bluewave

That GFS OP is a big outlier among its ensembles.

Newark only needs another week for the new longest run without measurable rainfall. Number of Consecutive Days Precipitation < .01 for Newark Area, NJ (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 26 1949-06-24 2 25 1939-11-30 3 24 1995-09-08 - 24 1980-02-15 - 24 1963-10-27 - 24 1959-09-27 - 24 1942-05-05 4 23 1991-11-09 5 22 1941-10-02 6 21 2023-11-20 - 21 2000-11-08 - 21 1985-11-03 - 21 1968-10-02 - 21 1935-05-28 7 20 2001-05-11 - 20 1999-06-13 8 19 2024-10-18

Yeah, the near record low dew points and humidity give the usual spots a boost in the radiational cooling department on mornings like this. https://forecast.weather.gov/product.php?site=BTV&issuedby=BTV&product=AFD&format=CI&version=1&glossary=1&highlight=off It`s also notable just how dry the airmass is, with Whiteface`s dewpoint of -13F.

It’s tough to get sustained cold any time of the year these days when what was originally forecast to be a modest ridge a few weeks ago expanded into a near record 591 dm ridge. Old forecast Verification

My guess is that the extreme AO shift this month is related to that nearly off the charts burst of forcing in the IO. It’s short term changes like this which can be tough to access much ahead of time due to the competing marine heatwaves across the tropics right now. It goes to the how extreme polar domain volatility has become over the last decade.

Yeah, there were hopes that the relationship prior to 14-15 would work out for the 16-17 winter. But the extensive fall Siberian snow cover strengthened the Pacific Jet instead. So after 14-15 and 16-17 it hasn’t really been used as much. https://www.aer.com/science-research/climate-weather/winter2017/ Summary Winter 2016/17 was characterized by warmth in Central and Eastern North America, Northern Europe, Central and East Asia but cold in much of Europe, the Middle East and Siberia. The dominant story in the fall was extensive October Siberian snow cover that resulted in very cold temperatures across Northern Asia in November. The strong temperature gradient across Asia provided fuel for a strong North Pacific Jet Stream that cooled sea surface temperatures in the mid-latitudes of the North Pacific. The strong sea surface temperature (SST) gradient in the mid-latitudes of the North Pacific maintained an active Jet Stream into the West Coast of the United States (US) resulting in cool temperatures and record rainfall along the US West Coast but flooded the rest of North America east of the Rockies with mild, maritime air. Low sea ice in the Barents Kara seas helped anchor high pressure in the region, especially Northern Europe, for much of the winter. Northeasterly flow around the high pressure, especially in January, resulted in an overall cold winter for Europe except near the center of the high across Northern Europe. Analysis of the relationship between warming in the Barents-Kara Seas and surface temperatures across the Northern Hemisphere (NH) suggest the record low sea ice in the Barents-Kara seas may have contributed to warm temperatures both across Northern Europe and the Eastern US. Extensive Eurasian snow cover and low Arctic sea ice in October contributed to an early and strong Siberian high that favors a weak polar vortex. However the most impressive polar vortex weakening and subsequent coupling with the troposphere took place in the fall followed by a relatively strong polar vortex and a positive Arctic Oscillation (AO) in mid-winter. This contributed to front ending cold temperatures with the back end relatively mild across the NH. There was a brief major mid winter warming (wind reversal at 60°N and 10 hPa) in early February but its impact was relatively minor and short lived in the troposphere. It is possible that the westerly phase of the quasi-biennial oscillation played a role in reducing the strength and duration of the major warming and its impact on the weather.

Wouldn’t be that big of a surprise since November and March have been warmer during the 2020s than they used to be back in the 2010s when those were pretty reliable cold months. Newark NOV…23….-0.4 NOV...22….+4.0 NOV…21….+0.1 NOV….20..+4.5 Monthly Mean Avg Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Mean 49.0 49.1 2023 46.6 46.6 2022 51.0 51.0 2021 47.1 47.1 2020 51.5 51.5 Monthly Mean Avg Temperature for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Mean 45.7 45.7 2019 42.8 42.8 2018 43.7 43.7 2017 46.1 46.1 2016 49.7 49.7 2015 52.0 52.0 2014 43.9 43.9 2013 44.4 44.4 2012 43.3 43.3

It seems to have had the opposite effect in 14-15 with one of the strongest +NAO +AO winters into March on record. October 2014 featured the 2nd fastest snow advance index on record to that point. Was reading some studies that the rapid Arctic warming could have altered the correlation from when the Arctic was more stable in the old days. Tough to know for sure since it hasn’t been used as much since the 14-15.

A number of locations across the region with either the driest first half of fall or very close. Time Series Summary for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1884-10-16 0.53 0 2 2024-10-16 0.77 0 3 1970-10-16 0.89 0 4 1878-10-16 1.06 0 5 1879-10-16 1.13 0 Time Series Summary for Trenton Area, NJ (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 2024-10-16 0.43 0 2 1970-10-16 0.97 0 3 1941-10-16 1.26 0 4 1897-10-16 1.49 1 5 2007-10-16 1.58 0 Time Series Summary for New Brunswick Area, NJ (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1994-10-16 0.52 1 2 2024-10-16 1.06 0 3 1941-10-16 1.09 0 4 1953-10-16 1.56 0 5 1914-10-16 1.80 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. 1 2024-10-16 0.89 0 2 1941-10-16 1.36 0 3 1953-10-16 1.78 0 4 2013-10-16 1.92 0 5 1948-10-16 2.01 0 Time Series Summary for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 1884-10-16 0.83 0 2 1886-10-16 1.19 0 3 2024-10-16 1.58 0 - 1881-10-16 1.58 0 4 1892-10-16 1.59 0 5 1910-10-16 1.68 0 Time Series Summary for WESTCHESTER CO AP, NY Click column heading to sort ascending, click again to sort descending. 1 2024-10-16 0.83 0 2 2009-10-16 1.40 0 3 1964-10-16 1.85 0 4 1986-10-16 2.16 0 5 2013-10-16 2.18 0 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. 1 2024-10-16 0.34 0 2 1982-10-16 1.43 0 3 1973-10-16 1.88 0 - 1967-10-16 1.88 0 4 1997-10-16 1.92 0 5 2013-10-16 1.98 0 - 1985-10-16 1.98 0 Time Series Summary for IGOR I SIKORSKY MEMORIAL AIRPORT, CT Click column heading to sort ascending, click again to sort descending. 1 1997-10-16 0.74 0 2 1964-10-16 0.76 0 3 2024-10-16 0.84 0 4 1948-10-16 1.54 0 5 1953-10-16 1.84 0

Near record 500mb ridge next few days followed by low 80s for the usual warm spots Monday into Tuesday. Then a few days closer to normal later next week. The next warm up near the end of the month should at least make it to 70s.

It’s new Pacific pattern outlined in this recent paper. This is why trying to compare this -PDO the pre 2015 Pacific hasn’t been working out. So we get this new persistent pattern with record marine heatwaves and Aleutian ridging. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2022GL101078 Remarkable Changes in the Dominant Modes of North Pacific Sea Surface Temperature The analysis revisits the calculation of the empirical orthogonal functions (EOFs) and principal components (PCs) of sea surface temperature (SST) in the North Pacific from 1950 to 2021. The first EOF and PC of SST has proven to be such a useful metric of variability in the North Pacific that it is called the Pacific Decadal Oscillation (PDO). We find that the period of persistent marine heatwaves beginning in 2014 caused a fundamental change to the first EOF and PC of SST (calculated using data from 1950 to 2021) as compared to the established PDO spatial pattern (calculated using data from 1950 to 1993). The second EOF of SST has also changed during this period, both in spatial pattern and in the amount of variance explained. A conclusion is that the PDO and other EOF based metrics may not be as useful in the future as climate continues to change. Key Points The calculation of empirical orthogonal functions and principal components of North Pacific sea surface temperature is revisited The period of persistent marine heatwaves since 2014 has caused most energetic modes to change A conclusion is that indices based on empirical orthogonal function analysis may not be as useful as climate continues to change Plain Language Summary The Pacific Decadal Oscillation (PDO) is a widely used measure of the temperature variability in the North Pacific Ocean. The PDO is the result of a well-known technique called empirical orthogonal function (EOF) analysis that isolates the most energetic modes of variability of the analyzed variable. The first time EOF analysis was applied to oceanographic data was in the 1970's when it was used to identify the most energetic modes of North Pacific sea surface temperature (SST). The first EOF of North Pacific SST has proved so useful as a measure that it received the moniker PDO. Our analysis suggests that a period of persistent marine heatwaves in the North Pacific since 2014 has been so powerful that this first mode of variability of SST has fundamentally changed and the PDO may not be as useful an indicator as it once was.

We have been getting a sample of the San Diego average fall rainfall pattern last few months without having to get on a plane. Monthly Total Precipitation for San Diego Area, CA (ThreadEx) Click column heading to sort ascending, click again to sort descending. Mean 0.30 0.23 0.53 2024 0.02 0.00 0.02 2023 0.05 0.01 0.06 2022 0.65 0.09 0.74 2021 0.50 1.01 1.51 2020 0.00 0.12 0.12 2019 0.11 0.00 0.11 2018 T 0.57 0.57 2017 0.08 T 0.08 2016 0.32 0.07 0.39 2015 1.24 0.43 1.67 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. 1 2024-10-16 0.34 0 2 1982-10-16 1.43 0 3 1973-10-16 1.88 0 - 1967-10-16 1.88 0

The ridges across the North Pacific and North Atlantic have been linking up into one continuous ridge during 4 out of the last 5 summers. So it’s no surprise the SSTs have been reaching record levels outside the traditional -PDO zones with so much subsidence and sunshine. The warm pool off of California and the strong ridge is a new feature which wasn’t there during the older -PDO era. Notice how there has been a continuous ridge and record SSTs underneath across much of the North Pacific. Same goes for the North Atlantic. The last strong -PDO in the early 1950s was defined more by the giant NP cold pool. These days it’s a record warm pool driving the -PDO. Also notice how the ridges back there were much weaker and covered a smaller area compared to the recent summers.

Tough to get rainfall here with record levels of ridging overhead and the 6 SD Pacific Jet pushed all the way up into Alaska.

This weekend was supposed to be closer to zonal with a weaker Southeast Ridge in the original long range forecast. But instead we are getting a near record 590+ DM ridge. So while the long range models can give a general idea of where the ridge axis will line up, the magnitude of the ridge usually overperforms the closer we get. So we should see near record highs early next week around 80° in the usual NJ warm spots . Then maybe a pullback closer to normal for a few days later next week. Then the next ridge amplification and warmer temps again after that. We could be looking at highs in the 70s near the end of the month when the daily mean high temperature is close to 60°.

Warm and dry Southeast Ridge pattern until further notice after this brief cooldown.

The main difference now is how much warmer the North Pacific is with this -PDO compared to around 1950. So this -PDO is the first to be defined more by continuing marine heatwaves. This is one of the reasons these record Aleutian Ridge patterns are persisting so much longer.

The offshore low is forecast to pull down dew points in the 20s this afternoon to further dry things out.

The correlations can work out for November to the winter provided the November events are extreme enough. The record South Carolina snow to start November 2014 was a good early sign of the cold 2014-2015 winter in the East. The record warmth in November 2015 and 2001 were early signals for the record winter warmth which was to follow.

Newark has a shot at its first 4 years in a row with 80° warmth after October 19th. This late season warmth has become a theme every year since 2021. It’s getting a boost this year from a near record 590+DM ridge. Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. 1947-12-31 87 0 1979-12-31 86 0 1950-12-31 85 0 2023-12-31 84 0 2001-12-31 83 0 1984-12-31 82 0 1978-12-31 82 0 1946-12-31 82 0 2022-12-31 81 0 2017-12-31 81 0 2003-12-31 81 0 1974-12-31 81 0 - 1963-12-31 81 0 2021-12-31 80 0 - 2007-12-31 80 0 - 1993-12-31 80 0 - 1982-12-31 80 0 - 1969-12-31 80 0 - 1961-12-31 80 0 - 1948-12-31 80 0

Yeah, we can try to outline some of the broad general themes for the winter in October. But the finer details usually have to wait until we get to the medium range. While the recent MJO is a little more amplified, it’s still closer to +2 than the better La Niña years near +3. It’s interesting how this pattern also matches the general La Niña strength. And the stronger ONI La Niña winters back to 2010 were the best of the multiyear groupings. Goes against the pattern of the weaker La Ninas being better from 1995 to 2009 than the really strong ones.

It’s little details like that which can be challenging detect much before we get to within the range of the 6-10 and 11-15 day forecast. The winter began with the near record Aleutian Ridge -PNA and very amplified MJO 6-7 forcing in December leading to the +13 warmest December at DFW. But we got the great MJO 8 in January salvaging the entire winter. Even though areas south of New England flipped back to the warmer and less snowy pattern in February. Unfortunately, we have had more examples of big MJO 4-7 transits weakening before 8 only to reload in 4-7 again. So we will probably need some help from the MJO 8 or even something else in order to avoid the winter pattern which has been locked in since February 2022.

The MJO forecasts look like we are following the warmer and less snowy groupings of La Ninas since 2010 in October 2011, 2016, 2021, and 2022 staying under +2. The better La Nina’s were higher than +2.8 like we got in 2010, 2017, and 2020. I will update the exact RMM number we reach in a few weeks. My guess is that these weaker MJO 4-6 Octobers were able to rebound stronger from December into January allowing the MJO 4-6 to have a strong influence on the pattern. The stronger MJO 4-6s in October were more muted in December allowing the other phases and factors to dominate. But even though 17-18 started out great through early January getting into phase 8, we did end up with record 4-6 activity from mid-January into February. So it was one case where the strong October MJO 4-6 reemerged mid to late winter. While 16-17 was a warmer La Niña winter, the MJO 4-6 activity wasn’t too outrageous. But the warmth was driven by the very amplified Aleutian Ridge which acted like a strong MJO 4-6 even though the RMM wasn’t as strong as say 2011-2012, 2021-2022, and 2023. In general the MJO 4-7 phases have been very amplified regardless of ENSO state since December 2015. We could even point to March 2012 as a bit of a precursor as to what would happen to the MJO several years later. It’s based on the MJO RMM amplitude and VP anomalies in phase 5-6 during La Niña Octobers since 2010. The stronger October MJO responses had better winters in NYC relative to the other La Ninas in the multiyear event group. Those stronger MJO 5-6 Octobers also had the more robust peak La Niña ONIs from fall into winter of the multiyear groups. All the La Niña winters around NYC since 11-12 have averaged warmer than normal. But even the warmer than average 17-18 and 20-21 winters had better snowfall than the other years in the multiyear group. In addition, we haven’t had any cold neutral ENSOs in the -0.1 to -0.5 peak range with a strong -PDO since 2010. So not sure how the relationship would work for any year with the official CPC ONI not getting colder than -0.5. The other thing to consider is that we don’t know how long this relationship will continue to work it. So I will update this post with some early ideas for the coming winter after we see how the MJO verifies for the month of October. http://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt https://origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php Multiyear La Niña groupings below with peak MJO 5-6 strength and the peak ONI from the fall into winter…….Strongest October MJO 5-6 and La Niña ONI leading to best NYC winters of the multiyear group bolded… October 2022…Phase 6 peak +2.177…..ONI….-1.0 October 2021….Phase 5 peak +2.087….ONI….-1.0 October 2020…Phase 5 peak +2.818….ONI…..-1.3 October 2017….Phase 6 peak +3.353….ONI….-1.0 October 2016….Phase 5 peak +1.800….ONI….-0.7 October 2011….Phase 6 peak +1.674….ONI….-1.1 October 2010….Phase 5 peak +2.880…ONI…..-1.6

Pretty much the October version of our recent highly amplified Aleutian Ridge and Southeast Ridge decadal winter pattern

The PDO at 500 mb is also near the most negative on record for the first half of October matching the SST index. This is a continuation of the record Aleutian ridge which has been in place this year. The poleward extension over the next 10 days will help to amplify the Southeast Ridge to near record levels for late October as the AO sees a near record increase also.