Winter 2024-2025 Thoughts

[donsutherland1]

Winter 2024-2025 Outlook

Rationale: The C3S appears reasonable given my base assumptions and scenario testing. Notable areas and areas where the outcome could diverge from the C3S forecast are highlighted on the maps.

Outlook:
The northwestern quarter of the United States has the highest risk of winding up somewhat colder than normal, especially in the Pacific Northwest where precipitation will likely be much above average.  Precipitation will likely be below normal across the southern tier of the United States and up the East Coast into southern New England. The drought in the northeastern U.S. will likely intensify during the winter. Spring could turn wetter in that region.

Select Snowfall Amounts:
Albany: 50”
Baltimore: 10”
Boston: 35” (its record streak without 4” daily snowfall will likely end)
Burlington: 75”
Buffalo: 95”
Charlotte: Trace (its record streak without measurable snowfall will likely continue)
Chicago: 40”
Detroit: 45”
Harrisburg: 20”
New York City: 16.5” (Statistical temperature-snowfall peers: 1952-53, 1998-99)
Newark: 18”
Philadelphia: 12”
Portland: 60”
Richmond: 4.5”
Toronto: 45” (114.3 cm)
Washington, DC: 8”

Note: Snowfall estimates have the highest risk of error, as synoptic factors that cannot be assessed at seasonal timeframes are involved.

Key Assumptions:
ENSO: La Niña but possibly cold Neutral
Relative ENSO: -0.5 or below
AO/NAO: Predominantly positive with some variability
PDO: Strongly negative to negative
PNA: Generally negative
EPO: Generally neutral to positive
QBO: Strongly positive

Additional Factors:

Impact of High Marine Heat Content in the North Pacific: High marine heat content in the Gulf of Alaska and Bering Sea, driven by marine heatwaves, has been associated with warmer winter temperatures in coastal regions. This can extend to broader climatic impacts, including potential warming in eastern North America.

MJO-NAO: The MJO-NAO connection has been strengthening in a warming climate, likely due to an extending jet stream that allows for more effective Rossby wave propagation.  The MJO has shown an increased tendency to spend more time in Phases 3-5, which tends to favor a positive NAO.  An ongoing marine heatwave in the Marine Continent area could elevate the risk of Phases 3-5/4-6.

NAO: Severe NAO blocks in September, as occurred this year, often precede winters with generally positive NAO regimes.

Scenario Range: Scenarios from 1980-present
Due to climate change and its impacts on the Northern Hemisphere cold pool (shrinking), atmospheric circulation (driven by Arctic amplification and marine heatwaves), and ongoing warming,  years prior to 1980 reflect a climate that no longer exists. Pre-1980 scenarios are low probability scenarios, particularly with respect to expansive cold anomalies and widespread prolonged snow cover that helps sustain the cold.

Winter 2016-17 (snowiest La Niña scenario used)
Winter 2001-02 (low probability, neutral-cold ENSO winter) to address the question, “What is a likely worst case?”

 

[psuhoffman]

6 hours ago, donsutherland1 said:

Winter 2024-2025 Outlook

Rationale: The C3S appears reasonable given my base assumptions and scenario testing. Notable areas and areas where the outcome could diverge from the C3S forecast are highlighted on the maps.

Outlook:
The northwestern quarter of the United States has the highest risk of winding up somewhat colder than normal, especially in the Pacific Northwest where precipitation will likely be much above average.  Precipitation will likely be below normal across the southern tier of the United States and up the East Coast into southern New England. The drought in the northeastern U.S. will likely intensify during the winter. Spring could turn wetter in that region.

Select Snowfall Amounts:
Albany: 50”
Baltimore: 10”
Boston: 35” (its record streak without 4” daily snowfall will likely end)
Burlington: 75”
Buffalo: 95”
Charlotte: Trace (its record streak without measurable snowfall will likely continue)
Chicago: 40”
Detroit: 45”
Harrisburg: 20”
New York City: 16.5” (Statistical temperature-snowfall peers: 1952-53, 1998-99)
Newark: 18”
Philadelphia: 12”
Portland: 60”
Richmond: 4.5”
Toronto: 45” (114.3 cm)
Washington, DC: 8”

Note: Snowfall estimates have the highest risk of error, as synoptic factors that cannot be assessed at seasonal timeframes are involved.

Key Assumptions:
ENSO: La Niña but possibly cold Neutral
Relative ENSO: -0.5 or below
AO/NAO: Predominantly positive with some variability
PDO: Strongly negative to negative
PNA: Generally negative
EPO: Generally neutral to positive
QBO: Strongly positive

Additional Factors:

Impact of High Marine Heat Content in the North Pacific: High marine heat content in the Gulf of Alaska and Bering Sea, driven by marine heatwaves, has been associated with warmer winter temperatures in coastal regions. This can extend to broader climatic impacts, including potential warming in eastern North America.

MJO-NAO: The MJO-NAO connection has been strengthening in a warming climate, likely due to an extending jet stream that allows for more effective Rossby wave propagation.  The MJO has shown an increased tendency to spend more time in Phases 3-5, which tends to favor a positive NAO.  An ongoing marine heatwave in the Marine Continent area could elevate the risk of Phases 3-5/4-6.

NAO: Severe NAO blocks in September, as occurred this year, often precede winters with generally positive NAO regimes.

Scenario Range: Scenarios from 1980-present
Due to climate change and its impacts on the Northern Hemisphere cold pool (shrinking), atmospheric circulation (driven by Arctic amplification and marine heatwaves), and ongoing warming,  years prior to 1980 reflect a climate that no longer exists. Pre-1980 scenarios are low probability scenarios, particularly with respect to expansive cold anomalies and widespread prolonged snow cover that helps sustain the cold.

Winter 2016-17 (snowiest La Niña scenario used)
Winter 2001-02 (low probability, neutral-cold ENSO winter) to address the question, “What is a likely worst case?”

 

Appreciate the thoughts.

For the record DC had 3.2" in 2002 and 3.4" in 2017 lol 

[donsutherland1]

1 hour ago, psuhoffman said:

Appreciate the thoughts.

For the record DC had 3.2" in 2002 and 3.4" in 2017 lol 

When I referenced 2001-02 and 2016-17, I was referring to snowfall across large areas, not for any specific city. There was a lot of variability on a city-by-city bases for all the of the scenarios tested.

[Roger Smith]

Don, in general I agree and believe it will be an active winter along a persistent storm track running approx STL-BFD-BTV, so coastal n.e. will often be in warm sectors but could see pre-frontal snow to rain a few times, and likely at least one or two significant coastal storms when and if pattern shifts south  briefly.

In western Canada as you indicate general expectation is a colder winter with lots of inland snow and the coastal storminess is already well on its way to verifying. I look for a lot of redeveloping scenarios PAC n.w to around s.e. CO, n.w. TX and OK-KS border to feed storm track I referenced. 

An average to above average sort of lake effect winter since a lot of the storm outbreaks will tend to pull in cold W-NW wraparound. Do you recall winter 1964-65? I was observing (as a teenager) in s Ontario west of Toronto, it was a non-stop parade of storms and all sorts of synoptics. Feb was especially volatile, record warm around Feb 10 and a big snowfall 25th (18"). I think NYC got 50F rain and strong winds from that one. If 1964-65 repeated it would be a very active winter getting off to a slow start in Dec and picking up pace rapidly in Jan. 

Another winter broadly similar was 1980-81 and a big storm like Jan 1-2 1999 would not be unexpected in the pattern apparently setting up. 

Lunar declination and tidal energy peaks favor peak storminess mid-Dec and Jan, and very late Dec, Jan. Secondary peaks would be likely but closer to a 5-9-5-9 day cycle than id-cycle secondary peaks. Feb gets into a faster wave modality on that (experimental) energy and would favor a weekly storminess peak on a near 5-8-6-7 day modulation.

 

[donsutherland1]

4 hours ago, Roger Smith said:

Don, in general I agree and believe it will be an active winter along a persistent storm track running approx STL-BFD-BTV, so coastal n.e. will often be in warm sectors but could see pre-frontal snow to rain a few times, and likely at least one or two significant coastal storms when and if pattern shifts south  briefly.

In western Canada as you indicate general expectation is a colder winter with lots of inland snow and the coastal storminess is already well on its way to verifying. I look for a lot of redeveloping scenarios PAC n.w to around s.e. CO, n.w. TX and OK-KS border to feed storm track I referenced. 

An average to above average sort of lake effect winter since a lot of the storm outbreaks will tend to pull in cold W-NW wraparound. Do you recall winter 1964-65? I was observing (as a teenager) in s Ontario west of Toronto, it was a non-stop parade of storms and all sorts of synoptics. Feb was especially volatile, record warm around Feb 10 and a big snowfall 25th (18"). I think NYC got 50F rain and strong winds from that one. If 1964-65 repeated it would be a very active winter getting off to a slow start in Dec and picking up pace rapidly in Jan. 

Another winter broadly similar was 1980-81 and a big storm like Jan 1-2 1999 would not be unexpected in the pattern apparently setting up. 

Lunar declination and tidal energy peaks favor peak storminess mid-Dec and Jan, and very late Dec, Jan. Secondary peaks would be likely but closer to a 5-9-5-9 day cycle than id-cycle secondary peaks. Feb gets into a faster wave modality on that (experimental) energy and would favor a weekly storminess peak on a near 5-8-6-7 day modulation.

 

I suspect that BC will see a stormy winter. Vancouver could see a lot of rain. Interior sections will probably see much above normal snowfall. Temperatures could also break on the cold side of normal.

[40/70 Benchmark]

Same page, Don.

[psuhoffman]

19 hours ago, donsutherland1 said:

When I referenced 2001-02 and 2016-17, I was referring to snowfall across large areas, not for any specific city. There was a lot of variability on a city-by-city bases for all the of the scenarios tested.

lol sorry I wasn’t picking on you’re forecast or your point. I was more just LOLng at the fact the mid Atlantic is screwed no matter what.  Even the colder “snowier” weak Nina +QBO seasons were god awful down here. It does matter for places north of 40. 

[donsutherland1]

4 hours ago, psuhoffman said:

lol sorry I wasn’t picking on you’re forecast or your point. I was more just LOLng at the fact the mid Atlantic is screwed no matter what.  Even the colder “snowier” weak Nina +QBO seasons were god awful down here. It does matter for places north of 40. 

No worries. I thought my discussion might have been unclear. Hopefully, things will turn out better than what I expect.