bluewave

End of August 2003. End of July 2019. The old heatwaves are being ridiculed when we're only in June! ➡️France has just experienced by far the hottest day ever measured since at least 1900, with an average national temperature around 30°C. ➡️With spectacular temperatures of 44 to 45°C across several French departments. ➡️131 absolute records broken. ➡️44 million people are overwhelmed by a red "heatwave" alert. ➡️Tomorrow, with the wind dying down, a "foehn wind" episode or so-called "flash drought" is expected in the Centre-West region, with a fire risk index at "extreme" to "very extreme." We've just rewritten history. Before tomorrow, when it could get even hotter.

The LI crew would really be complaining if this was a snowstorm.

The Euro forecast chart may show what was discussed in that post more clearly.

Models begin to build 90° heat to our west as we move into early July. Some models hold onto low pressure just to the east of New England. So they are currently split on whether the 90s make it here or stay to our south.

Strongest Southern Hemisphere +AAO since May 2023 as their winter gets underway. The SAM index reached a strongly positive value of +4.23 on June 21, which is a three-year high. That means that mean sea level pressure is currently trending higher than normal near Australia's latitudes, and the westerly wind belt that flows between Australia and Antarctica is located further south than usual for this time of year. This has been evident in the sort of weather we’ve seen lately across southeastern Australia, with fewer cold fronts, frequent blocking high pressure systems, and unseasonably warm temperatures. The last time the SAM index reached 4 (or higher) was in May 2023, when it peaked at 5.5. The values in the index are a measure of standard deviation from the norm in terms of mean sea level pressure. In very basic terms, it means we’ve seen a lot more highs than lows.

The extensive ridge driving the warm pool from east of Japan to the north of Hawaii is more of a 2nd EOF -PDO type pattern. This is why most of the analog dates for early July are established or developing La Niña years. You would want to see a deep trough set up from Japan to north of Hawaii heading into next winter to turn the PDO more positive.

May 2026 was a little cooler than May 2023 around Japan. But much warmer than 2015 and 1997. This relationship is reflected in the PDO values for the month of May. Plus the area off the Baja was much warmer than 2023. https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/v6/index/ersst.v6.pdo.dat May 2026 PDO -1.60 May 2023 PDO -2.46 May 2015 PDO +0.40 and +1.65 by July May 1997 PDO +1.29 and +2.35 by June Traditional strong +PDO pattern

When the warm pool extends from Japan to California it allows the PDO to move closer to neutral. The key to watch going forward will it be able to get positive and hold it. Recent years the daily PDO values have rebounded back closer to neutral but couldn’t get into sustained positive territory. When the PMM was this strong going into the summer of 2015, the PDO was at +1.65. July 2015 +1.65 PDO vs May 2026 -PDO at -1.60 https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/v6/index/ersst.v6.pdo.dat

While these very long range forecasts aren’t the strong suit of these seasonal models, the subsurface cold pool is near the Dateline by next March looks weaker than 1998. The warmth in the east looks similar to March 1998. But Nino 3.4 is also much warmer than 1998.

A little later than the developing super El Niños in 2023, 2015, and 1997. Those years all had record amplitudes in MJO 7-2 during March. AMJ 2023 and 1997 were also focused in these phases also

At least the record cold was extensive enough that month for the entire CONUS to average a little below the long term February average. https://www.ncei.noaa.gov/access/monitoring/monthly-report/national/201502 The February contiguous U.S. temperature was 33.1°F, 0.7°F below the 20th century average, ranking near the median value in the 121-year period of record. The average February maximum (daytime) temperature for the contiguous U.S. was 44.6°F, 0.2°F below average, while the average minimum (nighttime) temperature was 21.7°F, 1.2°F below average.

Good to finally see the first daily rainfall over 1.20 in NYC since 4-25. Data for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 2026-06-23 M 2026-06-22 1.24 2026-06-21 0.00 2026-06-20 0.00 2026-06-19 0.00 2026-06-18 T 2026-06-17 T 2026-06-16 0.00 2026-06-15 0.02 2026-06-14 0.25 2026-06-13 0.00 2026-06-12 0.90 2026-06-11 0.21 2026-06-10 T 2026-06-09 0.00 2026-06-08 0.00 2026-06-07 0.04 2026-06-06 0.26 2026-06-05 0.00 2026-06-04 0.00 2026-06-03 0.00 2026-06-02 0.00 2026-06-01 T 2026-05-31 0.00 2026-05-30 T 2026-05-29 0.00 2026-05-28 0.00 2026-05-27 T 2026-05-26 0.00 2026-05-25 0.18 2026-05-24 1.10 2026-05-23 0.75 2026-05-22 0.00 2026-05-21 0.15 2026-05-20 0.09 2026-05-19 0.00 2026-05-18 0.00 2026-05-17 0.00 2026-05-16 0.00 2026-05-15 0.00 2026-05-14 0.01 2026-05-13 0.01 2026-05-12 0.00 2026-05-11 0.00 2026-05-10 0.01 2026-05-09 0.24 2026-05-08 0.01 2026-05-07 0.16 2026-05-06 0.32 2026-05-05 0.00 2026-05-04 0.00 2026-05-03 0.00 2026-05-02 0.02 2026-05-01 T 2026-04-30 0.16 2026-04-29 0.20 2026-04-28 0.00 2026-04-27 0.00 2026-04-26 0.03 2026-04-25 1.36 2026-04-24 0.00

Yeah, these seasonal models are more or less just defaulting to ENSO correlations depending on the state ENSO is in at the time. So they really aren’t forecasts in the traditional sense. This is why none of the seasonal forecasts issued relying on them came close to the magnitude of the warmth experienced since December 2015. The common denominator to all the forecasts is that the ridge was magnitudes stronger than the original forecasts and the trough areas were generally weaker. None of these records were forecast beyond a week or two before they actually occurred. These extremes used to be very rare before December 2015 during months like March 2012 or January 2006. This is not getting very much attention since we have tended to normalize all the warmth. Plus record warmth during the winter doesn’t generate as much attention as the periods of extreme cold which have become few and far between. The last -10 month in the Northeast during February 2015 got much more attention than most of the +10 months since then have. I chalk this up to human nature which was conditioned to fear cold from thousands of years back to the ice ages which made survival so difficult. This is why so much of the population has moved to the sun belt areas. Back in the 1970s when -10 months were much more common, all the talk was about an impending return of another ice age. So imagine how much attention the 17 months below would be getting if they were all -10s instead of +10s. The super El Niño in 2015-2016 had 2 months go 10+ from December to March with 2023-2024 also having 2 months reach this mark. None of those months like the others were forecast from the long range seasonal guidance. It would be very challenging for any seasonal forecast to pick out the specific month and geographic location this coming 2026-2027 super El Niño that would potentially experience one of these extremes. Forecasters just don’t feel comfortable including +10s to their seasonal forecast maps. We seldom see much beyond a +1 to +3 area and sometimes up to +5. DEC…2015….NYC….+13.3 MAR…2016…MOT….+10.5 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5 DEC….2024…..LND…..+11.3 DEC….2025….CPR…..+12.1 JAN….2026….RIW……+10.2 FEB…..2026….LND…..+11.3 MAR….2026….PHX…..+12.5

The warm pool to the east of Japan began developing during the mid to late 2010s. It’s the first time the ocean there down to the subsurface has warmed this much in the modern monitoring era. It’s appears to be due to the record 500 mb heights leading to light winds and clear skies allow the ocean below to warm. When we had the colder pool in the EPAC in recent years it lead to the record low -PDOs. In the old days the -PDOs were driven by mostly the cooler SSTs in the EPAC rather than the warm anomalies from Japan to south of the Aleutians. Most researchers avoid the term permanent and use persistent or new as a description. What would need to have happen to reverse this pattern would be for low pressure and strong winds to persist in this location with more clouds. If this could be sustained for more than a few months, then there would be a shot at cooling the surface and subsurface. As long as the warm pool persisted off of California, then the PDO could transition to a more strongly positive level like we last saw back in 2015. Current model forecasts have this warm pool east of Japan persisting through December at the same time there is a warm pool off of California. So this effectively brings the PDO closer to neutral with overlapping warm pools from the West and East. Since these models aren’t the greatest for reliably beyond 8-15 days, we are just going to have to wait and see what the details will be. Plus they have missed the summer -PDO declines recent summers as the ridge to the East of Japan has verified much stronger than seasonal model forecasts. It appears that the subsurface reservoir of record warmth reaching to the surface has resulted in a feedback process between the ocean and atmosphere sustaining the pattern. While it’s still very early in the El Niño process, the big increase in WWBs near and off the equator so far hasn’t had the stronger winds and lower pressures to the East of Japan and to the south of the Aleutians like the developing super El Niño 1997 had during the spring. We would want to see the westerlies increase to the east of Japan and south of the Aleutians especially by next winter to have a chance to begin to get the PDO into more of a positive state.

It’s a favorable pressure pattern for sea ice retention with the deep low north of Alaska. We have been seeing this weak dipole pattern much of the time since 2013. Pretty much the opposite of the strong dipole pattern which was in place from 2007-2012 which lead to the multiple records. But the post below shows that the Euro has a cold bias on the DMI chart below. Still a colder pattern but nothing as cold as the Euro shows.