raindancewx

The local NWS had an interesting discussion today on the snow potential with the coming system. I usually blend the Euro, 3-km NAM and GFS to get precip totals here for Oct-May. But not in range yet for the 3-KM NAM. Precipitation will start in the northern parts of the state through the northern mountains Sunday night into Monday morning. Precipitation then spreads across much of the state during the day Monday as the jet stream increases and large scale QG lift increases. The combination of Q-vector divergence and frontogenesis in 700mb- 600mb layers will allow for banded precipitation across central and northern New Mexico. This analysis was mainly done with the 12Z GFS but looking at the ECMWF/Canadian/ICON models, there was not much difference with the GFS. The ECMWF produced quite a bit more snowfall and the ICON given its resolution produce finer detailed banded structures to the precip. So given the forcing, we really need to be careful Monday night for the possibility of impactful winter banded precip in which snowfall amounts could quickly increase. The lift in these bands could lead to much higher snowfall rates than what is forecast. And these bands are mesoscale in nature so nailing down the exact location and timing will be difficult in the next couple of days. Just realize there could be areas that get only 1-2 inches while not far away areas get 9 inches. For now we are more conservative with snowfall amounts through the end of the day Wednesday but that will be re-evaluated in the coming days. For now some of the higher mountain areas could push 12 inches of snow with anywhere from 2 to 6 inches possible in some of the lower elevations. Even the Rio Grande Valley could see 2 to 4 inches of snow during this time. The good thing is that much of the state will see very beneficial precipitation.

This is what I had for snow nationally in my winter forecast. I went with 2007 as the main analog - it's a pretty strong La Nina, has low solar, with slow cooling in Nino 4, following an El Nino, and it has low sea ice like this year. Atlantic looks fairly similar. The other years are in there to "fix it" in terms of some of the issues I had with it. 1995 is in there because it has similar tropical pacific SSTs so far to 2020, and it offsets the super low ACE of 2007 to a large degree, with its super high ACE. It also "fixes" some of the unusually low snow totals you'd have in the NE without it included. 2003/2012 have been decent non-ENSO match for a while (super weak monsoon, very hot in the West at times, landfalling NE tropical systems, etc), and last year is in there because it's recent and because I'm still somewhat skeptical on how cold Nino 4 will get. Generally, the areas expected to do well for snow (NW, Rockies, New England, Midwest) already are.

The forecast lows in Albuquerque in the mid-20s with the 10/25-10/27 storm add confidence to my idea of at least semi-regular cold dumps making it into the Southwest for the winter. Long-term, the coldest temperature in October is highly correlated with total lows at or below 32F from October to May. A low of 25 or 26 in October, would imply something like ~98 lows <=32F for Oct-May, even accounting for the urban heat island and global warming effects locally. The MJO looks like it will start November in phase six. That's warm nationally, but seven is a lot colder. I'm kind of expecting something like high amplitude 6, then weaker 7-8 for November. Still early though, the models don't seem to have a great idea on the MJO for the next ten days at the moment. If you get a 6-7-8 transition in early November, that's a lot like 2016. The 1999 and 2007 transition was 5-7 in November, about two weeks behind reaching phase six compared to 2020. In 1998, the transition is 5-6 in November. 1996 went all the way from 5 to 1. Not really a lot of years that go 6-8 in November. Hopefully the models will depict a different outcome, but this is probably what the CFS sees right now. I don't really expect November to be this warm though.

The progression of the pattern recently, with the -NAO collapsing into huge cold dumps in Montana sort of reminds me of late January to February 2019. You had pretty intense cold in the Midwest - briefly - in both the current setup and back then, and then basically record cold for an extended period in Montana. The period after Epsilon and the storm this week in CO/NM and the Plains is probably going to be pretty quiet. I'd expect things to get more interesting around Thanksgiving though.

Pick three similar years in Nino 3.4 in winter and see how close any of them are nationally when you ignore the other factors. These are the winters I consider La Ninas from 1931 to 2019. Look at 1984 and 1933, or 2011 and 1995 as an extreme example: La Nina 3.4 DJF 1973 24.63 1988 24.83 1975 24.90 1999 24.95 2007 24.98 1998 25.07 1970 25.09 2010 25.21 1955 25.22 1949 25.26 1942 25.31 1950 25.41 1933 25.51 1984 25.55 1954 25.56 1964 25.69 1938 25.72 2017 25.72 1995 25.74 2011 25.76 1971 25.76 2008 25.79 2005 25.80 2000 25.87 1974 25.93 1983 26.00 1956 26.10 2016 26.30

I'd like to see a winter as volatile as 1970-71, but the national map for October is pretty much opposite 2020, which to me implies big MJO differences. It's a ~record cold Colorado / warm East coast look. My take is if the MJO is in opposite phases (for sensible weather in the US) this close to winter, it usually won't realign with the current year. 1999-00 is close to this year in October, and 2007 is kind of in between. The ACE index in 1970 was only 40 in the Atlantic, and it was high solar and a -NAO. So I'm not huge on it. That said, pretty powerful La Nina and it followed two El Ninos, which is pretty rare. We had accumulating snow in October 1970, which is rare (~once a decade for Albuquerque). So I don't think it's terrible. It meets the criteria for me as a "regional" analog, but not close enough to be good nationally. Starting Oct 16, each 30 day period through Spring was either very hot or very cold here in the 1970-71 cold season, so it'd be an interesting thing to see. Mid Oct-Mid Nov and Mid Jan-Mid Feb had essentially the same high here in 1970-71, which is nuts. I caved to the models, and made the October analog blend 2003 (x5), 1995, 2007 when I saw the CFS late September. But the winter blend actually looks fine overall for October, better than what the CFS / Canadian had. Should have kept it. The unweighted blend of 1995, 2003, 2007, 2012, 2019 has been pretty decent for US temps for a while now, at least spatially. The main miss this month will be the NW west of Montana. Heading into this month, the models has +5 to +10 anomalies in Montana, and they're already cold for the month despite the warm start, with record October cold coming this week. The SE warmth being strongest in TX/FL-SC is a feature I'd expect to see in winter, same with the SW warmth being strongest in Southern California/Arizona. A lot of the warmth here will be destroyed in the next week, but we'll still finish warm.

The models have a lot of snow for the Northern NM mountains in the coming days. It seems like 6-18" is possible generally, but I wouldn't be surprised if some spots got far more since there are hints of snow Sun Night to Weds Morning in some spots.

I hope you understand how severe 1970-71 is in small doses if you use it as an analog - lots of very fast changes in airmasses. The January high in Albuquerque wasn't even below average here despite the severity of this week, which saw multiple lows below -10F: I do think the rapid/severe change in airmasses is part of the pattern for the next few months in at least the Rockies. We're going to see 80s to snow this month after 90s to snow last month in NM & CO.

This is the furthest south I've ever seen a model show snow in October. It does snow here in October some years, even in La Ninas, but it's still kind of amazing. Really does rival the September storm, as a huge temperature drop in a short time. I guess the September setup was 50 degrees cooler here, but still. Record cold in Albuquerque in October would be highs in the 30s and lows below 20 or so. The weather service has 40s for highs and some 20s lows. We did drop to 22 last October one night.

I was toying with something like that originally but moved away from it for a few reasons. Weatherbell's original 2020-21 outlook was basically your blend, +2012, i.e. 2016, 2017, 2018, 2019, 2012 as a blend. 1) The blend of those four years is very wet nationally. I think this is a pretty dry pattern for a lot of the US. Month to date, TX to CO and West has seen essentially no moisture this month (it will change soon though). 2016 and 2017 are night and day different for Western precip - record wetness in California one, and then ~5 months with no rain/snow in the other for places like Amarillo. 2) February 2019 is one of the coldest months on record for large areas of the US. I don't think we'll repeat it this year. The cold shot late January 2019 also rivalled the cold shots in the 1976-77 winter for severity in the Plains/Midwest/East. 3) 2018/2019 all had near record warmth in Nino 4 - which we don't have. Nino 4 is somewhat colder than the 1951-2010 average now. Just in the absence of the super hot Nino 4, I'd expect much more wintry conditions in the East in December (though I'd still go warmer than average). 4) Those are generally +PDO winters, which ties in with the precip being heavy. 5) I find La Nina strength/El Nino strength in an ONI /SST sense doesn't matter too much. But the year/year trends that match tend to produce similar teleconnections. So 2018 is a big warm up year over year in Nino 3.4, but the other three are cool downs.

I'm tempted to say "yes", but it'd be a bit arrogant at this point since the storm is still in the future and could fall apart or something. The rule is an upper low or closed low will appear in the SW domain, somewhere 30-38N, between Los Angeles and Dallas ten days after a 10 point drop in the daily SOI in one or two days. It doesn't work in June-September when the super subtropical highs that make the desert the desert are too strong. But someone looked at all the major SOI drops from 1990-2015 of 10 points and made a composite of it in winter, the "look" is for a low over the four corners. French name for the guy on Twitter, Jacque or something. 15 Oct 2020 1011.26 1009.50 -7.29 11.94 8.69 14 Oct 2020 1012.74 1010.20 -2.26 12.44 8.84 13 Oct 2020 1014.49 1010.00 10.31 12.58 8.77 If you look at the forecasts for Colorado/Northern NM, the low placement is right on time with the 17 point drop between 10/13 and 10/15, using the ten day rule. I find that the drops of 10 points with the SOI still very positive do lead to storms over the SW, but they tend to be completely moisture starved, and little more than dry cold fronts. That's why the recent drop coincides with a pretty big system on the models, but prior drops do not (although there was originally a system depicted around 10/13 following the crash early October). I had mentioned 10/24 in my forecast (from 10/10) as the approximate end of the dry spell in NM that began after the 9/9 system brought snow to NM and CO after highs in the mid 90s. More generally, I think the PDO looking more neutral lately and the Euro depicting a weakening La Nina are consistent with a storm down here. When La Ninas weaken or El Ninos strengthen (warming either way), the SW tends to get wet or cold. These are the years with accumulating snow in Albuquerque in October if it happens. It's a ~once a decade event since the 1930s. Monsoon Oct Nov Dec Jan Feb March April May Oct-May 1932 0.4 0.0 2.0 0.6 0.0 0.9 0.6 0.0 4.5 1967 0.2 1.0 2.8 0.0 2.0 1.4 0.0 0.0 7.4 1970 0.5 0.0 0.5 3.0 2.3 0.5 0.0 0.0 6.8 1973 0.3 0.6 0.1 9.3 0.6 2.0 0.0 0.0 12.9 1979 0.9 0.8 2.7 0.0 0.9 3.1 0.0 0.0 8.4 1986 3.2 0.6 0.2 4.9 4.9 0.2 2.2 0.0 16.2 1991 2.5 1.5 2.1 5.6 0.0 1.0 0.0 0.0 12.7 1996 1.1 2.5 0.0 4.7 0.9 0.3 2.9 0.0 12.4 2004 0.2 1.7 0.3 0.0 0.0 4.2 0.5 0.0 6.9 2009 0.8 0.0 0.7 1.0 0.9 0.8 0.0 0.0 4.2 The cold ENSO years with snow in October are pretty snowy/cold here in general: 1932 is frigid, 1967 is cold, the coldest day in the last 130 years here is in January 1971 (high of -1 I believe, low of -17), 1973-74 is snowy, and 1996-97 is pretty cold and snowy here. On Tropical Tidbits, 1967 is currently one of the top five SST matches globally for the past month, it's kind of a poor man's 1988.

The snowstorm depicted down here for late October is pretty unusual, but we do get accumulating snow even in some La Nina / cold Neutrals in that time frame. The CFS/Canadian depictions for October look pretty wrong now too, will be interesting to see if they get a better handle on the coming months.

I haven't looked in a few hours, but the SOI looked like it would see a few more substantially negative days by the end of the month on the European MSLP depiction. On the subsurface data, for 100-180W, most of the stronger La Ninas have had far stronger peaks than the current La Nina. Some of the weaker events (by ONI) have too. These are the subsurface peaks (by month), on a July-June basis for the La Ninas in the subsurface data (1979-2019). We'll likely beat some of these peaks in October, November or December but we're just approaching -1 now on the monthly data. 1998 -2.46 1983 -2.25 1988 -2.04 2010 -1.93 1999 -1.55 2007 -1.50 2008 -1.44 2011 -1.26 1995 -1.20 2005 -0.97 2017 -0.97 2000 -0.96 1984 -0.93

The SOI has been pretty negative for a few days now. I don't think this La Nina is super well connected to the atmosphere yet. That said, the weeklies look like they may drop below 25.0C in the Fall at some point - that's about as cold as it can get in Nino 3.4 in Oct-Feb. Strong La Ninas are below 25.0C in DJF. Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4 23SEP2020 19.6-0.8 23.6-1.2 25.7-1.0 28.1-0.5 30SEP2020 20.1-0.5 23.8-1.1 25.6-1.1 27.9-0.7 07OCT2020 19.5-1.2 23.4-1.5 25.5-1.2 27.8-0.8 14OCT2020 19.6-1.2 23.6-1.3 25.3-1.4 27.8-0.9 17OCT2007 18.6-2.2 23.5-1.4 25.3-1.4 27.9-0.7 The subsurface and weekly data is still very similar to 2007. The coldest reading on record for October in Nino 3.4 (1950-2019) is 24.41C in 1955. So still a way from that. If we finish at 25.3C in October that would be 8th coldest October from 1950-2019.

Whether it's the MJO or something else, I do expect a fairly reliable series of strong cold shots to dive down the Plains/Rockies every 45 days or so. (9/9 to 10/25 is 45-days ish).

What do you mean by my list of analogs? In my forecast I gave a core blend for the winter outlook, and then noted a bunch of other years that would likely be close in either the Fall or for only regions of the country rather than nationally. I don't really like 1973 or 1999 at all for the winter. 2007 and 2012 I do like a lot, low sea ice, colder east Nino zones v. west in fall. Some similar things for the Atlantic/Pacific

Not quite, but this is getting into almost non-BS range now - it's 10/24 ish as promised earlier in the thread.

I really don't know what you're referring to but it doesn't look like you'll answer. These are the hottest starts to October locally - pretty interesting set of winters. 1 1979-10-16 84.5 0 2 2020-10-16 82.0 1 - 1978-10-16 82.0 0 4 1991-10-16 81.9 0 5 1956-10-16 81.6 0 6 1963-10-16 81.5 0 7 1950-10-16 81.4 0 1950 is sort of like 2008, 1963 is extremely cold in both December & February. 1978 is very cold. 1979 is kind of a weird looking winter. 1991 had the Perfect Storm, may see something like that this month. 1991 is a very hot Plains / cold SW winter. 1956 is what CPC forecast essentially.

The NAO difference? In what? Wrong thread maybe? It does actually look like the NAO will rise substantially at the end of the month. Personally don't really care what the NAO does in Fall though, it's not a meaningful signal out here until later.

Saw somewhere Phoenix had 144 days that hit at least 100 this year. Some of the top years prior to 2020 include 2003, which is a good match to this October, and 1989. I used 87 degree highs here in La Ninas as a dirty metric, and we're at 112 of those. Thing is...a lot of the years with the crappiest monsoon precipitation and most consistent heat end up getting very cold. Examples include 1931, 1943, 1954, 2003, 2011, 2012. The crappiest La Nina winters are usually kind of average in at least parts of the Summer, say 2005, or 2017 as examples - not that dry and not that dry in the grand scheme of things. My analogs for winter had the final 80 degree high in Albuquerque around October 20th - that looks about right. Still think there might be something around 10/24 for at least Colorado, in terms of decent moisture. The SOI has been fairly negative in recent days, at almost the same time and magnitude as in mid-October 2007, and there was a storm that went through late October.

Here is an interesting thought for the winter: When is the last time, two same sign ENSO events produced the same outcome in the winter? In a row I mean. ENSO: 2009 and 2014? No. 2014 and 2015? No 2015 and 2018? 2018 and 2019? 2006 and 2009? 2004 and 2006? 2012 and 2013? 2003 and 2012? 2017 and 2016? 2016 and 2011? 2011 and 2010? 2010 and 2008? 2007 and 2008? 2005 and 2007? 2000 and 2005? My point with this is that 2017-2018 was a very hot/dry Western winter. So expecting the same outcome again is probably wrong, despite what CPC/IRI have.

I went with 2012 and 2007 as the main analogs in my forecast because those events were colder east in the Nino zones in Fall, and they have very low sea ice. But the cold in the Nino zones spreads out later on. The cold core below the surface has been about 140W for a while, so it doesn't really fit into any of the three blends listed above. My sense is the average departures for the four zones in winter may be pretty consistent against the 1951-2010 averages, probably around -1.0 overall, despite the possibility of a colder peak than that between now and December in Nino 3.4. I'm a believer in some form of the storm depicted for the NE later in the month - I've been expecting that for a while. I lean toward it being a strong Nor'easter that originates over relatively warm water rather than a hurricane or Perfect Storm type of deal. SOI - still amazingly similar for this brief negative period. 2007 has not been a good match for October so far, but to me that's an MJO thing, not because the La Nina is that different. Oct 12-15 10.7, -0.2, -5.5, -6.3 in 2007 Oct 13-16 10.3, -2.3, -7.9, -6.1 in 2020 The coming period with the cold dump in the middle of the country is similar to October 2012. Several of the cold-ENSO years following two El Nino winters are also pretty similar to this October so far - notably 1978 and 1988. 1959, another cold ENSO following two El Nino winters is also showing up a lot in the CPC 6-10 and 8-14 analogs. October may end up looking a lot like a blend of 1978, 1988, and 2016, all years following two-cold ENSO years. The model depictions with Montana and other areas of the NW, 5-10 above normal in October look wrong now with the highs in the 30s in the coming day for places like Billings (88 a few days ago - I live in a desert and we haven't topped 87 here this month for reference). This is my forecast for anyone who missed it. So far, close to 300 people have read it. Pretty happy with that actually. https://www.scribd.com/document/479516526/Winter-2020-21-Outlook,

What was up with the weird sexual comments about clouds earlier? I know it was you Chinook... It's not the 9/9 storm, but pretty impressive cool down in Billings from 88 earlier in the month to snow this week.

Pretty healthy La Nina with the warm version of the -PDO in September. I'd really like to see more of the North Pacific cool off with this event. This is probably the best shot at that for the next few years. The AMO actually cooled a fair bit in September, still very high AMO value though. We're almost in a warmed up -AMO, -PDO configuration, if you assume the oceans would be ~0.2C colder than now without the slow warming since 1981-2010. The Atlantic would look pretty cold with that extra 0.2C gone.

The NAO thing I use is designed on the assumption that the changes are random, and so it should be hard to find a good match to any given set of changes. What I do find is, if the NAO has several years with similar changes, the blends work much better if the prior Nino 3.4 SST is the same. So if you just looked at 2015-16, you'd see 1968 is an amazingly close match in April to May, and March to September, in terms of how the NAO changed. But, 2015 followed an El Nino and 1968 followed a near La Nina - so the NAO match fails. This is one reason I weight ENSO order pretty highly when I analog stuff. Here is 2015: 2015 1.79 1.32 1.45 0.73 0.15 -0.07 -3.18 -0.76 -0.65 0.44 1.74 2.24 1968 0.13 -1.29 0.40 -1.08 -1.76 0.33 -0.80 -0.66 -1.92 -2.30 -0.93 -1.40 So you've got near identical March to September and April to May NAO changes. That combo doesn't exist in very many years. But the 2015-16 winter NAO was very positive, and 1968-69 was very negative. So a blend of 1992/1994, which has near identical changes to 1968 in the NAO, but nearly matches the prior Nino 3.4 reading, produces a much better outcome. 1992 -0.13 1.07 0.87 1.86 2.63 0.20 0.16 0.85 -0.44 -1.76 1.19 0.47 1994 1.04 0.46 1.26 1.14 -0.57 1.52 1.31 0.38 -1.32 -0.97 0.64 2.02 1992: -1.31 (Sept-Mar), 0.77 (May-Apr) Nino 3.4 prior (26.76C) 1994: -2.58 (Sept-Mar), -1.71 (May-Apr) Nino 3.4 prior (27.64C) Blend: -1.95 (Sept-Mar), -0.47 (May-Apr) Nino 3.4 prior (27.20C) --> DJF NAO of +1.11 2015: -2.10 (Sept-Mar), -0.58 (May-Apr) Nino 3.4 prior (27.18C) --> DJF NAO of +1.31 Basically, you have to match on the two change periods first, but it works better if you get the prior Nino 3.4 reading to match. For 1950-2019, the r-squared for March NAO to the following DJF is about 0.10 - it's not too strong. None of the months are individually, but the two changes in combination are actually pretty hard to replicate even with 70 years of data, you usually end up with less than three good matches. My rule is no match should take me more than five minutes to make by eye-balling the data. The data also relies on only the monthly NAO readings from 1950-2019. So pre-1995, there really isn't enough data to get good matches, since I only use years that would have been available and known to make the NAO matches. Not every year can be replicated super well with the SST prior matching. But I find it gets the NAO sign (neutral, positive, negative) right almost all years, and is +/-0.4 for the seasonal DJF value 18/25 times since 1995. The average error is about 0.36 for DJF, which is somewhat better (~40%?) than guessing the 1995-2019 NAO winter value each year.