raindancewx

Euro seems to like a -1.0C La Nina, with a somewhat warmer Nino 4. I'd probably go warmer on both. I use the colder 1951-2010 basis anyway, and on those figures these are more like -0.8C / -0.3C anomalies anyway. CPC is going to switch to a 26.65C or so base line for 1991-2020 Nino 3.4 average next year (+0.08C from the current baseline), so there is little doubt this event will be classified as a La Nina at any rate.

To me the experts have been half right on the season. A lot of the forecasts I saw had a lot of tropical storms - that's clearly right. One of the years I had for Summer though was 2007, which had only 74 ACE despite 15 tropical storms. We could easily end up with 20 or more in the Atlantic by the end of the season, which is pretty historic by any measure, even with the naming of the fish storms. It looks like about ~30% of seasons since 1851 have above average ACE, so I guess it's interesting to me, as someone who works with statistics a lot because you don't tend to see ~30% outcomes five times in a row in real world situations, even if they are independently determined. You can think of it like getting a La Nina or an El Nino five times in a row, which are also 30% outcomes realistically, since you have about 20 La Nina and 20 El Nino winters in the last 60 years. You get ~four same sign ENSO events once in a blue moon, but we've never seen five. If you think of 26.0C or colder in winter as La Nina in Nino 3.4, then 2010-11, 2011-12, 2012-13, 2013-14 is damn close to four La Ninas in a row as a recent example. But five would be pretty incredible wouldn't it? The Atlantic is different from ENSO, so it's not a guarantee that the season won't be active. But I do lean to below average.

The Atlantic ACE index averages 105 for 1981-2010. So there hasn't been a below average ACE year since 2015. I wouldn't be shocked if it happened this year. Statistically, Sept 13 is the half way point for total ACE in the 1981-2010 period. We're at 48 ACE as of the last update, and it goes up ~1.5 points per day in September on average, which is about a day of 1.5 tropical storms as a very rough estimate. I don't see any long-lived spurts of major hurricanes for at least 2-3 days, so it's not going to change dramatically though 9/13 when the season will be half over. For the data on the CSU site I can't find a five year period since 1851 where the ACE was above 105 each year for five years in a row in the Atlantic. Four years is fairly common: 1891-1894 1998-2001 2016-2019 I understand something unexpected could happen, we could have three category five hurricanes Sept 20-Oct 10, but I definitely lean toward an ACE index of 80-120 at this point rather than 120-160, or 160-200. Historically, September finishes around 80, and then you get 20-30 more points Oct-Nov. The fast start has really slowed since late August with the MJO help fading. It's pretty hard to get a complete crap winter in the West if the ACE is under 160 - so I'm definitely rooting for that but we'll see how it goes.

My issue with 2008 has always been it was warming up in the tropics that year instead of cooling. So the fact that we're cooler in Nino 3.4 already, after coming off an El Nino, makes me think the La Nina is stronger than 2008-09. The bold in Nino 3.4 in August. In a lot of ways, 2008-09 is a poor man's 1995-96, so it's not terrible by any means. I've flirted with using it at times. The 2008 hurricane season was a lot more active than this season seems like it will be in the Atlantic. The NE tends to have higher snow totals roughly from DC to Maine in the higher ACE La Nina years. I can also tell you that generally, 2008 was a cold/wet summer in the Southwest, and this summer is opposite. For whatever reason, the hottest Summers in the Southwest in La Nina tend to precede the colder winters. The NE getting hit by several tropical storms this summer is a good sign for Nor'easters I think (kind of like 2003/2012). I just think a lot of them will be snow to rain or rain to snow events without enough cold air for the entire event. 2008 24.86 25.08 26.07 26.83 27.09 27.04 26.99 26.72 26.47 26.37 26.25 25.74 2020 27.14 27.11 27.76 28.17 27.65 27.38 26.99 26.30 -99.99 -99.99 -99.99 -99.99

My guess is the map is based on 1961-90 averages given the date listed at the bottom. But it is big and fairly detailed. I just assumed SE Canada would be somewhat lower in a more recent period. But there actually aren't a lot of good maps of Canadian snowfall out there from what I've seen.

Albuquerque had its second coldest September high since 1892 today, trailing only September 27, 1936 (46F). It was 47 today.

Whoops wrong map. This is Canadian snowfall - https://www.ccin.ca/home/sites/default/files/snow/snowfall_map.pdf

For the Chama to Moriarty zone, snow amount in NM so far seem to be 1-5" in populated zones from 6500-8500 feet, with the mountains seeing more.

I do like 2007, and I'm going to use it as one of my winter analogs but to me, there are still a couple problems with it. That said here is what I like about it: - La Nina with a relatively low-ACE Atlantic (currently the ACE is near average for 9/8, but the little tropical storms out there now only add around 1 point a day). Historically, the half way point for ACE is 9/13. So it's definitely becoming harder, fast, for a very active (~160+) ACE season to develop. - La Nina with a low-ACE NE Pacific - the NE Pacific is well below average. It's not real common to have both basins below average in a La Nina, but 2007 had both. - A lot of the recent La Ninas (1995-96, 2000-01, 2005-06, 2016-17, 2017-18, as well as cold Neutral 2013-14) had weakly positive or flat out positive PDO configurations Nov-Apr. I don't see that this year. The PDO could actually be the most negative it has been in 30 years for Nov-Apr from what I'm seeing. Will rival 1990-91, 1999-00, 2007-08, 2008-09, 2011-12 for a top five spot anyway in the last 30 years. - 2007 followed a 27.3C El Nino in winter 2006-07. A La Nina this year would follow a 27.1 El Nino in 2019-20. - 2007-08 was near the solar minimum. This is actually a bit of a wildcard since solar activity has been rising, slowly, since early 2020. - You did have pretty low sea-ice in September 2007, like this year. A lot of the recent La Ninas had higher sea ice (relatively). The cold ENSO years when sea ice drops below 4.3 million square km seem to be better in the West (2007, 2012, 2016) than those that don't (2010, 2013, 2017), with 2011-12 (4.3m) on the border, as it was cold in NM/TX but not elsewhere. The issues with 2007-08 are still substantial to me though: - I don't think this La Nina will be as strong as 2007-08, especially in Nino 4. - The QBO isn't a big factor for me, but I don't like the fact that it is near opposite of this year. The 2007-08 La Nina was very negative, trending up. This winter should be positive, trending up. If the trend matters more than the positioning, it is fine, but if the positioning (negative v positive) matters more, than it is a problem. - The Atlantic is warmer than 2007. - The 2007-08 La Nina continued into 2008-09. I'm not super convinced this will be a two year event, especially if it comes in a lot weaker than 2007-08 in Nino 4.

Happy snowy September 9th from the Southwest. In NM, the snow got down to about 7,000 feet. Only fell to 41 in Albuquerque unfortunately (although the record for September is 35 since 1931). All it took to go from 90-100 degree readings to snow was six hours of 40-70 mph winds in most places. Who knew? Believe it or not, some of the years with similar ENSO setups that I like do actually have fierce cold shots as a feature of the pattern in the SW in the second week of September. One of the more interesting years to look at is 1936, although I'm not going to use it as analog. 1995 actually had fairly intense cold dump into the SW in September. I'm getting a little concerned that there may be some very intense (although 1-3) dumps of cold into the West this winter. It's increasingly looking to me like the PDO is going to be the most negative it's been in a long time for one thing, I think below -1.0 is possible for Nov-Apr. Red River at 8,600 feet had it's earliest snow on a July-June basis since at least 1906, they have reliable weather records there for 1906-2014 in that town. It's not uncommon to snow there in September, but getting more than four inches is rare in September, and the prior earliest snow had been 9/17. Outside Santa Fe - Los Alamos -

This is Red River around 8 pm - would you say you guys had more or less by then?

Red River, at 8,600 feet above sea level in Northern New Mexico has reliable snow data for 1906-2014. It's never snowed in September before 9/17 in that time frame. The forecast for six inches would be third most snow in September for the 1906-2014 period too.

This stuff is surprisingly hard to find, but the trend in 2007 at the subsurface was pretty clearly to rapid cooling. There was a brief plateau, and then the bottom really fell out in September In any event, 2007 is the much better match, not just in the tropics, but certainly in the local weather. It makes more sense too, it's a ~27.3C El Nino transitioning to a ~25.0C La Nina in 2007, while 2010 was like a 28.1C El Nino to a 25.2C La Nina - much bigger change for only a year. To stay on pace with 2007, I think you'd have to see the subsurface fall to -1.0 at least by the end of the month.

My primary issue with 2007-08 is that Nino 4 eventually cooled off a lot too - to around 27.0C. It took an enormous amount of subsurface cooling to do it though. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt YR MON 130E-80W 160E-80W 180W-100W 2007 8 -.16 -.42 -.68 2007 9 -.35 -.69 -1.03 2007 10 -.52 -.87 -1.19 2007 11 -.54 -.97 -1.19 2007 12 -.49 -.87 -1.08 In the current setup, the subsurface cold seems to be slowly thinning, not deepening like in 2007.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 01JUL2020 21.1-1.1 25.5-0.5 27.3-0.1 29.1 0.3 08JUL2020 21.1-0.8 25.3-0.5 27.2-0.1 29.1 0.3 15JUL2020 20.2-1.5 25.1-0.6 27.0-0.2 28.8 0.0 22JUL2020 20.2-1.2 25.0-0.5 26.8-0.4 28.7-0.1 29JUL2020 20.1-1.1 24.7-0.7 26.3-0.8 28.4-0.4 05AUG2020 19.8-1.2 24.6-0.6 26.3-0.6 28.4-0.3 12AUG2020 19.9-0.9 24.8-0.3 26.4-0.5 28.3-0.4 19AUG2020 19.5-1.1 24.3-0.7 26.0-0.8 28.4-0.2 26AUG2020 20.0-0.6 24.2-0.7 26.1-0.7 28.6-0.1 02SEP2020 18.9-1.6 23.6-1.3 25.8-0.9 28.4-0.3 Pretty strong drops across the board this week. I still like at least an initial peak for the La Nina intensity in the Fall. But as long as Nino 4 is much warmer (by anomalies and actual temperatures), it will be hard for Nino 3.4 to cool too much I think. Look at 2010 or 2007 which peaked around 25.0C in Nino 3.4 - 01SEP2010 18.8-1.7 23.4-1.5 25.1-1.7 27.2-1.5 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 I actually like 2007 as an analog, but I'll have more on what I expect in the coming weeks for the winter. We're way warmer than 2010 at this point though.

I'm looking forward to seeing if any flakes will make it into Albuquerque. I don't expect any accumulation, it is after all going to be 95 or so on 9/7. I'm also very curious to see what the US national temperature anomalies look like after this plows through next week, my tentative winter analogs from August are remarkably close for September so far, but it may change dramatically this week and I'll have to see if a re-weighting is necessary.

One thing I've been looking at lately is how the ACE Index relates to severe cold outbreaks in La Ninas in the Southwest. In general, there are more cold days in lower ACE La Ninas if you use 10F below average in Nov-Feb as the threshold. But it doesn't hold super well for the rarer, more intense cold waves. Current ACE index is 45 - and we're about half way through the season now. The chart shows subsets, i.e. 1933-34 had four days in Nov-Feb that were at least 10F below average, of which, one was 15F below average. Cold Days Nov-Feb in Albuquerque by ACE Index La Nina ACE Index <=-10F <=-15F <=-20F 1933 258.6 4 1 0 1938 77.6 25 10 3 1942 62.5 3 0 0 1949 96.4 10 2 0 1950 211.3 11 5 4 1954 110.9 6 2 0 1955 158.2 12 5 2 1956 56.7 8 3 0 1964 169.8 10 3 0 1970 40.2 8 6 5 1971 96.5 11 7 1 1973 47.9 15 5 3 1974 68.1 21 10 4 1975 76.1 10 4 0 1983 17.4 5 2 0 1984 84.3 15 3 2 1988 103.0 13 2 2 1995 227.1 1 0 0 1998 181.8 4 0 0 1999 176.5 1 0 0 2000 119.1 11 2 0 2005 250.1 3 0 0 2007 73.9 10 0 0 2008 145.7 2 0 0 2010 165.5 11 7 3 2011 126.3 2 0 0 2016 141.3 3 0 0 2017 224.9 0 0 0 Weatherbell has this for the winter, if anyone is curious - fairly typical low-average ACE La Nina winter look.

There is a surprisingly strong signal in the historical data for early season snow in this part of the world if you get a La Nina that peaks relatively early, or if you get a La Nina with fairly low hurricane activity. I believe 2000 meets both criteria, but if you look it's in the data for other years too.

CPC has August Nino 3.4 SSTs 0.60C below the 1985-2014 average for Nino 3.4.The 26.3C value for August is still only 0.35C below the 1951-2010 average. Nino 4 is actually still about 0.1C above the 1951-2010 average in August (although a degree colder than last year). The official ONI value for JJA is -0.4C. The Nino 3 and Nino 3.4 readings for August are the coldest they've been awhile but both were -0.35C against 1951-2010. Nino 1.2 was -0.75C in August against 1951-2010. The figure in Nino 3.4 for August is almost identical to August 2016, but that La Nina (and it doesn't even qualify as one by older standards such as 1951-2010) ended in January in a CPC/ONI sense. I don't get the sense that this event will be as weak - the 2016-17 event finished with a 26.3C reading for Winter 2016-17 - the average in that zone is 26.5C long term and 26.58C for the CPC period - so the La Nina was over by then.

It's very difficult to get a good subsurface match for June-August that respects a) the big subsurface warm up in July, and b) the big subsurface cool down in August. A blend of 1984, 2003, 2010 has both rapid changes but isn't quite right on their severity, and has a fairly cool September for the middle of the US as the CFS/Canadian depicted for September. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt Year Jun Jul Aug 2010 -1.34 -1.36 -1.74 2003 0.13 0.53 0.03 1984 -1.15 -0.25 -0.22 Blend -0.79 -0.36 -0.64 2020 -0.62 -0.17 -0.81 There is a strong correlation in the subsurface data for August to Nino 3.4 Dec-Feb temperature - the historical data (1979-2019) implies a 25.74C Nino 3.4 in winter, plus/minus 0.72C at 80% certainty. That's an 80% chance of a cold ENSO between +0.00C and -1.50C against 1951-2010 Nino 3.4 averages. Worth noting, the severity of the cold below the surface may be flat lining again, or even set to rise again. It is interesting to me that the cold peak in May has not be matched again, at least so far.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 29JUL2020 20.1-1.1 24.7-0.7 26.3-0.8 28.4-0.4 05AUG2020 19.8-1.2 24.6-0.6 26.3-0.6 28.4-0.3 12AUG2020 19.9-0.9 24.8-0.3 26.4-0.5 28.3-0.4 19AUG2020 19.5-1.1 24.3-0.7 26.0-0.8 28.4-0.2 26AUG2020 20.0-0.6 24.2-0.7 26.1-0.7 28.6-0.1 Some warming this week in all zones in absolute SSTs outside Nino 3 which cooled. Still need Nino 3.4 to get colder than it is now for La Nina conditions in winter.

If the weeklies end up jiving up with the monthly data, by CPC standards, August 2020 will be La Nina level cold in Nino 3.4 (they use a 1985-2014 basis). On an older baseline, still kind of borderline, but very close. What's interesting is using 1951-2010, Nino 4 was still +0.4C in July, and even if the weeklies are right and August finishes at 28.4C in Nino 4...that's still average for Nino 4 which implies that zone will hinder a stronger La Nina from developing. If the subsurface cold is to reverse in Fall (if the Western warmth isn't destroyed in the coming weeks), you'd probably see the subsurface monthly data start to match up with 2000, which had some pretty cold Fall weather as the subsurface peaked and then reversed early by historical La Nina standards.

The MJO dying around phase 3 on 8/31 in a cold ENSO year is similar to 2012, 2011, 1996 - the CFS depiction of cold in the middle of the US for the month looks a lot like that blend.

Another thing is, when the ACE index is over 160 in the Atlantic heading into a La Nina winter, the composite pattern is very different from when the ACE is below 160. The recent La Ninas that were good for the West, 2000, 2011, 2016 - were all well below 160. While 1995, 2005, 2017 had values in the 200+ range and saw essentially no moisture or cold in the Southwest especially. The current ACE value is about 42 through 8/28. We're entering the peak of the Atlantic hurricane season, but it looks quiet through early September. so that 42 value should move closer to average than it is now. I don't really expect an ACE value under 80, but the meaningful point is around 150/160 - at that level is becomes almost impossible for the West to have a cold winter in a La Nina.

One thing to watch with the La Nina is when the event peaks. If you look at it on a constant 1951-2010 basis, the La Ninas that peak in the Fall (coldest Nino 3.4 relative to monthly average) are much colder in the US than the La Ninas that peak in the winter. In fact, none of the La Nina with a peak in the Fall are warm US wide, although 2011-12 was really only cold in NM and West Texas. There are some very hot winters included in the mix when you get a winter La Nina peak - 1998, 1999, 2005 are all in there. I'd imagine 1933, 1942, and 1949 are in the right grouping too, with 1938 in the left group.