bluewave

Models usually don’t get exact timing for the relaxation of a pattern which has persisted for several weeks. This is why I have been using the general recent climatology in December. Every year since 2011 from Philly to NYC there was at least 1 day reaching 55 or greater from the 17th to the 25th. That period is still 9-17 days out which is beyond the reliable model skill. It doesn’t mean every day or even most days were this warm since 2011. Some years it was only a 1 day warm up with other years more than a day reaching these temperatures. But the general December patterns over the years which have had a cold December 1-16th had moderated in the departures from the 17th through the 31st. The degree of this moderation has also been variable.

Miss the 2010-2018 KU benchmark era when we could lock in a 168 hr euro control run showing a near 950 mb low close to the benchmark and have it be correct. https://www.weather.gov/okx/Blizzard_Jan42018

Occasionally, we do get a colder month across the CONUS. This is the first several weeks of colder conditions since January. But these colder periods have been few and far between. So they tend to stand out when they occur and get more attention than the persistent warmth which has become the new normal. I will update the chart below when December data gets posted.

30 years since the mid 90s and over 100 years prior to that period isn’t a small sample size. What you describe as rigid is actually a very comprehensive approach which I have used with great success for long range outlooks. Since my approach is data driven, I haven’t come to any firm ideas yet on whether we can eventually shift back to at least some occasional benchmark tracks in the future. But the long term decline in snowfall has been unmistakable. So I leave open the idea of a bounce off these lows in coming years if we can weaken the Pacific Jet a bit. But this is very uncertain since the recent shifts have been so extreme.

We haven’t had a single average or above average snowfall season since the mid 90s without having at least one NESIS 1 or higher BM KU snowstorm. So KU benchmark storms have been mandatory for reaching average to above average snow since 93-94. Prior to the mid 90s this wasn’t the case in the much colder climate. We could string together a series of smaller snow events and reach into the 20s for snowfall.

Fits the Great Lakes cutter, I-78 to I-84 hugger and Rain-snow gradient, and suppressed Southern stream which has dominated since 2018-2019. Very difficult to achieve a true benchmark KU track with such a fast Pacific Jet. Way too many issues with kicker lows, amplified ridges pushing the gradient just north of NYC, and generally very poor wavelength spacing with so many shortwaves racing through the fast flow.

Ski resorts continue to be the big winner the overpowering Northern Stream of the Pacific Jet.

My early guess for January is that it will be warmer on average across the entire CONUS than last January was which finished as the 33rd coldest. All our multi year La Nina’s last 30 years have had one January which was on the colder side like last January while the others have been milder. But don’t have feel yet what the general 500mb pattern will be and where the warm and cold anomalies will set up or how much warmer specifically this January will be.

After midnight highs today. This happens quite a bit with Arctic fronts. Some of the great Arctic outbreaks from 77 to 94 would have had lower daily maxes if the front was just a little faster. SXUS51 KOKX 080557 OSOOKX New York City Metropolitan Area Weather Roundup National Weather Service New York NY 100 AM EST MON DEC 08 2025 CITY SKY/WX TMP DP RH WIND PRES REMARKS Central Park PTCLDY 38 24 57 VRB7 30.05R WCI 33 LaGuardia Arpt PTCLDY 40 21 46 W16G23 30.03R WCI 31 Kennedy Intl PTCLDY 37 27 67 W9 30.05R WCI 30 Newark Liberty PTCLDY 37 25 61 W8 30.04S WCI 31 Teterboro Arpt PTCLDY 36 25 64 W7 30.03S WCI 30 Bronx Lehman C N/A 37 27 65 W6 N/A WCI 33 Queens College N/A 39 27 60 W9 N/A WCI 33 Breezy Point N/A 37 N/A N/A W12 N/A WCI 30 Brooklyn Coll N/A 39 28 65 W10 N/A WCI 32 Staten Island N/A 36 28 75 W6 N/A WCI 31

This has been due to the inability of the models to resolve the split forcing pattern which has been in place this month so far. So the first 16 days of the month will verify significantly colder than the long range forecasts were indicating back in late November. La Nina’s often had colder patterns in December so this isn’t that much of a surprise. The interference pattern has created a cold MJO 6 type and not the canonical MJO 8 pattern and storm track. This is due to the forcing near the MJO 4-6 regions with the standing wave. So now that the models have a consolidation of forcing there as the forcing weakens over the Western Hemisphere, they are showing the seasonal moderation in temperatures we often see beginning in mid-December. The last few days have been the first time in a while that they are actually raising heights more than in earlier runs. So the ridge coming east faster is a function of the big Jet extension and MJO 4-6 forcing. Remember last early December how the models underestimated the mid to late December Jet extension and lower Pacific heights. New run faster Pacific Jet lowering heights more over Western North America and raising heights in the East

These charts below do a good job showing the current burst of stronger forcing in the MJO 4-6 areas. I suspect it’s one of the reasons we aren’t getting the canonical MJO 8 even with the RMMS in that space. This is why I like to look at the total forcing when they are out of alignment with the RMMS. Notice that the Pacific Jet hasn’t relaxed and we have a dominant northern stream. So even though we are experiencing a colder pattern since late November, the warmer storm track of the last 7 years hasn’t varied. This was the case during some of the colder intervals last winter also. Models are beginning to come into better agreement for the relaxation of the cold as the falling AAM and MJO 4-6 forcing supports a broad ridge across the U.S. mid to late month. This is a seasonal shift that we have seen frequently approaching mid to late December over the last decade. We had a big jet extension last December at this time also when the temperatures moderated.

The current standing wave in MJO 4-6 will consolidate the forcing there leading to a jet extension in around 10 days and the ridge getting pushed east with the falling AAM.

The runoff is leading to higher salt content in the drinking water supply for areas around NYC and NJ. https://apnews.com/article/new-york-city-reservoirs-salt-c5d67e6c626878d0993974498c4629b6 The suburban reservoirs that supply 10% of New York City’s vaunted drinking water are getting saltier due to decades of road salt being spread near the system — and they will eventually have to be abandoned if nothing is done to reverse the trend, city officials warn. https://patch.com/new-jersey/bridgewater/salty-taste-nj-drinking-water-linked-use-salt-brine-roads NEW JERSEY — Have you noticed a salty taste in your water recently? New Jersey American Water said it is due to the use of salt and brine for public safety during the recent extreme winter weather and ongoing drought conditions. The water company shared a notice with customers about the change in taste on Friday.

Has been a common theme in recent years with the heavy road salting especially behind the 18-wheelers.

Some reservoirs in NNJ dipping under 50% with the below normal rainfall since the fall of 2024. https://dep.nj.gov/drought/current-conditions/#reservoir-levels

Yeah, the combination of the warmest SSTs on record for the month of November across sections of the WPAC are boosting the Pacific Jet due to the thermal gradient with the Asia. Plus the record SST warmth around Australia and the Maritime Continent keeping the forcing going in the MJO 4-7 regions also contribute to a faster Pacific Jet. It looks like the long range EPS retrogrades the ridge back to the Aleutians while the ridge is still in the West. Eventually, a jet extension will probably push that ridge further east at least for a time. We also have the falling AAM lag which will lower heights near Greenland later in the month. EPS Strong MJO 4-7 forcing into mid-December

That long duration event helped Newark to reach the 6th snowiest calendar year since the 1840s. Time Series Summary for NEWARK LIBERTY INTL AP, NJ - Jan through Dec top 10 highest calendar year snowfall Click column heading to sort ascending, click again to sort descending. 1 1907 73.1 123 2 1867 72.0 0 3 1868 68.8 0 4 1978 65.8 0 5 1961 63.5 0 6 2003 63.3 0 7 1854 62.8 0 8 1916 62.7 31 9 1996 62.6 0 - 1862 62.6 0 10 1896 61.4 2

It’s the largest and deepest of the Great Lakes so it can absorb much more heat than the smaller and shallower lakes. So it’s still near record levels of warmth. Part of this is also related to Superior being closest to the record warmth this fall centered in Canada than the other lakes were. So this is an amazing set up for the near record snows that they experienced in November.

Lake Superior is still the 2nd warmest on record since 1995 for December 5th. https://apps.glerl.noaa.gov/coastwatch/webdata/statistic/pdf/all_year_glsea_avg_s.pdf

Places like Marquette are the big snowfall winner with this overpowering Pacific Jet and trough over the Great Lakes and Northeast with cold air flowing over the record warm Lakes. https://www.wpr.org/news/great-lakes-seeing-near-record-warm-waters-this-fall The Great Lakes are seeing near-record warm water temperatures right now, which means there’s a higher chance for lake effect snow when the weather turns cold.As of Thursday, all five of the lakes were around 4 to 5.5 degrees Fahrenheit warmer than their long-term average for the last three decades. That’s according to data from the Great Lakes Environmental Research Lab operated by the National Oceanic and Atmospheric Administration, or NOAA.

This was the 6th coldest December 5th low in NYC and 7th coldest max. Data for December 5 - NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1926-12-05 24 11 1.03 7.9 8 1886-12-05 22 13 0.37 5.3 M 1871-12-05 29 14 0.00 0.0 M 1935-12-05 37 15 0.00 0.0 0 1911-12-05 38 19 0.00 0.0 M 1901-12-05 27 19 0.00 0.0 M 2025-12-05 32 20 0.00 0.0 Data for December 5 - NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1886-12-05 22 13 0.37 5.3 M 1926-12-05 24 11 1.03 7.9 8 1901-12-05 27 19 0.00 0.0 M 1893-12-05 28 20 0.16 1.5 M 1871-12-05 29 14 0.00 0.0 M 1895-12-05 30 25 0.00 T M 2002-12-05 31 26 0.35 6.0 M 2025-12-05 32 20 0.00 0.0 0 1989-12-05 32 23 T T 0

That was some of my highest snow drifting in Long Beach since February 78.

If we had slightly weaker blocking in 09-10, then NYC could have challenged 95-96. During 10-11 we had over 60” at Newark from 12-26 to 1-27. But the pattern quickly reversed on February putting 95-96 out of reach. I am really grateful that I got to experience 10-11 as my last full winter living in Long Beach.

NYC and LGA continue their record under 4” daily streak while BOS moves into 2nd place for longest daily streak under 6”. Philly is getting closer to their longest daily under 5” streak. DC is currently at their 3rd longest run with no daily 12” amounts. State College is only a few weeks away from their new longest daily under 6” streak. Number of Consecutive Days Snowfall < 4 for NY CITY CENTRAL PARK, NY Click column heading to sort ascending, click again to sort descending. 1 1405 0 2025-12-04 2 1394 0 1932-12-16 3 1063 0 1952-01-27 4 1051 0 1963-12-22 5 794 0 1956-03-15 Number of Consecutive Days Snowfall < 4 for LAGUARDIA AIRPORT, NY Click column heading to sort ascending, click again to sort descending. 1 1405 1 2025-12-04 2 1051 0 1963-12-22 3 761 0 2020-12-15 4 746 0 1952-02-29 5 744 0 1981-03-04 Number of Consecutive Days Snowfall < 6 for Boston Area, MA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1772 0 1992-12-11 2 1378 0 2025-12-04 3 1373 0 1981-12-05 4 1369 0 1987-12-28 5 1054 0 1909-12-25 Number of Consecutive Days Snowfall < 5 for Philadelphia Area, PA (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 1440 0 1987-01-21 2 1438 0 2000-01-24 3 1433 0 1896-12-15 4 1423 0 1970-12-31 5 1409 0 1945-01-15 6 1405 0 2025-12-04 Number of Consecutive Days Snowfall < 12 for Washington Area, DC (ThreadEx) Click column heading to sort ascending, click again to sort descending. 1 8383 0 1922-01-27 2 8043 0 1958-02-14 3 5829 0 2025-12-04 4 5122 0 1936-02-06 5 4768 0 1979-02-18 Number of Consecutive Days Snowfall < 6 for STATE COLLEGE, PA Click column heading to sort ascending, click again to sort descending. 1 1434 0 1990-12-27 2 1418 1 2025-12-05 3 997 0 2009-12-08 4 835 4 1932-03-27 5 816 4 1956-02-01

Some degree of moderation in the East after the 16th fits December climatology since 1991. But exactly how much of a relaxation remains to be seen. A 10 to 15 day lag following the current AAM reversal would indicate some degree of moderation by near or after the 20th.