bluewave
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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.
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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.
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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.
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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?
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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.
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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.
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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.
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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
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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
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Pretty impressive warming this year as each month shows no signs of letting up yet.
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The 0z guidance is 3 to 1 in favor of a wet tropical moisture weekend. The Euro, CMC, and UKMET are wet. While the GFS took its turn as a drier model. The CMC will pull off a big win if we get a decent shot of moisture since it has been the most steady model from run to run showing this. https://moe.met.fsu.edu/cyclonephase/cmc/fcst/archive/23091900/99.html
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If we can figure out ahead of time when the Euro will be good like today or have poor skill like with Lee then we will really have something. I would love to develop an AI Euro error fixer that would make the Euro always have perfect forecasts.
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It was funny how that 18-19 El Niño composite with a far enough west Aleutian low and great +PNA appeared in December 2020. December +PNA -AO leading to the mid-month epic near 40” jackpot in BGM. Plus the record SSTs to our east gave a nice boost to the snowfall. So I kind of hope we can get a positive surprise like that this winter after expectations got lowered after the last few winters. The one fly in the ointment that December was how far the south based Greenland block built like we have been seeing in recent years. It was great for the BGM snow lovers and the tucked in storm track near SNJ. But it hurt us with the strong height rises east of New England for the late month Christmas flood cutter.
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Yeah, that’s why I am hoping that AI can eventually hone in on which models will be correct in a given situation. Plus the Euro is going to upgrade the resolution to 4 or 5 km in the next few years. Just hoping they they can improve the convective scheme so we can get performance closer to the mesos at times. But not sure how running that kind of resolution beyond 60 hrs on a global rather regional scale will play out yet.
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Yeah, I am very close to the airport near the shore but a bit north of where the Sandy high tides made it to. Areas just to my south flooded. We did the pizza tour recently and I really enjoyed Sally’s and Modern. Enjoying the colder mornings recently than my old area of the South Shore which didn’t radiate very well. The hot days also get tempered a bit here due to the cooling breezes south of I-95.
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We just never know sometimes when the Euro more westerly idea initially will pan out. Some of the mesos caught onto the better rainfall potential in NJ. We’ll see if the Euro idea of a slow moving and wet subtropical storm pans out for next weekend. This time the CMC is stronger, faster, and more amped up. Always a challenge to determine whether we get the slower and weaker low like the Euro shows or the stronger CMC storm. Either way things look wet for a few days as rains could arrive ahead of low with inverted trough feature tucked under 1030 mb high.
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Nice job. My hope is that any forcing near the Dateline can be more dominant so we get some semblance of and El Niño pattern. Even if only sporadically. Give me at least one month with an active STJ +PNA and a weak -AO and I will be happy. I don’t think the seasonal models are good enough to decipher how much coupling we get. We can remember the Euro was adamant on a favorable looking El Niño pattern as late as November 2018. All we need to do this time is have a better MEI response. But the strong MJO 4-6 that December didn’t get things started in an optimal way. Euro forecast for 18-19 Aleutian low far enough west to allow a cold El Niño winter in the East. MJO came right out of the gate strongly into 4-6 on the RMM in December. But you say hey look at that great forcing west of the Dateline. That little forcing cell east of Hawaii imparted a La Niña flavor with the -PNA trough out West. There was just enough forcing further west that December to tilt the scale toward La Niña and it stuck. A westward extension of forcing near the Maritime Continent can shift what otherwise looks like an OK seasonal composite. Overall a very La Niña-like pattern instead of cold El Niño
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I have been doing pretty well here at my new place near KHVN. Got about 1.37 in about 30 minutes a week ago. The whole side of the parking lot flooded to the top of the curb. So the further east you go recently the better you have done. Just hoping I can see a snowstorm up here like Nemo in 2013. Having a major ASOS so close by is a great benefit to knowing my observations with better precision. My little digital indoor outdoor thermometer has been very close to the airport temperature. They may even radiate slightly better there since the ASOS and airport is in a bowl lower than the surrounding area with a big hill a few blocks away. Great little airport but it does flood in heavy rains or big coastal surges.
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Starting to like one of the epic snowstorm tracks for Long Island from 2013 to 2018.
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It’s a challenge to align correctly. But the July 3.4 was 1.03 and the JJ MEI was 0.3. It only increased to 0.4 with 1.31 in august. The trades are stronger in September then they were in August so the +1.6 is really out of step with the previous stronger WWB activity in September 1987 and 1982 west of the Dateline. We will never be able to get an adequate sample size since this year is such an outlier for stronger El Niño readings over +1.5.
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The MEI only goes back to 1979. But there were only 2 years since then with a September Nino 3.4 at around +l.6 like this September so far. The years were 1982 and 1987. But both were very well coupled with much higher MEI than the most recent JA reading. So this may be the biggest MEI mismatch with the actual Nino 3.4 SSTs we have ever seen during an El Niño year. The OHC was also much higher in September 1982 at +1.86 to only +1.18 this month so far. https://www.cpc.ncep.noaa.gov/data/indices/ersst5.nino.mth.91-20.ascii https://psl.noaa.gov/enso/mei/ 2023….JA MEI…..+0.4….SEP 3.4….+1.6…-1.2 1987…..JA MEI……+1.5….SEP 3.4….+1.6….-0.1 1982…..JA MEI……+1.9….SEP 3.4….+1.5…+0.4
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Seems like whenever these 1030 mb highs move off the New England coast in the early fall there is often a subtropical or tropical system underneath. The CMC is most aggressive with development and track just to our west. Sometimes the CMC will score a coup over the GFS and Euro from a week out like late January 2021. But each case is different so you never know. At least it isn’t the Euro alone with a more amped up run than any model since we would probably automatically toss it with how erratic it has bee in recent years.
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That’s a weak IOD overall effect since the cooling is in too small a geographic area near Java to have much influence outside the region. Notice how much more it suppressed convection over the Maritime Continent back with the record 2018 event compared to today.
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It was easier in the old days before we had to be concerned about the WPAC warm pool. Notice how much warmer the WPAC is now than in 1997. That was also a legit +IOD pattern with the whole Western IO warm and Eastern IO and WPAC cold. Completely opposite of today. Also notice how much warmer now the rest of the oceans are now. So it’s as if the ENSO is getting lost in the mix of global potential forcing regions. So we get these really low RONI and MEI values. Making it more challenging as to which type of 500 mb pattern will occur in the winter.
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It would probably be more useful for seasonal forecasting if they issued seasonal MEI forecasts instead of for 3.4 ONI.
