donsutherland1

I’m not referring to a thaw, but the evolution toward what is expected to be the predominant winter pattern and also La Niña progression.

Morning thoughts... The warm air that sent temperatures soaring on the closing day of November in the region, produced yesterday’s monthly record high temperature at Caribou, is now located in Atlantic Canada. Earlier today, Halifax (59°) and Charlottetown (58°) set daily record high temperatures. Meanwhile, at 7:55 am, a band of snow stretched northward from approximately Elmira, NY to central Ontario and was headed eastward. Today will be variably cloudy, breezy, and cool. Temperatures will likely reach the lower and middle 40s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 43° Newark: 46° Philadelphia: 46° Tomorrow and Friday will be somewhat milder.

With 3.24” rain through 5 pm AKS, Juneau has now set a new December daily precipitation record. The old record was 3.11”, which was set on December 19, 1937.

I hope I am wrong, too. December will probably provide good insight into how things may evolve. If blocking breaks down after mid-December that could be an indication that winter will wind up warmer and less snowy than normal.

December started off with balmy early morning readings in the region. Afterward, temperatures fell throughout the afternoon. In northern New England, the temperature reached 60° in Caribou this evening ahead of the push of colder air. That broke the daily record high figure of 48°, which was set in 1975 and tied in 1991. It also set a new monthly record. The prior monthly record was 58°, which was set on December 5, 1950 and tied on December 12, 1950. That makes December the second consecutive month on which Caribou set a new monthly record high temperature. On the other side of North America, a wild storm was pounding southeast Alaska with high winds, heavy rain, along with exceptionally mild conditions. As of 4 pm AKS, the high temperature at Juneau was 48°. That tied the daily record set in 1906 and tied in 1997. In addition, 3.09" rain had fallen. That smashed the daily record of 1.44", which was set in 1997. In addition, that figure was just below the December precipitation record of 3.11", which was set on December 19, 1937. A large-scale hemispheric pattern change is now evolving. A sustained period of cooler than normal to near normal temperatures will commence in coming days. A fairly sharp cold shot is possible during the second week of December. There remains considerable uncertainty about the timing of the next change toward milder conditions. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance). Exceptional cold is unlikely through mid-December. The duration of the AO-/PNA+ pattern will be key to how long the colder pattern persists. Meanwhile, an extended duration much warmer than normal regime is now developing in parts of western Canada. Tomorrow through Friday could see record high temperatures in that region. Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December in the Middle Atlantic and southern New England regions. Both historic experience following exceptionally warm November cases suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park (2020 saw the temperature average a record 52.9° in November) went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -1.40°C. La Niña conditions will likely prevail at least through the winter. The SOI was +21.23. Today, the preliminary Arctic Oscillation (AO) figure was +0.303. On November 30 the MJO was in Phase 4 at an amplitude of 0.848 (RMM). The November 29-adjusted amplitude was 0.809. Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 2 mb is likely toward the latter part of the first week of December on account of Wave 1 activity. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall.

Morning thoughts... In the wake of yesterday's storm, it will be partly to mostly cloudy and cooler. Temperatures will hold steady or fall slowly. Likely high temperatures for the remainder of the day around the region (from 8 am and afterward) include: New York City (Central Park): 52° Newark: 51° Philadelphia: 48° The first week of December will likely see the temperature average near or somewhat above normal. 30-Day Verification: New York City (Central Park): Average daily forecast: 58.0° Average temperature: 59.1° Average error: 1.9° Newark: Average daily forecast: 60.3° Average temperature: 60.9° Average error: 1.7° Philadelphia: Average daily forecast: 60.7° Average temperature: 61.2° Average error: 1.5°

New York City is concluding its warmest November on record. The temperature soared into the 60s today as a storm continued to push northward to the west of the region. With a high temperature of 63°, Central Park pushed its monthly mean temperature to 52.9°. The previous record was 52.8°, which was set in 2015. Records go back to 1869. High Temperatures and rainfall amounts through 7 pm for select sites were: Allentown: 61°; 2.72" (old record: 1.05", 2016) Atlantic City: 65°; 1.43" Boston: 59°; 0.40" Bridgeport: 63°; 0.93" Islip: 63°; 0.83" New York City: 63°; 0.96" Newark: 65°; 1.08" Philadelphia: 67°; 0.98" Poughkeepsie: 66°; 0.94" December will start off mild before a period of cooler than normal to near normal temperatures commences. This cooler period could still give way to warmer readings at some point during the second week of December following a fairly sharp cold shot, but there is considerable uncertainty about the timing of this change. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance). Exceptional cold is unlikely. The duration of the AO-/PNA+ pattern could delay any warmup until near mid-month. An extended duration much warmer than normal regime will begin to develop in parts of western Canada starting during the first half of this week. Wednesday and Thursday could see record high temperatures in that region. Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December. Both historic experience following exceptionally warm November cases and the latest weekly and monthly guidance suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The ENSO Region 1+2 anomaly was -1.0°C and the Region 3.4 anomaly was -1.0°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.87°C and the ENSO Region 3.4 anomaly has averaged -1.40°C. La Niña conditions will likely prevail at least through the winter. The SOI was +28.18. Today, the preliminary Arctic Oscillation (AO) figure was -0.115. On November 29 the MJO was in Phase 4 at an amplitude of 0.860 (RMM). The November 28-adjusted amplitude was 0.888. Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 2 mb is likely toward the latter part of the first week of December on account of Wave 1 activity. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. Since 1970, there were 9 winters that saw the AO and EPO average +0.25 or above. Mean snowfall for Boston, Harrisburg, New York City, Philadelphia, and Washington, DC averaged 50% of the most recent 30-season mean. The largest snowfall deficits relative to the most recent 30-season mean figure were located in the Philadelphia to New York City corridor. In addition, 33% of cases saw less than 10" seasonal snowfall in New York City and 44% saw less than 10" seasonal snowfall in Philadelphia. Finally, on November 30, 1842 an early-season snowstorm blanketed parts of the East Coast. The heaviest snows were focused on portions on Middle Atlantic region, with perhaps the heaviest snows falling in Virginia, Maryland and Pennsylvania. Parts of that area received more than a foot of snow.

2 pm temperatures: Albany: 42° Poughkeepsie: 60°

A short video clip from early this afternoon:

Thanks Bill. I agree with you about potential periods of colder weather with opportunities for snowfall. It just doesn't appear to be a snowy winter. My 8-year-old doesn't like the idea that there won't be much snowfall, as he want to "make up" for last year's lack of sledding. I suspect Cohen is right about the role of persistently low Arctic sea ice. That situation might well be driving the higher snowfall, as warmer air holds more moisture. Recent moderate La Niña events haven't worked out well. Perhaps the larger area of warm SSTAs in the Pacific, which has had some impact on the MJO (more time being spent in the Maritime Continent phases) has influenced the outcome. Interesting point about the comparison of October and November temperature anomalies. That statistic adds confidence about the possible overall nature of the coming winter. I hope you had a great Thanksgiving Day holiday.

DCA _ NYC _ BOS __ ORD _ ATL _ IAH ___ DEN _ PHX _ SEA 1.0 1.5 1.9 2.3 -0.4 -0.1 2.6 1.8 3.0

Morning thoughts... Over the next 24 hours, a storm will track toward Lake Ontario and into Canada. Rain associated with that storm is already spreading northward through southeastern New York State and southwestern Connecticut. Today will see periods of rain, some of which will be heavy. A general 0.50”-1.50” rainfall with locally higher amounts is likely by the time the rain tapers to showers this afternoon or evening. The temperature will rise into the lower and even middle 60s on account of a strong push of warm air. The wind will likely gust past 50 mph. A thunderstorm is possible. Likely high temperatures around the region include: New York City (Central Park): 64° Newark: 64° Philadelphia: 66° In the wake of the storm, the tomorrow will be windy and cooler. The temperature could fall during the afternoon hours. In the Ohio Valley, parts of Ohio could see 4”-8” snow with locally higher amounts. Accumulating snow could extent into eastern Michigan, as well as western Ontario.

Through yesterday: Baltimore: 3rd warmest; Boston: 16th warmest; Philadelphia: 5th warmest; Washington, DC: 2nd warmest; and, Worcester: 3rd warmest.

Tomorrow a storm could bring moderate to perhaps heavy rainfall up the East Coast. Following the storm, the Southeast could see unseasonably cool temperatures. The core of this colder air will likely stay south of the region, but somewhat below normal to near normal readings are likely in parts of the Middle Atlantic area. Meanwhile, there are now early hints that an extended duration much warmer than normal regime will begin to develop in parts of western Canada starting during the first half of this week. Overall, December could start off mild before that period of cooler than normal to near normal temperatures commences. This cooler period could still give way to warmer readings at some point during the second week of December, but there is is still uncertainty. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance). Exceptional cold is unlikely. The duration of the AO-/PNA+ pattern could delay any warmup until near mid-month. Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December. Both historic experience following exceptionally warm November cases and the latest weekly and monthly guidance suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.5°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.90°C and the ENSO Region 3.4 anomaly has averaged -1.42°C. La Niña conditions will likely prevail at least through the winter. The SOI was +19.40. Today, the preliminary Arctic Oscillation (AO) figure was -0.026. On November 28 the MJO was in Phase 4 at an amplitude of 0.882 (RMM). The November 27-adjusted amplitude was 1.004. Based on the latest guidance, no significant stratospheric warming event is likely through the first week of December. Some warming above 2 mb is likely toward the end of that timeframe on account of Wave 1 activity. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. Since 1950, there have been four La Niña winters that started with a warm December in the Northeast and warmth across much of Canada, as is the current forecast on the monthly EPS, latest weekly EPS and latest CFSv2 monthly guidance: 1974-75, 1998-99, 1999-00, and 2011-12. All featured a warmer than normal winter and among the winter months that followed December, only January 2000 was colder than normal in the East. Median seasonal snowfall figures were as follows: New York City: 12.9" and Philadelphia: 13.1". Since 1970, there were 9 winters that saw the AO and EPO average +0.25 or above. Mean snowfall for Boston, Harrisburg, New York City, Philadelphia, and Washington, DC averaged 50% of the most recent 30-season mean. The largest snowfall deficits relative to the most recent 30-season mean figure were located in the Philadelphia to New York City corridor. In addition, 33% of cases saw less than 10" seasonal snowfall in New York City and 44% saw less than 10" seasonal snowfall in Philadelphia. 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 November. November will likely finish with a mean temperature near 52.9° (the warmest November on record).

Thanks for the kind words.

Under brilliant sunshine, the temperature soared into the lower and middle 50s this afternoon across the New York City area. Three photos from the New York Botanical Garden from this afternoon:

Morning thoughts... Today will be mostly sunny and mild. High temperatures will likely reach the lower and middle 50s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 55° Newark: 57° Philadelphia: 57° A storm will bring strong southeasterly winds, mild temperatures, and rain on Monday. Some areas could see a thunderstorm.

Under variably cloudy skies, temperatures rose into the lower and middle 50s across the region. Tomorrow will be partly to mostly sunny, but clouds will increase late in the day or during the evening. Readings will remain warmer than normal. Tomorrow into Monday, a storm could bring moderate to perhaps heavy rainfall to the Southeast and then up the East Coast. Following the storm, the Southeast could see unseasonably cool temperatures. The core of this colder air will likely stay south of the region, but somewhat below normal to near normal readings are likely in the Middle Atlantic and southern New England areas for a period. Meanwhile, there are now early hints that an extended duration much warmer than normal regime will begin to develop in parts of western Canada starting during the first half of next week. Overall, December could start off mild before that period of cooler than normal to near normal temperatures commences. This cooler period could still give way to warmer readings at some point during the second week of December, but there is is still uncertainty. The development of a AO-/PNA+ pattern has shifted the outlook toward colder temperatures during the first half of December (consistent with statistical guidance). Exceptional cold is unlikely. The duration of the AO-/PNA+ pattern could delay any warmup until near mid-month. Statistical guidance based on the ENSO state and teleconnections would typically favor a colder regime for the first half of December. Both historic experience following exceptionally warm November cases and the latest weekly and monthly guidance suggest that a warmer than normal December remains the base case even if the first half of the month winds up colder than normal. Almost 90% of cases with a November mean temperature of 51.5° or above in Central Park went on to record a warmer than normal December and just over three-quarters of such cases saw December register a monthly mean temperature of 40.0° or above. The ENSO Region 1+2 anomaly was -0.7°C and the Region 3.4 anomaly was -1.5°C for the week centered around November 18. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.90°C and the ENSO Region 3.4 anomaly has averaged -1.42°C. La Niña conditions will likely prevail at least through the winter. The SOI was +1.21. Today, the preliminary Arctic Oscillation (AO) figure was +0.528. On November 27 the MJO was in Phase 4 at an amplitude of 1.032 (RMM). The November 26-adjusted amplitude was 1.172. Based on the latest guidance, no significant stratospheric warming event is likely through the first week of December. Some warming above 2 mb is likely toward the end of that timeframe on account of Wave 1 activity. Since 1950, there have been five cases where a La Niña developed during June-July-August or afterward following an El Niño winter. 4/5 (80%) of those cases saw a predominant EPO+/AO+ winter pattern. The most recent such case was 2016-17. 10/11 (91%) of the La Niña winters that followed an El Niño winter featured a predominantly positive EPO. A predominant EPO+/AO+ pattern is very likely for winter 2020-21. It is likely that the Middle Atlantic and southern New England areas will see a warmer than normal winter with below normal snowfall. Since 1950, there have been four La Niña winters that started with a warm December in the Northeast and warmth across much of Canada, as is the current forecast on the monthly EPS, latest weekly EPS and latest CFSv2 monthly guidance: 1974-75, 1998-99, 1999-00, and 2011-12. All featured a warmer than normal winter and among the winter months that followed December, only January 2000 was colder than normal in the East. Median seasonal snowfall figures were as follows: New York City: 12.9" and Philadelphia: 13.1". Since 1970, there were 9 winters that saw the AO and EPO average +0.25 or above. Mean snowfall for Boston, Harrisburg, New York City, Philadelphia, and Washington, DC averaged 50% of the most recent 30-season mean. The largest snowfall deficits relative to the most recent 30-season mean figure were located in the Philadelphia to New York City corridor. In addition, 33% of cases saw less than 10" seasonal snowfall in New York City and 44% saw less than 10" seasonal snowfall in Philadelphia. 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 November. November will likely finish with a mean temperature near 52.7° (tied for the 2nd warmest November on record). Considering modeling errors, there is a possibility that 2020 could compete with 2016 for the warmest November on record. November 2015 had a monthly mean temperature of 52.8°.

I hope it ends soon. Another “non-winter” would be anything but satisfying.

While the pattern change after mid-December is not assured, there are enough hints on the guidance to suggest that it is plausible. We’ll see how things evolve. There can always be surprises along the way.

Boll expresses my own concern about the pattern evolution, namely the possible shift back to sustained warmer conditions in the extended range.

It’s tough to be certain at that timeframe. Should blocking be more persistent, more time would be available. If it breaks down more quickly than the opportunities could disappear fairly quickly, whether or not they are realized.

Hopefully, we can get something before the pattern changes after mid-December.

Both December 2000 and 2010 had a lot of blocking.

Morning thoughts... Today will be partly sunny and still mild for the season. High temperatures in the region will likely reach the middle and upper 50s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 57° Newark: 59° Philadelphia: 58° A storm will bring strong southeasterly winds, mild temperatures, and rain on Monday.