bluewave

Numerous papers on this new summer warming pattern of cooler in the middle and record warmth in the East and West.

The main issue is how dry it has been. Newark is currently in the upper 80s on a dry downslope flow behind the cold front. It will get cooler again over the next week. Last year Newark only made it to 87° in September. So it hasn’t had two consecutive Septembers not reaching 90° since 2003 and 2004. So when the ridge returns in September, it wouldn’t take much for the warm spots like Newark to reach 90°.

First -1.2 IOD in 3 years as they have become much more common over time with the warming SSTs near the Maritime Continent.

Today could be the warmest day of the week for high temperatures in the upper 80s.

The below normal dewpoints and dry conditions this month are helping the daily lows drive the cool departures for a change. Looks like a slightly cooler pattern will continue for the rest of the month. If we don’t see a reversal of this drier pattern, then there could be more 90° heat on tap in September since it would be easy to warm up with such a dry pattern once the ridge returns.

Yeah, this has been the opposite of the Dust Bowl pattern over the last decade. Record summer warmth in the West and East with less warm over the middle section of the CONUS. The Dust Bowl pattern had the record summer heat in the middle and cooler along both coasts.

Yeah, all the warming at Philly has been since 1981. The climate from 1875 to 1980 was very stable like the rest of the world and the U.S. There was a slight -0.6° decline in winter temperatures over this period. Since 1981 Philly is up +4.3° during the winters. This is the main reason the U.S. hasn’t seen a top 10 coldest winter since the 1970s.

That’s why so many people are moving out to the Desert Southwest. Many people are OK with the extreme summer heat and drought. Then they can take weekend ski trips during the winter to get their fill of snow and cold.

We had a record Southeast Ridge in July. So record Atlantic warm pool is in the mid-latitude band off the East Coast The record ridge back in the summer of 2023 was east of Canada leading to the record SSTs at higher latitudes.

The most important factor for our area is how strong the Northern Stream of the Pacific Jet has been since 2018-2019. So this has found ways to overpower what has been favorable teleconnection patterns in the past. This is why we have experienced the lowest 7 year winter snowfall average on record for many spots from Philly to Boston. Last winter featured what would have been considered favorable teleconnections in the past for snow. Just looking at the seasonal 500mb map, you could make the assumption that it could have been a snowy winter from the means. But on the 11 days NYC had their heaviest precipitation of .25 or more the average temperature was 41° degrees and a strong Southeast Ridge. So the storm track was too warm even if the background temperature of 34.8° was much colder. So the only metric I am interested in at this point for next winter is where the storm track sets up. If it continues the Great Lakes cutter, I-78 to I-84 hugger, and suppressed Southern Stream storm tracks, then it won’t matter what kind of poleward extension we get with the ridge near Alaska. This has been the dominant storm track with the record Northern Stream of the Pacific Jet. If we get to December and the storm track is still unfavorable, then we’ll know that it will be another well below average winter for snowfall. Hoping to see some improvement in this department. We will know soon enough by December when we get the early La Niña snowfall indicator which has worked nearly all of the time since the 1990s like it did last winter. Last December was below 4” and the rest of the winter finished well below average again. But with the record mid-latitude warmth we are currently experiencing, it would tend to support the Southeast Ridge and strong PacificJet being a factor again. Don’t mind warm winters as long as the storm tracks that are cold like we got in 15-16, 16-17, and 17-18. But there is very little we can do with a warm storm track.

Really comfortable pattern here the rest of the month as the next heatwave will miss well to out north with record mid 90s staying up near the tundra. This should be one of the more extreme late season over the top warm ups we have seen. Unfortunately, it will promote more drought and wildfire activity up in Canada.

We’ll probably see some degree of 500mb height rebound by the 2nd week of September since it’s so tough to sustain a trough in the East this time of year beyond a few weeks.

2007 was a much greater regime shift when looking at the bigger picture. The NSIDC didn’t forecast an imminent technically ice free summer below 1 million sq km at that time. But there were a few individuals in the Arctic community who did. If the record Arctic dipole pattern of 2007-2012 had continued into the 2020s, then the 2012 record would have been surpassed by now. Perhaps even producing a season in the 1 to 2 million sq km range approaching technically ice free. But the dipole reversal since 2013 featuring much lower summer pressures over the CAB has prevented the 2012 record from being challenged. 2020 came the closest but the relaxation of the dipole in August and lack of record Arctic cyclone preventing it from surpassing 2012. The last decade has featured a summer record mid-latitude ridging pattern across the Northern Hemisphere leading to the record heatwaves not on land and sea. It has featured lower pressures near the pole preventing a new record low. It’s interesting that a study released back in 2014 showed this new pattern developing before it emerged. They speculated at the time that it could lead to a remnant of summer Arctic sea ice remaining pretty far into the future if lower pressures continued over the Arctic during the summers going forward.

Most people who moved out to Phoenix did it with the understanding that they would have to reduce outdoor activities as the later morning and afternoons approached. But what they are finding now is that even the early mornings for extended stretches are becoming too warm to do even basic outdoor exercise like walking. The record number of 90° minimums this decade in the urban center has probably forced many to do more indoor exercise like the treadmill during the times of peak heat. 20-40 days with 90° minimums has become the norm during the 2020s. Time Series Summary for Phoenix Area, AZ (ThreadEx) - Jan through Dec Top 5 years with 90° minimums Click column heading to sort ascending, click again to sort descending. 1 2024 39 0 2 2023 35 0 3 2020 28 0 4 2025 21 132 5 2013 15 0 - 2003 15 0

It’s possible for JFK since they have had several last 90° days in August during recent years. But the usual warm spots like Newark can always sneak in more 90° days. Looks like our next warm up in the long range forecasts is for mid-September. First/Last Summary for JFK INTERNATIONAL AIRPORT, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Minimum 05-19 (2017) 07-20 (2013) 25 Mean 06-16 09-01 76 Maximum 07-12 (2023) 10-02 (2019) 127 2024 06-21 (2024) 91 08-28 (2024) 95 67 2023 07-12 (2023) 90 09-07 (2023) 92 56 2022 05-31 (2022) 94 08-27 (2022) 91 87 2021 05-22 (2021) 94 08-27 (2021) 93 96 2020 07-02 (2020) 90 08-27 (2020) 92 55 2019 06-27 (2019) 91 10-02 (2019) 95 96 2018 06-29 (2018) 91 09-04 (2018) 93 66 2017 05-19 (2017) 92 09-24 (2017) 92 127 2016 06-22 (2016) 92 09-09 (2016) 91 78 2015 06-21 (2015) 90 09-08 (2015) 91 78 2014 06-18 (2014) 91 09-02 (2014) 92 75 2013 06-24 (2013) 90 07-20 (2013) 96 25 2012 06-20 (2012) 94 09-01 (2012) 92 72 2011 06-09 (2011) 93 08-08 (2011) 92 59 2010 05-26 (2010) 91 09-08 (2010) 92 104

Looks like another season ending in the 4-5 sq million range for September average extent. Years like 2012 and 2020 dropping under 4million sq km have been the exception. So have years finishing over 5 million sq km like 2009, 2013, and 2014. So a very stable September minimum regime since the record declines back in the strong 2007-2012 dipole era. This reversal of the dipole has prevented us from exceeding the 2012 minimum so far. So we can say with confidence that 2007 lead to a regime shift in the sea ice. Extent and thickness have not been able to recover to the much higher pre-2007 ice. Even with multiple summer seasons with very favorable lower pressure circulation patterns for sea ice retention. The annual warmth in the Arctic has just been too strong to allow any type of recovery. 2024…..4.38 2023…..4.37 2022….4.87 2021……4.92 2020……3.92…2nd lowest 2019……4.32 2018…...4.71 2017……4.87 2016……4.72 2015…..4.63 2014…..5.28 2013…..5.35 2012…..3.60….lowest 2011……4.61 2010…..4.90 2009….5.36 2008….4.67 2007…..4.28 https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2024GL114546 A regime shift is an abrupt, substantial, and persistent change in the state of a system. We show that a regime shift in the September Arctic sea-ice extent (SIE) occurred in 2007. Before 2007, September SIE was declining approximately linearly. In September 2007, SIE had its largest year-to-year drop in the entire 46-year satellite record (1979–2024). Since 2007, September SIE has fluctuated but exhibits no long-term trend. The regime shift in 2007 was caused by significant export and melt of older and thicker sea ice over the previous 2–3 years, as documented in other studies. We test alternatives to the traditional linear model of declining September SIE, and discuss possible explanations for the lack of a trend since 2007. Current Jaxa extent

Enjoying the cooler weather here as my area made it to #2 on the all-time 90° day list this year at 15 days. Time Series Summary for NEW HAVEN TWEED AP, CT - Jan through Dec Top 5 years for 90° days Click column heading to sort ascending, click again to sort descending. 1 2022 17 0 2 2025 15 132 3 2010 14 0 4 1977 13 100 5 2021 12 0 - 2020 12 2 - 2012 12 3

It’s difficult for many of us who are cold and snow enthusiasts to understand why so many people choose to move to a place like Phoenix with such intense heat. I would enjoy visiting that region during some of the cooler times of the year since the Desert Southwest is one of the most beautiful parts of the country. You wonder how much more heat and drought it would take to actually slow the influx of new people into the area. In the mean time I hope they do all they can to try and expand the trees and shade.

The only stations I could find that made it to 100° from July to September in 1983 were in an around Philly. Monthly Data for July 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. DE NEWARK AG FARM COOP 105 NJ MOORESTOWN 4 E COOP 102 PA NORRISTOWN COOP 101 MD DENTON 2 E COOP 100 PA MARCUS HOOK COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA PHILADELPHIA WBAN 100 PA DREXEL UNIV COOP 100 NJ ATLANTIC CITY INTL AP WBAN 100 NJ INDIAN MILLS 2 W COOP 100 Monthly Data for August 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. MD CHESTERTOWN COOP 101 MD MILLINGTON 1 SE COOP 101 PA PHOENIXVILLE 1 E COOP 101 PA PHILADELPHIA WBAN 101 PA DREXEL UNIV COOP 101 MD CENTREVILLE COOP 100 DE BRIDGEVILLE 1 NW COOP 100 MD DENTON 2 E COOP 100 DE NEWARK AG FARM COOP 100 PA MARCUS HOOK COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA NORRISTOWN COOP 100 NJ HAMMONTON 1 NE COOP 100 NJ INDIAN MILLS 2 W COOP 100 Monthly Data for September 1983 for Mount Holly NJ NWS CWA Click column heading to sort ascending, click again to sort descending. PA PHILADELPHIA WBAN 102 NJ HAMMONTON 1 NE COOP 102 NJ EWING 3 WNW COOP 101 MD CENTREVILLE COOP 100 MD CHESTERTOWN COOP 100 DE BRIDGEVILLE 1 NW COOP 100 DE NEWARK AG FARM COOP 100 DE MIDDLETOWN 3 E COOP 100 PA MARCUS HOOK COOP 100 NJ SHILOH COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA NORRISTOWN COOP 100 PA READING 4 NNW COOP 100 NJ AUDUBON COOP 100 NJ LAMBERTVILLE COOP 100

The peak heat in 2010 was focused in July like we typically see. The most unusual heat in 1983 was the record heatwave coming so late on September 10th-11th. Could be related to the drought which developed that summer. That may be the last time that Queens reached 100° so late in the season. Monthly Data for July 2010 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. NY MINEOLA COOP 108 NY WANTAGH CEDAR CREEK COOP 107 NJ CANOE BROOK COOP 107 NJ RINGWOOD COOP 106 NJ HARRISON COOP 106 CT DANBURY COOP 104 NJ CRANFORD COOP 104 NY WEST POINT COOP 103 NJ TETERBORO AIRPORT COOP 103 NY SHIRLEY BROOKHAVEN AIRPORT WBAN 103 NJ NEWARK LIBERTY INTL AP WBAN 103 NY LAGUARDIA AIRPORT WBAN 103 NY NY CITY CENTRAL PARK WBAN 103 NJ TETERBORO AIRPORT WBAN 103 Data for September 10, 1983 through September 11, 1983 Click column heading to sort ascending, click again to sort descending. NJ PLAINFIELD COOP 100 NY NEW YORK LAUREL HILL COOP 100 NJ CRANFORD COOP 99 NJ NEWARK LIBERTY INTL AP WBAN 99 NY NY WESTERLEIGH STAT IS COOP 99 NY NY CITY CENTRAL PARK WBAN 99 NY WESTBURY COOP 99 NJ JERSEY CITY COOP 98 NJ CANOE BROOK COOP 98 NY NEW YORK AVE V BROOKLYN COOP 98 NJ ESSEX FELLS SERVICE BLDG COOP 98 NY DOBBS FERRY-ARDSLEY COOP 98 NY WEST POINT COOP 98 NY GARNERVILLE COOP 98 NY JFK INTERNATIONAL AIRPORT WBAN 98 NY VANDERBILT MUSEUM COOP 98 NY WESTCHESTER CO AP WBAN 98 CT NEW HAVEN COOP 98 Data for September 10, 1983 through September 11, 1983 Click column heading to sort ascending, click again to sort descending. PA PHILADELPHIA WBAN 102 NJ EWING 3 WNW COOP 101 MD CENTREVILLE COOP 100 MD CHESTERTOWN COOP 100 DE BRIDGEVILLE 1 NW COOP 100 DE NEWARK AG FARM COOP 100 DE MIDDLETOWN 3 E COOP 100 PA MARCUS HOOK COOP 100 NJ SHILOH COOP 100 DE WILMINGTON AIRPORT WBAN 100 PA DEVAULT 1 W COOP 100 PA READING 4 NNW COOP 100 NJ AUDUBON COOP 100 NJ LAMBERTVILLE COOP 100

So far we have had 4 summers since 2017 with the highest temperature of the year occurring in June or not getting surpassed later in the summer. This is a first for our area over such a short period of time. It makes years like 1953 even more challenging to match with 105° heat in September. Since heat getting established early peaks before we get to August and September. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ Jun-Aug Max Temps Click column heading to sort ascending, click again to sort descending. 2025 103 101 96 103 2021 103 97 99 103 2011 102 108 98 108 1994 102 99 95 102 1993 102 105 100 105 1952 102 98 92 102 1943 102 95 97 102 1988 101 101 99 101 1966 101 105 95 105 2024 100 99 100 100 1959 100 93 96 100 1953 100 99 102 102 1934 100 98 90 100 1923 100 99 92 100 2017 99 98 93 99 Monthly Highest Max Temperature for LAGUARDIA AIRPORT, NY Jun-Aug Max Temps Click column heading to sort ascending, click again to sort descending. 2025 101 100 91 101 2017 101 98 91 101 1952 101 97 90 101 2021 100 96 98 100 2008 100 97 88 100 1988 99 99 97 99 1956 99 94 92 99 1943 99 91 93 99 2012 98 101 93 101 1959 98 91 94 98 2024 97 97 95 97

Sea breeze activity really depends on the pattern. But I agree that the more weather stations we have the better. 2010 was the greatest sea breeze outlier that I ever saw living in Long Beach. Much of the spring into early fall was dominated by westerly flow. So it was the warmest summer on record to this day in Long Beach and other areas especially along the coastal plain. Most of the time anyone south of the LIE and Northern State usually get sea breezes. But this is more enhanced south of the Southern State and Sunrise Highway. So once north of the immediate South Shore the sea breeze has less cooling influence. Though it does have some effect especially by later in the day.

Maybe with the depth of the trough for early next week we can get another opportunity for some much needed rainfall.

My area east of HVN has been at +0.5 for August so far. So a nice step down from the record heat in June and July. The last few days here have been the coolest of the month so far.