bluewave

Yeah, the competing Maritime MJO forces in December actually enhanced the El Niño effect making it much warmer for the US than usual. So instead of the regular vanilla Canadian ridge, we got one of the strongest on record producing one of the warmest Decembers on record. The final composite for December was similar to a MJO 7 Nino composite that locked in due to the near record forcing over the WPAC near 7. Our last El Niño in December 2015 featured more record warmth centered further east due to the MJO 5 pattern getting stuck in place. Now the record westward forcing into the IO is producing more of a La Niña type pattern in January with a -PNA and Southeast ridge developing. The most recent extended GEFS keeps this pattern going well into January. While anything past 2 weeks is uncertain, we have seen these robust -PNAs in recent years last longer than expected.

NYC had fewer freezing or lower days this year than Raleigh, NC. Time Series Summary for NY CITY CENTRAL PARK, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature <= 32 Missing Count 1 2023 28 3 2 2012 38 0 3 1998 39 0 4 2020 41 0 5 1990 47 0 Time Series Summary for Raleigh Area, NC (ThreadEx) - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Min Temperature <= 32 Missing Count 1 2023 35 3 2 1990 39 0 3 2012 44 0 4 2020 48 0 5 1994 50 0 - 1946 50 0

Pacific Decadal Ociillation.

Nearly all the analogs centered near January 8th are La Niña or -PDO.

Either the standing wave in P2 is so strong, or the base state is more Niña-like so p3 in the RMM forecasts is following the general composite instead of the El Niño one. All the guidance agrees on the big Western trough in early to mid January.

Even during a borderline super El Niño, we still find a way to get a Niña-like pattern in early to mid January.

LGA got close to its first 60/60 year. Time Series Summary for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2016 58.7 0 2 2020 58.6 0 3 2012 58.5 0 - 2006 58.5 0 4 2023 58.4 3 5 2021 58.3 0 Time Series Summary for LAGUARDIA AIRPORT, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Total Precipitation Missing Count 1 2011 65.34 0 2 1983 60.84 0 3 1975 60.79 0 4 2023 59.65 3

We can add December to the list with 3 stations reaching 10.00”+. Monthly Data for December 2023 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. State Name Station Type Total Precipitation CT ANSONIA 1 NE COOP 11.33 NJ WANAQUE RAYMOND DAM COOP 10.67 NJ CHARLOTTEBURG RESERVOIR COOP 10.25

We are going into January with the lowest snow extent on record for North America and the whole Northern Hemisphere. These readings are normal for mid-November. https://www.star.nesdis.noaa.gov/smcd/emb/snow/HTML/snow_extent_monitor.html

The west biased -AO block actually verified stronger and peaked around the 16th. Then we had the historic blizzard when the Pacific became favorable around the 22nd-23rd.

The sensible weather in late December into Janaury along with the forecasts were indicating a big turnaround. Following the low 70s leading up to Christmas, we quickly picked up a T of snow before New Years. Then a short Arctic outbreak with NYC dropping to 11° on Janaury 5th. I remember mentioning how impressive it was to have a+500 meter KB block. Once it built back across the pole, the rest was history. The weeklies started looking great in late December. https://fox12weather.wordpress.com/2015/12/28/ecmwf-monthly-run-10/

MJO 2 with an El Niño isn’t a favorable pattern for us in January. The trough dives into the West and it pumps the ridge over us. That’s why the Jan week 2 forecasts have been correcting warmer. My guess is that the 2nd week may see warmer departures than the first week. Remember the MJO effects can be lagged.

The first we thing see in early January are the VP anomalies almost going off the scale with the record marine heatwave near 60E. While the MJO composites aren’t a perfect match, my guess is that the shift toward a -PNA week 2 of January is in response to this. A deep trough in the West is close to the MJO 2 El Niño composite. The MJO getting over to 3 would tend to build the ridge again in Canada. But any lingering convection near 60E could hold an undercutting trough in the SW. So we may go to an overlapping composite look for a time before the next step in the MJO becomes better defined.

Bradford, PA is currently at +9.0 and at their 2nd warmest December. Time Series Summary for BRADFORD REGIONAL AIRPORT, PA - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 39.0 0 2 2023 37.9 4 3 2021 36.0 0 4 2012 35.8 0 5 2006 32.9 0 6 1998 32.3 0 7 2001 32.1 0 8 2011 32.0 0 - 1984 32.0 0 9 1982 31.4 0 10 1990 30.7 0

Closer to the higher end of my +2.5 to +5.0 range worked out this month around the area. EWR…+5.4 NYC….+4.5 JFK….+3.5 LGA...+3.4 ISP…..+4.3 FRG….+4.5 HPN….+4.6 BDR….+3.0 HVN….+5.6 DXR….+6.1 POU….+5.1 BDL….+5.6

Warmer than Richmond for the 91-20 climate normals.

NYC just experienced the 3 warmest consecutive winter months on record with all 3 months above 41.0°. This lead to the lowest calendar year snowfall at only 2.3”. It was warmer and less snowy than the Richmond, VA averages. Jan 23…43.5° Feb 23….41.1° Dec 23...44.2° AVG……42.9° Dec 01…44.1° Jan 02…39.9° Feb 02….40.6° AVG…….41.5° Jan 98…40.0° Feb 98….40.6° Dec 98….43.1° AVG………41.2° Time Series Summary for NY CITY CENTRAL PARK, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Total Snowfall Missing Count 1 2023 2.3 6 2 1913 3.4 0 3 1973 5.6 0 4 1901 6.5 2 5 1998 7.5 0 6 1953 7.6 0 7 1931 8.0 0 8 1951 8.8 0 9 2012 9.6 0 10 1997 9.9 0 https://www.weather.gov/media/akq/climateRECORDS/RIC_Climate_Records.pdf Richmond, VA….Jan…38.3°…Feb…41.0°….Dec…41.8°…snowfall….8.8”

NYC currently in 2nd place for warmest December with highs forecast to reach 50° or warmer through Friday. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Dec Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 2015 50.8 0 2 2023 44.1 6 - 2001 44.1 0 3 2021 43.8 0 4 1984 43.7 0 5 2006 43.6 0 6 2011 43.3 0 7 1998 43.1 0 8 1982 42.7 0 9 1990 42.6 0 10 1891 42.5 0

Action Park was my favorite place to go during the summers in the 1980s. NW NJ is a beautiful area. I wish you the best of luck when you make your move.

We generally don’t do as well following SSWs during El Niños that weren’t already snowy before the event. December 1972 and 2006 only had a trace of snow or less in December like this year. The SSW in December 1965 even happened earlier and that December only had a trace. We can’t really count on a repeat of 15-16 since that was an extreme outlier compared to most other years. https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html Seasonal El Niño snowfall in NYC with only a T or less in December 2006-2007….12.4…..SSW…2-24 2015-2016….32.8 1997-1998…..5.5 1994-1995…..11.8 1972-1973…..2.8…..SSW….2-2 1965-1966….21.4….SSW…12-8 1877-1878…..8.1

This period is showing us something we haven’t seen before. While we will eventually see another 1” and 2” in NYC and surrounding stations, this long a streak hasn’t happened before. It definitely seems like a shift began to occur with the super El Niño in 2015. We had a record 8 warmer than average winters in a row since then. This December was another top 10 warmest at our local stations. But the 15-16 to 17-18 winters were still snowy. So it seems like those were still part of the snowier interval which began in 09-10. Then in 18-19 we began a 5 year run with much lower and frequently disappointing snowfall outcomes. This is when the warmer patterns began to overlap with less snowy.

The only periods since 18-19 that the Pacific wasn’t hostile were the 20-21 winter and January 22.

I know. She was one of the most gifted singer-songwriters of the last 30 to 40 years.

But that won’t be because if what happened from January 1st to 15th. El Niños with only a T of snow during December typically haven’t had as much snow as the ones with more December accumulation. We can’t count on an exception like 15-16 to recur again since that was such an extreme event. Seasonal El Niño snowfall in NYC with only a T or less in December 2006-2007….12.4 2015-2016….32.8 1997-1998…..5.5 1994-1995…..11.8 1972-1973…..2.8 1965-1966….21.4 1877-1878…..8.1