North America on the long term 9th December

Welcome to the start of this season’s long term outlooks for North America. This year we are trying to involve the entire continent with the usual models and climate driver analysis.

17th-23rd December

EC Monthly shows this week to feature troughing along the West Coast, and also shows some potential for New England and SE Canada. CFS likes Western US ridging and Eastern US troughing.

24th – 30th December

Again EC Monthly shows troughing in the Southwest US, benefitting California and the Four Corners states, and the opposite for the PNW with ridging. Ridging is forecast for the East Coast of US. CFS again shows the continuing of a Eastern US troughing and snowfall pattern, and Western US ridging.

31st December – 6th January

This week on EC Monthly shows ridging in the PNW region. It also depicts troughing for the Northeast US. CFS shows a strengthening SE ridge, Central US troughing and Pacific coast ridging.

7th-12th January

Some troughing on the West Coast of US, but most of the continent is dominated by a Southern ridge, with some troughing in the far north of New England

13th-18th January

This period shows troughing becoming more significant for the Midwest and the NE of the US. Meanwhile there is ridging in the SW and the PNW.

MJO

The GFS VP200 forecast shows the Indian Ocean standing wave remaining in place for the medium term, which isn’t as great for atmospheric rivers or trying to shift the pattern.

CFS keeps this theme running long term, so it is expected for the IO standing wave to stay this way throughout the month, amid some ups and downs of the signal. I’d expect it to slowly weaken this month, and complete its change into the new year, with the decline in the +IOD state.

This means that a deep cold pattern for the Eastern US is probably still not going to come until potentially early-mid January, as the tropical pattern starts to really evolve and get interesting.

The EC Weeklies are consistent with a strong IO tropical standing wave. The activity in MJO Phase 6 & 7 in January might make things more interesting for cold risks in the long long term, but for now, we are stuck with this base state. It all depends on the progression of the +IOD.

GWO

Recent GWO History
  1. We will remain in GWO Phase 8/1 for a few more days, thanks to the lingering +EAMT.
  2. From say the 12th-14th of Dec to the last week of the month, we should see a proper -GLAAM circuit.
  3. GEFS & GEPS show positive mountain torques around the Christmas period, with potential downstream impacts around the New Years period.
  4. We should see a more positive momentum circuit in the first two weeks of January.
  5. What this means is that we should see a strong Aleutian Low based on the current +EAMT over the next 10-20 days, pushing into the EPO domain, flooding the CONUS with Pacific air as the extension matures.
  6. We will see this impact continue until the progression weakens this after Christmas. We will see better chance for cold for the East in the New Year.

Stratosphere

Apart from the biased GEFS, the stratospheric polar vortex per measure of 10hPa and 50hPa zonal wind is strengthening. There’s a decrease of large wave 1 amplitude and a mild increase of wave 2 amplitude.

So a chance of a SSW are unlikely for December, and will probably increase towards the latter parts of the winter. An inducement of a -AO state will probably have to wait until later in the season, again setting back a deep cold early winter for the Eastern US.

Arctic Oscillation

FWIW CFS shows a -AO for the late December and early-mid January period, after some ups and downs in the medium term. EC Weeklies show a +AO for the late December to early January period.

North Pacific

Courtesy of Andrew Winters

The jet in the North Pacific extends in the next week, and then normalises in the middle of the month, while shifting towards the pole. The focus of the snowfall in the 15th-30th December period will be towards the PNW IMO, thanks to this poleward shift. Later in the month, as the jet retraction peaks, it may get less conducive. But I’d forecast

Chances for snow-bearing systems for the Southwest are not particularly high at this point, thanks to not a very forceful Sub-tropical jet stream at this point. But nonetheless the positive Pacific Meridional Mode (warm SSTAs southwest of California), still provides potential when the STJ probably expands in early-mid January. Ultimately we need Nino forcing to be stronger, and this won’t be a thing until the IO standing wave declines.

Conclusions

  • I expect a good run over the next 10 days for the PNW.
  • This good pattern of snow-bearing weather will eventually expand out to the majority of the Rockies, with the exception of the far Southwest for the 10-20 day period.
  • Tahoe and the Rockies should both do well out of this period, once the initial 10 days pass.
  • After the New Year, we should see deeper cold risks per the GWO cycle for the Central and Eastern North American regions.
  • The short term good pattern over the Eastern US will dissipate into ridging in the latter half of December. It might get more interesting in the days prior to January, with the aforementioned colder risk in Jan. This doesn’t mean there is no chance of snowfall, rather it is more limited.
  • After the current short term Southern US snowfall risk, chances will be lower until January, or at least the last week of December.

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. 

Japan on the long term 24th November

Here is the first long term outlook for Japan, focussing on the climate drivers and the model forecasts.

7th-9th Dec

GFS and EPS shows a common trend for a system right here. They both proceed with some sort of low from the south of Japan bringing rain in the 5th and 6th of Dec. Then the fetch from the NW comes down on the 7th, creating the potential for the first major Central Honshu snowfall event of the season, continuing into the 8th and 9th. This is a key period and setup to watch.

16th-18th Dec

EC Monthly Control shows not a lot after the 7th-9th December, and shows a low coming from the south bringing rainfall on the 15th, with a chance for some moderate snowfall for a Central Honshu on the 16th.

18th-20th Dec

After a rain-bearing low from the south on the 18th, EC Monthly shows an event of moderate-heavy snowfall on the 19th and 20th for Honshu and more moderate for Hokkaido.

21st-23rd Dec

This particular low brings heavy snowfall for Hokkaido in the 21st and 22nd of Dec, with potential for moderate snowfall on the 23rd, as per EC Monthly.

Climate Drivers

So in terms of the progression of the GSDM in the extratropics:

  1. We should expect positive torques and an increase in momentum in the next 10-15 days. This is observed by +EAMTs being prevalent, which increases ridging over China. This improves chances of snowfall for Japan, as it creates the NW fetch needed for the lake-effect.
  2. So the end of November and the first 10-12 days of December should be rather decent for Japanese snowfall, and could provide a solid early start.
  3. Mid-late December is likely to provide more chances for troughing to the South of Japan, bringing rain, and an otherwise relatively dry synoptic outlook. This doesn’t mean there is no chance of snowfall, just lower chances. Tropical and extratropical support for systems is unlikely.
  4. This support will enhance in the last days of December, and it is likely that January would have an improving atmosphere more conducive to snowfall in Japan.

MJO

The last days of November will be spent with a neutral MJO. Early December is likely to start with a return to (sort of) Phase 7-8 conditions for a short while, until we return to Phase 1 in the second week of December. Or it could be mostly Phase 1 forcing on the other hand. These will improve tropical forcing for Japan a little, and are reflective of the general state of momentum as discussed above. This is good for Japanese snowfall in the first week of December.

Arctic Oscillation

Apart from a short period of +AO in the troposphere, the Arctic Oscillation outlook is mostly neutral. So the Arctic domain effects upon Japan will be minimal at this point. There is SSW potential later in December or beyond, that may help Japan in January.

The Siberian High is currently quite strong and is expected to weaken to more normal strength.

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 Japanese 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.

European Winter Outlook 2019-20

I am back with a European-specific forecast, that caters to people watching weather patterns and snowfall across Europe, from the UK to the Alps, to Southern Europe.

Model Outlook

The combination of seasonal models provided by Copernicus leads us to a +NAO scenario, which would bring a wet/mild winter for the UK, possibly decent snowfall for the Northern Alps, and a poor snowfall season for Southern Europe.

QBO

13bbhFZl14.png
All the years that fit my current forecast for +5 to -10 for this season for QBO values at 30mb, minus strong Ninas and Ninos.

Above is my QBO analog for winter 2019-20. These factor in years that fit within the QBO value range that I am forecasting this year (roughly based on the forecast below).

qbo_wind.jpg
FU Berlin University

My QBO forecast for the next year is the red line in this image.

Key trends to note, based of this:

  1.  -NAO, deep Greenland high.
  2. Massive European trough.
  3. Deep troughing around Eastern US.
  4. Aleutian ridge.
  5. Eastern US pattern driven by NAO.

Probably not the most sturdy patterns imaginable indicated by the composite. But certainly a pattern that could drive snow and cold for the UK, the European Alps and the rest of Central and Southern Europe.

ENSO

Our current oceanic situation in the Pacific is a weak mainly Central Pacific El Niño, as presented below.

The pattern by the oceanic standard would be something like this:

So we see obviously deep European troughing in Southern Europe, making the Southern European Alps and the rest of Southern Europe big winners snow wise with troughing.

Typical Nino effects on Europe tend to be good for increased precipitation for the UK and the European Alps, but they also help to produce -NAO patterns and SSWs that can help bring cold and snow to these regions. These effects tend to amplified most when the Nino is weak-moderate and in late winter.

From an atmospheric state, we are currently in a GWO orbit for the past few months in the negative AAM values. This approach in the extratropics also sees a -NAO and European troughing.

Here is a composite for -AAM winters (sorry for the poor viewing of Europe, but you can see the rough troughing)

My take away for the GSDM pattern this season is a neutral to weak-moderately -AAM circuit this winter, particularly in early months. This pattern is good for meridional patterns that benefit the European Alps, especially the South, and places like the UK.

But as you can see, it is less amplified than the straight Modoki pattern. For this reason, and the intraseasonal effects of ENSO, I can see a favourable pattern from ENSO early on, and an even more favourable pattern later on, per ENSO effects.

Sea Ice and Snow

The Barents-Kara Sea is currently seeing an ice recovery bucking the weak sea ice trend of the current century. However it is still slightly below the 1981-2010 climatological trend. This may result in a somewhat of a +AO response compared to recent years, but I can’t see this being a strong influence, given it’s still below the mean.

The significantly lower than average sea ice anomalies in the Bering Sea right now and expected to continue into winter are expected to assist in ridging in the Aleutian region. This is probably on the wrong side of the globe to have too much impact, but it’s negative if anything.

Taking statistics just after the end of October, Siberian snow extent is higher than normal, which helps invoke a -AO situation and helps the development of a SSW. The Siberian High is already gearing into winter mode. One red flag is recent lower than average snow coverage close to Southeastern Europe, which may be a negative sign for the early winter ahead for that part of Europe.

North American snow cover is also higher than normal, which possibly would help deeper cold to come across the Atlantic.

Solar

Solar impacts for this year will be indicative of a higher chance for a -AO, benefiting European snowfall in the UK and Central/Southern Europe including the European Alps.

Atlantic

I am not a big user of the Atlantic for forecasting, but for the British and European blog readers, here we go:

The cold “blob” in the North Atlantic may allow for a colder winter for the UK and Europe as a whole. So it’s good for snowfall, especially lower down, but may reduce precipitation a bit.

The warmish SSTAs around Italy in the Mediterranean may be useful for Southern Alps snowfall/precipitation. It can also mean warmer temperatures however.

Stratosphere

I see a more likely chance than normal for stratospheric warming this winter. Why?:

  1. A descending -QBO will help chances for a SSW later on this winter, particularly for February.
  2. Brewer Dobson Circulation is to be stronger than normal in both of the NH and SH subtropics and average over the tropics this month. I expect a stronger than normal BDC over the winter. This increases ozone in the SPV during the winter.
  3. ENSO factors are sort of supportive at least from the oceanic perspective. The GWO should be more supportive later in the winter. 
  4. Higher than normal Siberian Snow Cover supports a SSW during this winter.
  5. Solar minimum is taking place at this point, favouring a -AO and potential stratospheric disruption.

This means that I predict a SSW from mid Jan – early March. Current signs of stratospheric weakening could eventuate into a minor SSW with some medium-long term implications, but I think the major event will be later in winter. The implications of this is more snowfall for the UK and for the European continent including Southern Europe.

The above graphic indicates EC is favouring a SSW or a Stratospheric disturbance of some sort in January and February. UKMO still thinks it will be stronger than normal per the mean, but some ensemble members are having more interest in the idea of a stratospheric disturbance.

Conclusions

This has been a hard one for me with various factors in play here. But running composites and all of the drivers through the methodology have got me firm on this map below:

  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.

And here is my snowfall anomalies map for illustrative purposes.

Thanks so much for reading. 

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 is meant to be interesting information, that can help to see what the season would be like. 

This took a lot of work over the last fortnight, so I appreciate your support. Starting in late November, my long range outlooks for North America will start! They will be produced every 2-3 weeks, looking out into the range of 10-30 days out. Stay tuned. 

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

North American Winter Outlook 2019-20

Welcome to my North American outlook, discussing the models and drivers to come to conclusions about the winter ahead. Discussion is reasonably technical, so if one wishes just to see the results scroll to the bottom.

Model Outlook

The above outlook from ECMWF doesn’t form a strong part of my conclusions, but the global model trend has been considered. Here is the summary of it:

  • December and February favourable for the Eastern US
  • January more favourable for the Western US

I can certainly see some of these ideas coming into practice, with a more favourable pattern for the West in January being a possibility with a mid winter lull for the East Coast. But I am more in favour of this happening a bit later in winter if it does.


QBO

13bbhFZl14.png
All the years that fit my current forecast for +5 to -10 for this season for QBO values at 30mb, minus strong Ninas and Ninos.

Above is my QBO analog for winter 2019-20. These factor in years that fit within the QBO value range that I am forecasting this year (roughly based on the forecast below).

qbo_wind.jpg
FU Berlin University

My QBO forecast for the next year is the red line in this image.

Key trends to note, based of this:

  1.  -NAO, deep Greenland high.
  2. Massive European trough.
  3. Deep troughing around Eastern US.
  4. Aleutian ridge.
  5. Eastern US pattern driven by NAO.

Probably not the most sturdy patterns imaginable indicated by the composite. But certainly a pattern that could drive snow and cold for the Eastern US. But it’s also a pattern that works well for the PNW, and not so much California and the SW. Basically it’s a pattern that works well for the Northern US, with cold temps not making it south as much.

ENSO

We are in a El Niño Modoki year. The pattern by the oceanic standard would be something like this. It focuses a ridge over Canada, and an Aleutian Low with a deep trough over the East Coast.

But we are also currently in a GWO orbit for the past few months in the negative AAM values. This focuses on deep troughing and cold over the North American Continent. This approach goes okay for the backend of the Rockies, and can actually help create deep cold in Southern US with the jet bringing cold Canadian air equatorward. This is laid out in the composite below.

Here is a composite for -AAM winters:

My take away for the GSDM pattern this season is a neutral to weak-moderately -AAM circuit this winter, particularly in early months. This pattern is good for cold in the Central US, and it actually helps moisture transport up to the East Coast storms.

These patterns are not going to be very favourable for California particularly early-mid winter. If we can see a more +AAM setup later in winter, probably February, it may see more snowfall. It bases a little better for the PNW.

North Pacific

Here is the latest SSTA forecasts for winter. The focus for warmth is in the Gulf of Alaska and immediately around the Aleutians. This helps ridging in this region, but the warmth is not quite on the coast. It is still a pattern that is not ideal for West Coast mountains and better for the Central and Eastern US.

I visualise this pattern in a rough manner below.

The slightly cold SSTAs is an ideal location for our Aleutian Low, which should be further south and west than normal IMO. This may help the West Coast’s chances later on as the warm “blob” weakens over winter and if a more +AAM pattern comes later in winter.

Sea Ice and Snow

Barents-Kara Sea Ice is expected to be a little bit lesser than normal, helping a -AO persist with higher than normal rates of Scandinavian blocking. This does well for the Eastern US, and less so for Western US.

The significantly lower than average sea ice anomalies in the Bering Sea right now and expected to continue into winter are expected to assist in ridging in the Aleutian region.

Taking statistics just after the end of October, Siberian snow extent is higher than normal, which helps invoke a -AO situation and helps the development of a SSW. North American snow cover is also higher than normal, which will help to build deeper cold earlier in the season and keep a cold theme throughout for the interior.

Atlantic

The EC SSTA forecast for the Atlantic side should be focused on the warm SSTs around the Bahamas. This may help to induce SE ridging.

Gulf of Mexico warm SSTAs should help to increase moisture for much of the East Coast. This will become less of a factor as the winter goes on.

Stratosphere

I see a more likely chance than normal for stratospheric warming this winter. Why?:

  1. A descending -QBO will help chances for a SSW later on this winter, particularly for February.
  2. Brewer Dobson Circulation is to be stronger than normal in both of the NH and SH subtropics and average over the tropics this month. I expect a stronger than normal BDC over the winter. This increases ozone in the SPV during the winter.
  3. ENSO factors are sort of supportive at least from the oceanic perspective. The GWO should be more supportive later in the winter.
  4. Higher than normal Siberian Snow Cover and low Barents-Kara Sea Ice supports a SSW during this winter.
  5. Solar minimum is taking place at this point, favouring a -AO and potential stratospheric disruption.

This means that I predict a SSW from mid Jan – March. Current signs of stratospheric weakening could eventuate into a minor SSW with some medium-long term implications, but I think the major event will be later in winter. The implications of this is more snowfall for the Eastern half of North America.

Conclusions

  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.

Thanks so much for reading. 

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 is meant to be interesting information, that can help to see what the season would be like. 

This took a lot of work over the last fortnight, so I appreciate your support. Starting in late November, my long range outlooks for North America will start! They will be produced every 2-3 weeks, looking out into the range of 10-30 days out. Stay tuned. 

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

Japanese Winter Outlook 2019-20

Hello to all those following the Japanese weather forecast this season!
As usual, I am writing a seasonal outlook, followed by several long term outlook updates over the winter. Today we will cover the models and the climate drivers that assist with the seasonal outlook.

Seasonal Models

There is an overwhelming consensus of the UKMO, ECMWF and the multi-model ensemble of Copernicus, and that is for ridging over Japan for the winter. This setup isn’t great for Japanese snowfall.

Sea Surface Temperatures

There are two points to make here:

  1. The warm SSTAs surrounding Japan demonstrate the potential for ridging around Japan for winter.
  2. The warm SSTAs in the Sea of Japan specifically allow a larger divide between warm sea surface temperatures and cold air aloft coming from Siberia. This would increase lake/sea effect snowfall in terms of strength and duration of events, rather than the exact timing of such events.

Siberian High

“The Siberian High is an important, yet relatively unknown driver for snowfall in the Japanese Alps. A strong, stable Siberian High provides very cold air down towards Japan, except if the High is too far west. This cold air from the Siberian High creates the lake effect, that provides the massive snowfalls in the Japanese Alps.

Snowy Hibbo two years ago

The Siberian High is affected by a number of things, including snow cover in the region and the AO. A negative AO causes a stronger Siberian High. The Siberian High is also affected by the snow cover in Siberia during October and November. An above average Siberian snow cover creates an early, potentially more stable Siberian High. It also correlates with a negative AO.

Snowy Hibbo two years ago

So this year is going to feature both lower than average Arctic sea ice cover and a higher than average Siberian snow cover, as you can see in the tweet below.

So this will have a positive effect for Japanese snowfall throughout the season. It could also indicate an earlier start to the snowfall season, with the Siberian High developing and strengthening earlier than normal.

ENSO

I expect a weak Nino Modoki event to prevail into the winter. What this means for Japan is based on composites, a somewhat warmer Central Honshu and a colder Hokkaido. But it also predicts a somewhat strengthened ability for lake-effect snowfall to fall, with a noticeable increase in And it also shows a stronger Aleutian Low in accords with normal Nino expectations.

MSLP anomaly for Nino Modoki/Central Pacific years

A negative East Asian Mountain Torque is not good for Japan, and it doesn’t help that we are in a -AAM phase, which is expected to continue into winter. But I expect frequent responding +EAMTs throughout the season to help counter this, so I don’t think this will be a negative factor IMO. A positive East Asian Mountain Torque increases the strength of the East Asian jetstream, which helps Japanese snowfall.

Arctic Oscillation

  1. Siberian Snow Cover is expected to be higher than average, so a -AO is more probable, which benefits Japanese snowfall.
  2. Arctic sea ice is lower than average, which also helps to force a -AO, in particular low sea ice in the Barents-Kara Sea.
  3. The QBO is expected to have an effect earlier in the season of subsiding stratospheric weakening, which encourages a +AO. But later in the season, the factors support a potential SSW, which helps a -AO scenario (or maybe sooner than we think, CFS forecasts a SSW in late November).
  4. The stratospheric polar vortex is expected to be stronger than normal going into November and possibly December.
  5. The Brewer-Dobson Circulation of ozone to the NH stratosphere is expected to be strong through both the NH and SH subtropics, and slightly above average over the tropics themselves.
  6. A SSW is probably most likely in January and February. But CFS is currently progging one in late November.

Because of the above factors, I expect a mild +AO to dominate early winter, unless the CFS forecast for a November SSW comes through. But I can see a -AO response in the latter two months of winter.

Conclusions

Expect an early start to the season. I’d also expect an above average season for Honshu. Hokkaido is probably more likely to be slightly above average. All the factors roughly line up for a snowy winter for Japan, which means there’s plenty of snow for skiing and boarding.

Thanks so much for reading. 

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 is meant to be interesting information, that can help to see what the season might be like. 

This took a lot of work over the last fortnight, so I appreciate your support. Starting in late November, my long range outlooks for Japan will start! They will be produced every 2-3 weeks, looking out into the range of 10-30 days out. Stay tuned. 

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

October Preliminary 2019-20 Winter Outlook

Okay it’s time to get ready to rumble for Winter 2019-20, so time to delve into the drivers. It’s a big and at some stages technical outlook, so if you want the summary, scroll to the Conclusions section towards the bottom. I encourage everyone to read my explanations and the reasoning, so we know why a winter turns out a certain way, it goes to the forecast or not. Anyway, onto the models….

The model outlook

The ECMWF model argues that winter will feature a Eastern US and Japanese ridge, reducing snowfall. It shows a +NAO, which means more snowfall, but less cold for the European Alps. The snow outlook in this is not good for the UK.

The UKMO seasonal agrees with ECMWF, producing very similar results. Japanese ridge, +NAO and Central US trough, all similar themes.

The North American NMME ensemble model shows warmer than normal temps for Japan and the Eastern US particularly, with more normal (but still relatively mild) temps for Europe and the Western US.

The models convey an overall +AO/+NAO outlook. Some people suggest this to be a point to at least express some question of the drivers. But the only way in my view to properly forecast a winter is to look and assess the drivers seperately and combine them into an outlook. So here we go…

QBO

13bbhFZl14.png
All the years that fit my current forecast for +5 to -10 for this season for QBO values at 30mb, minus strong Ninas and Ninos.

Above is my QBO analog for winter 2019-20. These factor in years that fit within the QBO value range that I am forecasting this year (roughly based on the forecast below).

qbo_wind.jpg
FU Berlin University

My QBO forecast for the next year is the red line in this image.

Key trends to note, based of this:

  1.  -NAO, deep Greenland high.
  2. Massive European trough.
  3. Deep troughing around Eastern US.
  4. Aleutian ridge.
  5. Eastern US pattern driven by NAO.

Probably not the most sturdy patterns imaginable indicated by the composite. But certainly a pattern that could drive snow and cold for the UK/Europe and the Eastern US. It’s also not a bad pattern at all for the PNW, not so great for the Southwest of the US.

Snow & Ice

Let’s start with my intital tweet and expand upon it.

Sources: ECMWF/Accuweather and NASA

So I expect a higher than normal October snow extent over Eurasia to continue. This would improve snowfall chances for Japan, Eastern US and Europe/UK, by forcing a -AO response and creating an environment more conducive to SSWs.

I also expect the current sea ice situation to continue bringing a similar tropospheric response for Japan, Eastern North America and Europe. This is forced by the low Barents-Kara Sea Ice linked to the AO and the stratosphere. The real interesting situation here is the very low sea ice towards the Pacific side of the AO domain.

ENSO

So firstly, we are currently in a Modoki Nino situation. What this means is that there are warm sea surface temperature anomalies in the Central Pacific, as opposed to the the original Eastern Pacific El Nino, closer to South America.

Just for the sake of the exercise and to be comprehensive, I am going to look at Modoki/CP Nino years including and since the 1970s:

The most robust connections to be made from this chart (and I tried various ideas), is the stronger than normal Aleutian Low, the Canadian blocking, and the troughing in the Eastern US. The European part of the composite is less clear, so take this analog as more about the Pacific.

Victor Gensini, with my annotations over it.

The other thing to note is the ENSO effect on the atmosphere. I often use the Atmospheric Angular Momentum charts to help us map out how the circulation around the Northern Hemisphere and ENSO plus various other drivers interact with each other.

I use this chart above to point out the long +AAM cycle over roughly the past year before the NH Summer. Given the cyclical nature of the AAM and the Global Wind Oscillation associated with it, I hedge on the tendency that we would largely lean towards this for much of winter. It is true that we may see more neutral or even +AAM conditions later in winter, January – February, and into Spring, but the start of winter is likely to start with more -AAM conditions, which could contribute to a better than normal start to winter.

Just as a reminder from last outlook, here is the -AAM composite

Lastly, let’s look at the actual ENSO forecast:

Accuweather/ECWMF

So we mostly see a weakish Modoki Nino event, coupled with a positive Pacific Meridional Mode event which warms the sea region close to California and out to Hawaii and the rest of the Pacific. These are all good signs for the Southwest of America, as well as the Eastern US. It also creates a pattern that isn’t so bad for Europe and Japan in terms of snowfall potential. But this year’s ENSO effects will center in the Pacific and downstream for North America.

North Pacific

Accuweather/ECMWF

Our current setup features warm seas across most of the North Pacific, focusing in the Aleutian Sea. This has meant troughing for the PNW and ridging for the Eastern US. However as the winter pattern expands the LWT (Long-wave trough) and the centre of the SSTAs changes, we may see the ridge shift east, shifting the associated trough and ridge east as well.

The anomalies themselves are weakening quite a bit from the current situation. And the forecasts I am looking at show some sort of gravitation towards Alaska of the Warm SSTAs, with the Aleutian warm SSTAs subsiding quite a bit. This may make the synoptic pattern better for the Eastern US and Europe further downstream. But it is also going to decrease snowfall for the Pacific Northwest.

And it also depends on the AAM and associated factors, an Aleutian low may come into play if we see more positive torques and a possible tendency towards a +AAM at some stage, like I was talking above.
 

Solar

We are currently in a solar minimum with it’s effects peaking upon the world over the next few years. It is correlated with a -AO and particularly -NAO winter, which would mean more snow and cold for Europe and the UK especially. Eastern US and Japan both also gain from this driver’s positioning.

Stratosphere

CFS/weatheriscool

Per the limited tools at my disposal, there are signs of minor stratospheric weakening in November and early-mid December, and perhaps something bigger later in February.

The Brewer-Dobson Circulation is expected to be above normal through the Northern Hemisphere at this point. It’s average in the tropics, and growing in the SH, because of stratospheric temperatures making ozone transport easier if they are colder. I’d say there is a favouring of above normal BDC this season, which means a Sudden Stratosphere Warming and subsequent -AO and -NAO are of a higher probability. I’d say the overall outlook for this driver looks good for Europe/UK, the Eastern US and Japan.

MJO

Tropical Tidbits

The MJO is forecast to be at it’s strongest in December and January. Phase 8-1-2 forcing is expected to be strong. This generally leans towards a -NAO and Scandinavian blocking in Phase 8-1. A lean towards Phase 3 and beyond towards Australia would force a +NAO.

In general the cold SSTs off Australia (Maritime Continent) are set to force a Phase 7-8-1-2 response in early-mid winter. Later in winter, I expect more of a Phase 1-2 and Phase 6-7 pattern focus, but also some of the other MJO phases with potential for some support for +NAO periods. But for the most part, I see a favouring of a -NAO, a potential SSW, more Eastern US snowfall. If anything, this would indicate a later winter for the Southwestern US.

Atlantic

I am not a big user of the Atlantic for forecasting, but for the British and European blog readers, here we go:

ECMWF/Accuweather

The cold “blob” in the North Atlantic may allow for a colder winter for the UK and Europe as a whole. So it’s good for snowfall, especially lower down, but may reduce precipitation a bit.

Conclusion

  • Snow & Ice conditions good for Eastern US, Japan and Europe/UK.
  • MJO largely good for European and UK snowfall, perhaps less so later in winter. Similar for Eastern US and Japan.
  • Oceanic ENSO good for Japan, Southwest US and Eastern US.
  • -AAM good for Europe, Eastern US and Japan, less strong later in winter.
  • Stratospheric conditions favourable for Eastern US, Japan and Europe/UK.
  • Solar minimum favourable for more snowfall for Eastern US, Japan and Europe/UK.
  • Atlantic favourable for a snowy UK winter and colder Europe.
  • QBO favourable for Eastern US, UK and Europe.
  • North Pacific favourable for Eastern US, less so for PNW.

So in terms of what this exactly means, region by region:

  • Japan should be in for an above average winter, particularly Hokkaido. I’ll look at the SSTs in the region and Siberia deeper in the proper Japanese outlook, so keep watch for that.
  • European Alps are forecast to receive a cold and snowy winter. It could be a good one for the Southern Alps, but there should also be good periods for the Northern Alps.
  • It is my opinion that the British Isles will see a snowier than average season, with cold periods. These prospects look best early and especially mid winter.
  • The Eastern US looks like it is set to have a good season as well, focused from the Central US early in the season, but more open to Nor’easters later in the season.
  • California is set to have an above average snowfall season, particularly in SoCal. Less snowfall, the further north you go.
  • The Southwest of US is set to have an above average snowfall season.
  • Utah and Colorado are set to have a slightly above average season IMO.
  • The Canadian/Northern US Rockies are set to have an average to slightly above average season, best falls are early in the season.
  • The PNW is set to have a below average season.

Stay tuned for the specific regional outlooks!

And to conclude the preliminary outlook is some of my forecast maps.

Yellow line is the jetstream. Red is the ridges/highs. Blue is the troughs/lows
Maps are for general purposes only, not specific, as to be expected in Paint.

Thank you for reading this preliminary outlook. I hope you are excited for the winter, and ready to provide long term forecasts 🙂

Late September Northern Hemisphere Preliminary 2019-20 Winter Outlook

The latest outlook from Copernicus is out, which uses modelling from ECMWF, UK Met Office, Met France and a few other European models.

What it shows us is:

  • Greenland Low and Azores High = +NAO, according to it.
  • Aleutian/Kamchatka Low, according to it.
  • -EPO ridging across Alaska and south into the Eastern Pacific.
  • European ridge, according to it.
  • Strong ridging over Japan, according to it.
  • Ridging over Eastern US and less ridging over the Western US, according to it.

What does this raw modelling mean for the snowy regions of the Northern Hemisphere:

  • An average season for Hokkaido, and a less than great season for Honshu.
  • An average, maybe slightly above average season for the Northern Alps, a below than average for the Southern Alps.
  • A decent season for the Western North America, a poor season for the Eastern US.

What do I think of this:

  • Obviously this is early days, so don’t take the modelling to heart.
  • The models have been reasonably consistent with a Greenland /Icelandic trough, alongside a responding Azores high. So the chances of a +NAO is growing for this winter. However many drivers are against this idea, and prefer a -NAO.
  • A +NAO in the way the models depict this event, would mean a wet and largely mild winter for the UK.
  • It also reduces the chance for snowfall bearing events in the Southern Alps, and focuses snowfalls on the Northern Alps.
  • Another consistent model feature is an Aleutian Low. I favour the scenarios thrown around that involve a low around Kamchatka and then further south. This is when the SST map comes into play:
  • The warm sea surface temperature anomalies will likely bring ridging to the Alaskan region. This means the Aleutian low will probably slide in southeast of Kamchatka.
  • Given that particular Pacific SST setup, you could see the jetstream following the less warm anomalies in between the two regions of warm SSTs, because of the contrasts between the temperature gradients. This would be particularly good for Tahoe/Mammoth snowfall and to a lesser extent Utah snowfall.
  • The warm SSTAs around the SE and Eastern US could assist with ridging in the region.

Other important things to note:

  • The Siberian High is expected to strengthen into it’s winter form earlier than usual.

This is expected to allow the lake/sea effect snowfall occur for Japan earlier than normal. It would also expand snowfall towards Eastern Europe and Scandinavia earlier than normal. Overall early snowfall cover over Siberia serves to enhance later snowfall prospects for Japan, the Eastern US and much of Europe.

  • The early snowfall cover over North America would allow deeper cold to be developed early, which would potentially lead to an earlier snowfall season for both the Western US (which is already beginning to see snowfalls) and closer to winter, for the Eastern US as well.
  • The drop in temperature in the polar stratosphere could allow an increase in ozone transport to the Northern Hemisphere Polar Vortex, via the Brewer-Dobson Circulation. For those who aren’t familiar with the stronger BDC, it means that a Sudden Stratospheric Warming is more likely, and that increases snowfall prospects for Europe, Eastern US and Japan.
  • The last thing I want to talk about is the extratropical and tropical signals.

These signals from CFS (above) and also models such as ECMWF, show in the case of the former Phase 1-2 MJO forcing through December and January, and in the case of the latter, it shows it throughout winter. What this means is there is continued correlation with troughing in the Eastern US associated with Phase 8 & 1. These developments are hopeful. But there is more to it.

We are currently in a strong -AAM owing to an underlying Nina-esque background state in the atmosphere. This will cycle through, but the current progged charts show a -AAM like environment, particularly in the first two months of the winter season.

I am not a massive fan of analogs, but I will use one in this case to demonstrate the effects the -AAM has upon the atmospheric circulation.

Above is a -0.5 and below -AAM composite for DJF. It shows us rough conditions for what I think will be featured in the 2019-2020 winter.

  1. Alaskan Ridging
  2. Deep low in the Central US.
  3. Greenland High
  4. European troughing/-NAO
  5. Japanese troughing.

So there would be a favouring of snowfall for the Central and Eastern US, based on my predictions, especially earlier on. The eastern side of the Rockies would do well according to the above chart, but I at this point favour more of a shift to a -EPO domain for the Aleutian High, with some development of the Aleutian Low. I could see instances with the Subtropical jet heading south of the Alaskan high, bringing strong snowfall to California and the Southwest.

Troughing also favours more snowfall for Europe and Japan. It also rebukes the idea of a +NAO I suggested above, according to the models. Models can be wrong, and many signals lead me to think a -NAO is certainly possible, perhaps not a particularly strong one however for this winter.

So my overall current thinking:

  • Early, good season for Japan, Eastern US and Europe.
  • A decent season for California, a poor season for the PNW, Colorado slightly above average perhaps.
  • Early Siberian High development, with a potential SSW later in the season.
  • Nina-esque atmosphere, cool neutral-weak oceanic La Nina.

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.

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