bluewave

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.

It’s interesting how close that Pacific forecast is to DJF 16-17 and 17-18. While we had the background SE Ridge, the Aleutian ridge built over the top at times for -AO periods. So getting those blocking intervals will be essential for near to above normal snowfall this winter. DJF 2016-2017 and 2017-2018

The Euro seasonal just came out today. It’s really hitting the Aleutians Ridge very hard. So if that is correct, then we will need blocking to have a shot at above normal snowfall. While we had a strong SE Ridge in 16-17 and 17-18, blocking intervals gave us above normal snowfall to go with the above normal temperatures.

At least for our area, there really isn’t much correlation between ENSO and snowfall. Snowfall amounts come down to how much blocking we get. Above normal snowfall and above normal temperatures has been the most common winter combination in our area since 2002-2003. That was the year the record snowfall and -AO/-NAO blocking patterns become more frequent. Above normal snowfall and above normal temperatures 7 years 20-21 17-18 16-17 15-16 12-13 05-06 04-05 Above normal snowfall and below normal temperatures 6 years 14-15 13-14 10-11 09-10 03-04 02-03 Below normal snowfall and above normal temperatures 5 years 19-20 18-19 11-12 07-08 06-07 Near normal temperatures and near normal snowfall 1 year 08-09

This fall is featuring the strongest -PDO pattern in years. It results in a warmer than average +EPO/-PNA pattern with a pumped up SE Ridge. Main question for the winter is will we get enough blocking to tame this pattern a bit? Second winters after extreme blocking like last year usually had follow up blocking.

Today was one of the easterly flow days that I mentioned yesterday when the warm minimums drive the departure. The high at JFK was +4 and the low so far of 67° is +13°. So the low could fall a few more degrees before midnight and still be close to +10°. CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 433 PM EDT MON OCT 04 2021 ................................... ...THE KENNEDY NY CLIMATE SUMMARY FOR OCTOBER 4 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1948 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 73 940 AM 84 1967 69 4 69 MINIMUM 67 214 AM 39 1996 54 13 47 AVERAGE 70 62 8 58

The latest extended EPS continues the warmer than average temperatures during the next few weeks. The deep trough digging into the West will keep pumping SE Ridge. Oct 4-11 Oct 11-18

Low 80s in the warm sector over Central NJ. Wrightstown MOSUNNY 81 66 59 S3

The 68° dew point at 7 am in October is just a few degrees off the record of 71° set back in 2018. https://forecast.weather.gov/product.php?site=NWS&issuedby=OKX&product=RWR&format=CI&version=1&glossary=1&highlight=off

Today is a preview of the next few weeks. Days when we get SW flow the maximum departures will dominate. When the flow turns more easterly with clouds and rain, then the warm minimums will drive the daily warm departures. There may be several days in the mix when the warm maxes and mins can equally dominate. Albany with the easterly flow warm +10 minimum CLIMATE REPORT NATIONAL WEATHER SERVICE ALBANY NY 432 PM EDT SUN OCT 03 2021 ................................... ...THE ALBANY NY CLIMATE SUMMARY FOR OCTOBER 3 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD: 1991 TO 2020 CLIMATE RECORD PERIOD: 1874 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 65 2:59 PM 83 1922 67 -2 58 1967 MINIMUM 56 3:34 AM 29 1945 46 10 37 AVERAGE 61 56 5 48 SW flow in our area with the +8 to +13 maximums driving the warm departures CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 435 PM EDT SUN OCT 03 2021 ................................... ...THE NEWARK NJ CLIMATE SUMMARY FOR OCTOBER 3 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1931 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 84 102 PM 85 1950 71 13 69 MINIMUM 56 553 AM 37 1945 54 2 48 AVERAGE 70 62 8 59 CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 435 PM EDT SUN OCT 03 2021 ................................... ...THE LAGUARDIA NY CLIMATE SUMMARY FOR OCTOBER 3 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1939 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 81 212 PM 85 2000 71 10 69 MINIMUM 63 640 AM 40 1974 58 5 55 AVERAGE 72 64 8 62 CLIMATE REPORT NATIONAL WEATHER SERVICE NEW YORK, NY 435 PM EDT SUN OCT 03 2021 ................................... ...THE ISLIP NY CLIMATE SUMMARY FOR OCTOBER 3 2021... VALID TODAY AS OF 0400 PM LOCAL TIME. CLIMATE NORMAL PERIOD 1991 TO 2020 CLIMATE RECORD PERIOD 1963 TO 2021 WEATHER ITEM OBSERVED TIME RECORD YEAR NORMAL DEPARTURE LAST VALUE (LST) VALUE VALUE FROM YEAR NORMAL ................................................................... TEMPERATURE (F) TODAY MAXIMUM 77 1214 PM 80 2000 69 8 68 2002 MINIMUM 56 540 AM 34 2003 52 4 48 AVERAGE 67 60 7 58

JFK needs 4 more days to tie the record set in 2010. Time Series Summary for JFK INTERNATIONAL AIRPORT, 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 2010 124 0 2001 124 0 1971 124 0 2015 123 0 2016 121 0 2005 121 0 1991 120 0 1963 120 0 2021 120 89 2012 119 0 2007 119 0