bluewave

Our actual pattern in late November was a perfect match for a November La Niña phase 5. We had the classic +PNA and -NAO pattern. But the block in the North Atlantic was more south based probably due to the record SSTs off the East Coast.

The last few weeks have been classic MJO phase 5. The strongest VP anomalies were too far west to be in the phase 6 region. The wave break a few days ago disrupted the whole pattern. Notice the big VP anomalies jump into Eastern Siberia. That’s probably a part of what all the models have a big -PNA in mid-December going against the Phase 6 +PNA for December.

The last few weeks have been a November phase 5 for a La Niña. We are just going into December phase 6 right now. The mid-December -PNA that the models have been adverting is the opposite of what to expect from a La Niña phase 6 in December. My guess is that losing the +PNA is related to the big West PAC wave break amplifying the Aleutians Ridge . That being said, it’s possible that the MJO can start having a bigger influence later in December. It could take another wave break to shake things up again.

A thread the needle SWFE has been our storm track of choice when the general pattern was challenging. The models seem struggle even more when a storm follows another one by only a few days. But I don’t really trust individual model forecasts for coastals until we get under 72 hrs.

The only trends that seem to matter for us are the ones that occur under 72 hrs. It would be great if we had a model that could get a 96-120 hr coastal storm track correct. Funny how models usually can get cutters right from a week out.

Another indicator that the pattern driving the fall record +EPO and current -PNA is on steroids.

Here in SW Suffolk about 75% of the trees have lost their leaves. But there are still a few trees that are still fully leafed out in brilliant colors. This may be some of the best color that we have seen in early December. The current photos coming in from NYC are just gorgeous.

It doesn’t look like the current MJO phase 6 is having much influence on the pattern. A MJO phase 6 during a La Niña is a strong +PNA. Currently getting the opposite now with a strong -PNA. We can only hope that if it goes into 7 that we get something resembling an actual phase 7 later in December.

We will need a SSW in January. There were only 3 La Niña Decembers with a strong -PNA and +AO. while 08-09 and 84-85 had SSWs in January, 71-72 didn’t. That being said, 3 years is a very small sample size and our climate has warmed quite a bit since then. But we would be happy to get some blocking to push back against the Pacific Jet for snow chances. https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html

It seems like the pattern forcing this near record -PDO is having a greater influence than just the La Niña alone. The -PDO is being driven by the extreme vortex in the Northeast Pacific. This caused a record +EPO in the fall. The vortex is next forecast to move to a very strong -PNA position. Unfortunately, this is combining with a very +AO pattern. The main question is what is forcing the -PDO instead of recent years with a more +PDO La Niña ? All the guidance has -PNA +AO until further notice

They have a site called confluence that reviews how the Euro did with some individual East Coast storms. The case below was for the January 2016 blizzard. It had too much storm suppression keeping the heaviest snows south of NYC. That was the one of the biggest NAM wins that we ever saw. https://confluence.ecmwf.int/display/FCST/201601+-+Snowstorm+-+US+east+coast 5. Good and bad aspects of the forecasts for the event Early signal (from Sunday 17 Jan 00z) and very consistent forecasts Too low accumulation over NYC Question about snow density for the case

This will be the first test of the newly upgraded Euro with a coastal storm in the winter. It had been having suppression issues with coastal storms in recent years. So if the models like the GFS and CMC are right about a track closer to our area, then they weren’t able to address this issue on the upgrade. But if the CMC and GFS go south then we’ll know the issue was fixed. While the Euro has been the top scoring global model in recent years, I have never seen any official statistics for East Coast storm track performance. Maybe the model is tuned for performance in Europe? Even though the Euro has struggled with East Coast storm tracks in recent years, it still does good with the EPS 500 mb teleconnection patterns. My only critique is that it can be too weak with ridges along the East Coast and show too much ridging near Alaska. This was the case recently with it having too weak a +EPO and too slow a Pacific Jet. It also seems like the GFS was a little faster to show the Pacific Jet flattening the Western Ridge and big -PNA drop.

The warmer pattern has actually moved up in time vs what the models were showing at the end of November. Both the 6-10 day forecasts and 11-15 were too cold. The warmer start to December so far and the warm up ahead of the cutter on Monday wasn’t even forecast. New 1-5 vs old 6-10 New 6-10 vs old 11-15

Another day with the high temperatures warmer than guidance. EWR….51 NYC….48 LGA….50 ISP…..49 JFK....49

While I don’t really know the inside details from the ECMWF, maybe the record warm Atlantic is causing it to underestimate the SE ridge and WAR? 168 hr Euro forecast for Monday 168 hr GFS closer to reality New Euro closer to original GFS stronger WAR Record SST warmth to our east

The Euro missed the warmup for Monday while the GFS will be closer to reality. Old runs GFS is closer New run Euro caves to GFS

Yeah, the amplitude of the December AO has gone way up since 2000. We seem to be getting more total December AO days above +3 and below -3. So some very impressive swings from year to year. https://ftp.cpc.ncep.noaa.gov/cwlinks/norm.daily.ao.index.b500101.current.ascii Total December AO days +3 or above and -3 or below 2000….-3….11 days 2001….-3…..2 days 2004….+3….2 days 2005....-3…..3 days 2006….-3…..8 days 2009….-3….21 days 2010….-3….11 days 2011….+3…..9 days 2012….-3…..4 days 2013….+3….5 days 2015…..+3….3 days 2016….+3…..4 days 2019….+3…..1 day 2020….-3……1 day 2021……+3….1 day so far

Those RMM charts probably won’t be a reliable indicator of the pattern in situations like this. https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf A Pacific MJO event is likely to destructively interfere with La Niña, and there remains uncertainty as to whether the MJO will maintain an organized structure, as evidenced by large ensemble spread in the RMM forecasts through mid-December. Any coherence of the intraseasonal signal is more likely to be south of the equator.

Current pattern looks more like a La Niña January phase 5.

Our weather patterns have become much more amplified in recent years. We were talking about the record high heights over Alaska during the fall of 2018. These extreme reversals have also been occurring with AO and NAO in the Atlantic.

You know something much more extreme than the typical La Niña is going on when Alaska records the deepest fall +EPO vortex on record.

Winter 60s have become more common over the years. LGA reached 60° yesterday and most stations were close. Our next chance for 60s will be on Monday. December is starting warmer than forecast. KEWR GFSX MOS GUIDANCE 12/03/2021 0000 UTC FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192 FRI 03| SAT 04| SUN 05| MON 06| TUE 07| WED 08| THU 09| FRI 10 CLIMO X/N 49| 32 49| 35 49| 45 66| 43 44| 34 47| 40 49| 44 58 31 46

That was the last time we had a top 10 coldest fall and winter. Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Year Mean Avg Temperature Missing Count 1 1871 51.7 0 2 1887 51.8 0 3 1875 52.0 0 4 1888 52.2 0 5 1869 52.4 0 6 1883 52.5 0 7 1917 52.7 0 - 1873 52.7 2 8 1889 53.2 0 - 1880 53.2 0 9 1876 53.4 2 10 1976 53.7 0 - 1872 53.7 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. Rank Season Mean Avg Temperature Missing Count 1 1917-1918 25.7 0 2 1880-1881 26.5 0 3 1903-1904 27.3 0 4 1919-1920 27.4 0 5 1874-1875 27.7 4 - 1872-1873 27.7 0 6 1904-1905 28.1 0 7 1935-1936 28.3 0 8 1976-1977 28.4 0 - 1884-1885 28.4 0 - 1882-1883 28.4 0 9 1892-1893 28.6 0 - 1887-1888 28.6 0 10 1878-1879 29.0 2

Same here. I continue to love snowstorms as much as I did when I was young. So the lack of cold doesn’t really bother me that much. I can still remember going to the bus stop for school in the brutally cold 76-77 winter. That was probably our only winter that could resemble something during the little ice age.

We definitely seem to be in the minority as an online community. Most people that I talk to like the fact that our winters have become so much warmer. While many of them would be happier living in Florida, their jobs and family are here. Winters have become warm and snowy or warm and snowless. Hard to believe our last cold and snowy winters were 13-14 and 14-15. Maybe we can eventually get another colder El Niño modoki winter.