bluewave

We have been leaning more on RONI in recent years reflecting the much warmer global oceanic state. Plus record WPAC warm pool north of the tropics has lead to the record low -PDO enhancing the La Niña background state. So the 2020s have been serving up a new type of La Niña background where it has been more defined by the WPAC warm pool than how cool the Nino 3.4 SSTs have been. It’s also interesting that the weaker RONI winters have been warmer in the multiyear La Ninas groups since 2010. 22-23 featured only a -0.83 weaker RONI and it was the warmest winter of the 3 year group. 16-17 had a weaker positive-0.73 RONI and it was the warmest winter of that two year event. Same for the 11-12 weaker RONI of -0.82 coming in as a warmer winter than 10-11 was. Multiyear La Ninas and DJF RONI https://www.cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt 25-26…….? 24-25….-1.12 22-23…..-0.83 21-22……-1.21 20-21…...-1.17 17-18……..-1.10 16-17……..-0.73 11-12…..-0.82 10-11……-1.42

Yeah, that is my early guess based on past multiyear La Ninas since the late 90s. There is usually one year with a strong +PNA December mismatch. The other surrounding Decembers had either a weaker positive or a negative PNA. So I will go lower on the PNA for December 2025 than the +1.70 we had in December 2024. But not sure yet whether it’s just a weaker positive or the PNA dips negative. Multiyear La Ninas and December PNA 2025…….? 2024….+1.70 2022….-0.66 2021….-2.56 2020…+1.58 2017…..+0.89 2016….-0.35 2011….+0.36 2010….-1.78 2008….-1.41 2007…..+0.14 2000…..+1.23 1999…..+0.21 1998…..-0.09

The Northeast finally got the drought update due to the lack of rainfall this summer.

There has been a new relationship between the -PDO and PNA especially during the 2020s summers. This was our first July streak of 5 consecutive -2 to -4 -PDOs. There has been a very strong +PNA signal leading to the record wildfires, record heat, and drought up in Canada. Past instances of -2 -PDOs in July were more -PNA. My guess is that this is related to the -PDO being more driven by the warmer SST anomalies than the colder ones which used to dominate -PDOs in the past. Recent July -2 to -4 -PDOs have been more +PNA Older -PDO below -2 in July were more -PNA

Yeah, remarkable subsurface warmth well beyond anything that we have seen before. So these record low -PDO values are just scratching the surface. We saw how quickly the SSTs rebounded after last winter. So this new dynamic helps this pattern to really persist.

Well June 20th through July 31st was top 3 warmest for many locations. Since that covers the typical peak heating period of the year, then by extension this will be remembered as an impressively warm summer. Especially with the record high dew points adding to the heat. The 10-11 winter didn’t have any memorable cold and snow before Christmas and after February 2nd. But record 60” snows in spots from 12-26 to 1-27 made it one of our snowiest winters. Even though the snowy period didn’t last that long.

The upper ridge in late June was able to build into the Great Lakes and Ohio Valley. This allowed the Bermuda high at the surface to expand back west through the Apps. So it created westerly flow to the coast. This current event had the upper ridge east of New England. So the Bermuda high expanded too far north to the east of ACY allowing onshore flow. So we can probably say this was a hybrid summer alternating between 2010-2013 patterns and 2018-2024 patterns.

The original idea of the heat this week coming in under June and July levels turned to be correct. This is what the models were originally showing before shifting to 102° heat in later runs. We haven’t had any 100° heat after August 13th since 1993. We also haven’t had 100° heat after August 10th since 2005. First/Last 100° Day Summary for NEWARK LIBERTY INTL AP, NJ Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. 1993 06-19 (1993) 102 09-03 (1993) 100 75 1953 06-21 (1953) 100 09-02 (1953) 105 72 1973 08-28 (1973) 100 08-28 (1973) 100 0 1948 08-26 (1948) 103 08-28 (1948) 102 1 2005 07-27 (2005) 101 08-13 (2005) 102 16 2002 07-04 (2002) 100 08-13 (2002) 100 39 1944 08-04 (1944) 100 08-13 (1944) 100 8 1949 07-03 (1949) 100 08-11 (1949) 102 38 2022 07-20 (2022) 100 08-09 (2022) 101 19 2001 08-07 (2001) 100 08-09 (2001) 105 1 2006 08-01 (2006) 100 08-03 (2006) 101 1 1955 07-05 (1955) 101 08-02 (1955) 100 27 2024 06-21 (2024) 100 08-01 (2024) 100 40

The Bermuda high has been shifting much further north during recent summers leading to more onshore flow here and record heat going to our north were the deep SW flow sets up.

Yeah, this has been the theme during this decade with the PDO values rising into the winter and spring. https://www.ncei.noaa.gov/pub/data/cmb/ersst/v5/index/ersst.v5.pdo.dat Oct 2021….-3.13……..Mar 2022….-1.67 Jul 2022....-2.64…….Jan 2023…..-1.24 Sep 2023…-2.99…….Feb 2024…..-1.33 Oct 2024…..-3.80……Mar 2025…..-1.15

I think what we have been seeing from that record warm pool east of Japan in the 2020s is a seasonal shift from the summer into the fall and winter. The SST anomalies have been peaking there during the summers. Then declining as we have moved into the winter. Notice how the -PDO readings have also been following this pattern. The summer into fall 2021, 2022, and 2024 displayed a similar process. The lowest -PDO readings have occurred in the summer and fall and have risen into the winter. So the 21-22, 22-23, and 24-25 winters were all rising PDO patterns off the strongly negative values of the summer and fall. The main theme is that this seasonal pattern has kept repeating. So the winter values can’t get high enough to reverse the PDO when it starts declining again into the summers. The SSTs are marker for the 500mb ridging which keeps returning to the same areas. So even when we had a weaker trough east of Japan last winter, the SSTs couldn’t fully cool down. This could be related to the deep subsurface warmth there. Then there could be a feedback process between the atmosphere and SSTs perpetuating the 500mb pattern and extended record SSTs and -PDOs.

Return to more comfortable temperatures next week into late August as the Erin recurve merges with the trough and keeps the 500 mb heights lower over the Northeast. August 18-25 August 25-31

Familiar pattern in recent years as the all-time record heat went to our north in Canada.

While we are only 6 summers into the 2020s, it’s been significantly warmer than the Philly to Newark corridor was back in the 1990s. If we continue this level of summer warmth for the next 4 summers, then it will have the highest number of 90° days on record. The previous leader for 90° days was the 2010s. Philly to Newark corridor average annual number of 90° days by decade 2020s….Philly….35…..Hightstown….39…..Newark….36 2010s…. 34….33…32 2000s….23…..21…23 1990s…..31…..20…29 1980s…..26….21….26 1970s……22….14….20 1960s……17…..20….21 1950s…..26……23…25 1940s…..26…..23….25

The record high of 98° at Augusta, Maine was two degrees under the August all-time high. They got the all-time June monthly record earlier this summer. Through August 11th this has been their driest summer on record. Also their first year reaching 98° or higher twice. Time Series Summary for AUGUSTA STATE AIRPORT, ME - Month of Aug Warmest High Temperature Click column heading to sort ascending, click again to sort descending. 1 1955 100 0 2 2025 98 20 - 1948 98 0 3 2001 97 0 - 1975 97 0 4 2002 96 0 - 1987 96 0 5 1953 95 0 - 1949 95 0 Time Series Summary for AUGUSTA STATE AIRPORT, ME - Month of Jun Click column heading to sort ascending, click again to sort descending. 1 2025 100 0 2 1995 98 0 3 2024 97 0 - 1988 97 0 - 1971 97 0 4 1955 95 0 - 1953 95 0 5 2021 94 0 - 2020 94 0 - 2005 94 0 - 1984 94 0 - 1963 94 0 - 1956 94 0 Time Series Summary for AUGUSTA STATE AIRPORT, ME June 1st through August 11th Lowest Rainfall Click column heading to sort ascending, click again to sort descending. 1 2025-08-11 3.00 3 2 1999-08-11 3.57 0 3 1949-08-11 3.80 0 4 1994-08-11 3.82 0 5 1952-08-11 4.31 0 6 2017-08-11 4.77 0 7 1965-08-11 4.80 0 8 1995-08-11 4.81 0 9 1950-08-11 5.06 0 10 1966-08-11 5.15 0

Both urban and rural NJ sections weren’t consistently as warm as they have been since 2010. Getting 30+ and 40+ days reaching 90° only happened from time to time with many cooler seasons under 20 days and even 10 days. These days most of the seasons are over 30 days with the cooler seasons under 20 or 10 days hard to come by anymore.

JFK has had nearly as many record and near record highs as Newark in the fall during recent years even though it’s a much cooler location. JFK had record heat into early November last year with the developing drought. So fall record heat has been a constant in recent years. JFK September and October numerous near and record highs since 2015 9/1 92 in 2012 92 in 2010 91 in 1969+ 9/2 93 in 1973 93 in 1961 93 in 1953 9/3 93 in 2015 93 in 1993 92 in 1957 9/4 93 in 2018 93 in 1985 92 in 1961 9/5 94 in 1961 93 in 2023 92 in 1985+ 9/6 93 in 2023 92 in 1985 90 in 1998+ 9/7 93 in 1983 92 in 2023 92 in 1978 9/8 92 in 2010 91 in 2015 87 in 2013+ 9/9 93 in 1959 91 in 2016 88 in 1964 9/10 98 in 1983 92 in 1989 90 in 1961 9/11 96 in 1983 91 in 1989 89 in 1961 9/12 91 in 1981 90 in 2005 90 in 1952 9/13 94 in 1952 89 in 1994 89 in 1957 9/14 89 in 1995 89 in 1972 88 in 1981+ 9/15 85 in 2008 82 in 2009 82 in 1997+ 9/16 89 in 1991 88 in 1998 88 in 1970 9/17 90 in 1991 84 in 2015 84 in 1969 9/18 90 in 1965 86 in 2021 86 in 1964+ 9/19 90 in 1983 87 in 2024 85 in 2022+ 9/20 85 in 1997 85 in 1983 84 in 2024 9/21 85 in 2016 83 in 2004 83 in 1989 9/22 91 in 1980 87 in 1961 86 in 1970 9/23 90 in 1970 89 in 1961 88 in 2017+ 9/24 92 in 2017 88 in 1970 86 in 1961 9/25 87 in 2010 85 in 2017 83 in 2011 9/26 87 in 1970 85 in 1958 82 in 1968 9/27 89 in 1998 87 in 2017 84 in 2014+ 9/28 82 in 1948 81 in 1961 81 in 1959+ 9/29 82 in 1948 81 in 2019 81 in 1959 9/30 84 in 1986 82 in 1959 80 in 1971+ 10/1 85 in 1986 84 in 1954 84 in 1950 10/2 95 in 2019 85 in 2013 82 in 2002+ 10/3 84 in 2002 82 in 2000 81 in 1969 10/4 84 in 1967 83 in 1959 83 in 1954 10/5 84 in 1967 83 in 2017 83 in 2002+ 10/6 88 in 1997 85 in 1995 83 in 1959 10/7 83 in 2007 83 in 1961 82 in 1997 10/8 90 in 2007 78 in 1959 77 in 2021 10/9 87 in 2011 82 in 1961 82 in 1959 10/10 86 in 1997 84 in 2017 84 in 2011 10/11 80 in 1960 77 in 2017 77 in 1969+ 10/12 83 in 1969 81 in 1962 79 in 1995+ 10/13 79 in 1995 78 in 2008 77 in 1989 10/14 82 in 1990 82 in 1975 80 in 2021 10/15 82 in 1975 79 in 2000 78 in 1990 10/16 79 in 2008 77 in 1964 76 in 1963 10/17 82 in 1963 76 in 1996 75 in 2016+ 10/18 77 in 1964 75 in 2016 75 in 2006 10/19 86 in 2016 75 in 1965 74 in 1998+ 10/20 81 in 1969 79 in 2021 79 in 1984 10/21 81 in 1963 80 in 1949 78 in 2024 10/22 80 in 2024 77 in 1984 77 in 1975 10/23 77 in 1978 74 in 2007 73 in 2017 10/24 74 in 2017 73 in 2001 72 in 2024+ 10/25 77 in 2001 73 in 2022 73 in 2021+ 10/26 78 in 1971 75 in 1989 75 in 1963 10/27 78 in 1963 75 in 1989 73 in 1964 10/28 81 in 2023 76 in 2010 75 in 1989+ 10/29 80 in 1971 74 in 2015 74 in 2014+ 10/30 79 in 1961 77 in 1950 73 in 2024+ 10/31 78 in 2024 75 in 1950 74 in 2004+ 11/1 82 in 2024 80 in 1950 77 in 1982

The warm spots like Newark have had plenty of September and October record heat in recent years. Just notice all the records and near records since 2015. This is why the tropical system tracks are going to be so important as we head into the fall. Since parts of the area have had their driest summer on record so far. We will need an assist from the tropics in either lowering heights or providing rainfall. If one or both of these factors fail to materialize, then there is nothing stopping more heat and ridging into the fall with an expansion of drought. Newark September and October record and near record highs since 2015 9/4 95 in 2018 95 in 1973 95 in 1964 9/5 95 in 2023 94 in 1985 94 in 1961 9/6 98 in 2018 97 in 2023 97 in 1983 9/7 96 in 2023 95 in 2015 93 in 2010 9/8 98 in 2015 94 in 1939 93 in 2010+ 9/9 94 in 1964 93 in 2016 92 in 1971+ 9/10 98 in 1983 97 in 1989 95 in 1931 9/11 99 in 1983 96 in 2013 96 in 1964+ 9/12 95 in 1961 93 in 2005 90 in 1952+ 9/13 94 in 2005 94 in 1952 93 in 1957+ 9/14 94 in 2016 92 in 2008 92 in 1931 9/15 94 in 1993 91 in 2021 91 in 1942 9/16 95 in 1991 92 in 1970 91 in 1958+ 9/17 95 in 1991 93 in 1972 91 in 1994 9/18 90 in 1992 90 in 1948 89 in 1965 9/19 93 in 1983 89 in 1946 88 in 2022+ 9/20 92 in 1983 88 in 1946 87 in 1985 9/21 90 in 1940 88 in 1998 88 in 1980 9/22 94 in 1970 93 in 1931 92 in 1980 9/23 94 in 1970 93 in 2019 93 in 1959 9/24 92 in 2017 92 in 1959 89 in 1970 9/25 91 in 1970 90 in 2017 90 in 2010+ 9/26 90 in 2007 90 in 1958 88 in 1970 9/27 91 in 1998 89 in 1933 88 in 2017 9/28 87 in 2014 86 in 2019 85 in 1954+ 9/29 89 in 1945 83 in 1959 82 in 2015+ 9/30 89 in 1986 85 in 1954 82 in 1960+ 10/1 85 in 1986 85 in 1950 84 in 2019+ 10/2 96 in 2019 86 in 2013 86 in 2002+ 10/3 85 in 2023 85 in 1950 84 in 2021+ 10/4 89 in 2013 87 in 2007 87 in 1959 10/5 93 in 1941 87 in 1967 86 in 2017 10/6 91 in 1959 90 in 1941 88 in 1997+ 10/7 88 in 1944 87 in 1946 85 in 1990 10/8 89 in 2007 85 in 1931 84 in 1990 10/9 88 in 2011 87 in 1990 86 in 1959+ 10/10 92 in 1949 90 in 1939 86 in 1958 10/11 88 in 1949 85 in 1954 83 in 1955 10/12 88 in 1954 86 in 1962 85 in 1949 10/13 89 in 1954 85 in 1995 83 in 1978 10/14 85 in 1975 83 in 1990 82 in 2021 10/15 86 in 1956 85 in 1960 84 in 2021+ 10/16 84 in 1958 83 in 1992 83 in 1963 10/17 90 in 1938 83 in 2016 82 in 1963 10/18 85 in 2016 80 in 1964 79 in 2007+ 10/19 87 in 2016 82 in 1945 81 in 1963 10/20 80 in 2021 80 in 1969 80 in 1947 10/21 84 in 2024 84 in 1947 81 in 2017 10/22 86 in 1979 83 in 2024 79 in 1984+ 10/23 87 in 1947 82 in 2024 82 in 1978 10/24 83 in 2001 78 in 1946 77 in 2017+ 10/25 79 in 2001 79 in 1963 78 in 2021 10/26 82 in 2023 79 in 1964 79 in 1963 10/27 81 in 1963 80 in 1947 78 in 2023+ 10/28 84 in 2023 82 in 1984 78 in 1989+ 10/29 78 in 1971 78 in 1946 76 in 1989 10/30 82 in 1946 80 in 1961 80 in 1950 10/31 83 in 2024 82 in 1946 79 in 1950

Yeah, the record SST warmth near the Maritime Continent has been leading to significantly more -IODs over time than we used to get.

It was pretty much wall to wall heat and ridging from June 21st through July 31st. We got a relaxation of this pattern for the first week of August. This current heat wave is a weaker reflection of what we got back in June and July. So the shift in the modeling for next week is the hurricane lowering heights in the East as it recurves west of Bermuda. Would like to see some improvement in the rainfall situation. Since we have seen time and time again how heat has remerged in September into October during dry patterns. We would at least need to keep the tropics active in Atlantic to have a shot at avoiding potential fall record heat when the pattern has been so dry.

Hopefully, we can get the Erin recurve west of Bermuda next week so the WAR gets weakened enough. Big shift to cooler on the EPS for the 18-25. Now the models have a trough along the East Coast instead of a ridge. Longer range will continue to be about the tropics. If we keep getting troughs in the East and tropical systems moving into the weakness, then maybe we can avoid 95+ heat after August 20th. But if the tropical moisture remains east, then the drought conditions will continue expanding. It’s already been the driest summer on record for spots like BDR. The tropics will continue to be the wild card into September. Since a continuing dry pattern and any lack of tropical systems and Eastern trough would allow the ridge to expand again. So the pattern could be mid-August warmth…late August closer to average…early September rebound in temperatures if we stay dry. But enhanced tropical activity in early September could push back against the heat by lowering heights over the Western Atlantic. Cooler trends for August 18-25 New runs Old runs

All the warm spots from Philly to Corona, Queens are pretty uniform around 30 days reaching 90°. 90° days for 2025 so far Philly…30 Highstown…32 TEB…31 EWR…33 Harrison….30 Corona…27

Warmer than areas to the east like Long Island which get regular cooling sea breezes. A few NJ COOP sites have been warmer recently. Harrison has been pretty close. NJ just happens to be a very warm area away from the sea breeze. Data for June 21, 2025 through July 31, 2025 Average Maximum Temperarure Click column heading to sort ascending, click again to sort descending. SEABROOK FARMS COOP 92.8 INDIAN MILLS 2 W COOP 92.6 NEWARK LIBERTY INTL AP WBAN 91.5 Newark Area ThreadEx 91.5 HARRISON COOP 91.0 TETERBORO AIRPORT WBAN 90.7 OCEAN COUNTY AIRPORT WBAN 90.6 TETERBORO AIRPORT COOP 90.5 HIGHTSTOWN 2 W COOP 90.2 BELVIDERE BRIDGE COOP 90.0 Belvidere Area ThreadEx 90.0 map Data for June 21, 2025 through July 31, 2025 Maximum Temperature Click column heading to sort ascending, click again to sort descending. NEWARK LIBERTY INTL AP WBAN 103 HARRISON COOP 103 Newark Area ThreadEx 103 OCEAN COUNTY AIRPORT WBAN 103 ATLANTIC CITY INTL AP WBAN 102 INDIAN MILLS 2 W COOP 102 Atlantic City Area ThreadEx 102 MILLVILLE MUNICIPAL AIRPORT WBAN 101 LONG BRANCH-OAKHURST COOP 101 CANOE BROOK COOP 101 TETERBORO AIRPORT WBAN 101 CALDWELL ESSEX COUNTY AP WBAN 101 ESTELL MANOR COOP 101 TETERBORO AIRPORT COOP 101 SEABROOK FARMS COOP 100 HIGHTSTOWN 2 W COOP 100 NEW BRUNSWICK 3 SE COOP 100 SOUTH JERSEY REGIONAL AIRPORT WBAN 100 SOMERSET AIRPORT WBAN 100 PHILADELPHIA/MT. HOLLY WFO COOP 100 SALEM COOP 100 EB FORSYTHE NEW JERSEY RAWS 100 PENNSAUKEN 1N COOP 100

This Kara-Barents or Urals ridge has become the most impressive Arctic 500mb height anomaly since the sea ice shift to much lower in 2007 with a new lowest maximum in March 2025.

Nice improvements in the temperature department on the 0z runs. The models get Erin back to near 70W off the Carolinas. So it erodes the ridge and lowers the 500mb heights. This causes the current warm pattern to end by early next week. Tropical systems are often the wild card for us after mid-August heatwaves. They can stay offshore like the current guidance shows and still weaken the WAR or Southeast Ridge. The new runs now have lower heights in the East in just 12 hours. So we need later runs to get the storm back near 70W for the relaxation of the heat to continue. Remember, the long range pattern all summer has been to build heights higher than the original forecasts. But it often takes a tropical system to disrupt heat patterns along the East Coast this time of year. New run Old run New run Old run