bluewave

There are a few differences here. Cycles, oscillations, and teleconnections, will always exist whether the climate is warming or not. But there have been an increasing number of studies linking changes to these climate modes as the climate warms. So in effect we get the steady background warming combined with the familiar patterns warming also. So when these intersect, we can get such an extreme pattern of warmth like in the PAC NW summer 2021 that it surprises many. But we can look at waves in the ocean and and see how this happens when they combine. These extreme weather and climate events are akin to constructive interference with rogue waves in the ocean. Just substitute atmospheric Rossby wave behavior. Also these more stuck weather patterns seem to lock in in warmer states like standing waves. The other challenge is that our climate is changing faster than the technology that creates the regional climate models. Plus waiting 30 years to confirm a pattern or trend doesn’t help when we need to forecast extreme events on much shorter time scales.

My guess is that that the timing is somehow related to these frequent December MJO 4-6 intervals which have been increasing in duration and intensity in recent years. But we would probably need a formal study which hasn’t been done yet.

Nobody is making light of the implications considering the historic and rapid global temperature rise in recent months. This is the first El Niño year with so much planetary warming in the early months of the event. Past instances like 15-16 were later in the winter. Whether the atmosphere has been in La Niña or El Niño, both 22-23 and 15-16 both tied for 2nd warmest Northeast winter. We recognize how every winter since the 15-16 super El Niño has been warmer to record warm. So our questions with this El Niño vs competing La Niña influences are strictly about any snowfall potential, STJ vs NPAC Jet, +PNA vs-PNA intervals, WPAC warm pool, MJO, ambient record NATL SSTs etc…

The real mystery is why the rate of December warming during recent decades has accelerated around the solstice at a number of Northeast stations in relation to the rest of the month? So we get the annual spike in temperatures leading up to holiday periods each year. This has been especially pronounced around the NYC Metro. It also shows up at stations further north. 1981-2022 December temperature change by time of month NYC….12-1 to 12-15…..+1.4……..12-16 to 12-31….+3.8 ALB…12-1 to 12-15…..+3.2………12-16 to 12-31…..+5.4

Since the warmer December pattern emerged in the Northeast most noticeably in 2011, our only two cold teleconnection years were 2017 and 2013. Those required strong 500 mb -EPO blocking. But it was by far the rarest teleconnection pattern pattern of the last 12 Decembers. So we are running 10 warmer to record warmer to only 2 colder with no cold ranking records. https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/regional/time-series/101/tavg/1/12/1895-2023?base_prd=true&begbaseyear=1981&endbaseyear=2010 Northeast December temperature departures 2022….+1.2…..La Niña 2021…..+4.5….4th warmest….La Nina 2020…+3.2….17th warmest….La Nina 2019…..+1.3….weak warm ENSO 2018….+1.6…..El Nino coupling issues 2017….-3.5…..La Niña 2016….+0.6….La Niña 2015…+11.7….1st warmest..Super Nino MJO46 2014….+3.9….14th warmest…weak El Nino 2013….-1.1…….Neutral 2012…+4.7….10th warmest…Neutral 2011….+5.0….8 th warmest….La Niña

We got a Niña background in December 2015 which was warmer than any previous December by a wide margin. Perhaps it was the interaction with the super El Niño that made it so extreme. The one paper on the event was focused on the strong MJO 4-6 which was the first for a super El Niño. We had mixed forcing elements in December 2018 with a Nina-ridge north of Hawaii and an eastward displaced +PNA El Niño ridge in Canada. But NYC did get the colder front loaded La Niña start to December before the warmer MJO 4-6 kicked in during the mid to later portion of the month. So we don’t have a great sample size of competing Niña-like influences December patterns in El Niño years since the super El Niño in 15-16. Dominant La Niña or El Niño patterns will usually be great in December with blocking like we saw in the 2009 Nino, 2010 Niña, and 2020 Niña. But last December was disappointing with a strong La Niña background and 2nd strongest -AO. So we missed out on the frontloaded La Niña period in December before the warmer mid to late winter Nina portion arrived. Decembers have really struggled to produce wintery weather for us regardless of ENSO or degree of coupling since 2011. Maybe it’s a shorter winter thing in warmer world when December sometimes act like a late fall month rather that early winter. Sometimes a great March can make it feel like we are getting our 2nd or third winter month.

6th lowest annual daily minimum extent. Most of the daily minimum extents have been in the 4s since the lower Arctic ice sea era began in 2007. 12 finishes in the 4s…3 in the low 5s…and 2 in the 3s. https://nsidc.org/arcticseaicenews/2023/09/arctic-sea-ice-minimum-at-sixth/ 1 2012 3.39 1.31 Sept. 17 2 2020 3.82 1.47 Sept. 16 3 2007 2016 2019 4.16 4.17 4.19 1.61 1.61 1.62 Sept. 18 Sept. 10 Sept. 18 6 2023 4.23 1.63 Sept. 19 7 2011 4.34 1.68 Sept. 11 8 2015 4.43 1.71 Sept. 9 9 2008 2010 4.59 4.62 1.77 1.78 Sept. 19 Sept. 21 11 2018 2017 2022 4.66 4.67 4.70 1.80 1.80 1.81 Sept. 23 Sept. 13 Sept. 19 14 2021 4.77 1.84 Sept. 16 15 2014 2013 5.03 5.05 1.94 1.95 Sept. 17 Sept. 13 17 2009 5.12 1.98 Sept. 13

Yeah, Saturday was the 4th coldest high temperature departure of the year so far at HPN. Anytime we get at least -10 for high or low departure it really stands out these days. Data for WESTCHESTER CO AP, NY Click column heading to sort ascending, click again to sort descending. Date Max Temperature Departure 2023-02-04 -16.1 2023-02-25 -15.3 2023-04-29 -14.4 2023-09-23 -12.7 2023-05-03 -10.7 2023-08-24 -10.2 2023-04-28 -10.1 2023-05-04 -10.0

All we can say that is the summer matched a warmed up weak El Niño MEI composite. September has had mixed El Niño and La Niña influences. So it wouldn’t be a surprise if we see more back and forth going forward like the models show. Obviously, El Niño winters are typically backloaded for their best effects. So it’s still way too early to know how the typically best part of the winter plays out. Our sample size of El Niño experiences since the WPAC warm pool has greatly warmed is pretty small. 15-16 was well coupled and we still got a Niña-like month in December before the heart of the season. So everything worked out once we got a great El Niño blocking pattern. 18-19 was showing signs from the fall of not being able to couple which carried though the winter. So hopefully we see improved coupling going forward in time for the typical back loaded portion of El Niño winters. Probably a range of possibilities based on competing Nino-like or La Niña influences. Obviously, we would want a clean El Niño pattern to dominate the typically back loaded portion with blocking and a great STJ.

I hear you. When we subtract the strongest El Niño background states from this summer we get a strong -PDO warm pool from Japan across the Pacific. Plus the record Niña-like WPAC warm pool which has been a nearly permanent feature over the last decade. The Atlantic being so off the charts warmer than what we have seen is probably boosting the ACE and weakening the shear from past states with the summer Nino regions were so warm.

I am not sure if it’s the residual forcing or just the very Niña-like SST profile continuing from recent years outside the immediate ENSO regions.

Because the forecast is more of the same for the next few weeks which will take us through the first half of the fall IO period with no strong Eastern Indian Ocean forcing like we got back in 2019.

The IOD mostly influences the Indian Ocean to Australia during the Northern Hemisphere fall when it peaks. When the forcing gets overpowering in the Western IO, it can strengthen the polar vortex and +NAO like we saw from the fall of 19 into the winter of 20. But so far, the VP anomalies over the IO are much weaker than that record breaking event. Weaker IOD fall forcing so far Record IOD in 2019 much stronger forcing signature.

I hear what you are saying about the Euro and EPS. The day 11-15 GEFS looks like it will end up doing better than the EPS. But it’s still showing the -PNA influence in the new day 11-15. We’ll see how it goes. New 6-10 Old 11-15 New 11-15

My one concern is the tendency for the day 11-15 forecasts to default to El Niño climo. But finally see that there will be other competing influences once day 6-10 forecast period arrives. This is how the long range EPS missed the more -PNA in its day 11-15 forecast. So we often have to wait to until day 6-10 in order to see what the actual drivers will be. New day 6-10 run more -PNA and Aleutians Ridge Old day 11-15 defaulting to more +PNA and stronger Aleutian Low

Just add 2° to the NYC September average temperature to compensate for the artificial cooling from the trees. Notice how much warmer the downtown NYC average temperatures have been this month. Even Montauk is several degrees warmer this month. The the new WTC station at Liberty Park is 2° warmer and it right on the water. So the actual temperature in Central Park away from the trees will finish above 70° in September. https://facilityexecutive.com/world-trade-center-weather-station-offers-insights-for-facilities/ Monthly Data for September 2023 for Upton NY NWS CWA Click column heading to sort ascending, click again to sort descending. State Name Station Type Mean Avg Temperature NY PORT AUTH DOWNTN MANHATTAN WALL ST HEL ICAO 74.7 NY WORLD TRADE CENTER WBAN 73.9 NJ NEWARK LIBERTY INTL AP WBAN 73.6 NY LAGUARDIA AIRPORT WBAN 73.5 NY MONTAUK AIRPORT WBAN 73.3 NY WEST POINT COOP 73.0 NY FARMINGDALE REPUBLIC AP WBAN 72.2 NJ HARRISON COOP 72.0 NY NY CITY CENTRAL PARK WBAN 71.8 NY JFK INTERNATIONAL AIRPORT WBAN 71.8 CT NEW HAVEN TWEED AP WBAN 71.7

Very Niña-like steep -PNA drop to start October as the models get closer. Would match the record warm pool and forcing near Japan. The RMM charts aren’t capturing it since the MJO is displaced further north of the equator closer to the warmest SSTs in the WPAC to the north of the Maritime Continent. So at least the first week looks like a strong coupled -PDO pattern. Just don’t want to see too many -PNA episodes like this during the winter.

The CFS is the only model that I can find that puts out an OHC forecast. Not that it’s such a great model by any stretch, but it doesn’t look like it makes it back to the peak of 1.40 we saw in June. Wonder what the max possible Nino 3.4 SST is should it level off only around 1.00 into October?

Winter blocking over the Western North American domain peaked in 13-14 and 14-15. Since then it has migrated to the warm season. The warm season blocks were actually more impressive than the cold season ones were. We need to shift the extreme blocks further west back to the cold season. It may be the only way to see a cold winter in the Northeast after the last 8 warm ones.

That was the strongest JF block on record for combined -EPO+PNA 500 mb heights.

Looks like a head-and-shoulders pattern in the stock market. https://www.schwab.com/learn/story/identifying-head-and-shoulders-patterns-stock-charts

We can’t get cooler weather anymore these days without some type of extreme of blocking. The EPS has been correcting stronger with the block to our north. So high temperature forecasts have been coming down with so much easterly flow. New run Old run

Would be nice if we could continue this blocking into the winter. No real cool air available in North America with the much warmer background global temperatures and hostile +EPO on the Pacific side. So the trough has been unusually warm this month. Recent drop in departures since the 15th has mostly been due to clouds and onshore flow limiting highs.

It’s been really warm here this month. There are a number of stations in New England that are still close to +5. The upper 70s dew points earlier this month we’re off the charts for this part of the country.