bluewave

Parts of Northern New England are on track for their latest first freeze on record.

After the near record warmth this week, the EPS has closer to normal temperatures next week. This means NYC may finally drop below 50°. But it will be among the latest first 40s on record. Since the EPO remains very positive, temperature departures rebound for the last week of October. Oct 11-18 Oct 18-25 Oct 25-31

Walt, do you know how the new Euro that was in parallel did? Looks like the upgrade tomorrow will be the biggest in a long time. It’s the first step toward the future convection permitting 4 to 5 km resolution. We are pleased to confirm the operational implementation of IFS Cycle 47r3 with the 06 UTC run, 12 October 2021 The upgrade will bring improvements to the assimilation and observations usage and a significantly improved physical basis for moist processes, necessary to facilitate further development of the Integrated Forecasting System (IFS) and future application at convection-permitting resolutions. The release candidate phase has been running in near real-time since 14 September. In a recent Webinar we explained the scientific background, its meteorological impact, and some new and revised products. Forecast users are recommended to read "47r3 Impact on Surface Weather representation", highlighting the changes with 47r3 in the characteristics of many frequently used forecast fields and products. We would also like to remind you of a change to the “Master Tables Version Number”, affecting allparameters in GRIB 2, and encourage you to check your data processing with the test data provided as soon as possible ahead of implementation. Detailed information can be found on the 47r3 implementation page. Please “watch” the page to get notified about further updates. https://confluence.ecmwf.int/display/FCST/47r3+Impact+on+Surface+Weather+representation IFS cycle 47r3 is delivering noteworthy changes in the characteristics of many of the forecast fields (such as precipitation) and forecast products regularly used by forecasters and others. These changes are probably more substantial, as a whole, than anything we have seen with any ECMWF cycle in the last 10 years. This page aims to highlight the key differences. It is common forecaster practice to adjust for perceived/known biases or weaknesses in model behaviour, and given the new characteristics application of these ("old") corrections to output from the new cycle may no longer be appropriate. Some such corrections can be discarded or toned down; other new ones may need to be introduced. Most of the changes with 47r3 are attributable to the new "Moist Physics" package, affecting cloud and precipitation in particular. However changes to the visibility and gust diagnostics will also have a substantial impact on occasion. Impacts are listed below, by parameter, with examples generally comparing output from cycle 47r2 (operational until 12 October 2021) and contiguous non-operational runs of 47r3 (operational from 12 October 2021). Unless stated otherwise examples are from HRES. "NEW CYCLE" on plots below means 47r3.

Top 10 warmest first 10 days of October for several of our stations. Time Series Summary for FARMINGDALE REPUBLIC AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Oct 1 to Oct 10 Missing Count 1 2007-10-10 68.9 0 2 2018-10-10 67.7 0 3 2017-10-10 67.1 0 4 2005-10-10 66.2 0 5 2013-10-10 65.9 0 6 2021-10-10 64.6 0 7 2002-10-10 64.4 0 8 2020-10-10 62.0 0 9 2019-10-10 61.8 0 10 2016-10-10 61.5 2 Time Series Summary for ISLIP-LI MACARTHUR AP, NY Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Oct 1 to Oct 10 Missing Count 1 2007-10-10 68.5 0 2 2018-10-10 68.0 0 3 1990-10-10 66.7 0 4 2017-10-10 66.6 0 5 2013-10-10 65.6 0 6 2005-10-10 65.5 0 7 2021-10-10 63.7 0 8 2002-10-10 63.3 0 9 1995-10-10 63.2 0 10 1997-10-10 63.0 0 - 1983-10-10 63.0 0 Time Series Summary for NEWARK LIBERTY INTL AP, NJ Click column heading to sort ascending, click again to sort descending. Rank Ending Date Mean Avg Temperature Oct 1 to Oct 10 Missing Count 1 1959-10-10 72.4 0 2 2007-10-10 71.8 0 3 2018-10-10 69.6 0 4 2017-10-10 69.5 0 5 1990-10-10 68.8 0 6 1941-10-10 68.5 0 7 2013-10-10 67.2 0 8 2021-10-10 66.9 0 9 1973-10-10 66.7 0 10 1949-10-10 66.4 0

It looks like the 80s could last into Saturday.

Could see an impressive late season warm up this week with more 80s. The EPAC tropical system phases with the near record Western Trough. This really pumps up the SE Ridge.

We had the record SST warmth east of Newfoundland last October also. That may be why we had the unusually south based -NAO/-AO last winter. But the La Niña didn’t couple last winter so it worked for us with the +PNA. Not sure how a La Niña with a south based -AO would work out. The block may try to link up with the SE Ridge and dampen a -AO effect at times. The Equatorial Atlantic is near record levels of warmth this October which could also impact the winter rossby wave train. Plus the PDO is much colder this October. All that being said, It always comes down to how the pattern actually develops during the winter. This early winter talk is always just speculation. October 2021 October 2020

October 2017 was our warmest on record. https://www.ncei.noaa.gov/news/national-climate-201710

The October MJO 5 link may be related to the MJO 5 forcing the stronger Urals Ridge which has been shown to weaken the SPV.

The current October MJO 5 matches the snowier La Niña years since 2000 with -AO and -NAO intervals. The only two coupled La Niña seasons since 2000 with below average snow and blocking were 2007-2008 and 2011-2012. The Octobers before those winters had a MJO 1-2 pattern.That being said, we can’t be sure this will continue to work for this winter. La Niña October MJO 5 before snowy seasons with blocking This year makes the list La Niña October MJO 1-2 composite before below normal snowfall and no blocking

With the record blocking patterns since 2002-2003, we have seen an unprecedented number of seasons when stations from around Newark out to Eastern LI recorded 40” or more of snow. This dramatic increase in snowfall has occurred during a steady increase in winter temperatures. Our older winters with 40”+ peak snowfall amounts used to occur with a NYC average temperature around 32°. But many recent 40”+ seasons featured a NYC average DJF temperature in the 35°-40° range. So this is a new combination of warmth and heavy snow for our area. Seasons since 1950 when at least one station from Newark to Eastern LI recorded 40”+ and the NYC DJF average temperature. 35°+ average temperature seasons bolded 20-21….36.1 17-18….36.2 16-17….39.3 15-16….41.0 14-15…31.4 13-14…32.9 12-13…36.8 10-11….32.8 09-10…33.8 08-09…34.2 05-06…37.3 04-05…35.4 03-04…32.4 02-03…31.2 00-01….33.5 95-96…32.2 93-94…31.2 86-87….34.8 77-78….30.8 68-69….32.9 66-67….34.1 63-64…33.2 60-61….31.7 57-58…33.2 55-56…32.8

It will all come down to how much blocking we get. Unfortunately, the seasonal models have very little skill at forecasting the correct phase of the AO and NAO. When the ENSO is coupled, they do much better with the North Pacific pattern. Darker oranges more skill Since 2010, the stronger La Ninas had more snow. During other periods, the weaker years had more snow. So there may not be much correlation between snowfall and La Niña strength. It really comes down to how much blocking we get

While record ridges have been dominating, models have a rare -4SD near record trough for the SW next week.

76° at Islip. This establishes a new annual record of 121 days reaching 75° or warmer. The high of 76° so far is average for September 10th. MacArthur/ISP PTSUNNY 76 Time Series Summary for ISLIP-LI MACARTHUR AP, NY - Jan through Dec Click column heading to sort ascending, click again to sort descending. Rank Year Number of Days Max Temperature >= 75 Missing Count 2021 121 84 2007 120 0 1991 120 0 2010 118 0 2011 117 0 2005 116 0 2001 116 0 2016 115 0 2015 115 0

Several more fall temperature benchmarks still haven’t been reached around the area with the warmth. NYC is yet to see the first 40s of the season and POU hasn’t had any 30s. So these firsts for the fall will be near the latest on record at both locations. This is in top of the already later average first dates since the 1951-1980 climate period. NYC latest first 40s First/Last Summary for NY CITY CENTRAL PARK, NY Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Difference 2005 05-25 (2005) 48 10-20 (2005) 49 147 2017 05-14 (2017) 46 10-16 (2017) 46 154 1995 05-11 (1995) 48 10-16 (1995) 48 157 1955 05-18 (1955) 48 10-16 (1955) 46 150 1969 05-27 (1969) 49 10-15 (1969) 46 140 1898 05-10 (1898) 47 10-15 (1898) 49 157 POU latest first 30s First/Last Summary for Poughkeepsie Area, NY (ThreadEx) Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Difference 1939 05-19 (1939) 39 10-15 (1939) 32 148 2018 05-01 (2018) 38 10-13 (2018) 38 164 1931 05-04 (1931) 34 10-11 (1931) 39 159 2015 05-14 (2015) 35 10-10 (2015) 39 148 2002 05-23 (2002) 36 10-08 (2002) 36 137 2011 05-08 (2011) 38 10-06 (2011) 36 150 Fall temperature benchmarks getting later over time NYC average first 40s….2010-2020….10-05…..1951-1980….09-24 POU average first 30s….2010-2020….09-27…..1951-1980….09-17

The record winds during the winter transported the MYI into the Beaufort giving it more chance to melt out during the summer. https://nsidc.org/arcticseaicenews/ Despite September total ice extent being high compared to recent years, the amount of multiyear ice as assessed from ice age (Figure 5e) reached a near-record low, with an extent of only 1.29 million square kilometers (498,000 square miles), just slightly above the value of 1.27 million square kilometers (490,000 square miles) at the end of the 2012 melt season.

The latest extended EPS keeps the warm +EPO going well into October. Some hints that the pattern may try to go more -EPO/-AO in November. But that is a long way out for the weeklies. Oct 11-18 Pattern change for November? Nov 8-15

Yeah, the PDO and PMM are driven by NP pressure patterns like the EPO. A strong +EPO vortex cools the SSTs and PDO. The -EPO ridge warms the SSTs and warms the PDO. We saw more of a -PDO drop developing over the summer with the deep low and record clouds near Alaska. But these pressure patterns can change very rapidly from month to month. So it’s tough to know how long any given pattern will last. We saw the rapid rise into last winter with the uncoupled La Niña and record blocking that took over after November.

This was the deepest September trough near Alaska since 2011 which pumped up the record ridge over Canada. We have usually been seeing record ridges in that area since 2013. The other exception was the deep vortex there for the 2019-2020 winter.

The Euro gets upgraded next week. Significant improvement in moist processes. This will eventually allow for 4-5km convection permitting resolutions in the future. It will be interesting to see what a global model looks like when run at resolutions like the HRRR and hi res NAM. Maybe this moist process upgrade next week will improve the east coast storm track suppression issue that popped up with one of the upgrades after 2013. We are pleased to confirm the operational implementation of IFS Cycle 47r3 with the 06 UTC run, 12 October 2021 The upgrade will bring improvements to the assimilation and observations usage and a significantly improved physical basis for moist processes, necessary to facilitate further development of the Integrated Forecasting System (IFS) and future application at convection-permitting resolutions. The release candidate phase has been running in near real-time since 14 September. In a recent Webinar we explained the scientific background, its meteorological impact, and some new and revised products. Forecast users are recommended to read "47r3 Impact on Surface Weather representation", highlighting the changes with 47r3 in the characteristics of many frequently used forecast fields and products. We would also like to remind you of a change to the “Master Tables Version Number”, affecting allparameters in GRIB 2, and encourage you to check your data processing with the test data provided as soon as possible ahead of implementation. Detailed information can be found on the 47r3 implementation page. Please “watch” the page to get notified about further updates. https://confluence.ecmwf.int/display/FCST/47r3+Impact+on+Surface+Weather+representation IFS cycle 47r3 is delivering noteworthy changes in the characteristics of many of the forecast fields (such as precipitation) and forecast products regularly used by forecasters and others. These changes are probably more substantial, as a whole, than anything we have seen with any ECMWF cycle in the last 10 years. This page aims to highlight the key differences. It is common forecaster practice to adjust for perceived/known biases or weaknesses in model behaviour, and given the new characteristics application of these ("old") corrections to output from the new cycle may no longer be appropriate. Some such corrections can be discarded or toned down; other new ones may need to be introduced. Most of the changes with 47r3 are attributable to the new "Moist Physics" package, affecting cloud and precipitation in particular. However changes to the visibility and gust diagnostics will also have a substantial impact on occasion. Impacts are listed below, by parameter, with examples generally comparing output from cycle 47r2 (operational until 12 October 2021) and contiguous non-operational runs of 47r3 (operational from 12 October 2021). Unless stated otherwise examples are from HRES. "NEW CYCLE" on plots below means 47r3.

Multiyear ice finishes at 2nd lowest on record with extent in 12th place.

The latest extreme rainfall event.

International Falls is headed for the latest first freeze on record as much of North America has well above average temperatures. Frost/Freeze Summary for International Falls Area, MN (ThreadEx) Each section contains date and year of occurrence, value on that date. Click column heading to sort ascending, click again to sort descending. Year Last Value First Value Season Length 2016 06-08 (2016) 30 10-08 (2016) 29 121 1919 05-08 (1919) 32 10-06 (1919) 25 150 1988 05-14 (1988) 31 10-04 (1988) 25 142 1968 05-23 (1968) 30 10-04 (1968) 27 133 1921 06-04 (1921) 29 10-03 (1921) 31 120 2017 05-24 (2017) 30 09-29 (2017) 32 127 1994 05-10 (1994) 26 09-29 (1994) 32 141 1920 05-13 (1920) 29 09-29 (1920) 28 138 2019 06-02 (2019) 29 09-28 (2019) 29 117 2015 06-01 (2015) 30 09-28 (2015) 28 118 Euro October forecast

Looks like the high was 68° with the minimum driving the warm departure.