bluewave

Yeah, the MJO 4-7 pattern has been dominant regardless of El Niño or La Niña since the December 2015 historic +13 departure in the Northeast and record MJO 4-7 amplitude for an El Niño. Every winter since then has been warmer to record warm. But we have still had a few MJO 8 opportunities along the way. January 16 was one which lead to the record late January snowstorm and brief subzero readings on Valentine’s Day around NYC. It was still one of our warmest winters on record due to the ridiculous warm start to the season in December. Our next MJO 8 was in February 17. While it delivered a nice blizzard around NYC Metro in February, it was also one of our warmest winters. The 17-18 winter started showing promise with the Arctic cold and the MJO 8 after Christmas and 950 mb Benchmark blizzard in early January. Then the pattern rapidly turned warmer in mid-January as the near record MJO 4-7 emerged. Record warmth in February followed with 80° warmth around NYC Metro. So the backloaded warmth pushed the winter into the warm column. The strat warm blocking and MJO 8 influence occurred too late into March so the winter finished warm again. The 20-21 winter had just enough warmer MJO activity for the winter to finish above normal. But the amplitude was muted just enough for a really nice snowfall outcome for many especially just inland from the immediate coast. While the 21-22 winter started with more December record +13 warmth this time around DFW with a very amplified MJO 5-7, we saw nice improvement during January with the coldest month for NYC in years near 30°. Very nice snows especially east of NYC to go with the MJO 8. But the winter still averaged warmer than normal. Then more MJO 4-7 issues in 22-23 and 23-24 with two completely different ENSO states and continuing record WPAC warm pool. The Pacific was so hostile in December 22, that it completely overpowered our 2nd lowest December -AO on record. Just when we thought the winters couldn’t get any warmer than 22-23, we finished again with one of our warmest winters in 23-24 with very strong MJO 4-7 forcing for such a strong El Niño. This made it an unprecedented 9 warm to record warm winters in a row for the Northeast. Looking forward to next winter, it appears like La Niña and -PDO will be in the menu yet again. I guess the one hope is we can put together some intervals closer to what we saw in the 20-21 and January 22. And not a repeat of the 22-23 La Niña. But this would require some MJO improvement like we got in 20-21 and January 22.

The interesting part is that we only had that extended pattern during the cold seasons in 13-14 and 14-15. It was associated with very strong blocking over the NE PAC domain. But the paper doesn’t mention the fact that this pattern has shifted to the warm seasons since then and has been largely absent during the winters. Notice how the models are building the ridge over the Western US during the start of June right on cue. Record Western warm season heat and drought have been a dominant feature in recent years. A prime example of this was the historic NE PAC blocking and heatwave in the Pacific Northwest during the summer of 2021.

The warm departure this month is mostly a function of the warmer minimums rather than the maximums. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of May Click column heading to sort ascending, click again to sort descending. Rank Year Mean Min Temperature Missing Count 1 2012 58.4 0 2 1991 58.3 0 3 2018 57.6 0 - 1985 57.6 0 4 2024 57.4 3 - 2011 57.4 0 5 2022 57.3 0 - 2015 57.3 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Month of May Click column heading to sort ascending, click again to sort descending. Rank Year Mean Max Temperature Missing Count 1 1991 79.5 0 2 2015 79.2 0 3 1965 77.8 0 4 1986 77.5 0 5 1993 77.2 0 6 1985 76.5 0 - 1944 76.5 0 7 2010 76.4 0 8 2018 76.2 0 - 1959 76.2 0 9 1977 76.1 0 - 1964 76.1 0 10 2004 76.0 0 11 2007 75.7 0 12 1980 75.4 0 - 1955 75.4 0 13 2022 75.2 0 - 1936 75.2 0 14 2024 74.9 3 - 1994 74.9 0 - 1941 74.9 0

I an not in the permanent camp yet. But I think next 5 years will give us enough data to make that call one way or the other. A large portion of the Eastern US has had an unprecedented 9 warmer to record warm winters in a row. If this doesn’t change by 2030, then I think we would have to entertain the idea of some type of shift to a new regime. So I will just take it one year at a time to see if there are any deviations from this pattern.

It actually seemed to work the opposite way in 2015. That year featured 462 ACE points in the WPAC for the 4th most active typhoon season on record. This was followed by the record WPAC warm pool for a super El Niño in 15-16 and historic December +13 and record MJO 4-6 for such a strong El Niño. So the WPAC has had no difficulty recharging its heat content. We even saw this in recent years with how rapidly the warm pool near Indonesia rebounded following the fall +IOD patterns. At this point I am not even sure what it would take to cool that region for more than a few months at a time. Accumulated cyclone energy - Pacific typhoon hide Season ACE TS TY STY Classification 1997 570.4 29 23 11 Extremely active 2004 480.6 31 20 6 Extremely active 1992 470.1 31 21 4 Extremely active 2015 462.9 26 20 9 Extremely active

Only the 4th time that Newark hasn’t gone over 90° in the spring since 2010. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 1 2022 98 0 2 2021 96 0 - 2016 96 0 3 2010 95 0 4 2018 94 0 - 2017 94 0 - 2013 94 0 5 2023 93 0 6 2012 92 0 - 2011 92 0 7 2015 91 0 8 2024 90 3 - 2019 90 0 9 2014 88 0 10 2020 86 0

The Rockies ridge is becoming more common in the summer than winter these days.

Very comfortable ending to spring with lows dipping into the 40s for the interior sections this week.

This was the 8th wettest Memorial Day on record for NYC. #1….2.49…1948 #2….1.90….1908 #3….1.65….2016 #4….1.28….2003 #5….1.15…..1984 #6…..1.11…..1983 #7……1.03….1912 #8…..0.96…2024

Yeah, it’s the highest Euro ACE forecast from the spring.

Where was this pattern last winter?

Some localized 2”+ amounts possible tomorrow to the north and west of NYC on the SPC HREF mean. The max is more robust. But it’s always uncertain if we can reach the max totals. So sometimes we end up with amounts in between.

This could be the first spring that one of our stations like Newark recorded at least a trace of rain on every spring weekend. Newark May 25-25…..T May 18-19…..0.04 May 11-12…0.38 May 4-5…..0.31 Apr 27-28…0.11 Apr 20-21…0.05 Apr 13-14…0.04 Apr 6-7…….T Mar 30-31…0.01 Mar 23-24….3.10 Mar 16-17…..T Mar 9-10….1.46 Mar 2-3…..1.31

A recent study confirms that a fundamental shift occurred with the Arctic sea ice around the 2007 season. The Arctic lost so much older ice that it makes it harder to set new extent records. This is why the 2012 low extent record has been so difficult to beat. While the 2020 season came close, it came up short of the 2012 record. This is also why no season since 2007 has been able to see a recovery to pre-2007 extents and thickness. Most seasons since then finished in the 4 to 5 million sq km range for extent since extents change more slowly with younger ice dominating the Arctic instead of older. https://www.nature.com/articles/s41586-022-05686-x Manifestations of climate change are often shown as gradual changes in physical or biogeochemical properties1. Components of the climate system, however, can show stepwise shifts from one regime to another, as a nonlinear response of the system to a changing forcing2. Here we show that the Arctic sea ice regime shifted in 2007 from thicker and deformed to thinner and more uniform ice cover. Continuous sea ice monitoring in the Fram Strait over the last three decades revealed the shift. After the shift, the fraction of thick and deformed ice dropped by half and has not recovered to date. The timing of the shift was preceded by a two-step reduction in residence time of sea ice in the Arctic Basin, initiated first in 2005 and followed by 2007. We demonstrate that a simple model describing the stochastic process of dynamic sea ice thickening explains the observed ice thickness changes as a result of the reduced residence time. Our study highlights the long-lasting impact of climate change on the Arctic sea ice through reduced residence time and its connection to the coupled ocean–sea ice processes in the adjacent marginal seas and shelves of the Arctic Ocean. Our analysis demonstrates the long-lasting impact of climate change on Arctic sea ice through reduced residence time, suggesting an irreversible response of Arctic sea ice thickness connected to an increase of ocean heat content in areas of ice formation. The large reduction of summer ice extent in the Alaskan and Siberian sectors in 2005 and 2007 triggered intensive ice–albedo feedback42,45 and initiated the perennial increase of ocean heat content in these areas44. This resulted in the stepwise reduction of residence time of sea ice in the Siberian sector of the Arctic, and hence a nonlinear response of the system. https://www.jpl.nasa.gov/news/with-thick-ice-gone-arctic-sea-ice-changes-more-slowly The Arctic Ocean's sea ice blanket has already lost most of its old ice and two-thirds of its thickness. The younger ice is thinning more slowly and variably. The Arctic Ocean's blanket of sea ice has changed since 1958 from predominantly older, thicker ice to mostly younger, thinner ice, according to new research published by NASA scientist Ron Kwok of the Jet Propulsion Laboratory, Pasadena, California. With so little thick, old ice left, the rate of decrease in ice thickness has slowed. New ice grows faster but is more vulnerable to weather and wind, so ice thickness is now more variable, rather than dominated by the effect of global warming. Working from a combination of satellite records and declassified submarine sonar data, NASA scientists have constructed a 60-year record of Arctic sea ice thickness. Right now, Arctic sea ice is the youngest and thinnest its been since we started keeping records. More than 70 percent of Arctic sea ice is now seasonal, which means it grows in the winter and melts in the summer, but doesn't last from year to year. This seasonal ice melts faster and breaks up easier, making it much more susceptible to wind and atmospheric conditions. Kwok's research, published today in the journal Environmental Research Letters, combined decades of declassified U.S. Navy submarine measurements with more recent data from four satellites to create the 60-year record of changes in Arctic sea ice thickness. He found that since 1958, Arctic ice cover has lost about two-thirds of its thickness, as averaged across the Arctic at the end of summer. Older ice has shrunk in area by almost 800,000 square miles (more than 2 million square kilometers). Today, 70 percent of the ice cover consists of ice that forms and melts within a single year, which scientists call seasonal ice. Sea ice of any age is frozen ocean water. However, as sea ice survives through several melt seasons, its characteristics change. Multiyear ice is thicker, stronger and rougher than seasonal ice. It is much less salty than seasonal ice; Arctic explorers used it as drinking water. Satellite sensors observe enough of these differences that scientists can use spaceborne data to distinguish between the two types of ice. Thinner, weaker seasonal ice is innately more vulnerable to weather than thick, multiyear ice. It can be pushed around more easily by wind, as happened in the summer of 2013. During that time, prevailing winds piled up the ice cover against coastlines, which made the ice cover thicker for months. The ice's vulnerability may also be demonstrated by the increased variation in Arctic sea ice thickness and extent from year to year over the last decade. In the past, sea ice rarely melted in the Arctic Ocean. Each year, some multiyear ice flowed out of the ocean into the East Greenland Sea and melted there, and some ice grew thick enough to survive the melt season and become multiyear ice. As air temperatures in the polar regions have warmed in recent decades, however, large amounts of multiyear ice now melt within the Arctic Ocean itself. Far less seasonal ice now thickens enough over the winter to survive the summer. As a result, not only is there less ice overall, but the proportions of multiyear ice to seasonal ice have also changed in favor of the young ice. Seasonal ice now grows to a depth of about six feet (two meters) in winter, and most of it melts in summer. That basic pattern is likely to continue, Kwok said. "The thickness and coverage in the Arctic are now dominated by the growth, melting and deformation of seasonal ice." The increase in seasonal ice also means record-breaking changes in ice cover such as those of the 1990s and 2000s are likely to be less common, Kwok noted. In fact, there has not been a new record sea ice minimum since 2012, despite years of warm weather in the Arctic. "We've lost so much of the thick ice that changes in thickness are going to be slower due to the different behavior of this ice type," Kwok said. Kwok used data from U.S. Navy submarine sonars from 1958 to 2000; satellite altimeters on NASA's ICESat and the European CryoSat-2, which span from 2003 to 2018; and scatterometer measurements from NASA's QuikSCAT and the European ASCAT from 1999 to 2017.

Would be a great winter KU pattern with +PNA -AO blocking.

Yeah, the warmer minimums are driving the departures again with the onshore flow keeping the high departures smaller than the lows. EWR Max…+2.1 Min….+3.3 LGA Max….-0.1 Min….+1.4

Models have scattered showers tonight or early Sunday. So we have a shot at having at least a trace of rain on every weekend this spring. I wonder if this has happened before? Newark May 18-19…..0.04 May 11-12…0.38 May 4-5…..0.31 Apr 27-28…0.11 Apr 20-21…0.05 Apr 13-14…0.04 Apr 6-7…….T Mar 30-31…0.01 Mar 23-24….3.10 Mar 16-17…..T Mar 9-10….1.46 Mar 2-3…..1.31

This May is a little warmer so far at +1.0 in NYC vs -0.5 last year.

The SST pattern in the North Atlantic began to shift around May 2023 from a record warm pool east of New England to a colder one. It has been associated this spring with all these backdoor cold fronts and low pressure east of New England. Unfortunately, models just aren’t very good beyond 10-15 days to know how much longer this pattern will persist. I am still not sure if this represents a shift to a newer SST and 500mb pattern or it’s just temporary blip associated with the strong Canadian blocking pattern which emerged last May. Plus trying to figure out seasonal hurricane track forecasts beyond 2 weeks out can be low skill. We usually have to wait for the tropics to become active and see what the 500mb steering forecasts look like. Beyond this hurricane season, it will be interesting to see if we can eventually get another cold winter month here. Some blocking and more of a trough to our east could get it done. Our last cold winter month was way back in January 2022.

Newark only made it to 90° this spring which is the 3rd coolest since the warmer pattern began back in 2010. While the planet is setting records for SSTs daily, we are one of the few places with a cold pool nearby. So it goes to show how strong that easterly flow has been. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. Rank Year Highest Max Temperature Missing Count 2020 86 0 2014 88 0 2024 90 8 2019 90 0 2015 91 0 2012 92 0 2011 92 0 2023 93 0 2018 94 0 2017 94 0 2013 94 0 2010 95 0 2021 96 0 2016 96 0 2022 98 0

Tough to keep track of all these rainfall records in recent years. https://x.com/tararosenblum/status/1793651432765186428

While we are averaging above normal, the high end temps here this spring have been muted. Places like Newark will finish spring near the low end of the 90° day count. Plenty of rainfall and convection like this morning along with enhanced onshore flow. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Mar through May Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 90 Missing Count 1 1991 8 0 2 1986 6 0 3 2002 5 0 - 1959 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 - 1936 4 0 5 2023 3 0 - 2017 3 0 - 2016 3 0 - 2010 3 0 - 2009 3 0 - 2001 3 0 - 1999 3 0 - 1996 3 0 - 1993 3 0 - 1992 3 0 - 1985 3 0 - 1974 3 0 - 1964 3 0 - 1962 3 0 - 1934 3 0 - 1931 3 0 6 2015 2 0 - 2013 2 0 - 2012 2 0 - 2007 2 0 - 2004 2 0 - 1998 2 0 - 1994 2 0 - 1990 2 0 - 1979 2 0 - 1976 2 0 - 1970 2 0 - 1957 2 0 - 1956 2 0 - 1949 2 0 - 1944 2 0 - 1943 2 0 - 1942 2 0 - 1941 2 0 7 2024 1 9

Nice Canadian airmass for the cooler weather fans by this time next week. So we still haven’t reached the point of extended heat yet. It’s been a challenge with all the onshore flow and clouds along with the rain.

The HRRR has convection with a MCV.

Yeah, it was my warmest day of the spring so far at 82° here just east of KHVN.