold that into July. It could be said that it has a bias towards potentially strengthening the Southern Hemisphere polar vortex in the upper stratosphere, but only time will tell, but it certainly doesn’t look amazing.

But it’s American compatriot in the GEOS (NASA model), shows a solution more like EC, and shows a potential for a longer term dip of the -AAO.

AAM/GWO

We see a trend over the month for a positive AAM to grow, which may be bad news come mid-late July, but for the next few weeks we see:

  • A pre-existing negative AAM base state which is good for Australian snowfall.
  • And potential for positive mountain torques that would help to disrupt the stratospheric polar vortex.

Thanks again for reading this European long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Charts courtesy of Tropical Tidbits, Weatherzone, Weathermodels, Accuweather, Michael Ventrice, Stratobserve and Victor Gensini

Image courtesy of Charlotte Pass.

Australia on the long term 5th June

Welcome back to this season’s long term outlooks for the Australian snow season. First we will look at the modelling for dates, and then the climate drivers.

14th-17th June

GEFS and EPS both show a trough peaking over Western Australia and falling down into Southeastern Australia and Tasmania starting either over the 14th and 15th, and pushing through the 16th of June, which may bring little for the Alps, could also be a signal for a warm and wet front, and it also could possibly mean a chance of some snowfall, which has been flirted with by GFS at times.


EPS shows more of a cut-off low scenario, and GEFS has a more trough-based scenario, and both have been slowly improving the prospects with this period.

23rd-27th June

EC Monthly Control shows dual troughs on the 23rd of June and 26th of June, both bringing snowfall to the Australian Alps. The ensemble mean doesn’t really connect with these ideas however, showing primarily ridging during this period.

On the North American model ensemble side, this period is forecast to feature ridging for SE Australia, but shows troughing over Western Australia.

2nd-7th July

You can see the LWT node for the date period above is relatively weak on the chart below south of Madagascar. But there may be something more interesting on the next cycle after that on the 2nd-7th July.

Antarctic Oscillation

The AAO is forecasted to stay positive over the next two weeks for the most part, and it is clear that we are in a positive AAO state of play for a while indeed. The brief more neutral reprieve may be a catalyst for the WA peaking system as it aligns well with this event on the charts.

As for when we will see a more solid negative phase of the AAO, it is looking possible that we will see an easing of the positive state in the 15th-25th June timeline, per EC guidance, but it is very possible the models are showing us a false end to this state as well. But looking relatively good of heading towards a more negative phase in the later stages of the month or possibly in early July. AAO states typically cycle around a month or so, which means these timelines generally go with that flow.

MJO

The tropical base state is looking like it will benefit the Phases 1-3 of the MJO in the Indian Ocean. This is possibly a reason for the consistent progs for a WA peaker pattern for the rest of the month.

For Australian snowfall, we would prefer the negative cool coloured signal to be over Phase 5 and 6 within our region.

There may be a possibility for the MJO to enter our region in the last few days of the month into July, but this is only a possibility at this point.

GWO

As to be expected, the Global Wind Oscillation is largely acting in the mold of the MJO staying around the Phase 1 zone, however also similar to the MJO it is being generally kept in the neutral influence area.

The negative phase around the 13th of June may assist the medium-term system around that time down here, but a general more positive trend would increase the zonal flow in our region, that may serve to get rid of the dominant ridging blocks, but also weakens the chance for cut-off lows that bring good snowfalls.

Disclaimer: There is lower skill associated with using long range model forecasts to find snow systems.

Thanks again for reading this European long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Australian Snow Season Outlook 2020

G’day everyone, it’s that time of year. And we have been thrust into the game with a major 50cm+ system over the last few days. We are here today to see if that will continue deeper into the snow season.

So we are going to look in this article about the potential for the season as a whole, using model analysis and climate drivers later on. If you aren’t keen for the technical details, the conclusions are near the bottom.

Verification

My prediction for 2019 at Spencers Creek was 176cm, we actually ended up with 228.8cm as our season highest snow depth. My third year of being outdone by Mother Nature. One may see this is good, but for me, it’s always a sign that more work needs to be done for this forecast to remain as close to the final depth as possible.

One thing I have found is that the arbitrary number is inflexible with the way I weighted climate drivers in the past few years. So you will notice that I will become more liberal than usual with that weighting process. But it is best to consider the final number for what it’s worth, and focus on the climate drivers themselves and the overall vibe of the season as depicted by the outlook. But that said, I will provide a number at the end.

Model analysis

EUROSIPS (including premier European models such as ECMWF and UKMET) paints a troughing picture for Southern Australia, particularly for the latter stages of the season. The troughing tends to favour the WA/SA part of the continent more, but it would lead to improved snowfall outcomes for SE Australia, just perhaps not as much as if that trough centered on the East Coast.

CANSIPS (Canadian model) points to a wet and cold outlook for SE Australia and the Australian Alps. This certainly would be a good sign for us.

CFS (American model) points to troughing peaking in the Bight. That’s not awful for us, there should be some systems that break through to the Alps, but that sort of setup emphasises sliding systems and as CFS forecasts, a wet outlook with prefrontal rains.

JMA (Japanese model) only covers May-June-July, but I am just showing it due to some interest in it’s abilities in the weather community, with it giving us a good outlook for snowfall at least in the early-mid season.

Climate Drivers

Okay, now with the models checked, we can do the traditional climate driver analysis. We will start at 194cm this year, our 10 year average, 8cm higher than last year’s 10 year average of 186cm. This is due to the last three years being consecutively very good seasons, in amongst an otherwise average decade. The use of this number reflects me trying to stay in with the current climate, but of course outliers pose a threat to a small base of years.

Pacific Decadal Oscillation

The PDO is currently negative and while the -SSTAs are weakening off the California coast, the North Pacific warm pool is forecast to stay in place. A negative PDO is forecast for this winter, which increases rainfall prospects for Australia a bit. Hence it increases snowfall chances a bit for us. 194 + 2cm = 196cm

Southern Annular Mode (SAM)

There is a fairly strong correlation between negative SAM and more snowfall for the Alps. I talked about the seasonal prediction of SAM here.

  • El Niño Modoki (the only seasonal prediction factor of SAM, other than a weaker correlation to Eastern Pacific Nino) is at a neutral phase, and is likely to get cooler towards winter.
  • July and August ECMWF and EUROSIPS modelling show some ridging around the South Pole, which increases the likelihood of a negative SAM, which is good for us, but only just in our favour.
  • Climate Change as a general trend is causing a more positive AAO.
  • The general trend if it continues to hold over this winter is towards a positive SAM.

Overall I think I will go with 196 – 8cm = 188cm, because I am falling towards that general trend. You would hope that there are some negative periods in that trend during the season, otherwise that moisture from the north that I forecast below is likely to fall as rain. The biggest caveat of all, is that there is a fine-line between “cold and moist”, so heavy snow, and “warm and wet”, so heavy rain. This is why the timing of negative SAM events is critical for a good season.

Indian Ocean Dipole/Northern Australia SSTs

This was causing some issues over the summer, contributing to the terrible recent bushfire season, in coordination with climate change. But now we are in better shape for the winter ahead with the IOD.

There is a correlation between the Australian snowfall and the IOD. I am growing more fond of more specific regional SST trends, rather than relying on big global ideas such as the IOD, so of particular note to us is the warm waters north of Australia. These will deliver good moisture to south-east Australia, to help fuel our snow systems. The major models all point to a negative IOD during winter, which is good news for snowfall in the Australian Alps. But keep an eye on the warm waters in the north here, as this is what will decide our fate in terms of moisture.

For here, 188 + 9 = 197cm.

El Nino-Southern Oscillation (ENSO)

There is a correlation between ENSO and Australian snowfall. The current model predictions show a fairly cool neutral state going into winter, perhaps borderline La Nina towards the end of the season. This would make our snowfall season a bit stronger especially towards late season, but the impact is likely to not be strong. What is important here is warm water is pushing towards Australia as part of local trends, so it does look somewhat decent (I do take this into account with the IOD section above).

Atmospheric Angular Momentum (AAM/GWO) (more here) indicator is become more neutral (albeit slowly) after a long period of strong positive cycles. I predict a warm neutral Atmospheric ENSO, and perhaps a weak Nina effect. I will put this in the win column, but only just.

197 + 3 = 200cm

Madden-Julian Oscillation

Australian snowfall and MJO have a very strong correlation. The CFS model shows a signal for Phase 1-2-3, the seasonal signal moving closer to Australia slowly as the season goes on . This is okay if we can get moisture from the Indian Ocean to come across, and at least it means that there is likely to be an active tropical signal throughout the winter.

The weakening in GLAAM/GWO positive cycles (see link in ENSO section for more info) means that the MJO is probably going to lose some of its strength, but I’d be surprised if we went into full-on -AAM cycles until later in the season. MJO tends to be stronger in oceanic La Ninas, particularly building towards a Nino (basically the opposite phase of which we are in).

I think there will be some sort of decent tropical signal, particularly with warm SSTAs in our region, 200 + 3 = 203cm

Sunspots

There is a weak correlation between a higher amount of sunspots and more snow, as found by Francisco Sánchez-Bayo and Ken Green. We are at the solar minimum, so I am going to cut off 2cm

203 – 2 = 201cm

Volcanoes

If a large stratospheric volcano explosion occurs, Australian snowfall substantially increases for that winter. None have occurred in the last year, so our forecast won’t be affected.

201cm, no change

Southern Australia SSTs

The bight is colder than average (link updates), which is good for Australian snowfall. The Tasman is a little warmer than average. The Bight is forecast by EC to stay cold at least until late-season, where it might start to warm up. CFS and CANSIPS like cold seas surface temperatures throughout the season, which is a good sign. Meanwhile, the Tasman is expected to heat up a bit more, but it’s not going to be crazy warm. Conditions particularly in the GAB are pretty good for the ski season, albeit deteriorating potentially into Spring.

201 + 6 = 207cm

So my final maximum Spencer’s Creek Snow Depth for this year is 207±30cm. This number has came around from hours of analysis, tinkering and changing. The model outlook in the first section of the blog, is roughly in favour of a snowier than average season, though it may come with significant rainfall. The 207cm figure is higher than the 10 year average of 194cm mentioned above. Taking this into account, I am forecasting a moderately better than average snow season for the Australian Alps.

In terms of when the season will be best, the factors seem to be weighing against each other, with the MJO being best earlier in the season IMO, and ENSO and the IOD being “better” later on in the season. I think it will be a pretty typical season, in terms of timing of snowfall, all in all. But as I said above, the AAO/SAM will be critical in determining this season’s fate.

I hope you enjoyed this analysis, and I will see you for a long range outlook before opening weekend. Please share this with skiing or boarding family and friends, I really appreciate all the support.

Thanks again for reading this Australian snow season outlook, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above.

Europe on the long term 23rd Feb

6th-10th March

Ridging dominates Western Europe, blocking snowfall for the UK and the Alps. The far eastern Alps may do a little bit better. Far Eastern Europe is set to do well in this period with troughing.

11th-15th March

Ridging dominates the European continent, with a +NAO in the Atlantic as a background feature, helping to pave out the Synoptics.

16th-20th March

The +NAO trough strengthens forcing a more zonal setup for the UK, ridging persists for both most of the UK and the Alps.

21st-25th March

The +NAO consolidates and brings zonal conditions for the UK and Scandinavia. Ridging continues over the European Alps.

26th-30th March

The +NAO weakens a bit, and allows ridging to move north back over the UK, while continuing to persist over the Alps.

Climate Drivers

The atmospheric momentum budgets show less positive deposits in the tropics after the spike in January, that had little consequence in terms of changing the pattern. Those tropical deposits are starting to pick up again, because the MJO is making another pass.

The positive deposits between approx 40N-60N and the negative deposits at approx 15N-35N have reestablished, which is essentially a consolidation of the status quo. This means that the strong Atlantic +NAO will continue and the +AO strong vortex state will persist for the next month or so.

The stratosphere is holding firm with a very strong polar vortex state. This means that the Arctic Oscillation is likely to stay positive for quite some time deep into March and probably beyond.

The past 10 days of the MJO being in Phase 6 is behind the somewhat neutralisation of the NAO, which will potentially help bring about decent snowfalls for the UK and the European Alps, as well as the rest of the continent.

After the tropical support has gone away in mid-March, Europe is likely to continue to be subject to bouts of European ridging as predicted by the EC Monthly model above, and to a +NAO base state, fuelled by a strong +AO.

Verification

Here are the predictions that I made in November for the European seasonal outlook:

  1. December is expected to more average like.
  2. January and February will be the months that define the image to look like this, the strongest months of the winter.
  3. Scandinavia should expect lower than average snowfall.
  4. UK should expect above average snowfall throughout winter IMO, with the best of the falls in January and February. The falls will be less climatologically significant in the highlands, but it should ultimately be a snowy and cold winter, presuming extratropical and stratospheric forcing goes our way.
  5. The Southern Alps should expect a very good snowfall season, based on a more equator-ward jetstream.
  6. The Northern Alps should expect an average-above average season.
  7. Eastern Europe should expect a colder and snowier than average season.
  8. The Pyrenees should expect an above average snowfall season IMO.

Unfortunately it didn’t really pan out this way:

  1. This did pan out okay.
  2. This of course didn’t pan out, the season didn’t improve in the way I forecasted.
  3. Scandinavia had a pretty good season (as far as I can tell using seasonal charts).
  4. The UK didn’t have a good season at all. So this big call did not pay off and was a failure.
  5. The Southern Alps started off well, but a relatively average winter hasn’t really qualified for an above average season overall.
  6. This is probably the best verification for me (the Northern Alps), it was mostly average and a little bit above average in some areas from what I can tell. Lower down, the verification has not been so great, with less snowfall.
  7. This prediction failed, with Eastern Europe having a pretty meagre season.
  8. And this one failed as well with much of the lower Pyrenees doing poorly. The higher slopes are doing about average, but overall not so great.

So overall Europe was milder and more zonal than I had expected, due to the base state failing to budge throughout the season. Limited stratospheric activity and a strong positive AO helped to fuel a poor snow season for much of Europe.

Thanks so much to everyone who has read the blogs throughout the season. I hoped you enjoyed reading them.

Disclaimer: There is lower skill asssociated with using long range model forecasts to find snow systems. 

Thanks again for reading this European long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above. Enjoy the spring’s worth of skiing, and you will see me again in September and October for next season! I will hopefully see you then.

North America on the long term 16th Feb

4th-8th March

Mild troughing for the Northeast US and the Southern California region. A SE Ridge is persistent in this period, together with a strong +AO and a +NAO. A very strong Aleutian Ridge is in progress as well, per EC Monthly.

9th-13th March

Western US troughing in this period is anchored by a SE Ridge and strong Aleutian ridging, together with a strong +NAO.

14th-18th March

The Western US troughing declines, but the Aleutian ridge and Eastern US ridging are still in place playing into a +NAO-esque Atlantic.

19th-23rd March

Troughing returns to the PNW/BC and the Sierras, again anchored by the Aleutian high and increased Eastern ridging,

24th-28th March

The trend of troughing for the Northwestern US down to Tahoe continues, with the Eastern ridging and Aleutian High still present.

Climate Drivers

The Arctic Oscillation remains in very strong positive territory. This has been assisting snowfall particularly in the Northwestern US, and in British Columbia and Alberta.

The MJO is expected to be briefly within the Phase 7-8 region, which may explain a slight tilt towards the Eastern US in terms of systems, and a slowing down of the snowy pattern for the PNW/BC region. But the +AO will ensure that this will probably not eventuate to much snowfall for the Eastern US. This favourability if you can even call it that, will slow down as we go into March, with the Western US expected to be the big winner of March again.

We see little activity in the stratosphere of consequence that may weaken the strong stratospheric and also tropospheric vortex. GFS notes some hints towards neutrality at the surface, but given the stratospheric base state I would suggest that the +AO theme that has been going on since the start of this year will continue.

The atmospheric momentum budgets show less positive deposits in the tropics after the spike in January, that had little consequence in terms of changing the pattern.

The positive deposits between approx 40N-60N and the negative deposits at approx 15N-35N have reestablished, which is essentially a consolidation of the status quo. A strong Atlantic (+NAO) will continue, the PNW will continue to be favoured in general and the Eastern US will be less favourable for snowfall.

Verification

So this has been a hard year for those involved in seasonal forecasts. Here are the predictions I made:

  1. The Interior of the East Coast on the Appalachians and further west is set to have a better than average snowfall season. The East Coastal regions are set to have a mostly average season.
  2. California is set to have a largely below average season. It won’t be absolutely abysmal though, with potentially improving conditions later in the season.
  3. The Southwest of US is set to have a largely average season, with New Mexico doing better than Arizona.
  4. Utah is set to have an average season. Which tends to be pretty good anyway.
  5. Colorado is set to have a mildly above average snowfall season.
  6. The Canadian/Northern US Rockies are set to have a mildly above average season.
  7. The PNW Coastal mountains are set to have a mildly below average season, but I can see them having a better early-mid season compared to California.
  8. The Central Interior US from the Great Plains to the Midwest to the Tennessee Valley is expected to have an above average season for snowfall and deep cold at times.

Per SNOTEL, other NOAA sources, and Rutgers Snow Lab:

  1. The Eastern US had a below average season, not an average one. Better than some others though.
  2. California did have a below average season. So I got that right. We might see some improvements in the next little while, but not as fast as I expected.
  3. I got the Southwest pretty well too, slightly above average in NM, and somewhat below average in AZ.
  4. I got Utah pretty well, perhaps doing a little better than expected.
  5. Colorado went pretty well for my verification.
  6. I got this pretty well for the interior PNW/BC Rockies.
  7. PNW/BC Coast started slow (compared to a decent start for California IIRC), but came out better than I thought originally, with a very good second half of the season.
  8. I did reasonably well in the Great Plains, it was more average in the Midwest, and failed further towards the south. The Central US ultimately didn’t get the strong levels of snow and cold I predicted for this season.

So I did well across most of the Western US, underestimated the PNW Coast a fair bit, and overestimated the Central and Eastern parts of the US in terms of snowfall.

I had expected troughing over the Central North America, instead it angled towards the Northwest, with ridging through the Eastern US.

As always, lessons to be learned, to improve for next season.

Thanks so much for reading. I hoped you enjoyed reading it. 

Disclaimer: There is low skill asssociated with using long range model forecasts to find snow systems. 

Thanks again for reading this North American long range snow forecast, follow me on Twitter @longrangesnow and subscribe to my email list by clicking on the tab on the main header above. I appreciate everyone who has taken the time to read the blog over the season, I will see you next year.