September 2018-19 Northern Hemisphere Winter Outlook

Welcome back to another Northern Hemisphere season for the Snowy Hibbo! So much more to learn, discuss and observe, so I am excited to see what happens this season. We will begin with an early seasonal outlook examining all of our ski areas, and what all of the climate drivers mean for them…

ENSO

We are currently in a neutral ENSO phase. The general consensus of the meteorological community is that we are going into a El Niño, specifically a more Modoki or a Central Pacific Nino event. This is important as a Modoki El Niño isn’t so good for the West Coast of the US. It is much better for the Eastern US. Climatologically, it’s also not very good for the European Alps and the Japanese Alps. However I’m not exactly convinced.

This August Niño 3.4 Plume show a weak-moderate El Niño (depending on who’s standards you follow). The major models (EC and it’s friends in EUROSIPS, as well as most of the NMME ensemble) agree upon this.

This is the Modoki Index forecast from the JMA, who were the ones who discovered Niño Modoki as a seperate event. The index is slightly more positive going forward, but not really at proper Niño event levels. So if this indicates no Modoki, despite various pointing to this very model and calling it a Modoki, what is this?

This is the EUROSIPS forecast for NDJ going into winter. During a true Niño Modoki, you see cooling around the South American coast at the equator, this doesn’t happen here. Yes it is weaker than the warm anoms further out into the Pacific, but they aren’t cooling. This is why none of the Modoki index forecasts I have seen show this as a proper Modoki, because of the warm Niño 1+2 anomalies off South America. This is why I think this event carries both hallmarks of ENSO in various ways, as we all know, no two ENSO events are alike. However you may see the -AO effect from ENSO that supports Europe & the Eastern US, as well as some support for systems on the West Coast. Japan is likely to see a neutral or slightly poor season, taking ENSO isolated.

Anyway I am not really drawing conclusions with ENSO as of yet, but I don’t see a clear Modoki or EP Niño event in my head personally. However my feeling is the effects on El Niño Modoki will be more dominant, with a setup on many models showing more of a warm anomaly towards the Central Pacific.

Stratosphere

For a bit of fun to start this section, here is the CFS Monthly charts (moving GIF) of the stratosphere over the Arctic. 

The takeaway here is a pretty average entry into winter stratosphere wise, but perhaps a tad early and slightly more dramatic exit (SSWs in February?). Definitely something to watch, but not to dwell upon. The CFS Weekly model at 10hPa 60 degrees North (note the inclusion of GEFS ensembles as well). 

There is a lead with the GEFS ensembles mean that show a weaker than normal progression in the next two weeks, countering the recent slightly above average progress of the strengthening SPV. The CFS Control seems to follow on from these GEFS ensembles, but the general CFS trend shows typical growth of the SPV until mid October. Then all of the CFS ensembles in a major consensus weaken (-AO drop possible around here), and stay weak throughout November into December. This is a very unusual event, but this could prompt a -AO stratospheric setup, which would promote a similar tropospheric regime. This would prompt good snowfall for Europe(though maybe not very cold), Eastern US and possibly Japan

QBO

The QBO currently is in a negative or easterly phase. But increasingly including with guidance from EPS and GFS, it seems clear that we may see a change towards a proper positive or westerly QBO just before or during winter, as shown by an upward trend on the chart. This would probably provide a fairly neutral effect from the QBO in isolation. A Easterly QBO would favour Europe and the Eastern US, and a Westerly QBO would favour the Western States of the US in terms of snowfall.

PDO

EC shows a rough +PDO with warm SSTs around the Coast, but no cold anomalies in the Pacific, which means the impacts on the Aleutian Low aren’t as pronounced, so it will stay further North. This is somewhat better for more snowfall towards the PNW and South Western Canada, unlike a normal +PDO.

MJO

CFS shows a MJO signal around Phases 7&8 during winter, which would indicate snowfall for the Eastern US, as well as Japan. However the lighter signal in the Indian Ocean indicates we could go through Phases 1-3, which would also give a chance for snowfall for the West Coast of the US. Generally during a El Niño event, the MJO’s strength and duration however is weaker than normal.

Snow & Ice

We are pretty much at the low of Arctic Sea Ice at the moment, so most of the areas we look at don’t have snow and ice at the moment, we have to wait until October and November. The one place we can look at is Greenland. Greenland’s snow season was above average well into the Spring, and coupled with an average melting season, there is still a lot of snow & ice on Greenland.

This would induce a high over Greenland, which in turn would assist high latitude blocking(-AO) and a -NAO bringing more snowfall for Europe and Eastern US. However with below average ice cover surrounding Greenland, these could dub down the effect of this. The general lack of sea ice cover in the Arctic would also slow down the progression of a -AO setup.

Solar

A brief mention is warranted for the solar minimum we are in at the moment. This increases the likelihood of a -AO, with more snowfall for Europe, Eastern US and possibly Japan.

General forecasts

First is the CFS model, that shows cool MSLP anomalies for Europe and the Eastern US, as well as a good setup for Japan.

The EC model shows cool 500mb anomalies for again Europe and the Eastern US, as well as the Aleutian Low (which I personally downplayed in the PDO section). Also shows a good MSLP setup for Japan.

So overall the models indicate favour of the Eastern US & Europe, as well as elements of Niño Modoki, Solar, Greenland Ice and the Stratosphere. However but a more canonical Niño would favour the Western US. And Japan sits there mostly neutral, still getting bucketloads of snow. Many more elements of this puzzle are yet to be deciphered, so you can bet we will back maybe later in the month, probably next month. Until then, stay cool.

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.

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