bluewave

The forcing is further west like the weaker or Modoki events for the month of September than the stronger ones. But the lack of VP anomalies extending north of the equator is very unusual along with the -SOI not producing any appreciable WWBs. So not really like strong or Modoki events in that regard. So this is another conformation of how weak the MEI has been. Not sure what impact a continuation of these weaker VP anomalies north of the equator may have beyond mentioning possible weak coupling like the MEI suggests.

This is the 1st time that Nino 4 made it to nearly +30 C during the month of September since 2015. The 1.2, 3, and 3.4 regions have all been higher during this time of year. So as long as Nino 4 remains this warm relative to the other regions, the forcing will continue to lean west. +30C SSTs are essentially a forcing magnet.

The stronger trades not letting 3.4 get much higher than the 1.6 peak around a month ago. I think the weaker EQSOI isn’t letting the SOI couple preventing the stronger WWBs we would usually get.

The cooler mornings over the last week feel pretty good compared to how warm the month started out. Even the UHI areas have had min departures in line with more rural areas. Data for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Date Min Temperature Min Temperature Departure 2023-09-15 58 -6.8 2023-09-16 62 -2.5 2023-09-17 62 -2.1 2023-09-18 64 0.2 2023-09-19 61 -2.4 2023-09-20 61 -2.1 Data for New Brunswick Area, NJ (ThreadEx) Click column heading to sort ascending, click again to sort descending. Date Min Temperature Min Temperature Departure 2023-09-15 55 -2.0 2023-09-16 54 -2.6 2023-09-17 49 -7.2 2023-09-18 56 0.2 2023-09-19 54 -1.4 2023-09-20 51 -4.0 2023-09-21 50 -4.5 Data for POCONO MOUNTAINS MUNICIPAL AIRPORT, PA Click column heading to sort ascending, click again to sort descending. Date Min Temperature Min Temperature Departure 2023-09-15 47 -3.0 2023-09-16 45 -4.7 2023-09-17 45 -4.3 2023-09-18 51 2.0 2023-09-19 43 -5.6 2023-09-20 41 -7.3 Data for DANBURY MUNICIPAL AP, CT Click column heading to sort ascending, click again to sort descending. Date Min Temperature Min Temperature Departure 2023-09-15 51 -1.7 2023-09-16 50 -2.3 2023-09-17 46 -6.0 2023-09-18 60 8.4 2023-09-19 51 -0.2 2023-09-20 46 -4.9

I think I can remember an AFD out of Mount Holly mentioning they had been evaluating which models were scoring best with storm tracks one winter in the last 5 years or so?

The departures and warmth rankings at Newark are identical to the rest of the region so no cherry pick involved. I only do that in deference to the large contingent of our posters that live in NJ. So yes the absolutes are usually higher in NJ. But warmth rankings are the same around the whole region. The first two weeks of September were near the warmest on record around the entire upper MA to NE region. https://www.nrcc.cornell.edu/wxstation/perspectives/perspectives.html

It’s the first time since 1983 with the warmest annual temperature occurring in September without tying with an earlier month. Monthly Highest Max Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Year Apr May Jun Jul Aug Sep Oct Season 2023 93 90 91 96 91 97 M 97 2022 88 98 96 102 101 93 76 102 2021 89 96 103 97 99 91 84 103 2020 69 86 93 96 94 89 79 96 2019 80 90 93 99 94 93 96 99 2018 84 94 96 98 96 98 82 98 2017 87 94 99 98 93 92 86 99 2016 83 96 91 99 98 94 87 99 2015 82 91 93 98 97 98 81 98 2014 83 88 92 96 93 95 79 96 2013 85 94 96 101 91 96 89 101 2012 88 92 99 104 95 92 81 104 2011 87 92 102 108 98 88 88 108 2010 92 95 98 103 98 98 79 103 2009 93 87 89 91 95 86 77 95 2008 82 87 99 98 91 92 79 99 2007 86 94 96 97 95 92 89 97 2006 83 94 95 98 101 85 82 101 2005 88 84 97 101 102 94 81 102 2004 88 92 97 91 92 87 76 97 2003 88 81 95 95 93 82 78 95 2002 97 90 96 100 100 91 86 100 2001 87 94 95 97 105 88 83 105 2000 78 94 96 93 92 88 82 96 1999 83 90 99 103 99 88 76 103 1998 74 90 94 98 93 92 79 98 1997 74 86 97 101 97 86 88 101 1996 88 99 92 91 92 92 78 99 1995 82 90 97 104 98 91 85 104 1994 92 95 102 99 95 92 78 102 1993 82 93 102 105 100 100 82 105 1992 79 98 90 97 95 90 83 98 1991 88 93 97 102 96 95 82 102 1990 94 83 92 98 93 91 88 98 1989 79 89 96 99 97 97 80 99 1988 74 94 101 101 99 86 81 101 1987 79 98 96 97 97 87 75 98 1986 80 95 94 100 90 89 85 100 1985 89 92 89 94 97 94 80 97 1984 77 89 97 95 93 88 82 97 1983 85 84 96 98 97 99 84 99

The 2nd week of the month was still pretty warm. But in our new warmer climate wasn’t as extreme as week 1. Data for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Date Max Temperature Min Temperature Avg Temperature Departure 2023-09-01 79 60 -4.3 2023-09-02 83 59 -2.6 2023-09-03 92 66 5.7 2023-09-04 93 72 9.4 2023-09-05 95 78 13.7 2023-09-06 97 77 14.5 2023-09-07 96 76 13.8 2023-09-08 92 73 10.5 2023-09-09 88 73 8.9 2023-09-10 81 70 4.2 2023-09-11 85 72 7.5 2023-09-12 87 69 7.3 2023-09-13 83 71 6.7 2023-09-14 81 63 2.0 2023-09-15 74 58 -3.6 2023-09-16 79 60 0.2 2023-09-17 79 56 -1.4 2023-09-18 70 62 -2.5 2023-09-19 77 59 -0.1 2023-09-20 78 58 0.3

The first two weeks of the month were endless summer as they they were one of the warmest on record. Since the 15th we have been pretty close to average against the warmer 91-20 climate normals. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Sep 14 Missing Count 1 1961-09-14 81.4 0 2 2023-09-14 79.0 0 3 1983-09-14 77.2 0 4 2015-09-14 76.9 0 5 1947-09-14 76.4 0 Time Series Summary for WESTCHESTER CO AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Sep 14 Missing Count 1 1961-09-14 77.8 0 2 1983-09-14 74.6 0 3 2023-09-14 74.5 0 4 2015-09-14 73.7 0 5 2016-09-14 72.9 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Sep 1 to Sep 14 Missing Count 1 2023-09-14 75.9 0 2 1983-09-14 74.1 0 3 2015-09-14 73.9 0 4 1980-09-14 73.1 0 5 2016-09-14 72.7 0

Sure. The PDO is essentially an Aleutian low index. +PDO has a giant cold pool and low pressure north of a Hawaii. Strong ridge and warmer waters underneath in -PDO. Read studies that the PDO and Aleutian low are regulated through SST changes in the WPAC. But sometimes the PDO isn’t very well coupled to the actual pattern like in 20-21 and Jan 22. So sometimes just using a persistence forecast based on the PDO SST signature doesn’t work. Plus now we have these non-canonical expressions with distortions to the original composites.

I also ready a study that the persistent +AO +NAO during those years was related to the IO forcing near India.

I know you have been a supporter of having the CMC on your side when making a forecast. I would have to say the model is the most Improved since recent upgrades. I wish we had a east coast storm statistical storm tracker which would score the models solely on forecasting the most accurate track. These Northern Hemispheric skill scores don’t tell us much about which model get our storm tracks right. But the skill on a hemispheric scale is great for temperature and teleconnection forecasts.

Models starting to converge on the wetter coastal hugger tucked in track. The CMC came east and the Euro west. So a compromise of about 65% of what CMC had and about 35% Euro. So two swings and a miss so far from the Euro with tropical tracks.

While the Euro has been running warm, it has Nino 4 as the warmest region near +30C during the winter. That would tilt the forcing further west and negate 1+2. Remember, we have not seen any 1+2 forcing due to the balance of the warmest waters being near 4. Much different from true based east events which weren’t near +30C in Nino 4 allowing 1+2 and 3 to dominate. I think the Euro is overdone since it’s now warmer in 4 than 09-10 and 15-16.

The super Modoki +PNA -AO was fine in January and February. But we had to reverse the MJO 4-6 super Nina-like Maritime Continent +13 December forcing. This provided probably the most extreme winter month to month variation since December 89 and January 90. But 15-16 was much more satisfying for the historic snowfall fans around NYC.

Thank you very much for posting that great information. I updated the title of this thread to incorporate this new and important study. If there is any way for you to post the full paper beyond the abstract I would really appreciate it. The beauty of science is that our understanding of things can grow based on new research. A cooling trend in summer (May-August) daytime temperatures since the mid-20th Century over the central United States contrasts with strong warming of the western and eastern U.S. Prior studies based on data through 1999 suggested this so-called warming hole arose mainly from internal climate variability, and thus would likely disappear. Yet it has prevailed for two more decades, despite accelerating global warming, compelling reexamination of causes that in addition to natural variability could include anthropogenic aerosol-induced cooling, hydrologic cycle intensification by greenhouse gas increases, and land use change impacts. Here we present evidence for the critical importance of hydrologic cycle change resulting from ocean-atmosphere drivers. Observational analysis reveals the warming hole’s persistence is consistent with unusually high summertime rainfall over the region during the first decades of the 21st Century. Comparative analysis of large ensembles from four different climate models demonstrates that rainfall trends since the mid-20th Century as large as observed can arise (though with low probability) via internal atmospheric variability alone, which induce warming hole-like patterns over the central U.S. Additionally, atmosphere-only model experiments reveal that observed sea surface temperature changes since the mid-20th Century have also favored central U.S cool/wet conditions during the early 21st Century. We argue that this latter effect is symptomatic of external radiative forcing influences, which via constraints on ocean warming patterns has likewise contributed to persistence of the U.S. warming hole in roughly equal proportion to contributions by internal variability. These results have important ramifications for attribution of extreme events and predicting risks of record-breaking heat waves in the region.

A -PDO +PNA occurred during an El Niño in 04-05. The SST profile across the Pacific and Atlantic is much different this time. Although the MEI is currently similar. Same goes for the much different profile with the 06-07 -PDO +PNA El Niño. Plus we have warmed quite a bit since then so we would really need to warm those composites up.

The -PDO isn’t responding int the canonical way. Notice that the warm pool east of Japan extends all the way to California and the Baja. Then we have the issue of how much coupling we get. The -PDO was strongly coupled last winter but not so much in 20-21. Also we had the coupling interruption in January 2022. Plus the El Niño is only weakly coupled now as per MEI and 500 mb composites. So no telling what the winter pattern will look like with so many mixed influences during the winter.

Maybe the big cold pool to our east in the wake of the recent hurricanes isn’t allowing a strong enough WAR for the more inland runner the CMC had been showing?

I think the last time the Euro locked into a KU at 120 hrs and never wavered was Nemo back in 2013. It’s rare for the Euro or any other model to get the right solution beyond the 0-72 time frame. We can remember how the Euro had the heaviest snows from DC to Philly in January 2016 the day before. But the NAM won that round showing the jackpot closer to NYC. The CMC nailed the late January 2021 snowstorm from a week out while the other models were more OTS.

The CMC has probably been the most improved model in recent years relative to what it used to be. Its big coup was being the first model to see the great snowstorm at the end of January 2021 from a week out. The CMC did better with Lee than the Euro did. But each new storm can be different as to which model does best. The Euro snuck in a win with the wetter forecast for NJ on Monday. So this is a bit of trial and error until AI can correct the models for us.

Still a bit of model spread for the weekend. While all models give us a decent rain, the CMC is stronger and further north. Guess more people would be paying attention if this was a winter forecast with P-type issues. CMC more of a stronger inland runner than the GFS and Euro. The CMC has really been holding steady compared to the other models.

The reason we were discussing the coupling and MEI is due to the difference between a weak and strong MEI El Niño summer composites for the NPAC and North America. For one thing, the blocking has been much stronger during summers with a MEI around +0.5 like we had this summer. That was the case this summer with the strong -EPO +PNA -AO blocking. Also at least one of the summers had a very active hurricane season. The more positive MEI summers around +2.0 had less blocking and a more dominant Aleutian low and quiet hurricane seasons. The Aleutian low was very weak this summer. The other difference this year is the much warmer background state with record global temperatures. This muted the cooling influence that we usually get in the CONUS during a developing El Niño of any degree of coupling. Several locations had their warmest summer on record. JJA 2023 Weakly coupled MEI composite Strongly coupled MEI summer composite

If all the past analogs of 5” or less snowfall seasons for NYC work out, then NYC should at least double the 2.3” from last season. 22-23…..2.3 23-24……? 19-20….4.8 20-21….38.6 01-02….3.5 02-03...49.3 97-98…5.5 98-99…12.7 72-72…2.8 73-74….23.5 31-32…5.3 32-33…27.0 18-19….3.8 19-20…47.6 00-01…5.2 01-02…25.4

Pretty impressive warming this year as each month shows no signs of letting up yet.