bluewave

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.

Looks like that deep low dropping SSE from Canada will produce some strong wind gusts here tomorrow especially eastern sections.

I think the cooler February reference was in regard to long ranger seasonal models like the CanSIPS and EPS monthly which had the cooler stock February El Niño composite for the Mid-Atlantic.

A top 10 warmest spring for many and some areas also top 10 driest.

Shifting back to the over the top warming pattern with temperatures approaching 100° in Montana and cooler to the south.

Yeah, a super El Niño can actually be warmer than expected when overlapping with Niña-like influences. First, the westward lean to the forcing back to MJO 7 probably helped drop the Nino-ridge further south than is typical for El Niño in February. Then the big ridge east of Japan and the strong +WPO along with the EPAC Nino forcing carved out a trough just off the West Coast leading to the -PDO. So the Nino trough typically in the Mid-Atlantic was suppressed out toward Bermuda. Also note the Aleutian Low splitting with a piece over the Bering and just off the West Coast. The one bright spot that month was the record STJ streak near DC and narrow snow band into Central NJ. But it was too narrowly focused to extend much beyond the localized geographic region.

Stations in NJ will finish spring near first place for the most 90 days. Time Series Summary for HARRISON, NJ - Mar through May 90° Days Click column heading to sort ascending, click again to sort descending. 1 2026 7 5 2 2018 6 0 3 2001 5 2 4 2021 4 0 - 2016 4 0 - 2010 4 10 - 2004 4 2 - 2002 4 3 5 2022 3 0 - 2017 3 0 - 2009 3 13 - 2006 3 1 - 2000 3 4 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. 1 1991 8 0 2 2026 6 5 - 1986 6 0 3 2002 5 0 - 1959 5 0 - 1896 5 0 4 2022 4 0 - 2021 4 0 - 2018 4 0 - 2000 4 0 - 1987 4 0 - 1977 4 0 - 1965 4 0 - 1939 4 0 Time Series Summary for NEW BRUNSWICK 3 SE, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. 1 2026 6 5 2 2016 4 0 - 2010 4 0 - 1976 4 0 3 2021 3 0 - 2017 3 0 - 2012 3 0 - 2009 3 0 - 2002 3 0 - 2001 3 1 - 2000 3 0 Time Series Summary for SOMERSET AIRPORT, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. 1 2026 5 5 2 2021 4 1 3 2022 3 0 - 2017 3 0 - 2012 3 0 - 2009 3 0 - 2002 3 0 - 2000 3 2 Time Series Summary for SUSSEX AIRPORT, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. 1 2026 3 6 - 2022 3 4 2 2023 2 0 - 2018 2 0 - 2013 2 5 - 2009 2 1 - 2002 2 0

Yeah, the PDO was able to be positive during the 1995-1996 weak La Niña winter. This weak La Niña winter had the ridges and troughs in the same general locations. But notice how the ridges this winter were so much stronger leading to the much warmer CONUS and less snowy outcome than 1995-1996. We can see the ridge extension to the east of a Japan during DJF preventing the PDO from going positive. Plus the more volatile NAO these days didn’t allow the -NAO to persist into the spring like we had back in 1995-1996. So March turned out to be a reversion to the warmer and less snowy 2020s mean.

Main issue has been the 500mb ridge east of Japan warming the SSTs below. So even though we have sufficient warming in the EPAC with the record +PMM, the warm pool under the ridge east of a Japan brings down the PDO. Long range models like the CFS have struggled with this ridge in their forecasts. So like we saw last summer, the actual readings verified significantly lower. FWIW, the CFS continues with the -PDO at least into early next winter due to the warm pool and ridging east of Japan persisting.

3rd spring in a row with the coolest high temperature departure occurring in May. Several spots have had a top 10 warmest spring so far. Very impressive temperature swings both earlier and later in the spring over short periods.

To the extent that we don’t typically see all 3 Memorial Day extended weekend days with measurable rain. The last time for NYC was back in 2021. Plus this weekend will rank very high on the rainiest Memorial Day weekends list.