bluewave

The patterns becoming more persistent are the result of the warming atmosphere and oceans. So observing these changes and incorporating them into forecast techniques is just pattern recognition. I take a very data driven approach so it’s more pattern persistence than persistence forecasting.

That Western Ridge has been very persistent for the La Niña years during the 2020s from summer into fall.

At least we aren’t getting the all-time October heat like out West which would equate to mid 90s here.

I would just leave out the regression to the mean part since the volatility in our snowfall since the 1990s in places like the NYC Metro has been beyond any historical mean. Islip has seen an all or nothing snowfall pattern since the 1990s with hardly any average seasons. The previous 30-40 year period was defined by mostly mean seasons with higher and lower seasons more rare. These days it’s either record high or low snowfall with very few average seasons which were much more common in the old days. The Western droughts continue to this day. But they have been moving around with the shifting stuck record 500 mb ridge positions. This has come with an acceleration of the water cycle which has lead to big swings between wet and dry against the overall drier pattern. Just noting the changes that have occurred. Since 2010 NYC Metro and other regional spots have experienced 12 out of 15 warmer to record warmer summers. So we have a 15 year period of observations for the summer new summer pattern. The same areas have experienced a record 9 consecutive warmer to record warm winters since 15-16. The remaining winters of the decade will give us more data to make a winter determination.

I get it. Sometimes you just have to laugh. But these patterns have been getting stuck in place and repeating across years and seasons in a way we haven’t seen before.

That isn’t my intention Just pointing out how anomalous the warmth out West has been. The interesting thing about this recent -PDO era in the 2020s is how much more of a ridge and warmth we are getting out West from the summer into fall than the older -PDO era. Must be related to the extreme marine heatwaves over the Pacific Basin.

Driest August 20th through October 3rd for ISP with only .30. Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. 1 2024-10-03 0.30 1 2 2005-10-03 1.33 0 3 2014-10-03 1.71 0 4 2019-10-03 2.14 0 5 1968-10-03 2.29 0 6 1963-10-03 2.30 16 7 2007-10-03 2.39 0 8 1973-10-03 2.40 0 9 2013-10-03 2.59 0

The record heat out West for early fall is on the level of the September into October 2015 super El Niño and 2022 La Niña. Time Series Summary for Cheyenne Area, WY (ThreadEx) - Month of Sep Click column heading to sort ascending, click again to sort descending. 1 2015 64.7 0 2 2024 64.0 0 - 2022 64.0 0 - 2019 64.0 0 3 1998 63.9 0 4 2021 63.6 0 5 2023 63.4 0 6 1963 63.1 0 7 1979 62.8 0 8 1990 62.2 0 9 2018 62.1 0 - 2005 62.1 0 10 1897 61.9 0

Still holding on at or above the 1.5C level.

It’s better that this occurring at the end of the growing season rather than closer to peak heating like we got from the 90s into early 00s with 100° heat and very little rain.

Your 9 winter average temperature since the 15-16 super El Niño is the highest on record at Detroit at 31.1°.

The fall into spring of 95-96 was the most perfectly balanced -EPO -WPO -NAO pattern we have experienced. It was still in a much colder climate back then before all the big marine heatwaves and global temperature increases. So the available Arctic air as displayed as in the record cold 93-94 pattern over North America was on par with some of the great Arctic outbreaks of the 1980s. That great Southwest Ridge near Baja was the icing on the cake for the snowiest season on Long Island to near 90”. Also notice that deep trough north of Hawaii which was effectively a near perfect +PDO atmospheric 500 signature even as it was a weak La Niña.

Unfortunately, extremes of wet and dry with very little moderation in between.

Warmer first week of October with temps near 80° in NJ into the weekend before we cool off again next week. The record breaking heat will be found out West. Fall temperature pattern for the CONUS similar to 2022 so far but a little warmer in the East.

The one constant since 15-16 is that the temperatures and Southeast or Western Atlantic Ridge have exceeded the given model seasonal forecasts. There has generally been a trough axis with varying depths near the West and an Aleutian Ridge. The finer points of how much snowfall and how warm the departure will be for a place like NYC usually has to wait until we get through October and even into December for conformation of early season clues. There seems to be a few issues at hand for a place like NYC. First the 2010 to 2019 decade was the snowiest on record. The heavy snows which began around 2010 or even to a lesser extent 2002-2003 reversed as the Pacific became increasingly hostile during the 2018-2019 winter right after the November snowstorm. There was a dramatic shift to warmer following the big global temperature jump in 15-16. So this has been the first 9 winter run of record to warmer temperatures.

Probably one of the driest starts to October for the CONUS away from the Gulf area.

It goes beyond the seasonal guidance though. The first idea that we were going to make a run on +13 during December 2015 didn’t really happen until the month had already started. So the medium range guidance was way off also from late November. While that was an exceptional event around the Northeast, there were 10 other months since then for parts of the U.S. with a near +10 or greater departure. They also didn’t have much notice before the month started. This is how the seasonal guidance from the various models have been biased so cool. Any location that registers a +10 for at least one winter month is going to skew the whole winter departure well beyond what any of the seasonal models were indicating. That’s why even if the model gets the longitude of the ridge axis correct over the U.S., the temperature departures near the strongest part of the ridge have blown way past what the seasonal model forecasts were indicating. Near +10 or greater departure months in the U.S. since December 2015 Dec…2015….NYC….+13.3 JAN…2017….BTV…..+11.0 FEB….2017….ORD….+10.3 FEB…..2018…ATL….+10.6 FEB….2019…MGM….+10.5 JAN….2020…YAM….+9.8 DEC….2021….DFW….+13.2 JAN….2023….DXR….+12.3 FEB….2023…..SSI…..+9.8 DEC….2023….INL…..+15.8 FEB…..2024….FAR…..+17.5

The forecast at 500mb looks like a blend of 21-22 and Feb 18. So yes if that verified it would be a departure from the deep Western Trough of 22-23. That being said, none of these seasonal models have been great at this range so the finer details will have to wait.

The temps from the CanSIPS forecasts have been biased way too cold last few winters.

The 13-14 winter was one of what I call the big 5 of modern times. The other winters were 95-96, 09-10, 10-11 and 14-15. 95-96 still stands as the greatest winter in NYC Metro for wall to wall cold and snow from November into April. 09-10 was the greatest winter for snowfall from DC to Philly. 10-11 featured the greatest 33 day snowfall around NYC Metro at just over 60” from late December into late January. 13-14 was one of the best for snow combined with cold in the Great Lakes. 14-15 was tops for Boston snowfall. The 95-96 winter was before the big global temperature jump in 97-98. So NYC Metro was still able to register their snowiest winter with parts of Long Island recording over 90”. The extended cold from November into April hasn’t been rivaled either as the world has warmed. The next big global temperature rise to a new higher baseline occurred in 15-16 and no winters since then have been able to rival 09-10 in the mid-Atlantic. Same goes for 10-11 around NYC and 13-14 for the Great Lakes and 14-15 near Boston. Now we have seen one of the greatest global temperature rises over the last year or so. These big temperature rises make it unlikely that we could see one of these big 5 repeat again in this much warmer climate. So we can probably retire those 5 years as analogs for the new warmer climate.

I don’t think anyone is betting early on that this winter will rival the magnitude of the trough digging into the SW. That was the strongest trough out there of the last decade. But less trough in the SW doesn’t equal a great winter here absent other changes to the pattern.

Driest September on record for ISP and FRG. Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Month of Sep Click column heading to sort ascending, click again to sort descending. 1 2024 0.24 0 2 2019 0.61 0 3 1985 0.81 0 4 1986 0.82 0 5 1965 1.01 0 6 1982 1.12 0 7 1980 1.28 0 8 2007 1.31 0 - 2005 1.31 0 9 1997 1.42 0 10 1976 1.49 0 Time Series Summary for FARMINGDALE REPUBLIC AP, NY - Month of Sep Click column heading to sort ascending, click again to sort descending. 1 2024 0.36 0 2 2019 0.50 3 3 2013 0.74 0 4 2007 1.34 0 5 2005 1.37 2 6 2022 1.76 0 7 2016 2.14 0 8 2017 2.19 0 9 2014 2.26 0 10 2001 2.32 0

The 22-23 winter was so warm in the East due to the Aleutian Ridge axis out near the Dateline coupled with the deep trough in the West. So this allowed the Greenland block based -AO to link up with the Southeast Ridge. While the WPO was positive, it didn’t have as much influence over the pattern for the East as other teleconnections. The 16-17 La Niña was very warm around NYC and the WPO was negative. 49-50 was the warmest La Niña winters of the older era and the WPO was negative also. So in the most general sense the 22-23 winter matched the winter pattern since 15-16 of an Aleutian Ridge and Southeast Ridge pattern. But it had an unusual combination of features not seen before in the same winter. I think all this talk of winters following exact past analogs is a bit of a misnomer. Since every new winter has combinations of features not seen before. This is where natural variability come in. So the current pattern since the summer has had some similarities to 2022. But to take that and say every feature going forward will be a carbon copy with no natural variability mixed in is misplaced. Plus exact magnitudes of winter warmth usually aren’t known until we at least see how the early winter verifies. Remember, none of the long range models as of November 2015 were forecasting a +13 December. The really big departures aren’t usually made known until we get into the short to medium range. 22-23 La Niña +WPO winter warm in the East 16-17 -WPO La Niña winter warm in the East 49-50 -WPO La Nina winter warm in the East