bluewave

There have been several winter shifts along the way since the late 1970s. The last time the CONUS had a top 10 coldest winter was back in the late 1970s with 1978-1979 being the coldest winter on record. 1976-1977 was the last time my area around NYC Metro had a top 10 coldest winter. The period from 1980 to 1994 saw some very impressive Arctic outbreaks where all-time cold was recorded around Chicago. 1994 marks the last time that Canada had a top 10 coldest winter. Places like the Great Lakes were able to register a top 10 coldest regional cold as recently as 2013-2014. But this was more localized than the late 1970s which had much more expansive cold. What has occurred since the 2015-2016 super El Niño is without precedent with 9 consecutive warm to record warm winter around the Northeast. But areas closer to the center of the continent were able to get some impressive but brief Arctic outbreaks in January 2019 and the 2020-2021 winter. But even the warmth in these regions has overshadowed these brief cold episodes. There are two factors at play. One the planet is warming to the rate that Arctic outbreaks are becoming shorter and less intense. The other is that marine heatwaves in key forcing regions tend to favor these giant standing waves which allow warm 500 mb ridge to stall over areas like we saw numerous times in recent years.

Just tied for the 5th latest freeze just east of the ASOS at HVN at 30.6° and the ASOS at 31.0°. Frost/Freeze Summary for NEW HAVEN TWEED AP, CT Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. 1949 04-11 (1949) 32 11-16 (1949) 31 218 2014 04-21 (2014) 30 11-15 (2014) 25 207 2022 04-05 (2022) 31 11-14 (2022) 29 222 1963 04-26 (1963) 31 11-13 (1963) 31 200 1956 05-09 (1956) 32 11-10 (2024) 31 184

The warmer shift began after the 09-10 El Niño during the summers around NYC Metro. We have had 12 out of 15 warmer to record warm summers since then. The warmer winter pattern began in December 2015 with 9 out of 9 warmer to record warmer winters in a row. The 3 cooler summers in 2014,2017, and 2023 were only slightly so. The interesting part of both shifts to warmer were that they were immediately preceded by an impressive cold pattern. June and July 2009 were 2nd coolest such period around NYC Metro. The very next summer was the warmest on record. Then we had the 2nd coldest February on record in 2015 around -11.4. Then the very next winter month in December 2015 came in at an historic +13.3. That December was around 50° degrees which was the equivalent of a very warm November around our area. It was our greatest monthly warm temperature departure.

They are extending the OP Euro to 360 hrs on Tuesday so the 384 hr GFS snowstorms will get some friendly competition. In IFS Cycle 49r1, HRES and the ENS control forecast become scientifically and computationally identical and both are run for 15-days at 00 UTC and 12 UTC, and 6 days at 06 UTC and 18 UTC. The superfluous ENS control forecast will be stopped in a future IFS upgrade, and the data stream currently known as HRES will become known as the “control” forecast.

Maybe we can get a storm once the retrogression finishes just after the 20th.

That’s the benefit of living at such a high elevation even after their warmest September and October by a wide margin. Time Series Summary for Denver Area, CO (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 2024-10-31 64.5 0 2 2015-10-31 62.8 0 3 1933-10-31 62.5 0 4 1947-10-31 62.2 0 5 2016-10-31 61.8 0 - 1963-10-31 61.8 0 Time Series Summary for Denver Area, CO (ThreadEx) - Month of Nov Click column heading to sort ascending, click again to sort descending. 1 1946 42.6 0 2 1991 29.6 0 3 1983 29.3 0 4 1929 23.1 0 - 1928 23.1 0 5 1908 22.9 0 6 1979 22.3 0 7 1956 21.3 0 8 1992 20.1 0 9 1972 19.4 0 10 2024 18.2 22

We don’t even need a very strong Alaskan +EPO vortex anymore since the west based Greenland Block this fall linking up with the Southeast Ridge has produced record warmth.

We are lucky this is happening during the fall and not the summer. Had this pattern started back in May or June places like Newark could have seen the first year with 10 days reaching 100°.They tried to make a run on 10 days back in 2022 but the rains came in time to interrupt the dry pattern.

At least we get some showers Sunday night before most of the rainfall with the system later next week probably misses to our east.

October finished at the 2nd warmest for the CONUS. The September and October period was warmest by a wide margin. Very impressive how much warmer this fall has been so far than the 2015 super El Niño.

The snowfall volatility since 1993-1994 has been unprecedented in the climate record. Very few average seasons especially at spots like ISP which was the opposite of the 1960s through early 1990s.Well above snowfall during the 2010s and well below in the 2020s.

Yeah, NYC went from 37.9” in the 2010s to 14.2” in the 2020s. Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.3 1.1 5.3 12.9 11.8 6.0 0.6 37.9 2018-2019 0.0 6.4 T 1.1 2.6 10.4 0.0 20.5 2017-2018 0.0 T 7.7 11.2 4.9 11.6 5.5 40.9 2016-2017 0.0 T 3.2 7.9 9.4 9.7 0.0 30.2 2015-2016 0.0 0.0 T 27.9 4.0 0.9 T 32.8 2014-2015 0.0 0.2 1.0 16.9 13.6 18.6 0.0 50.3 2013-2014 0.0 T 8.6 19.7 29.0 0.1 T 57.4 2012-2013 0.0 4.7 0.4 1.5 12.2 7.3 0.0 26.1 2011-2012 2.9 0.0 0.0 4.3 0.2 0.0 0.0 7.4 2010-2011 0.0 T 20.1 36.0 4.8 1.0 T 61.9 2009-2010 0.0 0.0 12.4 2.1 36.9 T 0.0 51.4 Monthly Total Snowfall for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Mean 0.0 T 2.6 4.4 7.1 0.1 T 14.2 2023-2024 0.0 T T 2.3 5.2 T 0.0 7.5 2022-2023 0.0 0.0 T T 2.2 0.1 0.0 2.3 2021-2022 0.0 T 0.2 15.3 2.0 0.4 0.0 17.9 2020-2021 0.0 0.0 10.5 2.1 26.0 T 0.0 38.6 2019-2020 0.0 0.0 2.5 2.3 T T T 4.8

Coastal sections could see 40-50 mph gusts later with the steep low level lapse rates.

November 2018 was the end of the great snowfall pattern which began in December 2009 with only a brief interruption during 2011-2012. Even the 2011-2012 season featured the snowiest October on record. Epic run of record breaking benchmark snowstorms. The 2018-2019 DJF period with the big squall and the end of January being the main event was the beginning of the hostile Pacific pattern.

This is the new era of Greenland and Iceland blocks linking up with the Southeast Ridge.

The big model test may be where the best rainfall sets up with the cutoff later next week. Hopefully we don’t see too much suppression. But that has been the trend since late August we need to reverse.

I guess the million dollar question is how much longer the this 2023-2024 warming rate lasts which is probably beyond the scope of the study. https://climatereanalyzer.org/clim/t2_daily/?dm_id=world

This was the 3rd warmest start to November away from the sea breeze behind 2022 and 2015. While the milder pattern continues, the stronger blocking than originally forecast will prevent any more 80° record warmth. So more modest warm departures than we have experienced since the end of October. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. 1 2022-11-07 65.4 0 2 2015-11-07 61.3 0 3 2024-11-07 60.7 0 4 1994-11-07 60.5 0 5 1974-11-07 60.1 0

Volatility of the AO and NAO domains continues to be the main theme. We had the record October AO swing recently from low to high in the raw index. This was following the record 500mb low pressure in August. Now the area south of Iceland is approaching the positive 500 mb height record for November at near +4.6 SD for next week. The block is coming in a little more south based than usual so the raw indexes are missing the magnitude of the 500mb anomaly.

72-73 still stands as Phillys least snowy winter even though it was significantly colder than many recent winters which had more snow. Top 5 lowest snowfall seasons at Philly and DJF average temperature 72-73…..T……36.0° 22-23….0.3….41.3° 19-20….0.3…..39.5° 97-98….0.8….40.4° 49-50…2.0….38.7° 11-12…..4.0…..40.7° 01-02….4.0…..41.3°

72-73 had a great backloaded winter in the Southeast with a record breaking snowstorm in February. 82-83 had the famous February Northeast snowstorm. 97-98 didn’t have any cold or snowy periods for many. 15-16 started with historic warmth but the lingering +PDO from 13-14 and 14-15 helped produce the heaviest snowstorm in NYC history in January and the first below 0° since 94 in February. The La Niña background influence through the MJO and -PDO combined with the borderline super El Niño to create the warmest winter in record along the Northern Tier and Canada in 23-24.

While it still looks warmer than normal, it’s a little less warm than the earlier runs. New run Old run

The models are correcting stronger with the blocking next week. New run Old run

The one common denominator to many of our recent winters has been some feature of the December pattern repeating for part or the entire winter. Last December it was the record breaking ridge over Southern Canada which locked in for the whole winter. In December 22 it was the Western Trough and the lack of snow in December which carried through the whole winter. December 21 had the warm pattern which returned in February following the great MJO 8 in January. December 2020 began with the great +PNA mismatch which carried through into mid-January. But since this allowed a trough to set up near the mid-Atlantic, that trough carried through the whole winter even when the PNA shifted. The snowy December also carried through the entire winter. December 2019 featured the very strong polar vortex and +AO which ran the table that winter.

The sensible weather is derived from the dominant forcing and 500mb weather patterns. While last January was colder relative to the means than December and February, the mean 500 mb anomaly ridge remained over Southern Canada. So December 500mb ridge anomaly locked in for the entire winter which is very rare for an El Niño.