Snowy Hibbo

Just on solar, arguably the benefits of the solar minimum will be reaped in the next few years just after the minimum. Just like winter itself, with it’s shortest day in December, but the coldest days tending to be in January or February. Just as with everything solar, it takes time and it isn’t as strong as we think it is.

FWIW I’d argue that -AAM in the extratropical circulation is good for the Eastern US and Europe troughing/cold, rather than a destructive force in terms of troughing. Going back to this tweet a few weeks back, we can see the -AAM regime in the Pacific for this specific timeframe. And it allows the Pacific to drive troughing stateside. Now of course the positive polar anomalies allow the cradling of this particular Central US trough, the main force that drives it across the CONUS is the deep contrasting anomaly train of waves behind it. In this sense in my view at least, we can see deeper anomalies from a -AAM, that can provide for more extraordinary cold events. Added momentum can provide for a more “interesting outlook”. It in terms of the United States can bring heavy snowfall (which for those who care, is why the possibly more +AAM circulation later in the winter would improve prospects for the SW of the US, as noted in the blog) to places like the PNW and California. And that can drive cold events in the Central and Eastern US as well. But in order to get stalling lows, and to gain a slowing of momentum that can produce strong mid-latitude anomalies, a favouring of negative AAM anomalies IMO is preferred (but of course it isn’t exclusive, given the right circumstances of course. A strong jetstream of a positive North American Mountain Torque can do good things for precipitation and produce varying types of potentially strong systems for the US East Coast. But if we shift our perception to Europe and the UK for a moment here (excuse these cumbersome tweet embeds, old tweets are the easiest way to get this across, sorry)... We see some momentum (noting @Tamara’s pinpointing of negative anomalies at 30N, with opposing westerly anomalies being created in the higher mid-latitudes) created in the North Atlantic. Worth noting in this scenario (I’m talking about the second tweet) is the low pressure troughs on Greenland and Iceland, that transport increased momentum across the Atlantic ensuring a mild and rainy outlook for the UK and Western Europe. This is completed in a +NAO scenario. So yes, there is more westerly momentum in the mid latitudes than one would like, to verify my outlook at this point in time. But IMO for what is ultimately worth (and with full respect to everyone else’s opinions, which they are entitled to), I believe that there is significant background forcing that can lead to a -NAO scenario. And I also see a -AAM helping to force a -EPO/+PNA, provided that the easterly momentum propagates to higher latitudes, which you can see in that AAM chart is starting to do so now. Easterly momentum in the mid-high latitudes for December onwards is obviously not a given (and that’s why -EPO/-NAO outlooks in the face of seasonal model forecasts are bullish), but in my mind it is the most probable outcome IMO. It seems like a logical progression to me, though some may call it convenient. I honestly see a mix of -AAM and +AAM regimes this winter, noting that there would be no real dominance of one particular background state. That’s why I see a good mix of good winter (snowfall) outcomes for much of the North American continent, with the exception of the PNW. An interaction between +AAM momentum in the north and -AAM momentum in the south might actually end up to work well for the CONUS as well.

You think a UK thread here would be something you’d be interested in?

Okay here we go, my preliminary outlook for October for the Northern Hemisphere. https://longrangesnowcenter.net/2019/10/12/october-preliminary-2019-20-winter-outlook/ 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. Enjoy

I’m not quite so sure I’m really confident in the Pacific regime either. Firstly the “blob” is weakening and is forecast to continue doing so over the winter. Start of August: A few days ago: The big problem with the present SSTAs is that the warm manifests at it’s strongest around the Aleutians, rather than the Alaskan region focus that we want. The anomalies themselves are weakening quite a bit. 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, but still the positioning of the last month’s worth of blocking is not ideal. So it’s improving, but the strength of the anomaly also may decrease in comparison to other winters. 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 point.

On average, more likely to see a February SSW in the MQI stage we are in. Not the most likely stage for a SSW to occur, but not the worst stage to be in. And of course if you run all three analogs together, you get this: It’s again like the QBO analogs I am using for my forecast, very much based upon a -NAO.

That Alaskan low in the latter frames has kinda confused me already. Not sure if it is a medium term pattern associated with the typhoon. Or a long term one in the making. Seems to work for the Eastern US nonetheless. Amplification of a stark contrasting -AAM pattern.

A sneaky little comparison between the NH (2018-19) and SH (2019) SSWs.

And...... I got these just to start as a base point, thought it was an interesting tropical setup. Phases 8-1-2 of the MJO for December. Strong Phase 1-2-3 for January. And Phase 6-7-8 for Feb. Phase 1-2-3 for March. There’s a pretty consistent pattern right there I reckon.

Yep, just going one step at a time. Trying to do the outlook in parts this season, firm up driver predictions as much as possible for the big outlook. Make it as easy as possible for Early November, when regional seasonal forecasts are expected, but it’s also when I am at my busiest Next order of business: MJO.

These are the two years that work with that table and my broad set of QBO analog years. Not bad.

I think I have my QBO analog. 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. My QBO forecast for the next year is the red line in this image, courtesy of FU Berlin. Key trends to note: -NAO, deep Greenland high. Massive European trough. Deep troughing around Eastern US. Aleutian ridge. Eastern US pattern driven by NAO. So not exactly the most sturdy idea, but certainly quite a hopeful pattern. Certainly aligns with the current -AAM situation as well, provided that holds into winter. Of course, just one piece of the puzzle.

The ENSO situation just got even more complicated.... lel.

This is the one I use: https://www.esrl.noaa.gov/psd/cgi-bin/data/composites/printpage.pl For correlations beyond the CONUS.