donsutherland1

The EPS ensembles have "discovered" the potential January 7-8, 2024 storm. But there remains considerable uncertainty with a risk that a Pacific trough could result in the storm's taking a track too far to the north and west to bring a moderate or significant snowfall to big cities from Philadelphia to New York City.

Feel free to do so, Walt. Have a great New Year.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH __ DEN _ PHX _ SEA 1.1 1.4 1.6 2.2 -0.1 -0.2 -0.3 -0.4 1.2

Week ahead numbers: If the above guidance is accurate, the long-awaited pattern change will arrive largely on schedule for the first week of January. The January 1-7 period will be the coldest 7-day period so far this winter. Severe cold remains unlikely. There will also be the prospect of snowfall, especially as the period closes. From this far out, even if a Pacific trough results in the potential 1/7-8 storm tracking toward the Great Lakes, prospects for at least a measurable snowfall are higher than they have been this winter on a regionwide basis.

Recent years have seen fewer hours during which the temperature was 32° or below in December:

New York City's second warmest December on record is nearing an end. Temperatures will remain somewhat above seasonal norms as 2023 wraps up as New York City's warmest year on record with an annual mean temperature of 58.0° (old record: 57.4°, 2012). The first week of January will likely feature somewhat below normal temperatures. However, severe cold appears unlikely. Initially, the arrival of a colder regime could coincide with a drier one, so snowfall prospects will remain limited. The second week of January could offer better opportunities for snowfall, as the retreat of cold air could occur while the pattern becomes wetter. There remains some uncertainty concerning the magnitude and duration of the colder period that could develop. At this time, it appears more likely than not that it will be seasonably cold or somewhat colder than normal with a duration of 1-2 weeks. The ENSO Region 1+2 anomaly was +1.6°C and the Region 3.4 anomaly was +2.0°C for the week centered around December 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +1.75°C and the ENSO Region 3.4 anomaly has averaged +1.98°C. A basinwide El Niño event is ongoing. The SOI was +10.74 today. The preliminary Arctic Oscillation (AO) was -1.505 today. Strong blocking in the final week of November, as occurred this year, has often been followed by frequent blocking in December and January. On December 28 the MJO was in Phase 1 at an amplitude of 2.103 (RMM). The December 27-adjusted amplitude was 2.028 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 44.5° (5.4° above normal). That would make December 2023 the 2nd warmest December on record. With 2023 virtually certain to be among the 10 warmest Decembers on record, 60% of New York City's 10 warmest Decembers have occurred since 2000, including 40% since 2010, and all have occurred since 1980. Records go back to 1869.

No record streak there.

December is concluding in mild fashion. Locations including International Falls, Milwaukee, and Minneapolis will see their warmest December on record. New York City will finish its second warmest December on record. Strong El Niño events like the ongoing event typically see most of their snowfall after the first half of January (approximately 75% of their seasonal snowfall). The historic snow drought that grips Baltimore, New York City, and Philadelphia makes the wait almost unbearable. Patience will continue to be required. Looking ahead to January, the picture is complex. The strong El Niño event is likely to see a continuation of the negative Pacific Decadal Oscillation (possibly -1.000 standard deviations or more relative to normal). That combination would be almost unprecedented. Since 1950, there are two cases where the ENSO Region 3.4 anomaly was +0.50°C or above and the PDO was -0.95 sigma or below (1954: El Niño winter and 2020 (neutral winter that fell just short of El Niño status). Composite 500 mb Anomalies: 1954 was characterized by expansive and deep cold across Canada. That is not the case this year. Moreover, the climate has warmed substantially since 1954. That likely rules out its temperature anomalies. 2020 had a somewhat similar trough-ridge pattern with much more expansive warmth. However, the current winter has a much more active subtropical jet. Hence cooler anomalies than January 2020 (due, in part, to more frequent precipitation) are likely across the southern tier of the CONUS. January 2020 can serve as a reference for a reasonable "worst case" scenario. The January 2020 map is below: The latest CFSv2 monthly forecast provides an illustration of the risks: January 2020 featured below average snowfall across the New York City and Philadelphia areas. Monthly snowfall amounts included: Bridgeport: 4.6"; Islip: 2.5"; New York City: 2.3"; Newark: 2.7"; and, Philadelphia: 0.2" What could go right? 1. The PDO- could erode substantially introducing a 1965-1966-style breakdown of the generally warm pattern (albeit with less Arctic air than was available then) 2. Atlantic blocking could predominate given some storm track opportunities for snowfall 3. The sudden stratospheric warming event could ultimately lead to colder air coming into eastern North America toward the end of the month, even if it initially flows into the West What could go wrong? 1. The PDO- remains strong (-1.000 or below) 2. Most of the impact of the sudden stratospheric warming event winds up in Eurasia 3. Atlantic blocking breaks down 4. The subtropical jet weakens At present, it still appears that the first 1-2 weeks of January could wind up closer to normal than has been the case for December. Such temperatures would mark a dramatic departure from the "torch" that defined the closing week of December (widespread anomalies of 8° or more above normal in the Northeast). Initially, the first week of January could start dry, but a wetter pattern could emerge afterward. The key question concerns whether there will be sufficient cold still available. Afterward, there has been persistent guidance suggesting that the trough could shift out West with possible ridging developing in the East (2020 lite?). The EPS ensembles have been showing the development of a PNA- during the second week of the month, which would support conditions conducive to the trough's shifting to the West. Severe cold appears unlikely in the Northeast through at least the first half of January. Big snowstorms (6" or greater) for Washington to New York City also appear unlikely through the first half of January (ensemble guidance + strong El Niño climatology). None of this means that winter has been canceled. It suggests that the best wintry conditions are not likely during the first half of January.

Baltimore’s record is now 701 days. Washington, DC does not have a record streak.

Some of the cherry blossoms have come into bloom in Central Park, too.

NYC is in a similar predicament. 685 days and counting (old record: 383 days).

Today will be New York City's 700th consecutive day on which it has received less than 2" of daily snowfall.

Today will mark Philadelphia's 700th consecutive day on which it has received less than 1" of daily snowfall.

That now happens about once every four years. The most recent occurrence prior to this year was 2020. Columbia, SC will have more such days for the first time since 1984 and only 6th time overall.

Baltimore saw its record stretch without daily snowfall of 1" or more reach 700 days today. Philadelphia will reach 700 days tomorrow. The unseasonably mild weather will likely continue through the remainder of December, but readings will be somewhat cooler than they were today. The first week of January will likely feature somewhat below normal temperatures. However, severe cold appears unlikely. Initially, the arrival of a colder regime could coincide with a drier one, so snowfall prospects will remain limited. The second week of January could offer better opportunities for snowfall, as the retreat of cold air could occur while the pattern becomes wetter. There remains some uncertainty concerning the magnitude and duration of the colder period that could develop. At this time, it appears more likely than not that it will be seasonably cold or somewhat colder than normal with a duration of 1-2 weeks. The ENSO Region 1+2 anomaly was +1.6°C and the Region 3.4 anomaly was +2.0°C for the week centered around December 20. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +1.75°C and the ENSO Region 3.4 anomaly has averaged +1.98°C. A basinwide El Niño event is ongoing. El Niño conditions may strengthen somewhat further this month. The SOI was +1.09 today. The preliminary Arctic Oscillation (AO) was -0.852 today. Strong blocking in the final week of November, as occurred this year, has often been followed by frequent blocking in December and January. Atlantic blocking is continuing to redevelop. On December 27 the MJO was in Phase 1 at an amplitude of 2.028 (RMM). The December 26-adjusted amplitude was 1.837 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied near 100% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 44.5° (5.4° above normal). That would make December 2023 the 2nd warmest December on record. With 2023 virtually certain to be among the 10 warmest Decembers on record, 60% of New York City's 10 warmest Decembers have occurred since 2000, including 40% since 2010, and all have occurred since 1980. Records go back to 1869.

New York City's second warmest December on record is concluding. Blossoms can be found in parts of the New York Botanical Garden.

After days of overcast skies, bouts of fog, rain, mist, and drizzle, the sun finally returned today.

In addition to ongoing record streaks without 1" or 2" daily snowfall in New York City, today will be Buffalo's record 307th consecutive day on which the temperature has not fallen into the teens. The latest first occurrence of temperatures in the teens was January 3, 2022. That mark could be beaten this winter.

Yes. It's one variable. It can be important, but other variables can more than offset it.

The MJO's current passage through Phase 1 during which the preliminary amplitude has reached as high as 2.028, is the strongest on record for Phase 1 for the last 10 days of December. Daily MJO data recordkeeping began in 1974.

With no snowfall in the forecast, today will become Baltimore's 700th consecutive day during which the City has not seen at least 1" of daily snowfall.

% of Below and Above Normal Days in New York City. The last year with a majority of below normal days was 2009 when 56% of days were cooler than normal.

That was likely it. It was a large lake.

I saw a caldera from an ancient explosion while out there, but don't recall the name of it. We even experienced a strong aftershock while there. I had spent time seeing a number of the Hindu temples (many in ruins) and a Buddhist temple.

I was there. It's a fabulous place.