Snowy Hibbo

Take the latest GFS run. There is an immense amount of +NAMT, caused by the pushing of the Alaskan ridge down into the Rockies. This is pushing in from the -EPO domain, and downwards, which flicks the jetstream down towards the tropics to connect with the still expected to continue WWB/MJO Phase 8-1, that will via tropical convection add to the precipitation and storm potential for this system. This system would have no upper level GOM links, it is just Pacific moisture with warm Atlantic bombing assistance with a very deep low with very cold temperatures out the back (look at the jetstream heading directly south). This should ensure a large snow bearing system in the 2-6 March period, if these work out as expected.

@Isotherm Just following on your comments in the Eastern US thread in here: It's not overally scientific in terms of gathering data, but in the next little while, there seems to be more purple (negative zonal winds), south of say 30S. These streaks of purple are in identifiable lines in the SHEM, that work in between the rossby waves, the cyclones and anti-cyclones. Then you have the well defined tropical setup with reduced/easterly winds in the IO, and more westerly winds in the Pacific. Then you have the negative zonal wind anomaly in the NP, caused by a number of highs in the region. But by and large the Polar jetstream looks rather strong North of 60N, and also within the Atlantic off the the Eastern US Coast. While there is plenty of things slowing down the pattern in the NHEM, there is not nearly as much there as in the SHEM, and it seems to be more erratic, in "clumps", rather than the stripes in the SHEM. This could be just inter-seasonal forcing. But I think the following pattern might just be what is causing it: Save for the low off Eastern South America (which has a corresponding stronger jetstream), the STR and low gradient is rather flat and remains so. Yet the lows are a bit further out from the poles at the moment, because we are in a -AAO pattern (notice the high right on the South Pole line). This is pushing things out, and has brought snow to the Australian continent in the past week or so. Now the -AAO is set to flip in March, which will move the lows back closer to the South Pole, and make the charts look more like this: The polar lows are back in towards the South Pole, which should create a roaring jetstream, as they look to be making a flat gradient with few deviations with the STRHs. This means we should start to see westerly momentum added in the SHEM in March, which would correspondly show up on the total budgets. - Zac

Yeah, I see that, but I am interested to see that this WWB hasn't affected anything in that world. I think that there is downstream patterns that occur onto the MT > AAM, via FT as the WWB passes Maritime Continent. It's something I will look into. As you said, there is a positive Torque addition in the NHEM sub tropical belt, not so much here in the SHEM, at least looking at FT.

No surprises there.... We are in a major WWB, and it is having a negative effect on the SOI, by pushing a more tropical signal out towards Tahiti. More interestingly, the one thing the WWB is not affecting is the FT It is near it's negative low point, which seems to be contrary to the massive addition of westerly momentum. I don't think it is a coincidence, that the only +FT in the last three months was during the only strong WWB in the Eastern Indian Ocean and Maritime Continent on and around the 25th Dec.

You mean verifying your own forecasts?

But what does this chart actually show?

This is the announcement.

A nice writeup from Tom above The highest AAM anomalies are actually on my side of the equator. And I think we can bring this down to what is happening with the current MJO wave caused strong WWB in the Pacific. Most of the recent WWB-associated activity has been occurring within the Southern Hemisphere. This explains the very negative SOI anomalies in the Pacific (because Darwin and Tahiti are both in the SH). The interesting thing is CFS notes this WWB continuing for a while, a whole month long. This would have continued impacts on extratropical weather down the pipeline. The activity heading out towards the Baja California, also indicates to me, the signs of a strengthening STJ, from the region up to the Eastern CONUS. It has been interesting not to see this activity, stir up major positive frictional torque activity, but perhaps it is the location, rather than the strength that prompts the +FT. I have some thoughts that are best for another time, but hopefully we see some big responses to quash negative AAM anomalies at 40N. The best way to do this starts with a +FT. Interesting times. - Zac

Well that went the opposite direction to my forecast, still doesn't matter in the bigger picture though.

Yes you are very correct. The more ensemble members showing snowfall, increases the chances of snowfall in the opinion of model. But don't take individual members too literally. Try and look at all the members as a mean, and look at what they mean together. IMHO you don't need to look at the actual mean to understand the direction of the wider model, you can use this chart.

You really want to have a ridge go straight on top of the West Coast like a proper +PNA to make a perfect setup again. I don't think that can happen, except maybe in the first days of March. What we really need is a decent lobe from the north, an outline of a -NAO, and some type of slowing down from a -EPO. It won't be incredible, but it should bring some snow. And at this point, that is what one wants.

https://longrangesnowcenter.blogspot.com/2019/02/north-america-on-long-term-9th-feb.html My last outlook of the season for long term prospects in North America, complete with a verification for this season's seasonal forecast. As you can see in there, my Eastern US forecast went the same as all of the other calls for a good winter. I am still thinking that we could see a late bloom in the next few weeks, but it doesn't change that most of the winter didn't amount to much. Anyway onwards and upwards.

It would be interesting to see the difference between blocking in the Barents-Kara Sea in 2017-18 and 2018-19, to see whether that bit less of ice cover in the current season has effected this very perculiar season. It's good to look at every factor possible.

It's interesting to ponder, but we will need to look at the dynamics behind the ENSO circlulation. For starters, we had a lot of a +AAM state, but it didn't act like it much at all.

Yep it is confusing me too. Surely that big trough pushes towards the Central US.