bluewave

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.

That’s a good point. While we usually see divergence in the 11-15 day forecasts, the GEPS and GEFS are going -PNA. This is in contrast to the +PNA EPS. So it appears that the GEFS and GEPS are going with the -PDO and record warm pool east of Japan. While the EPS is trying to put its eggs more the El Niño basket. It will be interesting to see how this tug of war between competing influences plays out.

The CFS won the September forecast at 1.66 and the Euro and AUS were too warm at 1.89 and 1.98. 3.4 has been stuck between 1.6 and 1.7 all month as the WWBs were a no show this month.

This could be the first time we didn’t get the usual pressure rise along the equator over Indonesia. So the eqsoi isn’t showing the same response. This is why we didn’t get the usual El Niño strong WWBs. The models didn’t do a good job with this since several like the Euro and Australian had Nino 3.4 averaging close +2.0 for September.

Hard to believe that the last major hurricane landfall in the Carolinas was way back in 1996. All tropical storms or lower end hurricanes. But flooding has been their biggest issue with multiple record breaking events such as Florence. https://www.aoml.noaa.gov/hrd/hurdat/All_U.S._Hurricanes.html

Just give me one to two solid months this winter with a raging STJ and some blocking. This new paper is another conformation of the semi-permanent La Niña background state due to the warming WPAC. It is similar to the recent papers showing the stronger and more persistent MJO 4-6 phases. So I am hoping for a decent El Niño pattern before we flip again back to La Niña.

The summer JJA 500 mb pattern most closely resembled the weaker MEI El Niño composite. Nothing like the one that proceeded the strongest El Niños. So the higher ACE and 500mb pattern both conformed with the weaker MEI. But the warmer climate allowed for parts of the U.S. to have one of their warmest summers on record. So the past cooling influence during developing El Niño summers was muted. Also a smaller Aleutian Low than both El Niño composites. JJA 2023 pattern -EPO+PNA record south based -AO Weaker MEI composite -EPO+PNA-AO Strong MEI summer composite weak blocking and strong Aleutian Low