donsutherland1

1997-98 is one example where Phase 8 was very warm in the East. I still don't think that Winter 2023-24 will be 1997-98 2.0. I do think that the long-range guidance has two big issues: sticks with continuity through weeks 5-6 too often or rushes pattern changes. I think this time around, we're facing the latter scenario. It increasingly appears that a transition is more likely to occur during the first week of January than last week of December. The Pacific jet streak that is forecast to develop is consistent with what has happened in past moderate or strong El Niño events and the MJO's passage through Phases 5-7 at a high amplitude. Things still working in our favor for improvement: 1. Weakening stratospheric polar vortex (favors Atlantic blocking, which has often been the case following the development of strong blocking during the last week of November--basically suggests a tendency toward what has occurred in the past). A major stratospheric warming event would be helpful for the second half of winter, but that's still a less than 50% probability. Model skill is very low beyond a week or so on these events. 2. There remains a hint that a "Greenland High" pattern could try to develop in early January. That pattern would favor troughing across the CONUS, including the East. The 12/9 ECMWF weeklies continued to show improvement for the first week of January. Potential issues: 1. The Greenland High pattern never fully develops 2. The stratospheric polar vortex begins to recover after weakening into early January (the latest forecast has pulled back somewhat on the magnitude of weakening) 3. Adverse impacts of multiple ongoing marine heatwaves (highest degree of uncertainty) The 12/9 CFSv2 weeklies have shifted to show a continuation of the warmth during the first week of January Even as there are some risks, I believe January will see some opportunities. I don't see any extreme cold shots through the end of December. I also don't buy into the "Snowmaggedon" pattern one Twitter/X account has suggested.

From WPC:

Last night’s HREF:

Some week ahead numbers: Note: The ECMWF ensembles are very likely exaggerating the probabilities of 1" or above and 2" or above snowfall in Washington, DC, all of which are from the storm that will impact the region today into tomorrow. The low temperature forecast for Washington, DC that is two sigma below the NBE estimate is 34°. Since 1884 when daily snowfall recordkeeping began, Washington, DC has seen only 6 measurable snow events when the December low temperature was 34° or above. The mean snowfall for such events was 0.4" and the median snowfall was 0.3". The highest such snowfall was 1.2" on December 15, 1981. There were two cases among them that followed a high temperature of 50° or above, as will occur this time around: December 24, 1911 (prior high: 52°; snowfall: 0.1") and December 16, 2019 (prior high: 57°; snowfall: 0.1"). Therefore, 0.5" or less seems far more likely than what is implied by the ECMWF ensemble members.

The temperature soared to 59° in New York City and Newark today. Tomorrow will likely see the temperature rise into the 60s in many parts of the region as a strengthening storm brings unseasonably warm air into the region. A significant rainfall is likely tomorrow into Monday. A general 1.50"-2.50" rainfall with locally higher amounts is likely. Strong southeasterly winds will gust past 40 mph. Coastal flooding and beach erosion are likely. The strong winds could bring down limbs and even some trees. Thunderstorms are possible as the cold front pushes across the region late tomorrow or early Monday. The rain will likely end as a period of wet snow or flurries north and west of New York City. New York City could see some snowflakes, as well. A cooler period will follow the storm. However, temperatures could again rise to above and perhaps much above normal levels as the winter solstice approaches. No Arctic air appears likely through at least the first three weeks of December and possibly the entire month. The ENSO Region 1+2 anomaly was +2.1°C and the Region 3.4 anomaly was +2.0°C for the week centered around November 29. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +2.18°C and the ENSO Region 3.4 anomaly has averaged +1.87°C. A basinwide El Niño event is ongoing. El Niño conditions will likely continue to strengthen somewhat further this month. The SOI was -20.66 today. The preliminary Arctic Oscillation (AO) was -2.186 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 7 the MJO was in Phase 5 at an amplitude of 1.732 (RMM). The December 6-adjusted amplitude was 1.736 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 68% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 40.8° (1.7° above normal).

Early clouds gave way to sunshine and the temperature soared to 59 degrees.

Such jet streaks often develop during moderate or strong El Niño events and high amplitude passage of the MJO through Phases 5-6-7. Below is a composite of Phase 5 (amplitude 1.5 or above) and El Niño Region 3.4 anomaly of 1.0 or above and then rolled forward five days. Day 0: Day 1: Day 2: Day 3: Day 4: Day 5:

A very mild weekend will lies ahead. Saturday will be variably cloudy and mild with readings in the lower and middle 50s across the region. Sunday will see the temperature rise into the 60s in many parts of the region as a strengthening storm brings unseasonably warm air into the region. A significant rainfall is likely Sunday into Monday. A general 1.50"-2.50" with locally higher amounts is likely. Strong southeasterly winds will gust past 40 mph. Coastal flooding and beach erosion are likely. The strong winds could bring down limbs and even some trees. Thunderstorms are possible as the cold front pushes across the region late Sunday or early Monday. A period of cooler air will follow. However, temperatures could again rise to above and much above normal levels as the winter solstice approaches. Overall, the first 10 days of December remain on track to finish with a solidly warmer than normal anomaly. No Arctic air appears likely through at least the first three weeks of December and possibly the entire month. The ENSO Region 1+2 anomaly was +2.1°C and the Region 3.4 anomaly was +2.0°C for the week centered around November 29. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +2.18°C and the ENSO Region 3.4 anomaly has averaged +1.87°C. A basinwide El Niño event is ongoing. El Niño conditions will likely continue to strengthen somewhat further this month. The SOI was -14.58 today. The preliminary Arctic Oscillation (AO) was -2.518 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 6 the MJO was in Phase 4 at an amplitude of 1.736 (RMM). The December 5-adjusted amplitude was 1.491 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 64% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 40.6° (1.5° above normal).

Perhaps not too surprisingly, the 12/8 ECMWF weekly forecast has bumped up 12/18-25 anomalies to 3C to 6C above normal of the NYC area (from 1C to 3C above normal on the previous run).

Bastardi had been tweeting maps showing a near historically cold 45-day pattern from 11/20 0z through 1/4 0z (the viability of that idea has disintegrated well before the end of that period). That may be the source of such expectations.

Most of the measurable snow days during El Niño winters occur during January and February. February has the largest share of days with 1”+ and 6”+ days (including 50% of 6”+ days) during meteorological winter during El Niño winters. So, a subpar December isn’t unknown during such winters.

Those were the zonal winds at 250 mb. Here's the 500 mb pattern:

December 1888 250 mb Zonal Wind Anomaly:

The MJO continues to slog through the Marine Continent right now. It still appears likely to exist Phases 4-6 around or just after mid-month. The ECMWF (bias corrected) has a notably slower passage, but it remains an outlier. At the same time, a powerful EPO+ Pacific Trough prevails. The combination of the MJO's progression and the EPO+ suggests that Arctic air will likely be unavailable to be tapped for the foreseeable future. Even as the upcoming weekend storm is followed by a period of cooler but not very cold weather, another warmup lies ahead. It still appears more likely than not that at least some colder air will begin to push into the region in the closing week of December, though the guidance could still be rushing the transition. At least for now, the question seems to concern more the timing of the transition (last week of December vs. first week of January) rather than whether there will be a transition. Of course, skill level at those extended timeframes is low. Fun EPO+ Facts for NYC: Since 1950, there were 6 cases where the EPO reached positive levels at least comparable to the current event for 3 or more days during the first week of December All 6 cases saw the lowest temperature during the December 21-31 period reach at least 22 degrees in NYC One-third of the cases saw one or more days of light measurable snowfall (highest total snowfall: 5.6", 1967) Snowfall after the first week of December for those cases came to the following amounts: 1951-52: 19.7"; 1952-53: 8.4"; 1952-54: 13.6"; 1967-68: 16.3"; 1987-88: 18.0"; 1996-97: 9.9" The biggest snowstorm following the first week of December produced the following amounts: 1951-52: 5.8"; 1952-53; 2.0"; 1953-54: 8.6"; 1967-68: 6.6"; 1987-88: 5.8"; 1996-97: 3.5" 1951-52, 1953-54, and 1987-88 were El Niño winters

Distribution of New York City's daily snowfall amounts by ENSO Phase and Month (1949-50 through 2022-23):

Winter's two-day visit complete with several bouts of snow flurries and even snow showers is over. Temperatures will begin to rebound on tomorrow with temperatures reaching the middle and upper 40s in much of the region. A very mild weekend will follow. However, a significant rainfall is likely Sunday into Monday. Strong southeasterly winds gusting past 40 mph will impact the region as the strengthening storm passes to the north and west of the region. Coastal flooding and beach erosion are likely. Thunderstorms are possible as the cold front pushes across the region late Sunday or early Monday. The temperature will likely reach or exceed 60° in many locations on Sunday. Overall, the first 10 days of December remain on track to finish with a solidly warmer than normal anomaly. The ENSO Region 1+2 anomaly was +2.1°C and the Region 3.4 anomaly was +2.0°C for the week centered around November 29. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +2.18°C and the ENSO Region 3.4 anomaly has averaged +1.87°C. A basinwide El Niño event is ongoing. El Niño conditions will likely continue to strengthen somewhat further this month. The SOI was -2.02 on December 6. The preliminary Arctic Oscillation (AO) was -2.301 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 5 the MJO was in Phase 4 at an amplitude of 1.491 (RMM). The December 4-adjusted amplitude was 1.551 (RMM). Based on sensitivity analysis applied to the latest guidance, there is an implied 61% probability that New York City will have a warmer than normal December (1991-2020 normal). December will likely finish with a mean temperature near 40.4° (1.3° above normal).

NYC actually fell to -1° on Valentine's Day 2016.

I raised a scenario where the PV could get stronger, but my thinking is that such a scenario is not on the table this winter. If I had to venture a guess, the odds of such a scenario playing out are probably less than 20%. I expect a generally weak SPV to persist through much of the winter.

The 5-10 or 6-10 day period could see cool readings. Tropical Tidbits is still using the old 1981-2020 base period, which understates the cold and overstates the warmth relative to the warmer 1991-2020 baseline that is now in use. The warmth rebounds for a time (check out days 10-15). It's not extreme warmth, but readings wind up in the middle and perhaps upper 40s (45 is the end value for Central Park) by the end of the 0z EPS run in the NYC area. The latest CFSv2 weeklies keep the warm anomalies going through the end of the month. The ECMWF weeklies continue to show a pattern evolution. If past years are representative, the change to a more favorable pattern might take somewhat longer than currently modeled. It seems that the weekly guidance has two big issues beyond two weeks: either a bias for continuity that frequently runs through weeks 5-6 or, when it breaks from continuity, the rushing of pattern changes. I still think January and February will offer opportunities for cold and snow. The last week of December could see cold start to return, but I wouldn't be too surprised if it takes until the first week in January. There has been notable warming of the stratosphere, focused on 5 mb to 10 mb. However, there's still no forecast for the kind of wind reversal that defines major warming events through 10 days (ECMWF ensemble mean). For now, the stratospheric vortex still looks to remain weak through the foreseeable future, which should afford higher blocking possibilities. There is a risk that once the stratosphere cools, especially if there is no zonal wind reversal, that could allow the stratospheric polar vortex to strengthen. There's no guidance showing such an outcome, but it has happened in some past winters. Such a development would cause problems for January and perhaps beyond. I'm articulating this risk, but I don't think it is the most likely outcome right now. Finally,there has been some chatter about extreme cold (e.g., single-digit-type cold for NYC) to end December/start January. I'm very skeptical of such calls. Numerous El Niño winters, even snowy ones, have not seen single-digit or colder peak cold in NYC.

I would be surprised if we don't see some snow flurries in the City. A somewhat heavier snow shower is possible, though most of those will probably occur outside of the City.

I created it with a prompt (18th century harbor scene following a snowstorm) using the DaVinci AI.

Phoenix had both its hottest summer and hottest fall. Phoenix added a record high today to its collection of record highs this year. Miami is all but certain to record its warmest year on record. 2019, 2020, 2021, 2022, and 2023 will all rank among its 10 warmest years on record. Miami's full-year records go back to 1896.

Tomorrow should be another cool, but not very cold, day. Some snow flurries and snow showers are again possible. Temperatures will begin to rebound on Friday with a very mild weekend following. A moderate to significant rainfall is likely Sunday into Monday. Strong southeasterly winds could impact the region as the strengthening storm passes to the north and west of the region. Coastal flooding and beach erosion are likely. Overall, the first 10 days of December remain on track to finish with a solidly warmer than normal anomaly. The ENSO Region 1+2 anomaly was +2.1°C and the Region 3.4 anomaly was +2.0°C for the week centered around November 29. For the past six weeks, the ENSO Region 1+2 anomaly has averaged +2.18°C and the ENSO Region 3.4 anomaly has averaged +1.87°C. A basinwide El Niño event is ongoing. El Niño conditions will likely continue to strengthen somewhat further this month. The SOI was -2.02 today. The preliminary Arctic Oscillation (AO) was -2.427 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 4 the MJO was in Phase 4 at an amplitude of 1.551 (RMM). The December 3-adjusted amplitude was 1.323 (RMM).

That’s an earlier version AI. The images are even better (but not yet comparable to top humans) on the more advanced tools. Here’s one from another AI:

I can understand. It’s a terrible experience that one often does not forget.