bluewave

I am happy that we got one of the earliest SSWs on record back in late November. It was a big reason that this was the first winter with below average temperatures and above average snowfall in 11 years around NYC Metro. It’s possible that if the SSW had occurred later in the season, then with the lag could have resulted in the benchmark track coming too late in March when temperatures would have been more marginal for heavy snows along the coast. As it was the SSW occurred in late November with a 2-3 month lagged response for the BM KU track to materialize. December snows were all Northern Stream clippers.

This was the 8th warmest March 1st to April 29th for NYC at 50.8°. Time Series Summary for NY CITY CENTRAL PARK, NY Warmest March 1 April 29 Click column heading to sort ascending, click again to sort descending. 1 1945-04-29 53.2 0 2 2012-04-29 52.8 0 3 2010-04-29 52.7 0 4 1921-04-29 52.1 0 5 2024-04-29 51.7 0 6 2016-04-29 51.0 0 7 2023-04-29 50.9 0 8 2026-04-29 50.8 0 9 2025-04-29 50.7 0 10 1985-04-29 50.2 0 11 1946-04-29 50.1 0 12 2021-04-29 50.0 0 - 2002-04-29 50.0 0 - 1977-04-29 50.0 0 13 1991-04-29 49.9 0 - 1903-04-29 49.9 0 14 1973-04-29 49.7 0 15 1979-04-29 49.5 0 16 1998-04-29 49.4 0 - 1986-04-29 49.4 0 - 1976-04-29 49.4 0 17 1910-04-29 49.2 0 18 2020-04-29 49.1 0 - 2006-04-29 49.1 0 - 1990-04-29 49.1 0 - 1987-04-29 49.1 0 19 1968-04-29 49.0 0 20 2000-04-29 48.9 0 - 1981-04-29 48.9 0 21 2022-04-29 48.8 0 22 2008-04-29 48.7 0 - 1938-04-29 48.7 0 - 1878-04-29 48.7 0 23 1963-04-29 48.5 0 24 2019-04-29 48.4 0 - 1913-04-29 48.4 0 25 2009-04-29 48.3 0 - 1995-04-29 48.3 0

This past winter was really interesting in that we got the warm pool east of Japan interacting with the warm pool off of California and the Baja. So it prevented us from getting a strong +PDO like we had in 1995-1996 with that weak La Niña. So while this was the best winter of the 2020s so far from NYC to Boston, the overpowering Northern Stream was only able to relax from late January to late February. This prevented the wall to wall historic snowy outcome from November 1995 to April 1996. Notice how much stronger the Northern Stream was this past winter compared to 1995-1996. My guess is that the warm pool east of Japan in concert with the much warmer climate may have increased the Northern Stream just enough to take the 1995-1996 historic snows off the table. But we still were able to get the outstanding February KU before the Northern Stream returned for March.

Yeah, I get the joking. It’s good to keep things light in here. We switched out of the traditional -PDO +PDO relationship following the big warming east of Japan after the 2015-2016 El Niño.This really increased following 2018-2019. So the current models are forecasting more of basin-wide warming where we get a zone of warm SSTs from Japan to the Baja. We saw that this past winter going into the spring with the record +PMM and remaining warm pool east of Japan. We will probably have to revisit this paper again after this event and see where things stand. https://www.nature.com/articles/s41558-025-02482-z Pan-basin warming now overshadows robust Pacific Decadal Oscillation The Pacific Decadal Oscillation (PDO) has served as a key index linking basin-scale climate variability to marine ecosystem changes in the North Pacific. However, recent apparent breakdowns of PDO–ecosystem correlations have raised concerns about the stability of the mode and its continued relevance in a warming climate. Here we show that basin-wide warming now overwhelms PDO-related sea surface temperature (SST) variability, although neither the PDO’s spatial pattern nor its strength have changed. We introduce the pan-basin pattern as a complementary index to describe the non-stationary SST baseline of the North Pacific. Regional SSTs increasingly reflect the superposition of these two signals, providing an explanation for weakened or inverted PDO–ecosystem correlations. Future use of the PDO index in management will require discerning the effects of internal dynamics from those of absolute changes in SST as extreme and no-analogue ocean conditions driven by interacting natural variability and anthropogenic warming become more common. We demonstrate that the leading mode of interdecadal North Pacific SST changes recently transitioned from the PDO to a pattern of unidirectional change across the entire basin (that is, the PBP). For the first prolonged period of the recent observational record, a negative ‘cold’ PDO phase failed to coincide with cool SST anomalies in the eastern Pacific—a harbinger of the increasing non-stationarity in relationships between the PDO and regional SSTs (Fig. 3d,e). Despite explaining proportionally less variance, ongoing robust PDO variability indicates that drivers of the mode’s SST anomaly footprint have been resilient to warming through the early twenty-first century (Figs. 1 and 2). As the PDO is a statistically emergent pattern integrating several processes (for example, stochastic Aleutian Low forcing, teleconnections with the tropics, and ocean Rossby waves)4,47, its future evolution will depend on how these contributing processes are cumulatively impacted by warming across timescales. Although the historical physical drivers of North Pacific decadal variability are relatively well understood4,48, the biophysical mechanisms through which ecosystems respond are less so. The PDO has historically served as a reliable proxy for SST in much of the North Pacific. However, as regional SST anomalies continue to diverge from those historically expected based on PDO signals (Fig. 3d–g), there will be a growing need to distinguish impacts associated solely with SST anomalies from those produced by the dynamics related to the PDO (for example, changes in upwelling, transport or source waters). For example, since the 2021 transition into the negative PDO phase (Figs. 3d,e and 4b,c), warming is superimposed on a cold PDO regime in the eastern North Pacific, leading to confusion in the community regarding the expected biological effects26. Further investigation into the mechanisms behind PDO–ecosystem relationships should prioritize discernment of temperature-specific effects on biology from the effects of other physical or biogeochemical processes. Given the ongoing stability of the PDO pattern, the PDO index probably remains a useful indicator of North Pacific climate variability, but perhaps with its ecological relevance in how it reflects changing dynamical processes rather than regional SST anomalies. As the PBP–temperature baseline climbs in concert with global ocean warming, local and regional SST anomalies that would historically have been associated with an exceptionally strong PDO and/or El Niño (for example, >2 standard deviations) will occur more frequently. For example, constructive signals between internal variability and secular warming from 2014–2020 contributed to warm temperature extremes during this period (for example, ref. 49). Quantification of the range of internal variability related to the PDO and other modes will be needed to constrain the potential for climate extremes resulting from interaction of internal variability and anthropogenic warming, leveraging approaches such as palaeoclimate records, long model simulations or large model ensembles50,51. Constraining internal variability and stability is also necessary for understanding the future of PDO impacts beyond the North Pacific (for example, theorized impacts on hydroclimate in western North America and northeastern Asia)52,53,54,55,56,57 and its role in modulating global climate. Global-scale trends and internal variability are now both important determinants of North Pacific climate48,58, with the influence of pan-basin warming surpassing that of the PDO within the past decade. The combination of long-term warming and natural variability has already begun to produce profound physical and ecological changes throughout the North Pacific, including severe marine heatwaves with ecosystem-wide impacts59,60, rapid sea ice declines and novel weather patterns in the Alaskan Arctic61, and new human–wildlife conflicts62. Management decisions based on historical baselines will fail to capture increasingly important emergent interactions between anthropogenic warming and internal variability. This increased uncertainty in associations between basin-scale variability and regional responses underscores the need for management approaches to incorporate dynamical modelling and prediction of North Pacific climate (for example, ref. 63), rather than relying on historical relationships with basin-scale indicators as predictors. Given that the internal variability of the North Pacific is especially strong, a similar emergence of pan-basin warming over internal variability is probably already occurring in other basins, suggesting that the recontextualization of indices of climate variability under warming is needed widely.

It will be interesting to see how things play out. But the long range models continue the warm pool east of Japan. We may have to wait until we get closer to the peak of this event to know for sure.

Nino 3.4 responding to the kelvin wave as it’s now the 3rd warmest for the date since the early 80s.

It has been mostly a brown lawn issue here since late 2024. But we did have our local reservoirs running low at times. Thankfully nothing as extreme as the water restrictions areawide back in 2002. The biggest issue for agriculture this spring has been the record temperature swing. While spring record warmth is arriving earlier these days, the last freeze date has held more steady. This has resulted in the big local crop losses.

It will be interesting to see if the coming El Niño can shift us out of this dry pattern which began in September 2024.

2009 was the last average temperature summer in Philly against the 1951-2000 mean. This was the first slightly cooler winter in Philly since 2015-2016. So it’s pretty representative of the wider trends across the region and nation.

I like to rely more on the ECMWF Nino plumes model than the CFS but we only get one update a month. My guess is that it will show another increase in ONI with the May 5th release as it initializes the current near record OHC for so early in the season. It may be that the Nino 1+2 regions not fully cooling off from the last very strong event in 2023-2024 could have something to do with the El Niño coming on so strong with only a 3 year gap between events. Notice that 2025 was the first full year following an El Niño so strong that stayed warm off of South America. Go back to the previous higher end events since the early 1970s and you will see they all significantly cooled compared to what happened in 2025. Also note how much warmer the entire North Pacific remained.

The climate has had three shifts to the warmer since 2009-2010. Our summers became warmer beginning with the 2010 summer. We haven’t had any cooler summers against the long term average like in 2009 or earlier since then which we would normally get every several years. The only three cooler summers since then against the recent much warmer means like 2023, 2017, and 2014 have been closer to or a little warmer than the older long term average. Most of the summers since then have been near the top rankings for warmth. Starting with December 2015, the U.S. winters have become much warmer to the point where we have seen many new top warmest winters for the CONUS and no significantly colder ones since then. The most recent temperature jump in 2023-2024 produced the #1 warmest CONUS winter on record that winter and the #2 warmest winter this year in 2025-2026. The concern going forward is that we will get another baseline temperature jump with this developing very strong El Niño for 2026-2027 that will just add to the previous ones since 2015-2016. I can fully understand your point of view that the climate has not rapidly changed. Since it’s human nature to normalize the recent 3-7 of weather as nothing unusual. Plus it may not be that obvious when we get used to more Mid-Atlantic style temperatures like used to be normal for VA.

We can see why the recently initialized models like the CFS are going higher. This is the first time since 1997 with an OHC reading reaching over 2.0° in April. Remember, 1982 didn’t reach this level of heat until October. Plus even 2015-2016 only peaked at 1.91 and not until October. My guess is that the ECMWF release on May 5th will increase its forecast over the April 5th levels once this record kelvin wave and OHC is initialized. So it appears we are on track for our first two El Nino events with a peak over +2.0 only separated by 3 years. We may not know what the ceiling is on this one until we get into late May or June. But it looks higher than 2023-2024 due to how strong this is becoming early on. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

It does look like May will at least start out cooler than average with all the blocking and the upper low parked over the Northeast. Will be interesting to see if we can get some improvement heading out toward Memorial Day. Still beyond the reach of the models.

2009 would probably be too big of an ask in this much warmer climate. It was the 2nd coolest June and July on record at spots like Islip. 2023 was our last summer with a developing El Niño that became very strong. Was cooler overall than the other 2020s summers so far but still not really cool by historical standards. Time Series Summary for Islip Area, NY (ThreadEx) 10 Coolest June 1 to July 31 Periods Click column heading to sort ascending, click again to sort descending. 1 1965-07-31 67.9 0 2 2009-07-31 68.2 0 3 1978-07-31 68.5 0 4 1979-07-31 68.7 0 - 1968-07-31 68.7 0 5 1992-07-31 68.9 0 6 1982-07-31 69.0 0 7 1964-07-31 69.2 0 8 1972-07-31 69.3 0 9 1985-07-31 69.4 0 10 2000-07-31 69.6 0 - 1996-07-31 69.6 0

You usually have to go back a day before to get the broader set to update. On the Xmacis2 site it’s easier to display. Islip had their 12th warmest spring average spring high through the 25th with Philly coming in 3rd place. Time Series Summary for ISLIP-LI MACARTHUR AP, NY mean max temp Mar 1 through Apr 25 Click column heading to sort ascending, click again to sort descending. 1 2012-04-25 58.9 0 2 2010-04-25 58.1 0 3 2025-04-25 56.7 0 4 1976-04-25 56.5 0 5 2023-04-25 56.1 0 - 2016-04-25 56.1 0 6 2002-04-25 55.9 0 7 1977-04-25 55.6 0 8 2024-04-25 55.5 0 9 1973-04-25 55.3 0 10 2021-04-25 55.2 0 11 1999-04-25 54.8 0 - 1991-04-25 54.8 0 12 2026-04-25 54.3 0 - 2008-04-25 54.3 0 13 2022-04-25 54.2 0 14 1987-04-25 54.0 0 15 2020-04-25 53.8 0 Time Series Summary for Philadelphia Area, PA (ThreadEx) mean max temp Click column heading to sort ascending, click again to sort descending. 1 1921-04-25 65.7 0 2 1945-04-25 65.0 0 3 2026-04-25 64.5 0 4 1977-04-25 64.1 0 5 2012-04-25 63.8 0