GaWx

Interesting! Could this be indirectly related to the cold bias of most models in the E US, especially in winter, that results from underestimation of the southeast ridge that has been cited by some pro mets as being largely due to the underestimation of tropical forcing from the near record warm Maritime Continent/W Pacific? I've learned about the idea that record warmth in the MC often makes the atmosphere in the US act as if the MJO is in the MC phases even when it isn't officially in addition to lengthening and strengthening actual MC phases. So with MC MJO phases tending to favor an SER, the models underestimating the forcing from the MC means underestimating the SER. This appears to be the main reason why it is underestimated though the underestimate of the blocking from the near record +AMO is likely an additional factor. Between these two factors, the SER is strongly underestimated, which often results in a NW shift in storm tracks and other features as model forecast time gets closer and closer. So if anyone ever wondered why modeled storm tracks so often shift NW, this appears to be the explanation. So, back to my original question to Bluewave, @jconsorand others. Is what they're talking about here related at all to the same underestimate of MC/W Pac forcing from record warmth that causes the SER to be undermodeled?

Thanks. Per ONI I still favor a strong fall/winter peak but with high end moderate (+1.3 to +1.4) on the low side and super (+2.0+) on the high side. That puts me +1.6 to +1.9 for most likely. But per RONI assuming a -0.4 adjustment due to very warm overall tropical SSTAs, anywhere from a high end weak (+0.9) to low end super (near +2.0) is reasonably possible for the fall/winter peak with +1.2 to +1.5 for most likely. ------------ Redifining Nino indices in a warming climate (relates to RONI): https://iopscience.iop.org/article/10.1088/1748-9326/abe9ed/pdf

Followup: Today's SOI did rise but only barely/much less than I thought with it still down at -9.48. That now tells me that the -SOI streak is safe to continue for a good number more days with it now at 11 days. It should end up at 17+ days as it looks now. Due to the combo of way above normal Darwin and significantly below normal Tahiti SLP, the GFS and Euro are suggesting a sub -50 SOI is quite possible on May 23rd. That would mean the lowest daily SOI since at least the -52 of 2/17/2017 and possibly the lowest since the -58 of 2/6/2010! It would also mean the lowest daily May SOI since 1997. May MTD is now at -8.3. With this very strong -SOI period coming next week, a sub -10 May of 2023 is now just about a certainty. That is a very strong indicator of an upcoming El Niño of an unknown magnitude.

Followup: Today's SOI of -9.86 is the 10th -SOI in a row and brings down the MTD to -8. The SOI will rise tomorrow and it will be a close call as to whether or not we get the 11th -SOI in this streak. If we end up with -SOIs the next two days, the streak would very likely go a good number of days longer thanks to low Tahiti SLP with a small chance it could even go through the end of the month. The chance for a sub -10 for May, overall, continues to increase. Since 1950, there have been 11 sub -10 May SOIs. Only one of those 11 Mays didn't precede a new El Niño that autumn/winter. That was 2005. The reason May of 2005 was sub -10 was that the preceding Nino of 2004-5 was still lingering into April and May in the atmosphere, which sometimes happens.

The MTD SOI continues to drop and is now down to -7 after eight days in a row of sub -10. That's the first time for that long of a sub -10 streak since Sept of 2019. The next seven days' SLPs at Darwin are forecasted to remain well above normal with a short term peak ~5/22. Also, Tahiti is starting from ~5/21 forecasted to have BN SLP for most of the rest of the month with some days MB. So, bottom line is that May will end up with a solid -SOI with sub -10 becoming increasingly likely, a strong leading indicator for El Niño.

Followup: similar with good chance of significantly BN SLP at Tahiti much of next week due to several pretty strong low pressures moving by to the south. It appears that most days for the rest of the month will be negative as it looks right now per model consensus.

As of 5/13, the SOI MTD is averaging -6, with the two stations contributing about equally to this modest negative. Looking at the model consensus out two weeks, it does appear that Tahiti SLP anomalies averaged out will be negative and Darwin positive. If anything, it appears to me that the SOI MTD will probably drop further as we go through the next two weeks. Thus, I see a realistic chance for -10 or so for full May SOI. IF that occurs, that would give this month the lowest SOI in at least 3 years and would be the lowest May SOI since 2015 and a decent signal for an oncoming El Niño. Since 1950, these Mays have had a sub -9 SOI: 1951, 1953, 1957, 1958, 1972, 1977, 1987, 1991, 1994, 1997, 2001, 2002, 2005, 2015 Of those 14, all were prior to an oncoming fall/winter Nino except 2001 and 2005. So, a sub -9 May is a pretty good indicator of an oncoming Nino.

Saying "potentially significant" is vague. Not only in using the word "potentially", but also the word "significant". One can argue that even just a moderate El Niño could be considered significant. One definition of significant is "likely to have influence or effect". A moderate El Niño is typically strong enough to have influence or effect. Most of us have known for quite some time that a moderate or stronger El Niño is likely on the way.

Thanks for posting this. We'll see whether or not this is a sign of things to come. Believe it or not, today's -31.31 is only the third sub -30 daily SOI since way back in July of 2020! Also, there has yet to be a long string of negatives this year. Actually, there hasn't been a negative daily string longer than 10 days since April of 2020! I'd want to start seeing longer than 10 day negative strings to have more confidence that the upcoming El Niño is starting to be significantly reflected up into the atmosphere. We're on a four day negative string now, which in itself isn't a big deal. Let's see whether or not this is going to turn into a much longer one.

Directly related to your 3rd Tweet regarding the idea of subtracting the warming of tropical oceans from the Nino 3.4 SSTA to produce a "relative Nino 3.4 index" or "RONI": "Another factor to consider is that the widespread ocean warmth may make it a little more challenging for the warm temperatures in the central-eastern equatorial Pacific to induce a tropical atmospheric response (maybe a reason for the current ENSO-neutral looking tropical atmosphere?). The reason is that the response of the tropical atmosphere depends on surface temperatures in the central-eastern equatorial Pacific relative to the surrounding regions. If those surrounding tropical regions are also warmer than average, then the bar is even higher for the Niño-3.4 region surface temperature anomalies to induce an atmospheric response (see footnote). The bottom line is that in terms of a push on the tropical atmosphere, we need to consider that the Niño-3.4 index may punch below its weight while it’s hovering in borderline El Niño territory, as it is now. However, if the central-eastern Pacific continues to warm up, we can expect that the atmosphere will feel that push eventually." Footnote: " This issue is why some, including Michelle of this blog, have advocated the monitoring of a relative Niño-3.4 or relative Oceanic Niño Index (RONI). The NOAA Climate Prediction Center monitors the RONI here. The RONI is simply our standard ONI (3-month average Niño-3.4 sea surface temperature anomaly) with the tropical average sea surface temperature subtracted. Such an index is less sensitive to a warming climate and, consistent with some of my earlier research, is more closely connected with changes in the tropical atmosphere than the standard ONI." ------------------------------ Since 2016, the RONI has averaged 0.4 C lower than ONI due to accelerated tropical ocean warming. So, my take is that the El Niño threshold based on RONI currently requires the ONI to reach +0.9 C and remain there for at least five straight trimonths instead of just +0.5 C for five trimonths to allow the atmosphere to act like there is a 3.4 based El Niño. Taking this further based on RONI: - moderate Niño currently requires ONI peak of +1.4 C instead of just +1.0 C - strong Niño currently requires ONI peak of +1.9 C instead of just +1.5 C - super strong Niño currently requires ONI peak of +2.4 C instead of just +2.0 C RONI might explain why the atmosphere in 2018-9 didn't act more typical of El Niño. Based on RONI, it would have been only warm neutral instead of weak El Niño. https://www.climate.gov/news-features/blogs/may-2023-enso-update-el-niño-knocking-door

1. Based on 1877-8 and 1888-9 being near normal in the NE US, I'm not going as far as to say "lock" to be warm in the NE US if 2023-4 ends up as a super El Niño. I'm be more in the "likely" (say ~70%) camp for that and ~25% chance for near normal. 2. In the SE US overall for the 7 identified super El Niño winters 1877-8, 1888-9, 1972-3, 1983-3, and 1997-8 were near normal. 1965-6 was colder than normal while 2015-6 was the only one warmer than normal. So, should it later look likely that 2023-4 is going to be super, I'd likely at that point lean toward near normal DJF temperatures in the SE along with wetter than normal for most places, especially nearer to the coast.

That's quite a rise forecasted for the PDO between April and July with still another 5 months to go even after that before winter starts. That suggests that a rise to low -1s is quite possible in July. That wouldn't be all that far from +0.50 being that there'd be five months to go. Do you know how accurate the various models are for the PDO? Are you aware of any biases?

I understand that the very low starting point minimizes the chance for it to rise enough to get to positive. But but based on a few cases of sharp rises when to a new Nino, might there be a small chance for at least a modest positive...say, DJF of +0.50+? Examples: 1. Nov-Apr 1883-4 was -1.4. DJF of the very cold 1884-5 was way up at +1.98. That's a 3.38 rise! 2. Nov-Apr of 1975-6 was -1.9. DJF of 1976-7 was up at +1.32. That's a rise of 3.22! 3. Nov-Apr of 2001-2 was -1.3. DJF of 2002-3 was up at +1.42 for a rise of 2.72! 4. Nov-Apr of 2022-3 was at -2.17. DJF of 2023-4 would reach +0.50 with a rise of 2.67. The rises in 1884-5, 1976-7, and 2002-3 would do it. The rises in 1884-5 and 1976-7 would actually give a strong +PDO (>+1.0) in 2023-4. So, there have been 38 new onset El Niños since 1855-6. So, 3 of 38 or 8% of them saw a PDO rise large enough to yield a +0.50+ in DJF of 2023-4. I used this table: https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat

Why do you say BEST case for PDO is neutral?

1. In the SE US, half of your 6 listed El Niño winters following strongly -PDO Nov-Aprils were very cold: 1957-8, 1976-7 (coldest winter on record), and 2009-10 (coldest winter since 1977-8). Of those, 1976-7 had way above average snow in the deep SE with my area getting snow an unheard of three times. 2009-10 had well above average snow in Atlanta and the SE overall. The other three weren't cold, but all had above average wintry precip at ATL thanks to one big winter storm each of those winters. 2. Using another PDO table that goes back into the late 1800s, the 1884-5 El Niño also followed a strongly -PDO in Nov-Apr: https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat That 1884-5 winter was quite cold in the E US, with NYC very cold with above average snow. Boston was also quite cold.

Also, 2023-4 is almost certainly going to me significantly stronger than just the +0.9 max anomaly in Nino 3.4 of 1976-7.

Whereas 2015-6, 1997-8, 1982-3, 1972-3, and 1965-6 were indeed supers with clearly warmer than normal at NYC, the supers 1888-9 and 1877-8 were actually near normal. Are you aware of that? Does that give you some doubt about the NE US torching should this go super?

In the new weeklies, Nino 1+2 warmed from +2.4 back up to +2.7, which ties it with 3-4 weeks ago for the warmest thus far this event. Nino 3.4 remained the same as last week at +0.4. Nino 4 actually cooled slightly from +0.4 to +0.3, while Nino 3 warmed slightly from +0.7 to +0.8. Compared to four weeks ago, Nino 3 warmed 0.6 while Nino 4 is the same.

1. Indeed, if this were to verify, it would be as of August east based (with 1+2 and 3 much warmer than 4) as well as strong in August. How would you expect it to look as it progresses to D, J, and F? 2. Note how warm the global oceans are projected to be as a whole! Less than 5% of the world ocean anomalies are blue while 80%+ are red!

The peak is 0.35 warmer than the prior run, but it does appear to have a warm bias in May.

Good point because I just looked and CAN and especially POAMA have not had anywhere near the warm bias of the Euro. Actually, POAMA looks like it has had no warm bias. Moreover, the latest POAMA (see 1st link below) is consistent with its prior forecast of +2.2 for JAS and has ~+2.5 for ASO while still rising! So, with its lack of warm bias, that's pretty ominous. CANSIPS (see 2nd link below), which appears to have no more than a small warm bias, is slightly warmer than its prior with a trimonthly peak of ~+1.85 (NDJ) vs the prior run's NDJ of +1.73. So, in summary after taking into account biases, whereas the Euro implies a trimonthly peak at strong as most likely (say ~+1.7) and the CANSIPS implies ~~+1.8, the POAMA implies a near alltime record of ~~+2.7! So, still tons of uncertainty and a clear conflict in the models! The Euro has not been too cool since 2004! So, if 2023 ends up again not too cool for the Euro, this POAMA would verify quite a bit too warm as the latest Euro *ignoring its strong warm bias* implies a peak likely only in the low +2s. POAMA: CANSIPS:

1. Unlike the April forecast, which warmed considerably vs March, this May forecast is about the same as April's when comparing the same months. It appears warmer in the animation only because of progression out another month, but each month through October is ~same. This new one still has ASO near +1.8 and SON is ~+1.90-1.95 per eyeballing. 2. As is pointed out in that Twitter thread by a reply from Alvaro (see below), the May Euro forecasts have had a significant warm bias with 2022, 2021, 2020, 2019, and 2017 verifying significantly too warm with only 2018 of the last 6 not being too warm. 2018 verified almost exactly right in May for ASO/SON with forecasts of +0.6/+0.8 vs actuals of +0.5/+0.8. More specifically: - 2022 verified much too warm with a May forecast of -0.29 for SON vs actual of -1.0. - 2021 verified much too warm with a May forecast of -0.02 for SON vs actual of -0.8. - 2020 verified much too warm with a May forecast of -0.37 for SON vs actual of -1.2. - 2019 verified too warm with a May forecast of +0.79 for SON vs actual of +0.3. - 2017 verified way too warm with a May forecast of +0.9 for SON vs actual of -0.7! (worst May bust on record) 3. I can add that 2016 per the Columbia University site verified almost exactly right for ASO/SON with May forecasts of -0.5/-0.5 vs actuals of -0.5/-0.6. 4. 2015 verified a bit too warm with a May forecast of +2.4 for ASO vs actual of +2.2 and a forecast for SON of +2.7 vs actual of +2.4. Note that this 2015 SON forecast issued that May of +2.7 is actually much warmer than the 2023 SON forecast just issued in May of ~+1.9 to +1.95. 5. 2014 verified much too warm with a May forecast of +1.5 for ASO vs actual of only +0.2! 6. 2013 verified very slightly too warm for ASO/SON with May predictions of -0.1 vs actuals of -0.3/-0.2. 7. 2012 verified significantly too warm with May forecasts for ASO/SON of +0.8/+1.0 vs actuals of +0.4/+0.3. 8. 2011 verified significantly too warm with May forecast for ASO of -0.2 vs actual of -0.8. 9. 2010 verified significantly too warm with May forecast for ASO of -0.9 vs actual of -1.6. 10. 2009 verified barely too warm with May forecast for ASO of +0.8 vs actual of +0.7. 11. 2008 verified perfectly with May forecast for ASO of -0.2 vs actual of -0.2. 12. 2007 verified a bit too warm with May forecast for ASO of -0.8 vs actual of -1.1. 13. 2006 verified barely too warm with May forecast for JAS of +0.4 vs actual of +0.3. 14. 2005 verified too warm with May forecast for JAS of +0.4 vs actual of -0.1. 15. 2004 verified barely too cool with May forecast for JAS of +0.5 vs actual of +0.6. So, one has to go all of the way back to 2004 to find the last time the Euro May forecast was too cool for its endpoint and even that was too cool by only 0.1. 16. 2003 verified significantly too cool (last time for that) with May forecast for JAS of -0.4 vs actual of +0.2. 17. 2002 verified a bit too cool with May forecast for ASO of +0.7 vs actual of +1.0. -------------------------------- Summary of Euro May forecasts: - 2022-2005: significantly too warm 10 times, moderately to barely too warm 5 times, correct 3 times, too cool 0 times!! - 2022-2005: average error +0.5! - 2022-2005: average error when actual El Niño verified +0.35 with it correct once, barely too warm twice, moderately too warm once, and way too warm once. For this reason and others, I feel that the chance for a super remains low. I'm favoring high end moderate to strong trimonthly peak (+1.3 to +1.9). - 2004-2002: significantly too cool once, moderately too cool once, barely too cool once. - So, too cool all 3 times 2002-4 but never too cool since 2005! Was the model changed in 2005? Columbia ENSO site: https://iri.columbia.edu/our-expertise/climate/forecasts/enso/

Unlike the April forecast, which warmed considerably vs March, this May forecast is about the same as April's when comparing the same months. It appears warmer in the animation only because of progression out another month, but each month through October is ~same. This new one still has ASO near +1.8 and SON is ~+1.90-1.95 per eyeballing. For this and other reasons, especially the strong warm bias of the Euro (more details about this in next post), I'm keeping chances of super at low with better chance of high end moderate or strong.

The weather has been near ideal from my perspective this week to this point. Much of the last few weeks has been very nice. Today is another great day, but tomorrow will start the increase in dewpoints. It is highly probable that we won't see another extended period similar to this until very late Sept and more likely October. So, I've been taking in every bit of this bonus early springlike period.

I received 2.5-3" of rainfall over the last few days.