bluewave

The EPS weeklies actually did a decent job beginning in late October into November seeing the general 500mb pattern. But the Western ridge verified much stronger skewing the total CONUS significantly warmer. This allowed our area to beat the guidance to the colder side for a change. The first colder winter with above average snowfall in 11 years for our region made it really stand out against the sea of warmth since 2015-2016.

CanSIPS was too cold overall across the CONUS during the 2025-2026 winter. It verified as the 2nd warmest winter on record across the CONUS. To be fair none of the models correctly forecast how warm and expansive the Western ridge would become. This allowed the East to turn out colder for a change than the seasonal models such as the CanSIPS were forecasting. But the magnitude and geographic coverage of the cold was limited compared to the expansive and record breaking nature of the warmth.

The last two years have been very dry across much of the CONUS. It will be interesting to see how things go with the developing super El Niño. The current pattern has been alternating between surges of Niña-like warmth and cooler El Niño-like intervals from the spring into early summer so far. But we have still been averaging out warmer than is typical this time of year for such a strong developing El Niño. So not sure if the precipitation will fully shift into a more Nino-like wet pattern or we still hold onto some reflection this Niña-like drought pattern. Ridges have been significantly stronger than usual across much of North America in recent years. So the more expansive high pressure has tended to really dry things out.

The long range forecasts from the CanSIPS have a strong cold bias. Notice how the model had a cold spring especially in the Great Lakes and Northeast from the older forecasts. Didn’t really begin to catch on until the March 1st update. But even then it was too cold. Verification 2nd warmest spring on record for the CONUS Climatologist49 ‪@climatologist49.bsky.social‬ Follow Spring (Mar-May) temperature departure from the 1991-2020 normal. Seems warm. ‪Climatologist49‬ ‪@climatologist49.bsky.social‬ · 20h Spring 2026 was the 2nd warmest on record for the Contiguous U.S. (2012). A majority of locations had a top 5 warmest spring compared to all springs since 1895 and many places had their warmest. Only a small area of the northern Plains had a cool spring compared to the full period-of-record. 2:07 PM · Jun 1, 2026 Everybody

NYC hasn’t had a month with above normal precipitation since May 2025. So the last 12 months actually made the top 20 driest for June to May. This is impressive given the overall wetter pattern since 2003. Time Series Summary for NY CITY CENTRAL PARK, NY Driest 6-1 through 5-31 Click column heading to sort ascending, click again to sort descending. 1 1966-05-31 27.85 0 2 1950-05-31 30.86 0 3 1965-05-31 30.93 0 4 1930-05-31 31.46 0 5 1954-05-31 32.13 0 6 1911-05-31 32.59 0 7 1959-05-31 32.63 0 8 2002-05-31 32.73 0 9 1882-05-31 33.45 0 10 1962-05-31 34.16 0 11 1877-05-31 34.24 0 12 1957-05-31 34.82 0 13 1963-05-31 35.08 0 - 1887-05-31 35.08 0 14 1955-05-31 35.17 0 15 1925-05-31 35.28 0 16 2026-05-31 35.44 0 17 1981-05-31 35.58 0 18 1907-05-31 36.03 0 19 1932-05-31 36.06 0 20 1892-05-31 36.23 0

We have a record 30C warm pool from the IO over to Nino 4. So the Nino forcing is linking up with forcing near the Maritime Continent. This is part of the reason that the models have the warmth in Canada and across the Northern Tier states as we head into June.

Probably a function of the more Niña-like -PDO with the WPAC warm pool. Plus the ongoing drought. So another case of the 500mb ridges becoming stronger more expansive during the 2020s than we have typically seen in the past.

Back to 90s by later this week at the usual warm spots as the below average rainfall and drought continues.

The Nina-like WPAC warm pool forcing in DJF 2015-2016 and 2023-2024 did enhance the warmth in the Northeast those winters above the typical super El Niño winters like 1997-1998 and 1982-1983. While the PDO was positive in 2015-2016, we got the record MJO 5 in December adding to the historic +13 warmth. 2023-2024 had both a -PDO and strong MJO 4-7 activity. So both winters featured record Niña-like MJO activity for super El Niños. But even without the Niña influence in 1997-1998, that winter was still very warm. Plus the winters have warmed since 1997-1998. So perhaps that winter would be just as warm today as 2015-2016 and 2023-2024 was even without the La Niña influence. Since the stronger Southeast trough in 1997-1998 was all Pacific air with the record east based super El Niño. Top 15 warmest winters in NYC Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 2001-2002 41.5 0 2 2022-2023 41.0 0 2015-2016 41.0 Super El Niño Nina Influence 3 2023-2024 40.6 Super El Niño Nina influence 4 2011-2012 40.5 0 5 1931-1932 40.1 0 6 1997-1998 39.6 Super El Niño No Niña influence 7 2016-2017 39.3 0 8 2019-2020 39.2 0 9 1990-1991 39.1 0 10 1998-1999 38.6 0 11 1948-1949 38.5 0 12 1889-1890 38.4 0 13 1952-1953 38.1 0 14 1982-1983 37.9 Super El Niño No Niña influence - 1936-1937 37.9 0 15 1996-1997 37.8 0 - 1932-1933 37.8 0

First time since 1988 here around HVN that the strongest May wind gusts occurred so late in the month. So an unusually strong late May storm system. Very impressive omega block for this time of year.

I think that it could also go beyond the RONI in that the 500 mb ridges are expanding in the mid-latitudes outside the tropical oceans which RONI measures. The 500 mb ridge across the North Pacific from east of Japan to south of the Aleutians has been unprecedented during the 2020s. Also note the slightly weaker mirroring of the pattern in the South Pacific to the east of New Zealand. So it’s been warming the SSTs underneath the ridge causing the -PDO to remain negative. In the old days ,the -PDO was more a function of colder SSTs off of California rather than the extensive warm pool from east of Japan to south of the Aleutians that we have today.

Yeah, we can see the overlapping influences between the El Niño, MJO, and -PDO heading into early June. The ridging showing up south of Alaska into Western Canada is the correlation with the El Nino and +AAM. The extension of the ridge further east across much of the CONUS is more -PDO and MJO 8-1 related for this time of year. So effectively a 500 mb composite in early June that reflects these influences. A coupled El Niño will vary in its sensible weather related to the other influences. Also the pattern in recent years of the 500 mb ridges becoming stronger and more expansive with weaker troughs during any given ENSO state.

Nice way to end the ski season up there.

My guess is that the recent drop was enhanced by the +EPO -PNA pattern in May.

Starting to see the seasonal -PDO drop heading into summer which has been common during the the 2020s.