bluewave

It will be interesting to see if Philly can record their first 3 consecutive years under 40.00” since the early 1990s . Long range precipitation forecasting is very uncertain. The hope is that the STJ can come far enough north with the developing super El Niño to increase the rainfall enough in coming months to get over 40.00” by the end of December. Many spots have been running drier than average starting with the big dip in rainfall in September into October 2024. Monthly Total Precipitation for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 2026 2.84 2.24 1.90 2.11 0.37 M M M M M M M 9.46 2025 0.93 2.05 5.36 2.83 6.22 2.20 4.61 1.73 1.79 2.02 2.30 3.35 35.39 2024 5.91 1.49 7.19 4.16 1.72 4.68 2.44 5.07 0.77 T 2.52 3.45 39.40 2023 3.36 1.32 1.99 5.17 0.24 4.24 5.24 3.25 5.99 0.72 2.75 7.92 42.19 2022 3.35 2.87 2.09 4.51 4.16 5.03 2.20 2.70 2.06 5.80 2.89 4.85 42.51 2021 1.55 4.64 4.21 2.69 3.24 3.06 6.72 6.18 4.61 4.81 0.46 1.64 43.81 2020 2.64 2.46 3.94 3.75 2.20 3.21 5.54 8.53 4.23 4.09 4.79 4.38 49.76 2019 3.92 3.27 3.85 3.02 5.22 7.94 6.03 2.78 1.16 3.87 1.16 5.21 47.43 2018 2.85 6.02 4.74 3.94 5.21 3.34 3.06 4.11 9.76 3.08 9.03 6.38 61.52 2017 2.91 1.30 4.26 3.15 6.33 1.86 5.35 6.05 3.86 3.66 1.30 1.31 41.34 2016 2.63 4.36 2.01 1.75 6.65 1.87 3.88 1.70 3.52 2.06 2.17 2.72 35.32 2015 4.52 2.36 5.52 3.58 1.19 8.88 3.16 0.98 6.27 3.76 1.89 5.14 47.25 2014 3.55 5.12 4.23 6.69 2.91 5.46 4.30 3.55 1.69 2.53 4.07 3.27 47.37 2013 3.34 2.12 2.42 2.32 2.33 10.56 13.24 5.91 3.26 2.45 2.73 5.20 55.88 2012 2.59 1.84 0.79 2.55 3.35 2.94 1.48 5.37 5.48 4.08 1.05 4.42 35.94 2011 3.39 2.65 4.29 5.29 1.91 2.56 2.71 19.31 10.27 3.71 3.87 4.37 64.33 2010 2.19 5.75 7.33 2.65 2.53 2.05 6.28 2.19 3.48 5.01 1.76 3.24 44.46 2009 2.70 0.84 1.62 3.99 4.84 4.79 3.35 10.29 3.65 5.51 2.06 8.86 52.50 2008 1.74 3.93 3.67 2.19 4.55 2.87 3.45 2.44 4.31 1.59 4.02 5.57 40.33 2007 3.35 1.73 3.82 9.05 2.68 4.02 3.44 2.94 0.58 4.66 1.45 4.41 42.13 2006 4.34 1.51 0.91 3.71 2.16 7.95 4.27 3.93 5.97 6.42 4.88 2.15 48.20 2005 4.45 2.61 3.66 5.32 1.27 3.31 4.31 2.57 0.21 8.68 2.86 2.97 42.22 2004 1.70 2.50 3.54 6.02 3.62 4.57 7.91 4.17 5.19 2.24 4.55 3.17 49.18 2003 1.93 5.04 4.09 2.20 4.17 8.08 2.01 3.26 4.66 4.45 2.63 5.46 47.98 2002 2.43 0.55 4.03 2.17 3.57 3.73 2.12 2.47 3.67 5.90 4.65 4.05 39.34 2001 2.77 3.04 5.44 1.49 3.99 5.93 1.30 0.97 2.58 0.83 0.56 2.11 31.01 2000 3.22 2.02 6.32 3.05 3.03 3.82 5.54 2.90 8.28 1.51 2.21 2.82 44.72 1999 4.89 2.95 4.02 3.31 3.70 1.16 1.22 5.32 13.07 3.55 2.31 2.99 48.49 1998 4.24 3.25 3.93 2.70 3.87 4.91 1.79 1.26 1.86 1.84 1.18 0.82 31.65 1997 2.80 2.48 3.91 2.58 2.32 1.49 2.38 4.56 1.59 1.83 3.49 3.09 32.52 1996 4.39 2.12 4.27 4.48 3.25 4.73 8.17 4.29 4.95 4.30 3.03 8.47 56.45 1995 3.10 2.41 1.67 1.96 2.67 0.62 2.92 1.15 3.55 5.99 3.34 2.15 31.53 1994 4.27 3.27 6.44 2.86 3.66 1.74 10.42 4.54 1.64 0.94 3.03 2.11 44.92 1993 1.97 3.03 6.61 4.20 2.42 1.52 1.98 5.18 6.66 2.69 2.23 3.69 42.18 1992 0.88 1.31 3.19 1.26 2.74 1.84 5.05 2.00 3.04 1.23 3.26 4.61 30.41 1991 4.10 0.75 4.13 2.81 1.82 3.36 4.79 3.86 3.58 1.61 1.55 3.86 36.22 1990 4.09 1.44 2.59 3.16 6.08 3.39 2.62 4.07 1.71 1.68 1.17 3.79 35.79 1989 2.41 3.25 4.41 2.27 6.76 4.73 9.44 3.92 5.03 3.44 1.79 1.21 48.66 1988 2.72 4.11 2.24 2.92 3.67 0.57 8.07 3.16 2.62 2.16 5.17 1.00 38.41 1987 4.58 1.17 1.16 3.63 3.15 2.01 4.82 3.72 2.78 2.62 2.08 1.68 33.40 1986 4.13 3.38 1.25 4.46 0.70 1.99 4.10 3.70 2.33 2.22 6.27 5.89 40.42 1985 1.55 2.44 1.95 0.52 4.99 1.88 4.66 2.82 5.78 1.54 6.09 0.98 35.20 1984 2.22 2.81 6.14 4.25 6.87 2.85 6.99 3.28 1.96 2.56 1.56 2.17 43.66 1983 2.81 3.53 6.95 8.12 7.03 2.75 0.68 2.57 3.45 3.69 5.71 7.37 54.66 1982 4.45 3.16 2.66 6.06 4.47 5.76 1.94 2.20 2.32 1.94 3.67 1.80 40.43 1981 0.50 2.94 1.61 3.60 4.53 4.40 4.54 5.11 2.83 2.68 0.95 4.14 37.83 1980 2.27 0.96 7.01 4.79 3.22 1.73 6.58 0.80 2.79 5.03 2.85 0.77 38.80 1979 8.74 6.44 2.43 4.08 3.98 4.34 3.95 5.95 4.89 3.84 2.48 1.67 52.79 1978 8.86 1.35 4.31 1.76 6.01 1.75 5.27 6.04 1.59 1.20 2.20 5.61 45.95 1977 2.61 1.33 4.19 5.59 0.70 5.33 1.47 8.70 3.44 3.11 7.76 5.19 49.42 1976 4.50 1.66 2.38 2.06 4.35 3.42 4.04 2.17 2.44 4.30 0.32 1.63 33.27 1975 4.00 2.91 4.68 2.97 4.99 7.57 6.32 2.21 7.21 3.24 3.14 2.89 52.13 1974 2.95 2.14 4.91 2.77 3.21 4.43 2.08 3.83 4.68 1.93 0.81 4.04 37.78 1973 3.93 2.96 3.52 6.68 4.14 7.88 2.39 2.03 3.39 2.16 0.64 6.34 46.06 1972 2.34 5.09 2.69 4.08 4.11 5.79 2.62 3.76 1.12 3.77 9.06 5.20 49.63 1971 2.13 5.43 2.58 1.84 4.10 1.01 4.84 9.61 5.83 3.84 5.37 1.21 47.79 1970 0.74 2.08 3.83 6.12 2.57 4.60 2.75 3.99 0.82 3.66 4.71 3.27 39.14 1969 1.57 1.88 1.92 1.68 3.30 7.31 8.33 2.66 4.38 1.13 1.97 7.23 43.36 1968 2.90 1.40 4.98 1.57 5.17 5.89 2.00 1.24 0.44 3.15 4.17 2.54 35.45 1967 1.67 1.82 4.53 2.17 3.49 4.12 7.11 7.08 2.96 2.00 1.99 5.88 44.82 1966 2.82 4.30 0.68 4.35 2.95 0.41 2.35 1.63 8.70 5.12 2.36 4.33 40.00 1965 2.35 2.18 3.19 2.33 1.23 2.85 3.22 4.05 3.02 2.02 1.05 1.85 29.34 1964 3.92 2.83 1.94 5.27 0.47 0.21 3.83 0.49 2.42 1.73 1.64 5.13 29.88 1963 2.31 2.19 3.94 1.13 1.06 2.88 3.13 3.35 6.44 0.09 6.67 1.76 34.95

At least we are doing better than areas just to our south. Through May 14th Philly is having their 4th driest March 1st through May 13th. The drought should help boost the high temperatures in the usual warm spots next week. Pretty impressive to see the GFS, Euro, and CMC all showing 95+ potential for the usual warm spots. Time Series Summary for Philadelphia Area, PA (ThreadEx) Driest March 1 to May 13 Click column heading to sort ascending, click again to sort descending. 1 1926-05-13 3.79 0 2 1938-05-13 4.20 0 3 1930-05-13 4.32 0 4 2026-05-13 4.38 0 5 2012-05-13 4.42 0 6 1995-05-13 4.64 0 7 1985-05-13 4.71 0 8 1969-05-13 4.77 0 9 1887-05-13 4.91 0 10 1883-05-13 4.98 0

Yeah, we had the split forcing in the 2023-2024 El Niño with the record warm pool near the Dateline and another center off of Mexico like we are currently seeing. The 1997-1998 El Niño had very east based forcing since Nino 4 was so much cooler. 2023-2024 was more of a full basin event rather than an east based one like 1997-1998.

While the NAM often had unrealistic precipitation amounts especially since it wasn’t upgraded in almost 10 years, it did do much better than other models with the warm nose at 700mb to 800mb and snow to mix precipitation timing. So we may just have to compensate for this by manually speeding up the snow to mix precipitation timing in situations which the other models are too weak with the 700-800 MB WAA. The other story is that the SPC HREF was one of the best models showing snow banding and extreme heavy precipitation amounts. It did very well with the late February KU and several flash flooding events over the years.

I like focusing on where the +30C warm pools are. Since the actual forcing driving our sensible weather follows those areas. The current forecast is for split forcing centers near the Dateline and off of Mexico in late May.That Dateline forcing is closer to near record Nino 4 and MJO 7 and the forcing further east is with the record +PMM.

Not much outside of the Great Lakes this spring. https://mesonet.agron.iastate.edu/plotting/auto/?_wait=no&q=24&which=cd&csector=conus&var=precip&w=rank&p=day&year=2026&month=4&sdate=2026%2F03%2F01&edate=2026%2F05%2F13&cmap=RdYlBu&cmap_r=on&_r=t&dpi=100&_fmt=png

JMA has the current velocity potential and an archive with 5 day to 3 month means. https://www.data.jma.go.jp/tcc/tcc/products/clisys/figures/db_hist_mon_tcc.html

Yeah, the last Nam upgrade was in March of 2017. It nailed the January 2016 event. Sad to see the SPC HREF go as its ensemble max snowfall was actually pretty good with the split bands west and east of NYC and 20”+ amounts for the February 2026 event. https://www.noaa.gov/media-release/review-of-jan-2016-blizzard-preliminary-snow-totals-validates-dc-measurement The preliminary Central Park measurement will be adjusted upward to 27.5 inches, which will become an all-time snowfall record for New York City when certified by NOAA’s National Centers for Environmental Information. A communication error between the weather forecast office in Upton, New York, and the Central Park Conservancy, which volunteers to take official snow measurements in Central Park, led to an inaccurate preliminary total of 26.8 inches. The snow team found the mistake when reviewing the Conservancy’s logbook.

Big Euro and AI upgrade. https://www.ecmwf.int/en/about/media-centre/news/2026/ifs-cycle-50r1-aifsv2-live A significant upgrade to ECMWF's Integrated Forecasting System (IFS), Cycle 50r1, has gone live today (12 May 2026) alongside an update to the Artificial Intelligence Forecasting System (AIFS v2). Cycle 50r1 introduces a more consistent and integrated approach to forecasting the atmosphere’s interactions with the ocean through fully coupled data assimilation, and improvements to known issues with accurately forecasting sudden, heavy, localised rain. It also brings more advanced representation of waves and sea ice. The update to the AIFS introduces, among other features, ECMWF’s first data-driven wave and snow cover forecasts. Florian Pappenberger, Director-General of ECMWF, said: “This is an important upgrade for ECMWF and for everyone who relies on our forecasts. IFS Cycle 50r1 strengthens our physics-based forecasting system, including through fully coupled atmosphere–ocean–sea-ice assimilation and new ocean and sea-ice capabilities. "With AIFS v2, we are expanding its performance, bringing a new generation of AI forecasting into operation, building on ECMWF’s technical competence, operational expertise and data infrastructure. Together, these advances reflect ECMWF’s commitment to innovation and close co-development with our Member and Co-operating States in delivering better forecasts, increasing the value to society.” Matthieu Chevallier, ECMWF’s Head of Forecast Evaluation, added: “The updates to these systems, being formally announced today, will together provide numerous benefits to users of our forecasts. Alongside the scientific and technical advances in coupled modelling and data assimilation, and innovation with AI techniques, we have responded to users’ feedback, for example, with new products. We look forward to hearing their reaction to the quality and accuracy of our forecasts, and on how it impacts their applications.” Forecasting improvements One of the most significant changes to the IFS introduced with Cycle 50r1 is a better representation of convective precipitation, which causes heavy rainfall and violent thunderstorms but is hard to predict because it occurs at smaller scales. The revised convection and cloud-microphysics scheme will reduce excessive stationary rainfall and, instead, represent more realistically how it moves from the ocean across the land. IFS users will also see the introduction of the new NEMO4-SI³ ocean and sea-ice model, bringing substantial improvements in forecasts and analysis over the marine areas, as well as over 40 new ocean and sea ice-related variables. Key improvements include a more accurate representation of how sea ice affects the power of waves and the interactions between waves and ocean currents, often at play in rougher seas. Other improvements for IFS include improved tropical upper-air temperature and wind forecasts, and improvements to temperature and humidity forecasts around the tropopause. For the Copernicus Atmosphere Monitoring Service (CAMS), one of two Copernicus services operated by ECMWF on behalf of the European Commission, the IFS update will enhance the atmospheric composition and greenhouse gas forecasts. The improvements range from the assimilated observations to aerosols and reactive gases, as well as enhanced input data on human-driven emissions. For AIFS, both the Single and Ensemble versions of the system are being upgraded to version two, with each introducing a new wave component. Eleven wave-related variables are being made available to users, enabling predictions, for example, of when we will experience rougher seas. In addition, the AIFS Single v2 wave component shows substantial improvement in the medium-range skill of wave forecasts compared to the physical model, IFS Cycle 50r1. ECMWF’s first data-driven snow cover forecasts are also being introduced with this upgrade. Again, the AIFS Single v2 forecasts show improved performance compared to IFS Cycle 50r1 forecasts, with the predicted snow cover fraction closer to observations. Victoria Bennett, ECMWF's Head of User Services Section, said: “These new cycles bring improvements to the models and introduce new products that address requests from users. In addition, with IFS, we have now removed the duplication between the old “HRES” single forecast and the Ensemble control and introduced other minor technical updates to reduce complexity. We have worked closely with users during the testing period, and with their positive feedback, we are excited to be making the switch.” All the upgrades to our systems are live with immediate effect.

This is the first that the +30C warm pool near the Dateline made it down to 100m in April with a developing El Nino. Notice how much warmer in all aspects we are than 2023 during the same time. You have to wonder if this continues leading to a slower cold pool formation than we typically see toward the later stages of the El Nino in the Western Pacific. We probably wouldn’t know until next winter whether it could cause this one to wind down more slowly than usual during the spring.

The westward lean is closer to the +ENSO MJO 7 composite with the ridge from coast to coast. But notice how the troughs are weaker in the coming forecast near the Aleutians and Baja. Similar to the weak La Niña this past winter when the ridge out West was stronger than the trough in the East. While it may be too early to draw conclusions about next winter, this would result in a weaker Aleutian Low and possibly a weaker low in the Southeast like we saw in 2023-2024 and 2015-2016 relative to 1997-1998 and 1982-1983.

No surprise that the El Nino is beginning to couple with a westward lean close to the +30C warm pool.

Other stations have done it further back in time with Caldwell being the most recent in 2021. Monthly Highest Max Temperature for CALDWELL ESSEX COUNTY AP, NJ Click column heading to sort ascending, click again to sort descending. 2021 84 90 91 91

It will be interesting to see what the pattern does in June following the mid to late May warm up. So far it appears we are in a pattern similar the warmer 2015 El Niño mid to late May as opposed to the cooler 2023 one. The 2015 analog is showing up on the day 8-14 analog composite. 2015 was a warmer summer here than 2023 was. New York, Climate Division 4 Average Temperature June-August higher ranks warmer with 2010 ranking #131 warmest June-August 2025 73.2°F 120* June-August 2024 74.0°F 127 June-August 2023 72.2°F 103 June-August 2022 74.1°F 128 June-August 2021 73.4°F 123* June-August 2020 74.3°F 130 June-August 2019 73.2°F 120* June-August 2018 73.4°F 123* June-August 2017 71.9°F 97* June-August 2016 74.2°F 129 June-August 2015 73.1°F 118 June-August 2014 71.6°F 92* June-August 2013 72.9°F 115* June-August 2012 73.4°F 123* June-August 2011 73.9°F 126* June-August 2010 75.2°F 131 June-August 2009 70.7°F 64* June-August 2008 72.5°F 108* June-August 2007 71.6°F 92* June-August 2006 73.0°F 117* June-August 2005 73.9°F 126* June-August 2004 70.6°F 62* June-August 2003 71.7°F 94* June-August 2002 72.9°F 115 * June-August 2001 72.0°F 100* June-August 2000 69.8°F 33

Hopefully, the developing El Niño can ease these historic drought conditions across the CONUS.

We lose some aspect of the past climate with every baseline temperature jump. But we have to wait until after the event to see specifically what changes will occur. The first one in 1997-1998 put a 1995-1996 snowy benchmark season out of reach for us. The same for the 1993-1994 record cold with benchmark snows in Central to Eastern PA. It was also the beginning of the all or nothing snowfall pattern which lead to more seasons of 30”+ and 18” or lower. Leading to a significant decline in the 19” to 29” winters which were common place from the 1960s to early 1990s. So every snowy season featured it least one KU benchmark event. The absence of KU events has been a feature of the low snowfall winters. It took around 9 years after that event 1997-1998 event for the warmth to make it to the Arctic leading to the big thickness drop and record lower range we have been in. Then a smaller jump in 2010 shifted the summer temperatures to a warmer base that we have been in. Then the historic December 2015 +13 kicked off the era of significantly warmer winters. Places like DC to Philly haven’t seen close to the cold and benchmark snow of the 2009-2010 winter. Same for the Great Lakes not repeating the benchmark snow and very cold conditions of 2013-2014. Plus the Boston historic snows in 2014-2015. Then the rapid warming of the WPAC east of a Japan following this event eventually leading to the faster Northern Stream of the Pacific Jet and decline in 2020s snowfall for us compared to the record snowy 2010s. We did get a nice bounce back winter in 2025-2026 with the first benchmark KU since 2020-2021 and 2021-2022. Still uncertain how the winter storm tracks will respond following this event. The 2023-2024 jump is most recent with 2 of the warmest winters on record occurring for the CONUS in the last 3 years. Hard to say how long the severe drought pattern which developed across the U.S and Canada following this event will last. It will be interesting to see if this 2026-2027 event can shift the pattern to wetter at least temporarily or shift us back to drier again following the event. Very challenging to do multiyear precipitation forecasting. It took 18 years between 1998 to 2016 for that baseline jump to occur. Then only 8 years between 2016 and 2024. Now all the models are indicating the first time for a +2.1 or greater ONI El Niño only 3 years apart and baseline temperature jump. So for the entire planet we are moving into an unknown zone with such rapid warming occurring over shorter intervals of time.

If you were following the seasonal forecasts last November, then you would have seen the ones keying in on the early stratospheric warming and easterly QBO influence warming were on the right track. But it took about 3 months to finally deliver the big KU event. Would have been nice if we didn’t have to wait 11 years for a both cold and snowy winter in what has become a sea of warm. https://opensnow.com/news/post/november-update-2025-2026-winter-forecast-preview

2009-2010 was a much weaker modoki compared to the 2023-2024 full basin event and what 2026-2027 is projected to be. Plus it occurred back in a much colder climate prior to the baseline temperature jumps in 2015-2016 and 2023-2024. This is why places from DC to Philly haven’t experienced anything close to those snowfall totals since.

Your local area has just finished the warmest 11 year stretch of winters into March following the big warmer shift in 2015-2016. Since the winters have still averaged below freezing, it still feels cold. But just not as cold as it had been in the past. So every local area has been affected to varying degrees by this warmer shift. This is why global and national temperatures are important since it shapes which will be felt locally. Places closer to the East Coast that have seen their averages climb to the mid to upper 30s over this period have definitely have felt warmer. It’s why this past winter felt so cold. This winter would have been closer to average in the old days. But relative to the post post 2014-2015 period it felt much colder even though many areas saw no record cold this past winter. It was great to see a return of the benchmark snowstorm tracks which had been absent for the past 3 seasons. The Detroit average 11 winter temperature through 2026 is 30.3°. The previous warmest 11 year stretch had been 28.9° ending in 1957. The earlier arrival of spring over this period resulted a 32.6° December through March average vs the previous highest 31.0° max in 2007. The biggest benefit of these warmer run of winters has been in the lake effect snow favored areas like Marquette. Warmer falls into winters boosted the Great Lakes temperatures and slowed the arrival of ice. So a great set up if you are a big lake effect snow fan.

The sensible weather in any given location is a function of the global temperatures which sets the range of options. It’s why the CONUS winters have shifted so much warmer after 2014-2015 compared to before. This is why your area in the Great Lakes hasn’t been able to experience a repeat of the 2013-2014 winter following the big global temperature jump in 2015-2016. Same for Central and Eastern PA not being able to experience a repeat of 1993-1994 benchmark for snow and record cold. Along with NYC Metro not seeing anything close to 1995-1996. It’s no coincidence that those two benchmark winters occurred before the first big temperature jump in 1997-1998. The climate state from 1997-1998 to 2014-2015 also produced benchmark winters for Boston in 2014-2015 and DC to Philly in 2009-2010 which haven’t been able to be replicated. Following the 2023-2024 temperature shift to warmer weather we experienced the #1 warmest winter and #2 warmest winter for the CONUS only two years ago apart. Even a relatively small temperature shift to warmer in the 1980s hasn’t allowed a top 10 coldest CONUS winter to happen again like we had in the 1970s. So every temperature jump has resulted in some aspect of the prior climate not being able to occur in the new warmer one. But we usually have to wait until after one of these jumps to start observing which elements of the earlier climate state haven’t been carried forward into the newer one.

We had a smaller temperature rise with the 80s into early 90s El Niño events since we were just coming out of the cooler climate prior to 1980. The first global first significant temperature jump occurred in 1997-1998. Then the next one in 2015-2016. Followed by 2023-2024. We didn’t find out what the CRCs were until after the events. So it’s going to take some time to know how all the details following this event also. https://www.nature.com/articles/s41467-025-66143-7 Climate regime shifts (CRSs), characterized by abrupt and persistent transitions between alternative stable states in the climate system, pose serious threats to ecosystems and human well-being. Understanding the potential drivers of CRSs is crucial, particularly in a warming world where CRSs are becoming more frequent. Here, using multiple observations and model simulations, we find that the likelihood of CRS occurrence significantly increases in the context of super El Niño events due to their remarkable climate perturbations. This higher probability is detected across various climate elements, such as surface air temperature, sea surface temperature, and surface soil moisture. In addition, we suggest that this boost effect of super El Niño events on CRSs will be greatly amplified under future greenhouse warming. Our findings underscore a deeper and more persistent climate footprint of super El Niño events, suggesting that early warnings and proactive measures are crucial for mitigating their escalating risks.

We will have to wait and see since we aren’t getting the extreme ridge over Canada like we had from May into June 2023 leading to the record air pollution in NYC from the Canadian wildfires. Notice how 2015 started off warmer in June than 2023 which set the pace for the whole summer. A much warmer winter has been a given with super El Niños like 1983, 1998, 2016, and 2024. But we did find a way to get a generally warmer summer in 2015 than 2023.

Looks like a gradual warming later in May following this coming cooler period. One thing to watch will be that we have a record +PMM now which is closer to the summer of 2015 El Niño than 2023 which didn’t have the strong +PMM. So it’s possible we get a warmer summer than 2023. But we would want to see how the transition from late May into early June verifies in order to know for sure. Stronger +PMM in summer of 2015 Weaker PMM in 2023 EPS forecast next 15 days

There was a recent paper released on this topic calling it the PCC. But we will probably need the data for this next event included to help develop the new idea. Remember, the climate models missed the sudden rise in temperatures in the spring of 2023. So it’s possible that the current climate modeling technology is developing too slowly to capture the faster changes that have been occurring. https://www.nature.com/articles/s41467-024-52731-6 Much recent work focused on whether equatorial Pacific cooling over past decades is driven by anthropogenic effects or arises from internally-generated climate variability, like the IPO. A definitive anthropogenic link to the recent trends would allow us to reliably predict a cooler tropical Pacific. As the tropical Pacific is known to be a climatic pacemaker, for (at least) the near-future this would mitigate global warming via ocean heat uptake and low-level cloud feedbacks. Instead, if the cyclic IPO dominates the recent cooling, we may expect a strong warming when it reverses. In support of the first possibility, we have identified an emerging climate change signal in the tropical Pacific across different observational datasets and we call it the PCC. The PCC has distinctive ocean-atmosphere dynamics that differ from those associated with the IPO. We further demonstrate that the recent trends during the satellite era, which have been the focus of significant attention, result from a combination of IPO and PCC. The emerging PCC SST trend pattern features a narrow band of cooling in the eastern equatorial Pacific and warming elsewhere. This SST change is linked to thermocline shoaling/SSH decreases in the central-to-eastern Pacific and dipole-like changes in zonal surface wind stress. In contrast, the recurrent IPO-driven SST trend pattern is characterized by a meridionally broader cooling in the eastern Pacific, zonal dipole-like thermocline/SSH changes and an overall strengthening of tropical Pacific zonal wind stress. We have shown that these distinct ocean circulation changes are a response to different wind stress patterns. These oceanic responses account for surface cooling in the eastern Pacific, with the thermocline shoaling playing a dominant role in the PCC cooling and enhanced zonal advective cooling mainly driving the IPO-related cooling. While basic geophysical fluid dynamics proved sufficient to attribute the observed oceanic changes to surface wind stress, we have not addressed the origins of the wind stress patterns associated with the PCC and the IPO. New research is needed to elucidate the wind changes, but our leading hypothesis is as follows. In response to GHG forcings39,40 temperature change in the upper troposphere are stronger than at the surface (Fig. S4), increasing atmospheric static stability. Consequently, the initial SST and surface wind response to rising GHGs might not be amplified as efficiently via Bjerknes feedback as is that for the internal modes on interannual to decadal timescales. Given the differences in thermocline and ocean current patterns associated with the PCC and the IPO, the coupled feedbacks related to ocean dynamics are also expected to differ, potentially contributing to distinct climate pattern formations for decadal variability and climate change. Additionally, climate variations outside of the tropical Pacific may influence the tropical Pacific trade winds26,27,41,42,43,44. Further, it has been argued that pronounced decadal-to-multidecadal SST variability in the Atlantic Ocean is also dominated by the response to the same external forcing that the tropical Pacific encounters45. Perhaps the co-occurrence of these long-term trends in different regions is not simply a direct response to rising GHGs but is influenced by inter-basin interactions. More work is needed to disentangle causal relationships among the long-term changes in different basins46,47. Throughout this paper we have taken for granted the widespread assumption that the IPO is an internal mode of the climate system. However, while we worked to distinguish between the recurrent IPO-related decadal variability and the emerging PCC signal, we are open to the possibility that these two may have become coupled together by anthropogenic forcing. They have much in common: shoaling of the thermocline in the east, enhanced upwelling somewhere in the central-to-eastern equatorial Pacific and an enhanced zonal SST gradient across the equatorial Pacific. It seems reasonable to postulate that if the response to radiative forcing is the emerging PCC pattern seen here, then it could initiate coupled ocean-atmosphere feedbacks that favor a negative IPO state that also has an enhanced SST gradient24. This might explain why the most recent IPO swing has been extreme and robust (Fig. S1b). If so, this suggests that in nature forcing is projecting onto natural modes of variability, while it is not clear whether climate models can reproduce this behavior. A new perspective on how internal variability interacts with the climate change signal will be needed in future studies.

The 365 day running mean never really went into La Niña in Nino 1+2 following the +2.1 ONI event in 2023-2024. Remember we were talking about the anomalous WWBs and warming there last winter during the La Niña which had the record +PNA for a La Niña which was more Nino-like. Seems like the unusual WWBs in EPAC during March 2023 with the rapid warming may be part of a different type of ENSO cycle than we have seen before. So this allowed only 3 years to go by before the El Niño emerged again on track for the shortest return period between two consecutive 2.1 or greater ONI events. We also had the record warming in early 2023 ahead of the usual El Niño lag which wasn’t present. I know most here are focused on next winter. But we don’t have any analogs for such big global temperature jumps only 3 years apart. It’s a big unknown how the details will unfold in regard to weather extremes. Since 2015-2016 happened 18 years after the last big rise in 1997-1998. The record increase in 2023-2024 was only an 8 year gap. Now we are talking only 3 years.