donsutherland1

Colder air is now pushing into the region as a storm pulls away from the region. A period of cooler than normal to near normal temperatures will predominate over the next two weeks, with some occasional milder than normal temperatures. There remains some uncertainty about the timing of the next change toward milder conditions. A milder pattern could develop toward the winter solstice. The closing 10 days of December could wind up generally warmer than normal. The duration of the current AO-/PNA+ pattern will be key to how long the developing colder pattern persists. 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 +9.24. Today, the preliminary Arctic Oscillation (AO) figure was -1.453. The preliminary PNA value was +1.650. On December 4 the MJO was in Phase 4 at an amplitude of 1.018 (RMM). The December 3-adjusted amplitude was 0.965. Based on the latest guidance, no significant stratospheric warming event is likely through the first two weeks of December. The warming above 3 mb in response to recent strong Wave 1 activity should abate toward the end of the second week of December. 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.

A quick video clip from East Lyme, CT:

It was east of there. I believe there was mixed precipitation near Melville.

MPING shows rain-snow mixes on Long Island.

Unfortunately, that appears to be the case.

I think we will get some breaks. I would be surprised if there are no additional periods where there is opportunity for some cold and snow.

One dominated by Pacific flow.

Morning thoughts... Today will be rainy and cool. Temperatures will likely top out in the lower and middle 40s this morning or early this afternoon in most of the region. Likely high temperatures around the region include: New York City (Central Park): 45° Newark: 45° Philadelphia: 46° The storm will likely bring accumulating snow to parts of New England, but will be a “near miss” for most of the Middle Atlantic region into southern New England. Final Snowfall Estimates: Boston: 3”-6” Caribou: 8”-14” Concord: 6”-12” Hartford: 2”-4” Portland: 4”-8” Providence: 2”-4” Worcester: 7”-14” In the wake of today’s storm, a period of colder weather will follow.

There will probably be at least one more shot at winter precipitation before the pattern changes.

A sustained period of cooler than normal to near normal temperatures is poised to develop this coming weekend following a storm that will bring a general 0.50"-1.50" rainfall from Philadelphia to New York City, with lesser amounts north and west of that line and higher amounts to the east of that line. Accumulating snow is likely in much of New England, including the Boston area. Likely snowfall amounts include: Boston: 2"-4" Caribou: 8"-14" Concord: 5"-10" Hartford: 2"-4" Portland: 4"-8" Providence: 1"-3" Worcester: 6"-12" Since 1950, there were 5 storms that brought 2" or more snow to Boston and no measurable snow to New York City during the December 1-10 period. The biggest snowfall in Boston during these storms occurred during December 5-6, 1981 when Boston picked up 12.9" snow. The single such case with an AO-/PNA+ pattern and a cool ENSO Region 3.4 anomaly occurred during December 8-9, 2001 when Boston saw 4.3" snow. There remains 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) in parts of the Middle Atlantic region. Exceptional cold is unlikely through mid-December. A milder pattern could develop toward the winter solstice and the closing 10 days of December could wind up generally warmer than normal. The duration of the current AO-/PNA+ pattern will be key to how long the colder pattern persists. Meanwhile, an extended duration much warmer than normal regime will persist in western Canada through the middle of next week. Today, record high temperatures there included: Fort Providence, NT: 35° (old record: 29°, 2009) Norman Wells, NT: 32° (old record: 26°, 1972) Watson Lake, YT: 36° (old record: 27°, 2016) Wrigley, NT: 32° (old record: 24°, 1972) 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 +6.23. Today, the preliminary Arctic Oscillation (AO) figure was -1.777. The preliminary PNA value was +1.650. On December 3 the MJO was in Phase 4 at an amplitude of 0.960 (RMM). The December 2-adjusted amplitude was 0.983. Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 3 mb is likely toward the latter part of the first week of December on account of strong Wave 1 activity. Recent guidance is a bit more impressed with the warming. 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... Today will be partly to mostly cloudy. Rain will likely develop. Temperatures will likely reach the upper 40s and lower 50s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 50° Newark: 52° Philadelphia: 51° The storm will likely bring accumulating snow to parts of New England, but will be a “near miss” for most of the Middle Atlantic region into southern New England. Providence will likely see 1”-3” snow and Boston will pick up 3”-6”. From Philadelphia to New York City, a general 0.50”-1.50” rainfall is likely with lower amounts north and west of that line.

A sustained period of cooler than normal to near normal temperatures is poised to develop. Initially readings will run somewhat above normal, but the colder regime could move into place near or during the coming weekend following a storm that could bring significant precipitation to the region. The storm could end as snow north and west of New York City and Newark. There remains some possibility that the precipitation could end as a period of wet snow or flurries even in the I-95 Corridor. 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) in parts of the Middle Atlantic region. Exceptional cold is unlikely through mid-December. A milder pattern could develop near mid-month. 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 has now developed in western Canada. Record high temperatures included: Calgary: 61° (old record: 55°, 1939) Claresholm, AB: 65° (old record: 51°, 1993 and 2015) Faro, YT: 45° (old record: 39°, 1992) Fort Simpson, NT: 49° (old record: 31°, 2009) Mayo, YT: 47° (old record: 39°, 1969) Norman Wells, NT: 49° (old record: 23°, 2009) ***New December Record*** Paulatuk, NT: 35° (old record: 29°, 1987) Watson Lake, YT: 42° (old record: 39°, 2004) Wrigley, NT: 52° (old record: 27°, 2009) ***New December Record*** At Wrigley, the 52° (11.0°C) temperature exceeded both the December monthly record (46°/7.8°C, December 13, 1944) and the November monthly record (48°/8.9°C, November 23, 1954 and November 3, 1974). The previous latest 50° (10.0°C) temperature occurred on October 27, 1962 when the temperature reached 50° (10.0°C). In recent years, there has been a disproportionately high frequency for high temperature records in western Canada. For example, in Calgary where the temperature record goes back to 1881, 61 record high temperatures have been set or broken from 2000 or later vs. 16 record lows (3.8:1 ratio). Those numbers are 25 and 3 since 2010 (8.3:1 ratio). Tomorrow could see additional 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 +11.31. Today, the preliminary Arctic Oscillation (AO) figure was -0.711. On December 2 the MJO was in Phase 4 at an amplitude of 0.982 (RMM). The December 1-adjusted amplitude was 0.953. Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the second week of December. Some warming above 3 mb is likely toward the latter part of the first week of December on account of strong Wave 1 activity. Recent guidance is a bit more impressed with the warming. 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.

Those are all valid points, DT. I don’t think the current state of the La Niña will be maintained throughout the winter. I suspect it is approaching or perhaps near its peak right now and then will begin to fade. My temperature anomalies are December-February anomalies. A March 2017-type scenario is one possibility if the La Niña fades faster than I think it will. I suspect that we’ll see the ENSO Region 3.4 anomaly rise above La Niña levels (on a monthly average) in February or March, but the December-February figure will be consistent with La Niña. I am a bit more worried about what happens with the stratospheric polar vortex (SPV) for the second half of winter. But, as far as I know, there’s no real skill beyond a few weeks when it comes to forecasting the SPV. Finally, I could be wrong on a regional or larger basis when all is said and done. It wouldn’t be the first time (and almost certainly would not be the last time).

Morning thoughts... Today will be partly to mostly sunny and milder. Temperatures will likely reach the upper 40s and lower 50s in most of the region. Likely high temperatures around the region include: New York City (Central Park): 49° Newark: 52° Philadelphia: 52° A storm could bring a significant rainfall to coastal areas and at least some accumulating snow inland early this weekend followed by colder weather. The rain could even end as some snow or flurries in the I-95 Corridor.

A sustained period of cooler than normal to near normal temperatures is poised to develop. Initially readings will run somewhat above normal, but the colder regime could move into place near or during the coming weekend following a storm that could bring significant precipitation to the region. The storm could end as snow north and west of New York City and Newark. The 12z ECMWF was even more aggressive in pushing the snow into both cities. 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 has now developed in western Canada. Record high temperatures included: Dawson, Yukon Territory: 35° (old record: 25°, 1978) Faro, Yukon Territory: 47° (old record: 44°, 1997) Juneau: 52° (old record: 51°, 1929) Seattle: 60° (tied record set in 1939) Teslin, Yukon Territory: 44° (old record: 41°, 1963) Watson Lake, Yukon Territory: 45° (old record: 39°, 1963 and 2004) Tomorrow through Friday could see additional 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 +15.78. Today, the preliminary Arctic Oscillation (AO) figure was +0.160. On December 1 the MJO was in Phase 4 at an amplitude of 0.951 (RMM). The November 30-adjusted amplitude was 0.850. 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. However, gradual cooling should commence afterward. 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.

For reference, the World Meteorological Organization (WMO) issued its provisional report on the state of the global climate in 2020. Key takeaways: 1. 2020 will be among the 3 warmest years on record despite a La Nina. The last 6 years will be the warmest 6 years on record. 2. 80% of the ocean experienced a marine heat wave at some point this year. 3. The Arctic sea ice extent minimum was the second lowest on record and the Greenland ice sheet continued to lose mass. 4. The Atlantic basin recorded a record 30 tropical cyclones. The full report can be found at: https://library.wmo.int/doc_num.php?explnum_id=10444

Prime Minister Ardern is a truly outstanding leader. She has accomplished a lot of significant things during her short tenure in office.

Not always. But if one sees a shift consistent with La Niña, one can have greater confidence in the overall idea that relies on ENSO, etc. There will likely be variability during the course of the winter.

There were also numerous records in eastern Canada. For additional perspective, Caribou’s previous latest 50 degree minimum occurred in November 21, 1954 (51 degrees) and its next such minimum occurred on April 26, 1986 (50 degrees).

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°