raindancewx

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?

I saw gusts to 71 mph at Albuquerque on sustained winds of 47 mph out of the East at one point. But to be honest...that's actually pretty common here. The east wind is the main reason Albuquerque gets 10 inches of snow long term rather than 15 or 20, the wind just destroys the snow. I was looking at my method for calculating what the PDO will do in Nov-Apr (in aggregate), and the best match I got was 1961-62. PDO was around -0.4 for March-August on the Nate Mantua method (I think it will be this year too when the Mantua PDO comes in sometime in the next week), and I think Nino 1.2 will be around 20.0C on the monthlies for October (they tend to run much warmer than the weeklies). Anyway...a lot of the closest years for Nino 1.2/March-Aug PDO blends have essentially a super -PDO. I wasn't really expecting that, but it'd be interesting if it verified. Still have to see the August PDO value though, and see if there are any last second changes with Nino 1.2. I mention this because you can get unusual cold/dry air dumps into the West if the PDO goes really negative. It's not a cold signal at all for the East.

Red River, New Mexico, at 8,600 feet above sea level has reliable weather records for 1906-2014. The local NWS is calling for six inches of snow with this storm in that town. That would be the third highest September snowfall on record there - and only behind 1936 and 1971. Getting up to 4 inches of snow in September is pretty common at that elevation (~once a decade) but more than that is pretty rare. For the 1906-2014 period, there is also no record of accumulating snow earlier than September 17th.

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.

Severe cold tends to sporadically dump into the Southwest during La Nina years with low ACE. Look at the record cold outbreaks in CO, NM, etc - they tend to be in La Ninas. I think January 1971 was -17 in Albuquerque. 2010-11 isn't a great example since it had fairly high ACE, but you did see negative readings in February down here. In some sense there were hints of this in June, when there was a rogue snow storm pretty far south with lows in the 40s in some spots down almost to Mexico.

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.

If La Nina persists into say, February, August is looking like the first La Nina month. Magnitude of the cold is La Nina, just have to see the duration now. 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 There is still a lot of heat below the western part of Nino 4 that should move east or spread out with time, but the cold should hold on in Nino 3.4 through at least September. I still expect something a fall peak in severity and some of the ENSO models show that.

The weird thing about 1913 is the national pattern in August 2020 is almost opposite to July 1913 - this August has a blotch of cold in the Midwest and a warm West overall. July 1913 is nearly perfect as an opposite. It did finally hit 100 here for less than five minutes the other day - at 5:05 pm, but not at at 5:00 or 5:10 pm.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 03JUN2020 23.1-0.3 26.0-0.7 27.3-0.4 29.0 0.2 10JUN2020 22.2-0.8 25.7-0.9 27.1-0.6 28.8 0.0 17JUN2020 22.2-0.5 25.7-0.7 27.2-0.4 29.1 0.2 24JUN2020 21.6-0.8 25.8-0.4 27.6 0.1 29.3 0.5 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 There is some erosion in the cold near South America, but still borderline La Nina conditions overall. If Nino 3 and Nino 4 remains above -0.5 though it is likely Nino 3.4 will warm up a bit eventually, for a little while anyway..

We keep trying to hit 100 degrees in August down here for the first time in 25+ years - but something always seems to go wrong. Today, a moist East wind arrived through the canyon gap right as Albuquerque hit 99 degrees at 4:00-4:30 pm...

The subsurface is now pretty supportive of a La Nina compared to a few weeks ago, although I think the cooling will reverse to some extent over the next few weeks.

Best shot at a -NAO this winter is January from the NAO predictors I have. Still early though. Change from April to May and March to September as a blend is a strong NAO predictor over the past 20 years. If the NAO is near 0/neutral in September, the best blend for matching the NAO will be 1966-67 (x2), 2003-04, 2007-08. There is some tendency for very cold years to come after the solar min year (July-June basis). NAO Sept-Mar May-Apr DJF 1975 2.17 1.08 0.23 2018 2.60 0.88 0.50 NAO Sept-Mar May-Apr DJF 2017 -1.35 -3.64 1.30 1994 -2.58 -1.71 1.36 2017 -1.35 -3.64 1.30 2017 -1.35 -3.64 1.30 2017 -1.35 -3.64 1.30 Mean -1.60 -3.16 1.32 2019 -1.39 -3.09 1.27 NAO was positive in March, so it will be hard for Sept-Mar to be too negative - but obviously if the NAO is very positive or very negative in September, this will change - NAO Sept-Mar May-Apr DJF 1966 -1.01 0.97 0.01 1966 -1.01 0.97 0.01 2003 -0.31 0.19 0.07 2007 -0.72 0.49 0.65 Blend -0.76 0.66 0.18 2020 ?? 0.61 This blend seems solid intuitively - you have four years following El Ninos, and it is a La Nina-ish blend. Blend Dec Jan Feb Mar 1966 0.7 -0.9 0.2 1.5 1966 0.7 -0.9 0.2 1.5 2003 0.6 -0.3 -0.1 1.0 2007 0.3 0.9 0.7 0.1 Mean 0.6 -0.3 0.2 1.0