raindancewx

Looking back, there are actually quite a few stronger El Ninos with active hurricane seasons in September. Another silly example of forcing not being used correctly to me. We're at about 65 ACE, and it will grow somewhat more with the storm to hit the Carolinas. A bit ahead of the most active El Ninos in the previous warm AMO cycle. But not dramatically. Most of you seem wedded to the idea that years like 1965 and 1957 were well coupled El Ninos, but of course, the 30-year average ACE in September for 1935-64 is something like 44. The 1991-2020 average is more like 60-ish. So we're not even as far above the recent average as those older strong El Ninos like 1957 and 1965 that I think everyone agrees are well coupled in other ways. A lot of El Ninos actually have pretty impressive early season hurricanes and total activity, call it June-September, and then die prematurely in October from what I can see. https://psl.noaa.gov/gcos_wgsp/Timeseries/Hurricane/hurr.atl.ace.data 1951: 57.8 ACE in September 1953: 58.6 ACE in September 1957: 63.7 ACE in September 1965: 60.9 ACE in September 2002: 46.8 ACE in September 2003: 111.1 ACE in September (if considered an El Nino) 2004: 155.0 ACE in September 2006: 59.6 ACE in September 2018: 72.8 ACE in September 2019: 93.4 ACE in September

Here is what BOM says about declaring El Nino. For my purposes, this El Nino started in March, and is already half over. So it's actually peaking at the surface between now and 11/1. Subsurface will have fits and starts through Oct/Nov before steadily weakening. Unlike winter, the greatest Spring periods for severe cold and precipitation in the West are during the most rapid ENSO transitions. You can look back at Spring 1973, 1988, 2005, 2017, 2019, 2023, etc to see this effect. The joke is the Summer temp profile was a pretty strong match to actual Nino 3.4 SST correlations in the Pacific, despite the constant bitching about how there is no forcing. Who cares? If you're getting El Nino conditions in the expected way, does it matter if not all the signals show up as you'd expect? Given how weak the correlation is, in theory it takes remarkably warm SSTs to drive such a good match - which of course we had in June-August. El Niño and positive Indian Ocean Dipole underway An El Niño and a positive IOD are underway. The declaration of these events, and their concurrence over spring, reinforces the Bureau's long-range rainfall and temperature forecasts, which continue to predict warmer and drier conditions for much of Australia over the next three months. The confirmation of an established El Niño increases the likelihood that the event will be sustained through the summer period. Oceanic indicators firmly exhibit an El Niño state. Central and eastern Pacific sea surface temperatures (SSTs) continue to exceed El Niño thresholds. Models indicate further warming of the central to eastern Pacific is likely. Broadscale pressure patterns over the tropical Pacific reflect El Niño, with the 90-day Southern Oscillation Index (SOI) at −7.7. Recent trade wind strength has been generally close to average, but was slightly weaker than average across the tropical Pacific in August 2023 for the first time since January 2020. Overall, there are signs that the atmosphere is responding to the pattern of SSTs in the tropical Pacific and coupling of the ocean and atmosphere has started to occur. This coupling is a characteristic of an El Niño event and is what strengthens and sustains an event for an extended period. Climate models indicate this El Niño is likely to persist until at least the end of February. El Niño typically leads to reduced spring and early summer rainfall for eastern Australia, and warmer days for the southern two-thirds of the country. A positive Indian Ocean Dipole is underway. The Indian Ocean Dipole (IOD) index is +1.25 °C for week ending 17 September. This is its fifth week above the positive IOD threshold (+0.40 °C). The longevity of this trend, combined with the strength of the dipole being observed and forecast, indicate a positive IOD event is underway. All models predict this positive IOD will persist to at least the end of spring. A positive IOD typically leads to reduced spring rainfall for central and south-east Australia. When a positive IOD and El Niño occur together, their drying effect is typically stronger and more widespread across Australia.

My two main analogs for the winter are 1982 and 1951 at this point. 1951 had a major mid-continent, mid-September cold shot. Not exact, but it's a -PDO, east based El Nino...it's more the tilt of the pattern that is off, v. the actual indices per se.

This time of year, the PNA has no actual correlation to Nino 3.4. But the PDO does, and so I do think I'm on the right track going with the PDO as the temperature predictor for the winter and the ENSO as the precip predictor. This is my tentative blend for the winter. It's not super different than the Canadian, although obviously more blue south of Alaska. The out-of-season heat waves in Mexico in developing El Ninos tend to precede very cold periods there. The hot season on the plateau is more like March-May. The heat there means the monsoon process/subtropical jet/moisture etc was moved from its normal latitude to the north or south, allowing dry air to work in, instead of the rainy season. The corresponding movement in the winter allows cold dry air to accompany much colder lows on the plateau and it gets very cold. Years like 1982 have monthly record heat in June, and then severe cold in winter. Again...volcanic Summer in Mexico - 1982 was too. The five hot "developing El Nino" Junes on the Mexican highlands - Most El Ninos are cold in June in Mexico - so it's been interesting looking at those five as a hint for what the subtropical ridges will do.

The Navy guy already linked it a month or so ago, but there is a pretty good paper out about volcanic effects from Tonga. Before this paper, I've mentioned that volcanoes tend to screw up the placement of the ITCZ which has lots of implications for weather outside the tropics. https://essopenarchive.org/users/304243/articles/657090-long-term-surface-impact-of-hunga-tonga-hunga-ha-apai-like-stratospheric-water-vapor-injection I've been saying for ages now that March is favored for very powerful storms in the West with both high solar and volcanic activity. You can see the little blue area for precipitation in the paper for my area. Now look at JJA - it's not a horrible match for the Summer in North America. It was very hot over the Mexican plateau - El Ninos are correlated to warmth in Mexico but it tends to be strongest as a signal on the West Coast there, not inland and high up. The East had a fairly cool Summer. You can see the tendency is to flood Canada with warm air for winter, while Kamchatka / Japan remain cool in winter. That's maybe a pseudo +PNA v. displaced +WPO type look. Long-term impact surface temperature and precipitation anomalies forced by the stratospheric water vapor cloud from Hunga Tonga - Hunga Ha'apai.

PDO is still extremely negative. https://oceanview.pfeg.noaa.gov/erddap/tabledap/cciea_OC_PDO.htmlTable?time,PDO 2023-08-01T00:00:00Z -1.68 El Nino, with -PDO values in August on this scale. 1951, 1953, 1963, 1969, 1991, 1994, 2006 I've been seeing people say this September is like 2004 because of the hurricane activity in the Atlantic / weak El Nino sense. In a sensible weather look though those Septembers have been nothing alike so far. We're actually at like B- similarity to early September 2015, which also had a big hurricane Bastardi and some of the other famous dudes thought would hit the East Coast. I think it was Isaias? (Edit: It was Joaquin). We certainly are not similar to 2009 at the moment. The cold in the West is wrong by placement in 2015 v. 2023 but you at least have a warm streak in the Plains and Northeast like this year.

This Summer in some ways reminds me of 2016. That was a winter that had Nino 1.2 warm relatively, with the western areas somewhat cool. So you had a strong subtropical jet / western storminess in winter, following a very hot Summer. The global upper level pattern was different in the Summer, especially on the Atlantic side, but you could do a lot worse for a 500 mb match than combing something like 1982, 2016, 2019 for a match to 2023. I'm not a fan of the QBO as a relevant metric, but the -QBO years do seem to be better matches right now. 1951, 1972, 2009, 2019, and a few others. The bigger El Ninos have tended to be near average QBO readings - 1997, 1982. The 2015-16 El Nino got blamed for breaking the QBO from what I remember, in terms of the regularly scheduled timing. The joke is the stuff that is determined by actual SSTs, like precipitation - looks very similar to the major El Ninos. It's just that the temp patterns are not great matches. The temps are more correlated to the PDO though in terms of spatial layout in the US. You can bitch and moan about the influence not behaving like you want - but this is pretty close. The upper high over TX was stronger than in the matching years, and CA had remnants from a hurricane...but its not like it's completely opposite the major El Ninos or something.

-PDO doesn't favor snow in the Mid Atlantic in El Nino. I said no correlation, not positive. They get so little snow that their good years are more fluky, even in El Ninos or favorable periods. But it is a negative feature for areas in the Northeast with more snow. In non-El Nino years, -PDO is bad for all of you, since it usually comes with La Ninas. Typically it is bad for the Southwest as well. The -PDO years favor warmth in the East and dryness in the Southwest deserts.

I looked at all the "counter" cyclical winters for PDO v. ENSO today, using Nov-Apr for the PDO. I'm using the old PDO index, not the stupid normalized index that replaced it. So 2009-10 as an example comes in slightly positive for Nov-Apr. Anyway, these are the El Ninos with a -PDO or a La Nina with a +PDO. Just about all of them have a major "snow hole" in the Northeast, which I'm defining as Virginia and north. When I say snowless/low snow, I don't mean no snow. Just that the entire region is below average in a notable way, despite surrounding areas or neighboring areas of the US/Canada being quite snowy. I'm basing these on snow maps for July-June from the MRCC site. The counter cyclical ENSO/PDO years seem to have more consistent storm tracks. So the Northern stream stuff whacks the same areas over and over and the southern stream stuff whacks areas over and over, and those tracks don't really vary much. A lot of other years have much less consistent tracks, and so you get less spread in the anomalies whether high or low for a given spot. https://mrcc.purdue.edu/CLIMATE/welcome.jsp 1933-34 - interior NE snowless 1938-39 - interior Virgina snowless 1942-43 - New England snowless 1983-84 - NJ / CT / E. PA snowless 1984-85 - Snowless outside W. NY 1985-86 - snowless outside W. NY 1995-96 - very snowy 2000-01 - snowless PA/VA 2005-06 - snowless NE US 2017-18 - snowles central VA/DC 1951-52 - low snow NJ, e. PA, W. NY 1953-54 - snowless 1958-59 - low snow NJ, E. PA, CT 1963-64 - low snow Maine, W. NY 1965-66 - low snow NY/CY/N PA 1968-69 - low snow PA, NJ, VA, W. NY 1972-73 - low snow PA/NJ/Southern NY & New England 1994-95 - snowless 2006-07 - low snow outside W. NY/PA 2019-20 - low snow outside Maine

For Boston, if you graph all El Ninos out by the PDO value for Nov-Apr, there is a pretty clear signal for the -PDO El Ninos to see less snow. That signal vanishes completely by the time you get to Philadelphia, and we also have no PDO snow signal in El Nino locally. Every blend I've been able to come up with has near normal snow for most of the Northeast US, outside of Southern New England, which is generally consistent with the image below.

Apparently, it was in December though? It's not like the warm pool wasn't there in December. You can predict whatever you want. But I'll take my chances on the PDO given that the western warm pool will continue to weaken relative to norms while the ENSO will be most pronounced relative to norms in that time frame.

There's never really been any correlation between the PNA and Nino 3.4 in December. It's best to treat ENSO as something that can, but doesn't always influence the various indices. The PDO on the other hand, is very strongly correlated to the PNA, much more so than ENSO in Dec-Jan. For Feb/Mar the PDO/ENSO essentially tie. I'm very much more on board with riding the PDO early for temps, and then dulling canonical El Nino effects later if you still have -PDO / +ENSO in Feb-Mar. https://psl.noaa.gov/data/correlation/table/corr.table_dec.txt

Locally, I can't find any 12-month periods with meaningfully less than ~4 inches of rain back to 1892. Our local "wet" season of July-Sept may finish under 1-2 inches at this point (v. 4" as average). El Nino precipitation long-term is about 10-30% above average by season. But even average precipitation on an annual basis would require a massive shift, since we only average 0.5"/month from Oct-May. My point with this is that US precip patterns in Jun-Aug look similar to a lot of the bigger El Ninos. So the subtropical jet / Pacific farting up moisture aspect of the El Nino looks correct, even if it is just from enhanced ocean heat rather than the canonical air pressure patterns. For June-Aug, you have pretty diametrically opposite correlations to the -PDO and +ENSO. So I don't find it surprising that some areas are responding to the -PDO and others to the +ENSO pattern. The -PDO is actually more correlated to the response by Indonesia than ENSO is in Summer.

This is my original map of the idea with site specific snow totals. So less snow as the yellow zone moves north.

I think the 60F annual temperature threshold is probably somewhere near Richmond in real time tbh. Just to be clear - the map I made is 7.25C to 18.25C in increments of 2.75C. So it's not exactly 5F, but very close. Part of the issue you guys have is that it's rarely cold enough for good snow outside of core winter, like 12/15-3/15 roughly. Here in the desert, it's certainly warming at night. But it still gets really fucking cold sometimes in Oct-Nov, and Apr-May. So we get fairly regular fluky snow in those months. You guys don't really have that to fall back on once the core season starts to warm/shrink. In the past five years alone I've had lows in the 30s every month from September-May. My point is the increase in moisture is more meaningful when its spread out over a longer zone of opportunity for snow. But you guys have a tight window for snow. Not like here when we've had snow over a foot of snow in Oct-Nov, Mar-Apr just in the past five years.