Global Average Temperature and the Propagation of Uncertainty

[LibertyBell]

12 hours ago, bluewave said:

The 75 year winter warming has actually been more significant in those regions with our area coming in a few degrees behind.

 

 

I wonder why it is that certain areas, like the northern Rockies have either remained steady or even cooling.  Maybe the very high elevations of that region make them immune....for now.

 

[chubbs]

30-year running average snowfall for some Northeast sites, focusing on I95. Plotted on a log scale, to highlight percentage changes between sites. Table below shows changes in current 30-year mean vs mean in 1970, 1990 and 2000. The sites with the lowest snow are in decline. Further north the picture is mixed, coastal I95 has increased at the expense of the interior.  I'd expect declining snow to spread slowly and unevenly north with time.  Note that we only have snowfall information for our cooler past.

 

[bluewave]

There are some recent studies on why the Northeast has been one of few places that have seen snowfall increases into the 2010s. Record SSTs provided more fuel for the snowstorms when blocking forced favorable tracks. But at some point the blocking and storm tracks shift and the warmth ultimately reduces snowfall. We have been seeing more of this since 18-19. So we’ll have to see if the 2010s was some type of grand finale for record snowfall and declines become more common in 2020s along the I-95 corridor.

 

https://journals.ametsoc.org/view/journals/wefo/29/6/waf-d-14-00056_1.xml

Abstract

On 8–9 February 2013, the northeastern United States experienced a historic winter weather event ranking among the top five worst blizzards in the region. Heavy snowfall and blizzard conditions occurred from northern New Jersey, inland to New York, and northward through Maine. Storm-total snow accumulations of 30–61 cm were common, with maximum accumulations up to 102 cm and snowfall rates exceeding 15 cm h⁻¹. Dual-polarization radar measurements collected for this winter event provide valuable insights into storm microphysical processes. In this study, polarimetric data from the Weather Surveillance Radar-1988 Doppler (WSR-88D) in Upton, New York (KOKX), are investigated alongside thermodynamic analyses from the 13-km Rapid Refresh model and surface precipitation type observations from both Meteorological Phenomena Identification Near the Ground (mPING) and the National Weather Service (NWS) Forecast Office in Upton, New York, for interpretation of polarimetric signatures. The storm exhibited unique polarimetric signatures, some of which have never before been documented for a winter system. Reflectivity values were unusually large, reaching magnitudes >50 dBZ in shallow regions of heavy wet snow near the surface. The 0°C transition line was exceptionally distinct in the polarimetric imagery, providing detail that was often unmatched by the numerical model output. Other features include differential attenuation of magnitudes typical of melting hail, depolarization streaks that provide evidence of electrification, nonuniform beamfilling, a “snow flare” signature, and localized downward excursions of the melting-layer bright band collocated with observed transitions in surface precipitation types. In agreement with previous studies, widespread elevated depositional growth layers, located at temperatures near the model-predicted −15°C isotherm, appear to be correlated with increased snowfall and large reflectivity factors Z_H near the surface

 
The pattern produced record 80° warmth at Newark in February 2018 before record March blocking produced 30” snows on Long Island. 
 

The Western Atlantic or SE Ridge has been at record levels during the winter since 2015-2016. So a first 8 warmer winters in a row NW Atlantic warm pool also at historic levels of warmth.

 

 

NYC

Feb 23…+5.2

Jan 23…+9.8

Dec 22…-0.6

…………..+4.8

 

Feb 22….+1.4

Jan 22….-3.2

Dec 21….+4.7

……………..+1.0

 

Feb 21….-1.7

Jan 21….+1.1

Dec 20…+1.7

…………..+0.4

 

Feb 20…+4.8

Jan 20….+6.5

Dec 19….+0.8

…………….+4.0

 

Feb 19….+0.9

Jan 19….-0.1

Dec 18…+2.6

…………….+1.1

 

Feb 18…+6.7

Jan 18….-0.9

Dec 17…..-2.5

…………….+1.1

 

Feb 17…..+6.3

Jan 17….+5.4

Dec 16….+0.8

…………….+4.2

 

Feb 16….+2.4

Jan 16….+1.9

Dec 15….+13.3

…………….+5.9

Blocking since 2018-2019 has been building down toward this record NW Atlantic warm pool. So in concert with a hostile Pacific last December we had record low snowfall for such a-AO.

 

Never before nearly -3 SD 2nd strongest December -AO block linking with SE  Ridge. 
 

In past only much weaker blocks would link up with SE Ridge. The stronger -AO -PNAs in the past with colder SSTs off the East Coast didn’t have such prominent SE Ridge linkages in Northeast.

 

 

 

[Typhoon Tip]

Yup Bluewave ...  aware of the SST paper(s) wrt coastal plain snow increases over the last 20 to 30 years. I was going to mention this but you beat me to it 

[LibertyBell]

and dont forget the paper on the great January 2016 blizzard that gave us our first 30+ inch blizzard with true blizzard conditions for 12 hours straight!

 

[bluewave]

1 hour ago, Typhoon Tip said:

Yup Bluewave ...  aware of the SST paper(s) wrt coastal plain snow increases over the last 20 to 30 years. I was going to mention this but you beat me to it 

Yeah, this is still significant even allowing for under measurement of older storms by todays standards. The right blocking to force the classic benchmark track is a necessary ingredient. Otherwise, the record warm Gulf Stream just enhances the SE Ridge.

https://theconversation.com/why-a-warming-climate-can-bring-bigger-snowstorms-176201

The warming ocean plays a role

The historic blizzard that buried Boston under nearly 2 feet of snow in January 2022 was fueled by ocean waters in the western Atlantic that are warmer than normal. That’s also part of a consistent pattern.

 

Top 10: Boston's and New York's biggest snow storms

Seven of Boston's and New York's 10 biggest two- to three-day snowfall totals on record happened since 1995.

Table showing the years of New York and Boston's biggest snow storms and the depth. The January 2022 blizzard was Boston's 7th largest snowfall total

Boston	Snow depth	New York	Depth
2003	28 inches 28 inches	2016	27 inches 27 inches
1978	27 inches 27 inches	2006	27 inches 27 inches
1969	26 inches 26 inches	1947	26 inches 26 inches
1997	25 inches 25 inches	1888	22 inches 22 inches
2013	25 inches 25 inches	2010	21 inches 21 inches
2015	24 inches 24 inches	1996	20 inches 20 inches
2022	24 inches 24 inches	2010	20 inches 20 inches
2005	23 inches 23 inches	2003	20 inches 20 inches
2015	22 inches 22 inches	2011	19 inches 19 inches
1978	21 inches 21 inches	1941	18 inches 18 inches

The oceans have been absorbing more than 90% of the additional heat attributable to rising atmospheric greenhouse gases from human activities, particularly burning fossil fuels. The oceans now contain more heat energy than any time since measurements began six decades ago.

Scientists are studying whether global warming may be driving a slowing of the ocean conveyor belt of currents that transport water around the globe. Satellite imagery and ocean measurements show that warmer waters have “piled up” along the East Coast, a possible indication of a slowing of the Atlantic Meridional Overturning Circulation.

Moisture evaporated from ocean water provides much of the energy for both tropical and mid-latitude extra-tropical cyclones, known commonly as nor’easters

[Typhoon Tip]

It would not shock me if future findings hone changes in the total atmospheric circulation mode are at least partially causal related to why the SST warmth has increased from roughly the VA Capes to the D Straight ( relative to those latitudes) ...

I'm interested also in the thermocline; sub surface delta and the integrated OHC in those regions, too.

There may be concurrent factors. 

The thermalhaline imbalance causing buoyancy to increase may certainly play a role in/"IF" slowing of the AMO is confirmed.  But I also suggest that changes in the winter seasons', sea sfc wind stressing patterns (possibly related to perceived lower frequency of intra seasonal -NAO phase states over recent decades) as playing a role.  

Less -NAO phase state over the longer mean, means there is more for SE/S return flow tendencies over far eastern N/A and the NW Atlantic Basin ... perhaps suppressing upwelling to some degree.

[LibertyBell]

19 hours ago, bluewave said:

Yeah, this is still significant even allowing for under measurement of older storms by todays standards. The right blocking to force the classic benchmark track is a necessary ingredient. Otherwise, the record warm Gulf Stream just enhances the SE Ridge.

https://theconversation.com/why-a-warming-climate-can-bring-bigger-snowstorms-176201

The warming ocean plays a role

The historic blizzard that buried Boston under nearly 2 feet of snow in January 2022 was fueled by ocean waters in the western Atlantic that are warmer than normal. That’s also part of a consistent pattern.

 

Top 10: Boston's and New York's biggest snow storms

Seven of Boston's and New York's 10 biggest two- to three-day snowfall totals on record happened since 1995.

Table showing the years of New York and Boston's biggest snow storms and the depth. The January 2022 blizzard was Boston's 7th largest snowfall total

Boston	Snow depth	New York	Depth
2003	28 inches 28 inches	2016	27 inches 27 inches
1978	27 inches 27 inches	2006	27 inches 27 inches
1969	26 inches 26 inches	1947	26 inches 26 inches
1997	25 inches 25 inches	1888	22 inches 22 inches
2013	25 inches 25 inches	2010	21 inches 21 inches
2015	24 inches 24 inches	1996	20 inches 20 inches
2022	24 inches 24 inches	2010	20 inches 20 inches
2005	23 inches 23 inches	2003	20 inches 20 inches
2015	22 inches 22 inches	2011	19 inches 19 inches
1978	21 inches 21 inches	1941	18 inches 18 inches

The oceans have been absorbing more than 90% of the additional heat attributable to rising atmospheric greenhouse gases from human activities, particularly burning fossil fuels. The oceans now contain more heat energy than any time since measurements began six decades ago.

Scientists are studying whether global warming may be driving a slowing of the ocean conveyor belt of currents that transport water around the globe. Satellite imagery and ocean measurements show that warmer waters have “piled up” along the East Coast, a possible indication of a slowing of the Atlantic Meridional Overturning Circulation.

Moisture evaporated from ocean water provides much of the energy for both tropical and mid-latitude extra-tropical cyclones, known commonly as nor’easters

Hey Chris, I've always been interested in the number of 20 inch snowstorms each city on the east coast has had-- has Boston had the most or Baltimore? I think it's one or the other.

Also doesn't JFK, LGA or EWR or all of them have more 20 inch snowstorms than NYC does?  I know that February 1961 and February 1969 were both at or above 20" at JFK.  February 1983 was also at or over 20" at the airports.

Maybe NYC edges them out because of their longer period of record but I remember several snowstorms where the airports hit 20" and the Park did not.

 

Offhand here are the ones I remember for JFK..... Feb 1961, Feb 1969, Feb 1983, Jan 1996, Feb 2003, Jan 2016

 

 

[ORH_wxman]

1 hour ago, LibertyBell said:

Hey Chris, I've always been interested in the number of 20 inch snowstorms each city on the east coast has had-- has Boston had the most or Baltimore? I think it's one or the other.

Also doesn't JFK, LGA or EWR or all of them have more 20 inch snowstorms than NYC does?  I know that February 1961 and February 1969 were both at or above 20" at JFK.  February 1983 was also at or over 20" at the airports.

Maybe NYC edges them out because of their longer period of record but I remember several snowstorms where the airports hit 20" and the Park did not.

 

Offhand here are the ones I remember for JFK..... Feb 1961, Feb 1969, Feb 1983, Jan 1996, Feb 2003, Jan 2016

 

 

Pretty sure BWI And BOS both have 10 storms of 20"+. Baltimore used to have more but Boston caught up with 4 in the last 10 years to Baltimore's 1.

[LibertyBell]

10 minutes ago, ORH_wxman said:

Pretty sure BWI And BOS both have 10 storms of 20"+. Baltimore used to have more but Boston caught up with 4 in the last 10 years to Baltimore's 1.

Yes, I remember some theories on why Baltimore was so far ahead back then and why they were more favorable for 20" HECS than the other cities (especially moreso than NYC and Boston, who are both significantly northeast of them.)

 

[tamarack]

58 minutes ago, ORH_wxman said:

Pretty sure BWI And BOS both have 10 storms of 20"+. Baltimore used to have more but Boston caught up with 4 in the last 10 years to Baltimore's 1.

I've found only 9 for BWI - may have missed one.  PWM/BGR also have 9.

2/1899
1/1922
3/1942
2/1979
2/1983
1/1996
2/2003
2/2010
1/2016

#10: 2/9-10/2010, 19.5"
 

[ORH_wxman]

8 minutes ago, tamarack said:

I've found only 9 for BWI - may have missed one.  PWM/BGR also have 9.

2/1899
1/1922
3/1942
2/1979
2/1983
1/1996
2/2003
2/2010
1/2016

#10: 2/9-10/2010, 19.5"
 

You are correct...I double counted 2003 for some reason.

[tamarack]

28 minutes ago, ORH_wxman said:

You are correct...I double counted 2003 for some reason.

Boston reigns alone!

[Typhoon Tip]

3 hours ago, Typhoon Tip said:

It would not shock me if future findings hone changes in the total atmospheric circulation mode are at least partially causal related to why the SST warmth has increased from roughly the VA Capes to the D Straight ( relative to those latitudes) ...

I'm interested also in the thermocline; sub surface delta and the integrated OHC in those regions, too.

There may be concurrent factors. 

The thermalhaline imbalance causing buoyancy to increase may certainly play a role in/"IF" slowing of the AMO is confirmed.  But I also suggest that changes in the winter seasons', sea sfc wind stressing patterns (possibly related to perceived lower frequency of intra seasonal -NAO phase states over recent decades) as playing a role.  

Less -NAO phase state over the longer mean, means there is more for SE/S return flow tendencies over far eastern N/A and the NW Atlantic Basin ... perhaps suppressing upwelling to some degree.

While on the subject...

"  https://phys.org/news/2023-03-deep-ocean-currents-antarctica-collapse.html  "

interesting little nugget.  Ironically... here we're discussing a very similar phenomenon - actually... the exact same phenomenon, but in this case, the polar southern Hemisphere.   The 'thermal haline buoyancy' stuff is threatening to shut down that circulation engine down there (haline means the salt content)

The way it works is the fresh water flux is lighter than salt water and "floats" over top.  Cold salt water sinks...particularly as it cools, and those downward 'chimneys' then pull the surface water back N from the south to compensate for the mass deposition to the ocean depths.  ... BUT, here's the key: if there is buoyant fresh water ... effectively 'blocking' that (even in fraction do to turbulent mixing...) that impedes the downward mass. With less mass moving downward, less drag on the surface --> the conveyor system is weakened.

Fairly large pallet of consequences loaded up for the canvas of the planetary future with that to put it lightly...

[LibertyBell]

27 minutes ago, tamarack said:

Boston reigns alone!

Perhaps we could round up 19.5 to 20 inches though

[GaWx]

From @bluewave post:

"The pattern produced record 80° warmth at Newark in February 2018 before record March blocking produced 30” snows on Long Island."

 In addition to the influence from CC, both the Feb of 2018 E US warmth/record high H5 heights and subsequent Arctic blocking/cold/snow in March of 2018 were made possible by one of the most extreme "major" SSWs on record. This major SSW was centered on 2/12/2018:

https://acp.copernicus.org/articles/19/10303/2019/acp-19-10303-2019.html

 Though not always, it has been common for there to be strong warmth in the E US during the first 15 days after recent major SSWs followed by a sharp change to colder during days 16-30 for those SSWs that propagate downward into the troposphere and then lead to the development of a -AO.

[LibertyBell]

9 minutes ago, GaWx said:

From @bluewave post:

"The pattern produced record 80° warmth at Newark in February 2018 before record March blocking produced 30” snows on Long Island."

 In addition to the influence from CC, both the Feb of 2018 E US warmth/record high H5 heights and subsequent Arctic blocking/cold/snow in March of 2018 were made possible by one of the most extreme "major" SSWs on record. This major SSW was centered on 2/12/2018:

https://acp.copernicus.org/articles/19/10303/2019/acp-19-10303-2019.html

 Though not always, it has been common for there to be strong warmth in the E US during the first 15 days after recent major SSWs followed by a sharp change to colder during days 16-30 for those SSWs that propagate downward into the troposphere and then lead to the development of a -AO.

Is there a place for data where SSW are ranked or rated like la ninas and el ninos are-- that is, weak, moderate, strong, super?  I would love to see that data as well as the date on which they occurred.  Have we ever had a major SSW early in the season that influenced the entire winter (say, in November?)

What you said about warmth going to cold gives a good explanation why many of our best winters had a mild November followed by a snowy winter.  I noted a 7 for 7 outcome between 1955-56 and 1993-94 for winters with over 40 inches of snow and mild Novembers in NYC.

[bluewave]

55 minutes ago, GaWx said:

From @bluewave post:

"The pattern produced record 80° warmth at Newark in February 2018 before record March blocking produced 30” snows on Long Island."

 In addition to the influence from CC, both the Feb of 2018 E US warmth/record high H5 heights and subsequent Arctic blocking/cold/snow in March of 2018 were made possible by one of the most extreme "major" SSWs on record. This major SSW was centered on 2/12/2018:

https://acp.copernicus.org/articles/19/10303/2019/acp-19-10303-2019.html

 Though not always, it has been common for there to be strong warmth in the E US during the first 15 days after recent major SSWs followed by a sharp change to colder during days 16-30 for those SSWs that propagate downward into the troposphere and then lead to the development of a -AO.

 

The record WPAC warm pool drove the record MJO leading to the SSW.

https://wcd.copernicus.org/articles/1/657/2020/

In the beginning of February 2018 a rapid deceleration of the westerly circulation in the polar Northern Hemisphere stratosphere took place, and on 12 February the zonal-mean zonal wind at 60^∘ N and 10 hPa reversed to easterly in a sudden stratospheric warming (SSW) event. We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave. The dynamical and statistical analyses indicate that the main tropospheric forcing resulted from an anticyclonic Rossby wave breaking, subsequent blocking and upward wave propagation in the Ural Mountains region, in agreement with some previous studies. The ensemble members which predicted the wind reversal also reasonably reproduced this chain of events, from the horizontal propagation of individual wave packets to upward wave-activity fluxes and the amplification of wavenumber 2. On the other hand, the ensemble members which failed to predict the wind reversal also failed to properly capture the blocking event in the key region of the Urals and the associated intensification of upward-propagating wave activity. Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9540765/

The predictability of Northern Hemisphere sudden stratospheric warming (SSW) events is considered in 10 subseasonal to seasonal (S2S) forecast models for 16 major SSWs that have occurred since 1998, a larger sample size than has been considered by previous works. The four factors that most succinctly distinguish those SSWs with above average predictability are a preconditioned vortex prior to the SSW, an active Madden‐Julian Oscillation with enhanced convection in the West Pacific, the Quasi‐Biennial Oscillation phase with easterlies in the lower stratosphere, and the vortex morphology (displacement more predictable). Two of these factors appear to not have been considered in previous works focusing on a large sample of events. Most of these effects are not statistically significant at the 95% level due to the still relatively small sample size, though all would exceed a 90% criteria at least marginally. Combined, however, they account for 40% of the inter‐event spread in SSW predictability, thus indicating that SSWs with favorable precursors are significantly more predictable.

[Typhoon Tip]

35 minutes ago, GaWx said:

From @bluewave post:

"The pattern produced record 80° warmth at Newark in February 2018 before record March blocking produced 30” snows on Long Island."

 In addition to the influence from CC, both the Feb of 2018 E US warmth/record high H5 heights and subsequent Arctic blocking/cold/snow in March of 2018 were made possible by one of the most extreme "major" SSWs on record. This major SSW was centered on 2/12/2018:

https://acp.copernicus.org/articles/19/10303/2019/acp-19-10303-2019.html

 Though not always, it has been common for there to be strong warmth in the E US during the first 15 days after recent major SSWs followed by a sharp change to colder during days 16-30 for those SSWs that propagate downward into the troposphere and then lead to the development of a -AO.

It wasn't an an extraordinarily prominent event but it definitely behaved in the characteristic downward propagation of the warm intruded mass...  The timing also situates well with the advent of blocking later in March that year.  

[tamarack]

20 minutes ago, LibertyBell said:

Is there a place for data where SSW are ranked or rated like la ninas and el ninos are-- that is, weak, moderate, strong, super?  I would love to see that data as well as the date on which they occurred.  Have we ever had a major SSW early in the season that influenced the entire winter (say, in November?)

What you said about warmth going to cold gives a good explanation why many of our best winters had a mild November followed by a snowy winter.  I noted a 7 for 7 outcome between 1955-56 and 1993-94 for winters with over 40 inches of snow and mild Novembers in NYC.

Works for NYC, but not for the local long-term (1893-on) co-op.  AN November temp, snowfall averages 94% of average.  BN temp, 107%.  May not be statistically significant as annual snow is quite variable (though not as variable as at NYC).

 

[Typhoon Tip]

I also tend to agree that the preceding E N/A 'warm synoptic burst' was circuited to the warm intrusion in the stratosphere.  

Whether or not that can ultimately ( and probably so...) linked back to the Pac MJO interference pattern or not, I have noticed in the past that warmth over continents in general tends to precede the advent of SSW's ... 

[GaWx]

1 hour ago, LibertyBell said:

Is there a place for data where SSW are ranked or rated like la ninas and el ninos are-- that is, weak, moderate, strong, super?  I would love to see that data as well as the date on which they occurred.  Have we ever had a major SSW early in the season that influenced the entire winter (say, in November?)

What you said about warmth going to cold gives a good explanation why many of our best winters had a mild November followed by a snowy winter.  I noted a 7 for 7 outcome between 1955-56 and 1993-94 for winters with over 40 inches of snow and mild Novembers in NYC.

 This source has extensive SSW data since 1980 in table 3 with rankings of minor, major, and extreme. Note that Feb of 2018 is ranked as "extreme", one of only eight out of the 43 in the table:

https://acp.copernicus.org/articles/23/1259/2023/acp-23-1259-2023.pdf

 There are no November SSWs in that table. One of the most memorable in terms of influence on the E US is the extreme SSW of 1/1/1985, which lead to extreme cold due to record blocking 2.5-3 weeks later. But even extreme SSWs don't always propagate downward enough to later lead to cold.

[ORH_wxman]

1 hour ago, LibertyBell said:

Perhaps we could round up 19.5 to 20 inches though

Boston has two storms that are similar too....they had 19.8" in the 3/3/60 storm and 19.4" in the 2/16/58 storm.

[GaWx]

1 hour ago, bluewave said:

The record WPAC warm pool drove the record MJO leading to the SSW.

https://wcd.copernicus.org/articles/1/657/2020/

In the beginning of February 2018 a rapid deceleration of the westerly circulation in the polar Northern Hemisphere stratosphere took place, and on 12 February the zonal-mean zonal wind at 60^∘ N and 10 hPa reversed to easterly in a sudden stratospheric warming (SSW) event. We investigate the role of the tropospheric forcing in the occurrence of the SSW, its predictability and teleconnection with the Madden–Julian oscillation (MJO) by analysing the European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecast. The SSW was preceded by significant synoptic wave activity over the Pacific and Atlantic basins, which led to the upward propagation of wave packets and resulted in the amplification of a stratospheric wavenumber 2 planetary wave. The dynamical and statistical analyses indicate that the main tropospheric forcing resulted from an anticyclonic Rossby wave breaking, subsequent blocking and upward wave propagation in the Ural Mountains region, in agreement with some previous studies. The ensemble members which predicted the wind reversal also reasonably reproduced this chain of events, from the horizontal propagation of individual wave packets to upward wave-activity fluxes and the amplification of wavenumber 2. On the other hand, the ensemble members which failed to predict the wind reversal also failed to properly capture the blocking event in the key region of the Urals and the associated intensification of upward-propagating wave activity. Finally, a composite analysis suggests that teleconnections associated with the record-breaking MJO phase 6 observed in late January 2018 likely played a role in triggering this SSW event.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9540765/

The predictability of Northern Hemisphere sudden stratospheric warming (SSW) events is considered in 10 subseasonal to seasonal (S2S) forecast models for 16 major SSWs that have occurred since 1998, a larger sample size than has been considered by previous works. The four factors that most succinctly distinguish those SSWs with above average predictability are a preconditioned vortex prior to the SSW, an active Madden‐Julian Oscillation with enhanced convection in the West Pacific, the Quasi‐Biennial Oscillation phase with easterlies in the lower stratosphere, and the vortex morphology (displacement more predictable). Two of these factors appear to not have been considered in previous works focusing on a large sample of events. Most of these effects are not statistically significant at the 95% level due to the still relatively small sample size, though all would exceed a 90% criteria at least marginally. Combined, however, they account for 40% of the inter‐event spread in SSW predictability, thus indicating that SSWs with favorable precursors are significantly more predictable.

 I've read several articles written by Dr. Lee about certain setups in the troposphere often leading to SSWs via "heat flux". This one cited that high Scandinavian SLP coexisting with a very strong surface cyclone centered just off of NE Greenland is a pretty good indicator of an SSW soon after:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2019JD030940

 One of these strong SLP dipoles occurred during early Feb of 2018, just before the 2/12/2018 SSW. It just so happened that it also existed in early Feb of 2023, just before the major SSW of 2/16/2023.

[bluewave]

55 minutes ago, GaWx said:

 This source has extensive SSW data since 1980 in table 3 with rankings of minor, major, and extreme. Note that Feb of 2018 is ranked as "extreme", one of only eight out of the 43 in the table:

https://acp.copernicus.org/articles/23/1259/2023/acp-23-1259-2023.pdf

 There are no November SSWs in that table. One of the most memorable in terms of influence on the E US is the extreme SSW of 1/1/1985, which lead to extreme cold due to record blocking 2.5-3 weeks later. But even extreme SSWs don't always propagate downward enough to later lead to cold.

This is another list that you can use.

 

https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html

[LibertyBell]

2 hours ago, GaWx said:

 This source has extensive SSW data since 1980 in table 3 with rankings of minor, major, and extreme. Note that Feb of 2018 is ranked as "extreme", one of only eight out of the 43 in the table:

https://acp.copernicus.org/articles/23/1259/2023/acp-23-1259-2023.pdf

 There are no November SSWs in that table. One of the most memorable in terms of influence on the E US is the extreme SSW of 1/1/1985, which lead to extreme cold due to record blocking 2.5-3 weeks later. But even extreme SSWs don't always propagate downward enough to later lead to cold.

wow that 1985 arctic cold shot was the coldest I've ever experienced.....but there really wasn't much snow associated with it, just that big cold shot around Inauguration Day and then it went back to above normal in February (like so many of those 80s winters-- January arctic cold-- and dry followed by February mild and rainy.)

 

[LibertyBell]

2 hours ago, bluewave said:

This is another list that you can use.

 

https://csl.noaa.gov/groups/csl8/sswcompendium/majorevents.html

Thanks Chris, some of those from the late 50s and 60s are strongly connected to very snow winters, but the ones from the 70s, 80s and late 90s are not lol.  I wonder what changed?

also-- are these becoming less frequent?  I see there has been one every year or every other year up through the 2000s, but not so in the last 10 years.

 

[LibertyBell]

2 hours ago, ORH_wxman said:

Boston has two storms that are similar too....they had 19.8" in the 3/3/60 storm and 19.4" in the 2/16/58 storm.

I would include those too-- NYC had either 19.7 or 19.9 in PD2 (what an annoying total lol), got to round that to 20"...especially since JFK had 26" in that storm!

[LibertyBell]

6 hours ago, tamarack said:

I've found only 9 for BWI - may have missed one.  PWM/BGR also have 9.

2/1899
1/1922
3/1942
2/1979
2/1983
1/1996
2/2003
2/2010
1/2016

#10: 2/9-10/2010, 19.5"
 

Found out today is the anniversary of that March 1942 storm!

1942: A slow-moving low-pressure system brought 11.5 inches of snow to the nation's capital on March 29, 1942. It still stands as the highest March snowfall on record in Washington, D.C. on a single calendar day. Also, Baltimore, Maryland recorded an imposing total of 21.9 inches of snow on the same day. On the flip side, eight days later, the temperature in D.C. soared to 92 degrees on April 6, 1942, and it remains the highest temperature on record for April 6.

 

I wonder how much we got up here from it?

 

Amazing Baltimore got almost twice DC's total in that storm.

[bluewave]

9 hours ago, LibertyBell said:

Hey Chris, I've always been interested in the number of 20 inch snowstorms each city on the east coast has had-- has Boston had the most or Baltimore? I think it's one or the other.

Baltimore and Philly beat Boston in the snowiest 7 day challenge by a few inches.
 

Maximum 7-Day Total Snowfall 
for Baltimore Area, MD (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Rank	Value	Ending Date	Missing Days
1	44.5	2010-02-11	0

 

Go

Maximum 7-Day Total Snowfall 
for Philadelphia Area, PA (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Rank	Value	Ending Date	Missing Days
1	44.3	2010-02-11	0

 

Maximum 7-Day Total Snowfall 
for Boston Area, MA (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Rank	Value	Ending Date	Missing Days
1	40.5	2015-02-02	0