raindancewx

Nino 4 looks like it is cooling at the surface, but still pretty warm below. It does look like the cold is bleeding West, which is what the models show, and what happened in years like 2007.

There is another nice cool down coming in a few days after some unusual late heat. CFS currently has a super hot October for much of the Northwest, but I have my doubts. Will likely change meaningfully in the next few days.

I don't do Fall outlooks, but if I had done a Fall outlook, you really can't find a better match long-term than 1995 for the Nino zones. But I do expect 2007 to take over later in the fall. This is Nino 3.4 1995 27.57 27.49 27.75 28.10 27.82 27.59 27.08 26.23 2007 27.24 26.88 27.10 27.50 27.46 27.37 26.71 26.14 2020 27.14 27.11 27.76 28.17 27.65 27.38 26.99 26.30 Nino 4 - 1995 29.04 28.91 29.03 29.14 29.31 29.18 28.93 28.65 2007 28.97 28.66 28.66 28.73 28.84 28.90 28.68 28.48 2020 29.16 28.97 29.07 29.15 29.00 29.09 28.89 28.50 The biggest problem with 1995 is the PDO I think - 2020-03-01T00:00:00Z -0.82 2020-04-01T00:00:00Z -0.57 2020-05-01T00:00:00Z 0.09 2020-06-01T00:00:00Z -0.08 2020-07-01T00:00:00Z -0.38 2020-08-01T00:00:00Z -0.28 https://oceanview.pfeg.noaa.gov/erddap/tabledap/cciea_OC_PDO.htmlTable?time,PDO 1995-03-01T00:00:00Z 0.75 1995-04-01T00:00:00Z 0.83 1995-05-01T00:00:00Z 1.46 1995-06-01T00:00:00Z 1.27 1995-07-01T00:00:00Z 1.71 1995-08-01T00:00:00Z 0.21 90% of the time, maybe more, the PDO values are -2 to +2. So +1.7 in July 1995 and -0.4 in July 2020 is a massive difference. Even the August difference is still pretty substantial. It popped back up too - to +1.2 in September, and on/off again was pretty positive through Spring. Nino 1.2 has been warming. If that continues into October, then the PDO won't go as negative as it looked a few weeks ago. If it really warmed up a lot, it might even go positive, but I don't expect that. You can see cooling lately in some of the areas you'd want for a -PDO on Tropical Tidbits (by the coast of Western Canada), but also hints of cooling east of Japan where you'd want cooling for the +PDO. This is what I have tentatively for winter, with the analogs removed, since people need to come up with their own ideas - Here is how the analog package looks compared to September. It is also similar on solar, ENSO trends, and actual US temperatures for July-September (assuming the forecast NE/Western heat continues to burn off cold in those areas). You can see that the transition in the La Nina is the same in my analogs as on the CFS. I was a bit surprised to see the cold eastern Atlantic show up in September in both 2020 and the analogs, because it definitely warms up by winter.

The analogs I have look like the -QBO years because 2007 is the analog I trust most, even though it is still flawed. However, late winter and spring do look like the +QBO years on my blend for the winter. 2007-08 had a -QBO but it was rising, like this year. I find that the trend is about as reliable as the actual QBO anomaly for large areas of the country. I'm skeptical to bet the farm on only ENSO/QBO DJF seasonal averages. To me 2010-11, 1995-96, 1988-89, 1973-74, 1964-65 are also very different winters. I actually don't consider 1995 a bad analog, but it's mostly for how similar the ENSO has been all year, not the surrounding stuff like the PDO or AMO. It's not going to be similar on hurricane activity either, we're at less than half the 1995 total ACE in the Atlantic to date even with 23 named systems. Here is how these years looked for the QBO v. 2020, to me, they look very different with unusual tendencies in 2020 that would suggest erratic QBO behavior later on. I don't have QBO data at 45mb, but this is 30mb. 1964 3.94 5.26 5.46 5.94 6.32 2.23 -0.56 -0.57 -0.67 0.42 0.71 0.04 1973 -4.40 0.08 3.40 6.28 8.12 8.63 6.94 5.86 5.51 5.20 4.92 2.31 1988 7.81 6.17 5.86 6.59 5.46 0.42 -3.96 -2.58 -2.29 -1.53 -0.84 -2.42 1995 8.38 8.01 8.79 11.79 14.92 15.62 11.74 9.53 6.98 3.43 -0.77 -4.57 2010 -16.02 -16.98 -19.68 -23.57 -26.28 -25.05 -9.84 1.45 6.58 10.83 12.16 10.97 2020 -2.51 -3.20 -4.36 -5.03 -4.86 -2.78 0.34 4.78 -999.00 -999.00 -999.00 -999.00 64 up up up up down down down down 73 up up up up up down down down 88 down down up down down down up up 95 down up up up up down down down 10 down down down down up up up up 2010 down down down up up up up up You can see trend wise, 1964 is backwards (opposite) as is 1973. 1995 trended down mid-year, while we are trending up. You do have the right idea for Jan-Aug in 2010, but the QBO looks to me like it will keep going up the rest of the year. It didn't in 2010. Does that matter? Maybe? The magnitudes seem like they could be pretty close in 2010 through Fall and then be very different in winter. If you care about the trend I think 2016 is probably better than 2010 as a match. At a high level, I know 2010 and 1988 were both active monsoon years, without record setting heat in the West in the Summer. 1995 is closer in that regard too. To me, if the QBO was meaningfully similar through August, you wouldn't see something like a near all-time strong Western Monsoon in 1988 and a near all-time weak Western Monsoon in 2020. Some of that is solar driven, but the QBO is supposed to impact tropical weather and by extension subtropical weather like the monsoon. I think part of it is Nino 4 dropped much faster in 2010 and 1988 than this year. It had dropped like from 29.5 to 27.5 or something in 2010 January to August. It's only fallen 0.6 or so this year. My real issue with 2010 is you're talking about a ~3C year/year drop in Nino 3.4 We're not getting that this year, this isn't the La Nina version of 2015-16. Even 1988 had like a 2.5C drop. I'm looking for like a 1.6C drop y/y (27.1C to 25.5C).If you pulled up August 1964, it was super cold in the entire West - complete opposite this year. 1973 is warmer, but still nothing like this year. In 1995, you have a similar looking August and September nationally, with the slower decay of Nino 4 like in 2007 and this year.

This is the updated subsurface comparison to 2007. To me it kind of looks like 2007 but everything happens 4-8 weeks later. So maybe the September flat-line in 2020 is the 2007 flat-line in August, and then the La Nina peaks in October? I guess we'll see. It's possible though that we really won't see much change in the subsurface for a while.

Mathematically, I'd say for relevance, if you scored the 11 La Ninas for similarity to this year in the third weekly reading for September, you'd rank it like this, with Nino 1.2 difference multiplied by one, Nino 3 and 4 multiplied by two, and Nino 3.4 multiplied by three. 2005, 2010, 2016 are the worst matches, with 1995, 1999, 2000, 2007, 2011 the top matches. September does look a lot like 1999 at the moment. The models favor the La Nina becoming centered west of where it is now, which is consistent with current observations and how 2007 developed. My analogs look a lot like July, August and September nationally with the same kind of East core Fall to Central core Winter look the Jamstec/CFS show for the La Nina, so that's why I'll be riding 2007 fairly hard, even though it should be a weaker La Nina overall. Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 20SEP1995 20.2-0.2 24.0-0.9 26.1-0.7 28.4-0.3 (0.2) + (0.4 x 2) + (0.2 x 3) + (0.2 x 2) = 2.0 23SEP1998 20.5 0.1 24.1-0.7 25.5-1.2 27.6-1.1 (0.5) + (0.5 x 2) + (0.7 x 3) + (0.6 x 2) = 4.8 22SEP1999 19.3-1.2 23.8-1.1 25.8-0.9 27.9-0.7 (0.7) + (0.2 x 2) + (0.1 x 3) + (0.3 x 2) = 2.0 20SEP2000 20.1-0.3 24.2-0.6 26.1-0.6 28.5-0.2 (0.1) + (0.6 x 2) + (0.2 x 3) + (0.3 x 2) = 2.5 21SEP2005 19.6-0.9 24.7-0.2 26.8 0.1 28.9 0.3 (0.4) + (1.1 x 2) + (0.9 x 3) + (0.7 x 2) = 6.7 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 (1.5) + (0.0 x 2) + (0.1 x 3) + (0.2 x 2) = 2.2 24SEP2008 21.3 0.8 25.1 0.2 26.4-0.4 28.1-0.6 (1.3) + (0.4 x 2) + (0.8 x 3) + (0.1 x 2) = 4.7 22SEP2010 19.3-1.2 24.0-0.8 25.1-1.6 27.1-1.6 (0.7) + (0.4 x 2) + (0.8 x 3) + (1.1 x 2) = 6.1 21SEP2011 19.8-0.6 24.3-0.6 25.9-0.9 27.8-0.9 (0.2) + (0.7 x 2) + (0.0 x 3) + (0.4 x 2) = 2.4 21SEP2016 21.2 0.8 24.8-0.1 26.3-0.4 28.5-0.2 (1.2) + (1.2 x 2) + (0.4 x 3) + (0.3 x 2) = 5.4 20SEP2017 19.3-1.1 23.9-1.0 26.3-0.4 28.7 0.0 (0.7) + (0.3 x 2) + (0.4 x 3) + (0.5 x 2) = 3.5 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 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 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 01AUG2007 19.6-1.5 24.1-1.2 26.4-0.6 28.7 0.0 08AUG2007 19.3-1.6 23.8-1.3 26.2-0.7 28.6-0.1 15AUG2007 19.7-1.0 24.0-1.0 26.3-0.6 28.6-0.1 22AUG2007 19.2-1.4 23.8-1.2 26.1-0.7 28.5-0.1 29AUG2007 18.4-2.1 23.7-1.3 26.1-0.7 28.4-0.2 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 Still pretty similar to 2007. Although Nino 1.2 is warming it looks like. Also, the Nino 4 readings are warmer than 2007. Way colder than 2017, 2016 at this point. Nino 3 is also a lot colder than 2011. All that said, still well behind how cold Nino 3.4 and 4 were in 2010 by this time. Looks substantially colder in some zones than 2000, 2005, 2008 too.

No 90s down here since the cold snap mid-month. We're likely done until next May or June. That should be one of the larger breaks in 90 degree we've had in a while after around 90 days that were 90 or hotter this year (average is ~64). I've been working on my winter forecast. Still watching the hurricane season for the winter forecast. After the current storms die out mid-week I'm somewhat hopeful we get an extended break in storm or at least hurricane formation for a bit. We've never had a cold Western winter since the 1930s in a La Nina with the ACE over 160. I still lean toward around 135 ACE total, but it could jump to over 160 if it keeps up at this pace for the remainder of the year. I don't really buy ~40 storms for the season though.

It's been interesting trying to find a good match to the September 2020 US temperature pattern. It's pretty unusual to get a core of heat in the NW with a cold Central US look in September in a La Nina. Some El Nino years are actually similar: 1953, 1957. 1987, 1991 aren't terrible either. Neutral years 1966 and 1967 are both very hot in the NW, but very cold - way too cold - in the Southeast in September. 1974 also fits this description (probably near record heat NW but also record cold TX). 1975 too. 1993 is kind of the right idea, cold middle, warm east/west, but the cold is too far east. Same in El Ninos 2006, 2009. La Nina years like 1933 and 2017 are actually near opposite - which I find encouraging as they are terrible Western winters - top five for heat and dryness in most places. The closest La Nina September is probably 1999. September 2008 is kind of the right idea, but not as extreme as this year. 2011 is like 1993, too far east. A lot of the cold anomalies will burn off in the Rockies by the end of the month - so this may end up pretty close, especially if the South cools a bit with the wetness in the 6-10 day outlooks. You can see a lot of the same weird features - heat core in Oregon, SD/Kansas colder than Nebraska relatively. Summer 1999 was extremely cold in the Southwest, so I don't really think it's a good analog for winter, which gets at how strange this month is. Outside the Northeast, 1999 is almost opposite to 2020 for Summer, but similar in September. We're definitely very different from 1933 & 2017 - cold core Oregon warm core Minnesota - exact opposite of this year for the western 2/3 of the US. Anti 1933/2017 is fairly close (but too cold) to my winter idea at this point.

Some people asked about me about NE snow and ACE. This only seems to work in La Ninas, but the correlations are not that strong for Boston. Philly has never had a good snow year in a La Nina if the ACE is low enough, in ~14 tries. There does seem to be a soft limit in Boston around 60 inches until the ACE in a La Nina hits 130 or 140 (no values over 60" in 17 tries below 135 or so). Similar for NYC - no seasons more than +50% for snow if the ACE is under 130-140 (in 17 tries). Philadelphia has no good seasons with low ACE La Ninas: Even last week, I was hopeful that the ACE would finish around 90 this year, but I think 95-175 is pretty safe for like a 90% confidence interval, given we'll be ~2/3 through the season end of day tomorrow and around 90 ACE. I can't imagine we'll finish with ~40 storms like we're on pace to do, but we'll see. 2007 had 15 storms and only 72 or something for ACE (~5/storm), so the ~88 for 22 is similar so far (4/storm). I should have had more faith in my tentative winter analogs over the statistical stuff, they had 135 ACE or so for 2020. NHC seems to like to name a lot of subtropical and borderline storms now, so I could see 30-35 storms named by year end, and still around 4 ace/storm.

My point isn't so much that the pattern is a perfect match in 2019-20 and 2004-05 in the NE or nationally, just that it's a lot closer than 2002-03 and 2019-20 which is probably a closer ENSO/QBO match, but much worse for actual temperatures. The point is that incorporating the year/year tendency seems to have helped pick a better year since randomly picking which of the best QBO/ENSO matches to use doesn't seem to really add anything. Last year was another good example of the low-solar El Nino thing for Boston - temperatures in winter are pretty correlated with total snow, and you've never had more than a +50% snow season in a low solar El Nino back to the 1800s, with over 90% of the years below 45 inches. So it's not shocking that 2004-05, which wasn't really low solar (my cut off is 50 sunspots/year), was a better winter. The MJO also behaved a lot like 1997-98 last year at times, with help from a similar bad IOD pattern for a lot of the US and all of that. I've said before, I'm not a big fan of the QBO as a meaningful indicator. There is no good, strong QBO match by both magnitude and timing to this year anyway given the timing of the switch in trend downward to upward in the anomalies in Spring. Snow totals in La Ninas in the Northeast are pretty directly correlated to the ACE index in the Atlantic, so that's something to watch. The season looks like it will quiet down a lot after Wednesday once Paulette and Sally are dead or at least dying/extratropical. Teddy may be the only thing left, since Vicky should die off pretty quick. I am looking forward to seeing what Ray comes up with, I reckon he owes you all about 80 inches of snow from the past two years in Boston.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 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 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 08AUG2007 19.3-1.6 23.8-1.3 26.2-0.7 28.6-0.1 15AUG2007 19.7-1.0 24.0-1.0 26.3-0.6 28.6-0.1 22AUG2007 19.2-1.4 23.8-1.2 26.1-0.7 28.5-0.1 29AUG2007 18.4-2.1 23.7-1.3 26.1-0.7 28.4-0.2 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 Still almost identical in Nino 3 and Nino 3.4 to 2007. But Nino 4 has fallen behind. There was actually pretty substantial warming in Nino 1.2 too. Nino 3.4 has also fallen a tiny bit relative to 2007 now too.

If you try to reconcile trends in the QBO and trends in the ENSO pattern year/year you get the same outlook as my actual (tentative) winter analogs more or less. Last year the y/y trend in Nino 3.4 and the QBO matched with 2004, and the winter was pretty similar, so I think I have the right idea for what to expect this year given that the QBO/ENSO trend blend matches my analogs. The up/down you see is whether the QBO trend was moving up or down from the prior month. You can see each trend was the same for Jan-Aug in 2004 and 2019, and the ENSO trend was El Nino after warm Nino 3.4. I think the ENSO trend matters a lot, because 2002 was actually a very close QBO/ENSO match, but it had a very different prior year ENSO. So 2019-20 looked nothing like 2002-03 nationally. These are from my winter outlook draft - Something like this for 2020-21. I'l refine it if September comes in very different on the monthly QBO index though. You can see, the trend in each month in the blended average matches 2020. So you'd expect the QBO to be around +6 for September, or at least higher than August. The year over year ENSO drop is probably more like 27.1 to 25.5 than 27.9 to 26.1, but it's close enough. I went with a blend because the La Nina / near La Nina +QBO winters following El Ninos are all pretty poor matches for either QBO intensity, or monthly trends. 1966 is way out for -QBO intensity early on. 1973 has the wrong month/month trend in most months. 1980 was trending up all year, so the timing is off. 1998 is off a lot by timing and magnitude. So the best matches are 2010 and 2016, but even they aren't that strong really. We're not going to see the 3C drop off in Nino 3.4 those two years had, and the 2020 QBO is way more positive each month compared to 2010.

This is a top five cold start to September here since 1931, through 9/13 (~43% of the month). Will be very curious to see if we can finish with a cold September. It does look warmer for the next week, but no 90s in the forecast. Any incoming smoke from the West Coast fires could also hold down temperatures during the day if it makes it out here in a thick plume.

The ACE index in the Atlantic is still remarkably low for how many storms we've had named this year. Even if the second half of the season was ~50% above average, we'd finish around 125 ACE. Pretty promising development for the West. After Tuesday/Wednesday, everything may either be dead or on land or extra tropical, except for Teddy. I don't really think Sally or Paulette are going to hurricanes real long either. The La Nina years with near average ACE in the Atlantic and low ACE in the East Pacific are pretty good winters for the West generally (1974, 1975, 1988, 2000, 2007)

My take is a weaker version of 2007 is the right idea. But I'm open to a stronger La Nina if the event can keep pace this month with 2007 in September. The bottom really fell out in 2007 in the Fall. That's the real test. The warm western Nino 4 subsurface was still there in 2007, even well into September - The models missed how strong it got: -1.5C ONI (forecasts were generally -0.5 to -1.0) I mentioned earlier, if you plot August subsurface against Dec-Feb SSTs in Nino 3.4, you get 25.75C as the estimated strength of the La Nina, give or take 0.75C, at about 80% certainty. So below 2007-08 (25.0C in winter in Nino 3.4) is pretty unlikely. But it wouldn't really be too shocking if it got close to that strong. My instinct is this event will be strongest in Fall, maybe as low as 25.5C or something in September, October or November given that week one of September was 25.8C on the weeklies. Nino 4 and the PDO are both the coldest they've been in a while, which is almost like an indication that the system is less resistant to a stronger La Nina than it has been in a while.

I had kind of forgotten about this since it didn't apply last year, but La Nina after El Nino is a pretty consistent and reliable cold signal for the interior Northwest. In the last 10 cases, an area by Idaho, Wyoming, and Oregon is always either cold, or near average, even in cases when the US is mostly torching. If you look at the areas north of the San Francisco to SD-NE line, that zone is never completely warm in any of the ten most recent La Nina after El Nino winters. There is also a pretty strong warm signal for Texas - 7/10 years feature +3 or hotter winters somewhere in Texas. Even Florida and the Southwest don't have that. The three composite looks that show up by month - cold interior West, cold Northwest, cold NW to Midwest - I actually have analogs that support all three to some extent. So it looks pretty reasonable to me. I think the January look is the closest to what will happen of the three months, but still want to see how the observations in September in the tropics pan out.

I'm with the one guy on the ice storms. I think there will be 2-3 big ice storms for the east this winter. I can't help but notice that despite very different setups since 2006, the lowest sea ice extent Septembers (<4.3m square km) tend to favor the West for cold in cold ENSO years (2007, 2012, 2016) while the higher years do not (2008, 2010, 2013, 2017), with 2011 (4.3m almost exactly) a NM/West TX special (it was very cold that December here). The east of course is warm in those lowest ice years, while the higher ice cold ENSO years are pretty cold for the east and very hot for the west. We don't really have sea-ice extent data for the 1950s/1960s, but the historical look backs I've seen imply that those years had sea ice around 5m in some Septembers when the Atlantic was very warm especially for that era. A lot of those cold ENSO years are also pretty cold in the West, 1954, 1955, 1961,1964 as examples. In other words, I don't think it's the volume of sea ice itself, I think its something being near the cyclical physical ice-extent minimum in a cold ENSO that may favor it (I say cyclical, because eventually we'll beat 2012, but not soon). The Northwest has a very strong tendency to be cold in La Ninas following El Ninos (1970, 1973, 1983, 1988, 1995, 1998, 2005, 2007, 2010, 2016 is the most recent composite for that). Every one of those years has at least someone cold (or relatively cold in national blow torches like 2005-06, and 1998-99) in the Northwest, between San Francisco and the Nebraska/South Dakota border. Not a single exception. I don't think it's the La Ninas themselves favoring the NW for cold those years, it's the big time cool down y/y that favors the cold for them up there, just like the big warm ups favor cold down here rather than the actual El Nino strength or type. If you look, there is no direct correlation between cold ENSO strength and temps in most NW cities, just like there isn't for warm ENSO and temps down here, it's the trend up or down that favors cold for the West. You can find other similar years, the current temperature anomalies for September in the US look like a lot like a blend of 2008/2011 for instance, but I'd still favor the La Nina following El Nino years overall, even though 2011 is the run away top match for similar temperatures here since June, and fairly close in Nino 3.4 for a few months now. The problem is a lot of the recent La Ninas are pretty similar to this May-August in Nino 3.4. The NAO and PDO both generally look wrong to me for Eastern cold, but I wouldn't expect the NAO to be completely positive for the winter. I do think there will be a moment with either rapid changes in MJO forcing or La Nina rapidly weakening, along with slowly rising solar activity that will allow the NAO to go negative. Winters like 2009-10, 2010-11, 2012-13 that had -NAO conditions at times and were generally trending more active in terms of solar conditions, even though 2009-10 and 2010-11 were both pretty low for solar activity. We hit a 12-month minimum of 1.7 sunspots/month (bottom 1% for all 12-month solar periods back to 1749) through February 2020 and have been (very) slowly trending up since. This is solar activity for 2009 and 2020 by month. 2009 1 2009.042 1.3 2009 2 2009.123 1.2 2009 3 2009.204 0.6 2009 4 2009.288 1.2 2009 5 2009.371 2.9 2009 6 2009.455 6.3 2009 7 2009.538 5.5 2009 8 2009.623 0 2009 9 2009.707 7.1 2009 10 2009.79 7.7 2009 11 2009.874 6.9 2009 12 2009.958 16.3 2020 1 2020.042 6.4 2020 2 2020.124 0.4 2020 3 2020.206 1.5 2020 4 2020.288 5.4 2020 5 2020.373 0.2 2020 6 2020.455 5.8 2020 7 2020.54 6.3 2020 8 2020.624 7.6

Using the 1951-2010 averages, Nino 4 has only been cooler than average for four months since mid-2012. It has been tracking similarly to 2007 this year. Will be interesting to see if that can continue for a while. A much cooler Nino 4 in September means the US should be a lot warmer than last October in most places too. 2007 28.97 28.66 28.66 28.73 28.84 28.90 28.68 28.48 28.11 27.91 27.61 27.42 2020 29.16 28.97 29.07 29.15 29.00 29.09 28.89 28.50 average 28.08 27.97 28.07 28.33 28.63 28.65 28.55 28.41 28.40 28.42 28.39 28.27 My sense is Nino 4 will have trouble falling below 28.0C this Fall-Spring. But we'll see. Still warm below Nino 4 after all.

High was only 55 today once again. So around ~30 degrees below average for the high. This is one of the coldest starts to September here on record, at least for highs. I think it's 6th place - 81.5F (down from 89.1F as recently as 9/8). Based on the historical 9/11-9/30 data for 1931-2019, roughly ~40% chance of a cold month (2F below average high or colder), less than 5% chance of a hot month (2F above average high or hotter), but still most favored for +/-2F compared to average. The high tomorrow is supposed to be in the 70s, so should drag the monthly average down some more.

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

Today was the second coldest September high in Albuquerque back to 1892 - only 47F. Trailing only 9/27/1936. No high had ever been below 61 during Sept 1-15 in Albuquerque, from 1892-2019. The average high for the last 100 years on 9/9 is 85F - so legitimately close to 40 below average. Monthly high here dropped from 89.1 through 9/8 to 84.4 through today. It's actually almost unprecedented in the records to go from a hot August to a cold September - I'm a little skeptical yet that September will be able to remain below average.