bluewave

Starting the day with the low temperatures close to +20. We are right around record warm minimums for the date. Newark....currently 65°..avg....46°....+19....record min...64°...

Adding a cutoff to the mix just adds to potential model error later in the forecast period.

https://nsidc.org/arcticseaicenews/faq/#area_extent What is the difference between sea ice area and extent? Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method. A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated. Extent defines a region as “ice-covered” or “not ice-covered.” For each satellite data cell, the cell is said to either have ice or to have no ice, based on a threshold. The most common threshold (and the one NSIDC uses) is 15 percent, meaning that if the data cell has greater than 15 percent ice concentration, the cell is considered ice covered; less than that and it is said to be ice free. Example: Let’s say you have three 25 kilometer (km) x 25 km (16 miles x 16 miles) grid cells covered by 16% ice, 2% ice, and 90% ice. Two of the three cells would be considered “ice covered,” or 100% ice. Multiply the grid cell area by 100% sea ice and you would get a total extent of 1,250 square km (482 square miles). Area takes the percentages of sea ice within data cells and adds them up to report how much of the Arctic is covered by ice; area typically uses a threshold of 15%. So in the same example, with three 25 km x 25 km (16 miles x 16 miles) grid cells of 16% ice, 2% ice, and 90% ice, multiply the grid cell areas that are over the 15% threshold by the percent of sea ice in those grid cells, and add it up. You would have a total area of 662 square km (255.8 square miles). Scientists at NSIDC report extent because they are cautious about summertime values of ice concentration and area taken from satellite sensors. To the sensor, surface melt appears to be open water rather than water on top of sea ice. So, while reliable for measuring area most of the year, the microwave sensor is prone to underestimating the actual ice concentration and area when the surface is melting. To account for that potential inaccuracy, NSIDC scientists rely primarily on extent when analyzing melt-season conditions and reporting them to the public. That said, analyzing ice area is still quite valuable. Given the right circumstances, background knowledge, and scientific information on current conditions, it can provide an excellent sense of how much ice there really is “on the ground

The forecast details beyond 7 days may be lower skill than usual. It looks like the EPS is struggling with the wavelengths following the big Epsilon ET. So we’ll probably have to wait and see how the late October into early November forecast evolves. New run Old run

Temperatures are off to the races away from the marine layer. Wrightstown MOSUNNY 77 66 69 S7 Scranton SUNNY 75 59 57 S9 Hartford PTSUNNY 73 60 63 SW9

Temperatures around the area are starting out with minimums within a few degrees of the warmest daily minimums. These are the warmest low temperatures on this date since 2016. Newark Liberty DRZL/FOG 61 61 9 JFK.....low of 60 so far Newark Area, NJ Version: 15.4 (created 2020-07-31) Period of record: 1931 through 2019 10/21 62 in 1984 62 in 1979 58 in 2016 New York-Kennedy Airport Area, NY Version: 15.4 (created 2020-07-31) Period of record: 1948 through 2019 10/21 60 in 2016 60 in 1984 58 in 1979

Yeah, it was a sharp El Niño snowfall gradient favoring Central NJ. 86-87 BDR...22.1 ISP.....22.5 LGA....23.2 JFK....23.1 NYC...23.1 EWR...32.6 TTN...37.1

The 1980s was the only decade that NYC didn’t go over 30” in a single season. https://www.weather.gov/media/okx/Climate/CentralPark/monthlyseasonalsnowfall.pdf Max snowfall season in NYC 2010s....61.9 2000s....49.3 1990s....75.6 1980s....27.2 1970s....50.7 1960s....54.7 1950s....44.7 1940s....63.9 1930s....52.0 1920s....60.4 1910s....50.7 1900s....53.2 1890s....55.9 1880s....44.6 1870s....60.2

The last few days set the new all-time extent anomaly record.

Yeah, 1988 was the last time NYC dropped below 32° in October. It was also the most recent time POU and MPO dropped under 20° in October. Time Series Summary for NY CITY CENTRAL PARK, NY - Month of Oct Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1936 28 0 2 1976 29 0 - 1925 29 0 - 1887 29 0 - 1879 29 0 3 1940 30 0 - 1869 30 0 4 1988 31 0 - 1975 31 0 - 1974 31 0 - 1969 31 0 - 1871 31 0 Time Series Summary for Poughkeepsie Area, NY (ThreadEx) - Month of Oct Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1988 18 0 - 1974 18 0 - 1952 18 0 - 1936 18 0 2 1987 19 0 - 1985 19 0 - 1976 19 0 - 1972 19 0 - 1950 19 0 Time Series Summary for Mount Pocono Area, PA (ThreadEx) - Month of Oct Click column heading to sort ascending, click again to sort descending. Rank Year Lowest Min Temperature Missing Count 1 1917 12 0 2 1936 13 0 - 1907 13 0 3 1969 15 0 - 1939 15 0 - 1904 15 0 4 1988 16 1 - 1972 16 0 - 1933 16 0 - 1928 16 0 - 1916 16 0 - 1905 16 0

The 60s dew points returned right on schedule. Some spots may challenge their warmest daily minimums next few days. KEWR GFS MOS GUIDANCE 10/20/2020 0600 UTC DT /OCT 20 /OCT 21 /OCT 22 / HR 12 15 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 00 06 X/N 72 63 77 63 75 TMP 62 66 70 70 67 66 66 65 66 72 75 74 71 68 67 65 65 69 73 66 61 DPT 59 60 60 60 61 61 63 63 63 64 64 64 64 62 60 59 58 55 52 50 54 CLD OV OV OV OV OV OV OV OV OV OV BK BK BK OV OV OV BK BK SC SC CL WDR 10 16 21 21 02 03 06 07 12 20 20 21 19 22 23 31 35 36 01 05 05 WSP 01 04 04 04 03 02 02 01 01 06 09 09 05 04 04 04 05 07 06 05 05 Newark Area, NJ Version: 15.4 (created 2020-07-31) Period of record: 1931 through 2019 10/21 62 in 1984 62 in 1979 58 in 2016 10/22 64 in 1979 63 in 1984 62 in 1970

At least for a La Niña October, that drought ridge along the West Coast is out of place.

The PDO isn’t following the La Niña playbook this fall. This was one of the biggest PDO increases during a La Niña in October. But as we have seen since the record North Pacific warming in 2013, these monthly values can really jump around a lot. Last winter we went from positive in December to negative during January and February. It all comes down to how the North Pacific ridge behaves.

Those are the new free maps. All we need now is for someone to generate free ECM MOS. https://www.weather.gov/media/mdl/Shafer-AMS-ext-abstract.pdf

Yeah, looks like this warmer WAR pattern should persist at least into the last week of October.

That area was in a perfect spot to take advantage of the strong block near Greenland this month. The strong WAR seems to have kept the TPV locked in along the west side of Hudson Bay. So a strong -NAO/-AO isn’t much of a help for us if the WAR is too amplified.

We are getting a late October version of our recent summer warm ups. Clouds, high dew points for this time of year, and onshore flow. Same old pattern with the big ridge parked near New England. KEWR GFS MOS GUIDANCE 10/19/2020 1200 UTC DT /OCT 19/OCT 20 /OCT 21 /OCT 22 HR 18 21 00 03 06 09 12 15 18 21 00 03 06 09 12 15 18 21 00 06 12 N/X 58 74 63 76 64 TMP 64 64 61 60 60 60 61 68 72 71 68 67 66 65 66 71 74 73 70 67 67 DPT 49 51 52 53 55 57 59 61 61 61 62 62 63 64 64 64 64 64 64 63 62 CLD BK BK BK OV OV OV OV OV OV OV OV OV OV OV OV OV BK BK OV OV BK WDR 14 15 14 13 11 11 15 19 22 23 10 04 06 07 14 19 20 19 19 21 29 WSP 05 06 04 03 02 01 03 04 05 05 03 02 02 02 03 05 08 08 06 04 03

2nd big snowfall October in a row for the Great Falls area. Time Series Summary for Great Falls Area, MT (ThreadEx) - Month of Oct Click column heading to sort ascending, click again to sort descending. Rank Year Total Snowfall Missing Count 1 1925 18.5 0 2 2019 17.0 0 3 1975 16.6 0 4 1919 15.5 0 5 2020 14.2 13

It has been the only cooler than average part of the US since the Super El Niño in 2016.

Warm in the East and cold with record early snows in Montana this week. Very familiar La Niña background pattern in recent years. The SE Ridge or WAR continues to dominate. GEFS temperature departures for the next 7 days

The models have plenty of clouds and an S To SE flow this week. So that’s why they hold the highs in the 70s instead of 80s. Still a +10 or higher departure on the warmest days. Maybe somebody in Central Jersey can make a run on 80° with more sun and SSW flow than forecast. KEWR GFSX MOS GUIDANCE 10/18/2020 1200 UTC FHR 24 36| 48 60| 72 84| 96 108|120 132|144 156|168 180|192 MON 19| TUE 20| WED 21| THU 22| FRI 23| SAT 24| SUN 25|MON CLIMO N/X 51 67| 56 72| 61 73| 63 78| 63 75| 60 72| 54 66| 48 44 62

Pretty late in the season for a 588 DM ridge over our area this week.

First 30s of season at places like ISP this morning is close to the average since 2010. A little over a week later than during the 2000’s. First/Last Summary for ISLIP-LI MACARTHUR AP, 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 Minimum 04-11 (2019) 10-10 (2010) 149 Mean 04-28 10-19 172 Maximum 05-13 (2010) 11-01 (2017) 190 2019 04-11 (2019) 36 10-19 (2019) 38 190 2018 04-24 (2018) 36 10-18 (2018) 35 176 2017 05-04 (2017) 39 11-01 (2017) 36 180 2016 04-17 (2016) 37 10-11 (2016) 39 176 2015 05-02 (2015) 39 10-18 (2015) 33 168 2014 04-25 (2014) 38 10-20 (2014) 35 177 2013 05-05 (2013) 39 10-21 (2013) 39 168 2012 04-30 (2012) 36 10-13 (2012) 32 165 2011 05-06 (2011) 38 10-28 (2011) 37 174 2010 05-13 (2010) 38 10-10 (2010) 37 149 First/Last Summary for ISLIP-LI MACARTHUR AP, 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 Minimum 04-17 (2009) 10-02 (2009) 137 Mean 05-09 10-10 153 Maximum 05-22 (2002) 10-24 (2005) 167 2009 04-17 (2009) 32 10-02 (2009) 38 167 2008 05-20 (2008) 39 10-18 (2008) 39 150 2007 05-08 (2007) 39 10-13 (2007) 39 157 2006 04-29 (2006) 37 10-13 (2006) 38 166 2005 05-13 (2005) 37 10-24 (2005) 36 163 2004 05-05 (2004) 38 10-05 (2004) 39 152 2003 05-18 (2003) 38 10-03 (2003) 34 137 2002 05-22 (2002) 37 10-14 (2002) 39 144 2001 05-08 (2001) 37 10-07 (2001) 39 151 2000 05-16 (2000) 39 10-08 (2000) 39 144

All the extra ocean heat on the Siberian side is really slowing the freeze-up this October. So the the extent is currently the lowest on record for this time of year well below 2012. The Siberian heatwave this year was one of the most extreme events we have seen.

We have been warm and snowy regardless of La Niña, neutral, or El Niño last 20 years or so. The main difference between La Niña and El Niño has been the timing. La Ninas generally start out with the coolest departures early and transition to warm later on. 17-18 had coldest week of winter before January 5th flowed by 80° in February. El Niño is reversed. +13 during December 2015 followed by the historic late January blizzard and below 0° day for NYC in February. The other difference is the El Niño’s usually have a strong STJ and La Ninas a strong NPAC Jet.