Roger Smith

Presumably the tracked component began on Oct 27 and its motion is prograde at low latitudes so the closer it gets to the center of the circle, the closer to the equator it has tracked. The current location is where the red portion of the track begins (on Dec 5 as posted). The labels around the outside of the graph show that the frame of reference is as follows ... left is around 60 deg W longitude (tropical N Atlantic near Trinidad), bottom is around 30 deg east (east Africa), right is 120 deg E (w Indonesia) and the top of the square is 150 W (south of Hawaii). The component being tracked (almost always a generally prograde motion from west to east, you can see one brief retrograde period labelled early Nov) is anomalous tropical convection. The MJO assumption is that this will anchor the dynamics of the higher latitude ridge-trough pattern that drives the jet stream in the mid-latitudes. So to sum up, the diagram tracks the motion of this forcing over about two months with 45 past days and 15 future days projected. In this case the feature has crossed the equatorial Pacific and moved across at least part of central America where it has begun to drift closer to the equator. It is progged to continue that motion for 2-3 days and then slowly reverse back towards the subtropics. There is no longer-range projection shown but one could assume the later December into January track would take it across Africa into the Indian Ocean. But I don't follow it myself, just aware of what others think it may mean to long-range prospects. Because it's not my main focus I may have some of these details wrong, so perhaps somebody more familiar with the diagram can set us straight. I think the phrase Maritime Continent is a reference to the many islands of Indonesia and the Philippines as well as Australia and New Zealand in general terms. What I would not swear to is that the diagram is meant to convey equal differentials of longitude, it may be somewhat schematic on that, and the scale of the latitude range is not really clear but I assume the circle is the tropic of Cancer and the center of the diagram is the equator. It would probably be rare for the tracked component to get to any latitude much greater than 25 N.

Friday's daytime max of 30F at NYC would have been the sixth lowest maximum for the date. The record low max was 22F in 1886. Also colder were 24F in 1926, 27F in 1901, 28F in 1893, and 29F in 1871. The 30F was set to replace 31F (2002) for lowest of the past 99 years, but the daily max then crept up to 32F before midnight, so all of the above was amended as a few more days crept into the mix at 31 or 32 F. The minimum of 20F (despite the much greater urban heat island now present) was lower than all but six years, most of them well back in the records. The lowest reading was 11F in 1926, followed by 13F in 1886, 14F in 1871, and 15F in 1935. Also colder were 19F lows in 1901 and 1911 (and 2025 also tied 20F 1893). Friday was (until the slight evening rise) slightly colder than the same date in 1989. A benchmark cold day early in December in relatively recent times would be Dec 3, 1976 (max 23, min 9 both records) followed by Dec 3, 1966 (max 25, min 15 with 14 the following morning before a massive warming trend culminating with a record high 66F on the 9th). I remember reading my own backyard thermometer (30w Toronto) in that 1966 period when I was a high school senior, at my home weather station we went from a low of -2 F to a midnight high of 60 F over those same days, and there was a very high barometric pressure with the cold spell. There was no snow on the ground either except for traces from a light fall before the cold snap, the November had been very wet and mild.

White rain gradually turned to powdery snow at 1.5" hour rates, ski resort locally is opening this weekend and saying wow, glad we didn't invest in snowmakers after all. ... 32 F, hills are nearly impassable locally.

Enjoyed reading all that in part because it tends to reinforce what I was thinking about this coming winter, lots of cold air masses with extreme cold potential at times especially in the Midwest U.S. ... the storm on Tuesday looks like it wants to explode off Cape Cod and will be a formidable storm for Nova Scotia, perhaps this cycle will move up in time slightly and eastern New England will be seeing a major event but at the moment it looks to be more like a moderate one except perhaps on the cape. The 18z GFS is just one arctic high after another for central regions, could be running some -5 to -10 anomalies this month. And I believe there is a very good correlation of Dec to Jan temp anomalies, 1989-1990 being a significant exception.

Will be interesting to see if this system can get enough organization to surpass 1-2 inches anywhere, at least it doesn't have much danger of WAA becoming a problem, the air mass is brutally cold as far south as n AR and n MS at present, but clearly the missing ingredient is energy, worst case scenario is just 6-12 hours of light barely accum snow with 0.5"type totals, but with the relatively warm water in Chesapeake Bay interacting with the weak easterly flow it could deliver 1.5 to 3.0 inches in a few spots, I hope. By the way, the latest GFS run looks like the coldest Dec since 2014 or even 1989 in some parts of the country, just one arctic high after another. I think you're in for three or four at least minor snowfalls and few days very much above 40 F.

A workaround for calculating means with traces is to find the sum, and divide it by the number of years. (not =AVERAGE(A1:A30) but =SUM(A1:A30)/30 (for 30 years). Easy peasy. Disclaimer, my excel program is 2007 vintage, and they may have "improved" that procedure out of existence. But I can add columns where I cannot average them. Also if you wanted to know how many traces there were in 156 years or however many, the procedure there is =COUNTIF(A1:A156,"T") (just saying A because I am Canadian, your data may be in column USA). Free laffs with this stats lesson. I used "T" in my example and not "Tr" or "trace" but use whatever form your traces actually show up, I have NYC data with T and Toronto data with Tr ... and I found that on average about 20 to 25 per cent of days have a trace report.

Both me and Jebman are within shouting distance of the middle of the table. Whodathunkit?

Please note, all other scoring is located back before December forecasts started to appear, so scroll back past the first of those (from Scotty) and past the intro post for December (which I never did edit into scoring) and all the scoring will be found in one combined November scoring table and annual update. Tom continues to lead the contest and it looks like a very interesting scenario for the contest with severe cold on some guidance and in some forecasts (but not all). Meanwhile, the four seasons contest is now final and here are the results of that ... Four Seasons 2024-2025 Final Report after Autumn 2025 scoring 12 points to each seasonal winner, 10 points down to 1 point for rest of field, and 1 point for all entrants with at least 2 of 3 contests entered. (2025 annual leader to end of November, Tom, had a low score in Dec 2024 which explains how this is closer than the points contest for annual 2025) ___________________________ winter _______ spring ______ summer_______ autumn ________________ Contest year FORECASTER ____________TOTAL_pts___TOTAL_pts __TOTAL_pts ___Sep Oct Nov_ TOTAL _pts __TOTAL Points ___ Consensus __________ 1771 _ 9.7 __ 1767 __7.4 __ 2088_ 10 ___ 676_688_595 _ 1959 _ 10 ___ 37.1 so_whats_happening _____1662 __ 8 ___ 1805 __ 8 ___ 2038 __ 8 ____670_676_569 _ 1915 _ 7t ____ 31 RJay _____________________ 1703 __ 9 ___ 1689 __ 5 ___ 1972 __ 5 ____674_612_701 _ 1987 _ 12 ____ 31 Don Sutherland1 _________ 1587 __ 5 ____1733 __ 6 ___ 2088 _ 10____654_634_633 _ 1920 _ 8 ____ 29 Tom ______________________1417 __ 1 ____ 2053 _ 12 ___ 2154 __12 ___590_700_583 _ 1873 _ 3 ____ 28 Scotty Lightning _________ 1542 __ 4 ____1741 __ 7 ___ 2052 __ 9 ____738_650_507 _ 1895 _ 4 ____ 24 wxallannj _________________1800 _ 10 ___ 1561 __ 3 ___ 1906 __ 2 ____662_650_635 _ 1947 _ 9 ____ 24 hudsonvalley21 __________ 1532 __ 3 ___ 1933 __ 9 ___ 1950 __ 4 ____690_700_509 _1899 _ 5 ____ 21 StormchaserChuck ______ 1328 __ 1 ____1953 __10 ___ 2010 __ 7 ____490_570_ ---_ 1060 _ 1 _____ 19 BKViking _________________1805 _ 12 ___ 1621 ___ 4 ___ 692 __ 0 ____490_666_571 _ 1727 _ 1 _____ 17 wxdude64 _______________ 1653 __ 7 ___ 1436 __ 1 ___ 1980 __ 6 ____550_578_310 _ 1438 _ 1 ____ 15 RodneyS ________________ 1488 __ 2 ____ 1474 __ 2 ___ 1938 __ 3 ___ 552_772_591 _ 1915 _ 7t ____14 Roger Smith _____________ 1617 __ 6 ____ 1368 __ 1 ___ 1880 __ 1 ____738_554_469 _ 1761 _ 2 ____ 10 Yoda ____________________ -- -- __ 0 ____ -- -- ___ 0 ___ 542 ___0 ___ 678_686_595 _ 1959 _10 ____10 ___ Normal _____________ 1387 __ 1 ___ 1440 ____1 ____ 1778 __ 1 ___ 664_578_454 _1696 _ 1 ____ 4 Ephesians2 _____________ -- -- __ 0 ____ -- -- ___ 0 ____ --- ___0 ___ ---_ 574_ 531 _ 1105 _ 1 _____ 1 ___________________________ So we have a tie in points at the top (although Consensus is the contest winner too) ... I will declare it a tied win for RJay and so_whats_happening, meanwhile DonSutherland1 also had a strong finish into third place and contest leader Tom was just a bit off his previous pace to end up in fourth, but with so many totals just a few points ahead of Tom he was only able to advance slightly this past season -- the points differential is not making much impact on his overall contest lead, as you can see there has not been a large spread in the autumn points for most of the forecasters. Yoda had a very good first season after joining in August, finishing second in points for autumn. I don't score Persistence in the four seasons contest but probably Persistence would have been lucky to add any points to Normal's basic total.

Table of forecasts for December 2025 FORECASTER __________________ DCA _NYC _BOS __ORD _ATL _IAH ___ DEN _PHX _SEA Mercurial ______________________ +4.0 _+2.0 _+1.0 __-0.5 _+0.5 _+2.0___ -1.0 _ -3.0 _ -1.5 hudsonvalley21 ________________ +1.3 _+1.4 _+1.0 __ -1.6 _+1.7 _ +1.5 ___ +0.4 _+1.8 _-0.3 Scotty Lightning _______________ +1.0 _+1.0 _+0.5 __ -1.0 _+0.5 _+1.0 ___+1.0 _+1.0 _+0.5 ____ Normal ____________________ 0.0 __0.0 __0.0 ____ 0.0 __0.0 __0.0 ____ 0.0 __0.0 __0.0 wxallannj ______________________ -1.0 _ -1.1 __-1.3 ___ -0.7 _+0.8 _+1.7 ___+2.0 _+2.2 _+2.5 DonSutherland1 ________________-1.0 _ -2.0 _-2.0 ___ -3.3 _+2.5 _+1.6 ___+1.4 _+1.1 _ +0.1 BKViking _______________________-1.2 _ -1.3 _ -1.7 ___ -1.7 _+0.9 _+1.2 ___ +1.3 _+2.2 _+1.5 ___ Consensus ________________ -1.3 _ -1.7 _-1.8 ___ -2.8 _+0.7 _ +1.1 ___ +1.0 _+1.5 _+0.5 so_whats_happening __________ -1.4 _ -1.3 _ -1.6 ___ -2.6 _+0.8 _+1.2 ___+1.1 _ +2.1 _ +0.6 Tom ____________________________-1.9 _ -2.7 _-2.8 ___ -3.9 _-0.9 _+0.5 ___+0.6 _+1.5 _+1.1 RJay ___________________________ -2.0 _-2.0 _-2.0 ___ -3.0 _+1.2 _+0.5 ___+1.0 _+1.5 _+0.5 RodneyS _______________________ -3.6 _-3.0 _-2.3 ___ -4.7 _-2.5 _+0.9 ___+1.3 _+0.5 _+0.5 Roger Smith ____________________-4.0 _-3.8 _-4.5 __ -5.9 _ -3.3 _ -1.5 ___-3.6 _ -2.9 _ -2.4 wxdude64 ______________________-4.4 _-3.1 _-3.3 __ -4.7 _ -2.5 _ -0.7 ___-0.9 _+0.8 _+2.3 ----------------- (highest and lowest forecasts above are color coded; all forecasts are below normal for ORD) __ Persistence ___(Nov 2025)___ +0.4 _-0.8 _-0.5 __+1.1 _+3.5 _+5.4 ___+5.7 _+3.9 _+2.1 ===================== ____ Table of Snowfall forecasts for winter 2025-26 ____ FORECASTER __________________ DCA _NYC _BOS __ORD _DTW _BUF ___ DEN _SEA _BTV wxallannj _______________________23.0 _28.0 _ 28.0 __45.0 _44.0 _89.0 ___44.0 _18.0 _ 99.0 Tom ____________________________ 19.5 _ 31.1 _ 44.5 __ 40.1 _42.4 _102.4 __ 54.8 _ 6.1 _ 81.4 hudsonvalley21 ________________ 18.0 _ 22.0 _ 31.0 __ 32.0 _42.0 _93.0 ___52.0 _ 4.0 _ 88.0 wxdude64 _____________________ 15.6 _ 28.6 _ 41.1 ___30.3 _45.5_ 101.5 ___ 66.2 _ 4.7 _ 93.3 BKViking _______________________ 15.0 _ 32.0 _ 41.0 __40.0 _22.0_ 96.0 ___ 58.0 _13.0 _ 80.0 Rjay ____________________________ 15.0 _ 21.0 _ 44.0 __50.0 _33.0_ 100.0 ___65.0 _ 6.0 _ 90.0 ___ Consensus _________________ 15.0 _ 22.5 _ 39.5 __40.1 _42.2 _ 94.5 ___ 55.2 _ 6.1 _ 87.5 Scotty Lightning _______________ 15.0 _ 20.0 _ 25.0 __ 30.0 _45.0 _85.0 ___ 50.0 _ 5.0 _ 95.0 so_whats_happening __________ 14.0 _ 23.0 _ 39.0 __ 42.0 _40.0 _91.0 ___ 38.0 _ 4.0 _ 87.0 Roger Smith ____________________12.8 _ 25.6 _ 50.7 __ 57.3 _ 61.5 _115.7 ___ 70.0 _12.5 _ 88.8 DonSutherland1 ________________10.0 _ 20.0 _ 40.0 __ 37.5 _45.0 _ 92.0 ___ 40.0 _ 6.5 _ 80.0 RodneyS ________________________ 6.7 _ 18.9 _ 35.7 __ 44.4 _49.1 _ 99.9 ___ 55.6 _ 9.1 _ 70.4 Mercurial ________________________1.0 _ 10.0 _ 20.0 __ 30.0 _ 30.0 _70.0 ___ 65.0 _ 6.0 _ 60.0 ___ snowfall to date (Dec 2) _____ Tr __ Tr __ Tr _____ 11.9 __ 6.9 __ 11.0 ___ 0.2 _ 0.0 _ 11.6 ===================== Consensus for snowfall is the median of 12 forecasts

TEMP _________DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA -4.0 -3.8 -4.5 -5.9 -3.3 -1.5 -3.6 -2.9 -2.4 SNOW _______ DCA _ NYC _ BOS ___ ORD ____DTW ___ BUF __ DEN _ SEA _ BTV 12.8" 25.6" 50.7" 57.3" 61.5" 115.7" 70.0" 12.5" 88.8"

Anyway, had a look at guidance and I can see some signs for optimism with this, but verbatim it looks just 2-3 F too warm to give much snow in the urban areas, could start off as snow and end as snow with sleet and rain during most of the event, 33-35 F zone would mix considerably. The optimism comes from the antecedent conditions getting a chill from the current snow event going through the GL region chilling the boundary layers of the arctic high following in ahead of your Tuesday storm. Also it does not look like very robust warm air advection is likely. If it would shift 50-100 miles south and the 540 dm thickness would stay south of JFK that would be ideal for accumulations of 5-8 inches with this but I think those are going to fall around POU into w CT.

There has never been a larger snowfall on Dec 2nd than 3.9" which happened in 1929 (NYC data). Another similar event was 3.8" 2nd-3rd 1903. The daily records for 1st to 3rd are 1.5" (1880), 3.9" (1929) and 3.0" (1903). A somewhat larger 8" snowfall happened on 4th of 1957 but early December does not have much going for it in the heavy snow department, Nov 30 1882 did better than all of those efforts (8" plus another inch on Dec 1). Maybe before records began in 1869 there was something bigger. I found several instances of severe cold in this part of the early winter that did not bring much snowfall, for example 1875 and 1926. (this is not meant to offer any sort of prediction, I am just looking at the guidance for this event for the first time now)

<<<<< DECEMBER NYC RECORDS 1869 to 2024 >>>>> _________ High max ___ high min _____ Low max ___ Low min ___________ Max prec ___ Max snow ___ Max 2d snow _ Dec 01 ___ 70 2006 __ 52 2001 ____ 18 1875 _____ 8 1875 __________ 1.72 1920 ___ 1.5 1880 __ 9.0 1882 ** Dec 02 ___ 66 1970 __ 52 1982 _____ 24 1876 _____11 1875 (27) _____2.16 1974 ___ 3.9 1929 __ 3.9 1929 * Dec 03 ___ 69 1998 __ 53 1998 _____ 23 1976 _____ 9 1976 __________1.63 1925 ___ 3.0 1903 __ 3.8 1903 Dec 04 ___ 74 1998^__ 59 1998 _____ 22 1889 ____ 10 1882 (34) ____ 1.84 1983 ___ 7.5 1957 __ 8.0 1957 Dec 05 ___ 70 2001 __ 56 1973,82 __ 22 1886 ____ 11 1926 (24) _____ 1.28 1993 ___ 8.0 2003 __ 8.0 2003 * Dec 06 ___ 71 2001 __ 58 2001 ______ 22 1926 ____13 1871, 1926_____ 1.60 1884 ___ 6.0 2003 __14.0 2003 Dec 07 ___ 75 1998 __ 54 2022^ ____ 26 1869 ____ 10 1926 (30) _____1.98 1908 ___2.0 1886 __ 6.0 2003 ** Dec 08 ___ 65 1927 __ 52 1951 ______ 19 1882 _____10 1882 __________ 1.54 1917 ___ 2.0 1928 __ 2.0 1928 Dec 09 ___ 66 1966 __ 54 1966 ______ 18 1902 ____ 7 1876 ___________2.54 2014 ___5.8 2005 __5.8 2005 * Dec 10 ___ 70 1946 __ 54 1946,66 ___ 16 1880 ____ 3 1876 (17) ______ 1.62 1878 ___ 1.4 2013 __ 5.8 2005 ** Dec 11 ___ 66 2021^__ 53 1887 ______ 20 1876 _____ 6 1880 (27) _____ 2.41 1992*___3.6 1960 __ 3.6 1960 * Dec 12 ___ 68 1931 __ 55 2015 ______ 20 1988 _____ 5 1988 ___________1.60 1983 ____11.6 1960 _15.2 1960 Dec 13 ___ 67 2015 __ 55 2015 ______ 20 1960 _____ 8 1960 __________3.03 1909^___8.0 1917 _11.6 1960 ** Dec 14 ___ 67 1881,2015_ 53 1901,2001,15_21 1902 ____12 1976 (31) _____2.22 1897 ____5.8 2003 __ 9.5 1917 Dec 15 ___ 68 2015 __ 53 2015 _______ 20 1874,1914_ 8 1874 _________1.34 1981 ____ 12.7 1916 __12.7 1916 * Dec 16 ___ 63 1971 __ 54 2021*_______ 19 1886 _____ 7 1876 (15 17th)_ 2.25 1974 ___6.8 1896 __12.7 1916 ** Dec 17 ___ 62 2000 _ 50 1888,2015 __ 15 1876 _____ 1 1919 (21) ______2.28 1888 ____6.7 1932 _ 10.5 2020^ Dec 18 ___ 63 1937,84 47 1996 _______ 11 1919 _____-1 1919 ___________2.21 2023* ___4.5 1887 __ 7.8 1932 Dec 19 __58 1899,1931 _ 45 1949,57,2017_ 16 1884 __-1 1884 __________1.19 1934 _____ 9.1 2009 __ 9.1 2009 * Dec 20 __ 60 1895,1999,2002_54 1957 __7 1884 __-4 1942 (8) _______1.92 1874 ____15.8 1948 __15.8 1948^ Dec 21 ___ 65 2013 __ 51 2013 ________ 9 1871 _______ -2 1871 _________ 2.49 1973 ___ 4.0 1884 __16.0 1948 Dec 22 ___ 71 2013 __ 61 2013 ________ 18 1989 _____ 4 1872 (28) _____ 2.18 1983 ___ 10.3 1959 __13.7 1959 Dec 23 ___ 66 1891,1990_57 1990 _____ 10 1883 _____-1 1883 __________ 1.83 2022^ __ 6.0 1963 __10.3 1959 ** Dec 24 ___ 72 2015 __ 63 2015 _______ 13 1872 _____ 6 1983 (22) _____ 1.42 2003 ___11.4 1912 __11.4 1912 Dec 25 ___ 66 2015^__57 2015 ________ 13 1983 _____-1 1980 (20) _____ 1.30 2002 __ 7.0 1909 __12.3 1883 (7.3+5.0) Dec 26 ___ 63 1936,82_ 50 1964 ______ 12 1872 _____ 3 1914 (15) ______ 2.36 1947 __ 26.1 1947 _ 26.1 1947 * Dec 27 ___ 63 1949 __ 57 1949 ________ 15 1872 _____ 6 1872 ___________ 1.39 1930 ___ 7.8 2010 _ 26.4 1947^ Dec 28 ___ 65 1982, 2008 __49 2024^ __17 1894 ____ 8 1917 (35) _____ 1.35 1926 ___ 6.6 1990 __ 7.8 2010 ** (7.2 1990) Dec 29 ___ 70 1984 __ 55 1984 ________ 8 1917 _____ -6 1917 ___________ 2.52 1901 ___ 4.0 1880 __ 6.6 1990** Dec 30 ___ 65 1984 __ 52 1948 ________ 2 1917 ____ -13 1917^ _________ 1.69 1912 __ 12.0 2000 __12.0 2000 * Dec 31 ___ 63 1965 __ 51 1965 _________ 6 1917 _____ -7 1917 ____________ 1.40 1948 ___4.0 1948 __12.0 2000 ** -- - - - - - - - - - - - - - - - -- NOTES: ... Temp values in brackets after low min show that day's max if it was not also the low max record. ... For 48h record snow values, which always run from previous date to current indicated date ... ... * indicates all precip fell same day, and ** indicates all fell previous day. The rest have some on both days. other notes: ^ 4th max 72 1982 ^ 7th high min 54F (2022) replaced 53F (1951, 1956) ^ 11th new record 66F 2021 broke 64F 1879. * 11th 2.35" 2008 (not record), 3.28" Dec 11-12 2008. ^ 13th 2.97" R 1941 ^ 16th-17th 2d snow 10.5" 2020 (6.5 + 4.0) * 16th 54F high min 2021 replaced 48F 1971 * 18th rainfall record replaced 1.30" 1876 ^ 19th-20th 2d snow 10.9" 2009 (9.1 + 1.8) also 10.0" 1874 20th ^ 23rd high precip 1.83" (2022) replaced 1.61" (1913) ^ note also 23rd new highest diurnal range at NYC (58, 8 = 50 range), replaced 48 from Mar 28, 1921 (82, 34). ^ 25th max 64 1889 ^ 26th 18.0" snow 1872, 12.2" 2012, (26-27 2d snow 2010 of 20.0") also 11.2" 1933 26th ^ 28th _ 49F high min (2023) replaced 47F 2008. xx 29th _ As the severe cold deepened in 1917, 2.0" snow was recorded on this date. ^ 30th min -6 1933 (max 12 29th, 16 30th)

A reminder to regular contest entrants (in main general interest forum) that Dec and winter snowfall forecasts can be posted now. Also an invite to all -- Dec is a good month to begin entering the contest because of the snowfall contest portion and also we look at seasonal scoring leaders too, but the main contest runs January to December so the invite is really for 2026 participation.

A reminder to regular contest entrants (in main general interest forum) that Dec and winter snowfall forecasts can be posted now. Also an invite to all -- Dec is a good month to begin entering the contest because of the snowfall contest portion and also we look at seasonal scoring leaders too, but the main contest runs January to December so the invite is really for 2026 participation.