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Pattern December to Remember

smast16 said:
This says that fall storms are often tells, well I hate to break it to ya, but there was a very definite and noticeable lack of fall storms.
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There was a very strong slow moving fall storm in early November that gave the Gulf coast, S GA, coastal SE and N FL very heavy rain and gusty winds. I experienced it.
 
NickyBGuarantee said:
What’s funny is the models are pointing at this death ridge eventually retrograding up towards Greenland and eventually our Greenland block shows up in force.. probably won’t be until the last week of December or so
Click to expand...

That's not how this works. A blocking ridge (or trough) that moves from west to east is definitely not "retrograding" because it's in the same direction as the background flow (which is also west to east), that would be actually be a "prograde" motion. What's far more likely happen to develop a -NAO from +NAO is the blocking high over the Barents Sea & Scandinavia would retrograde westward w/ time if the N Atlantic storm track is sufficiently excited by a slow moving, West Pacific MJO event that migrates into the western hemisphere.

See for example:

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0289.1.xml

On the other hand, for the NAO+ to NAO− transition events during P2, a comparison between Figs. 8b and 9b shows that the transition events coincide with the NAO− (NAO+) anomaly being markedly enhanced (weakened). A comparison between Figs. 8b and 9b also shows for the NAO+ to NAO− transition events that the SBL (Scandinavian Blocking) is enhanced and exhibits a westward-displaced position. The strengthening and westward-displaced position of the SBL (Scandinavian Blocking) within P2 takes place with the intensification of the NAO− anomaly. Thus, the NAO+ to NAO− transition appears to be connected to the excitation of the enhanced SBL (Scandinavian Blocking) pattern. These results suggest that the enhancement of the SBL (Scandinavian Blocking) pattern plays a role for the NAO+ to NAO−transition events. Thus, the NAO+ to NAO− transition event is likely to coincide with an increase in the amplitude and the westward-displaced position of the SBL (Scandinavian Blocking) pattern. As noted by Cassou (2008), a greater frequency of occurrence of the SBL (Scandinavian Blocking) can lead to an NAO+ to SBL (Scandinavian Blocking) to NAO− transition.


From Part II of this study

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0290.1.xml?tab_body=fulltext-display

"It is found that the NAO+ to NAO− transition is more likely to occur when the SBL (Scandinavian Blocking) is enhanced, with the route NAO+ to SBL to NAO− taking place."

An analogous result is found for NAO+ to NAO− transition events when the SBL is strong (Fig. 3b). The difference of the composite NAO index between the weak and strong SBL (Scandinavian Blocking) strengths is statistically significant at the 90% confidence level with a Monte Carlo test. This result indicates that an enhanced SBL (Scandinavian Blocking) pattern favors the transition from the NAO+ to the NAO− event.


Prior to the NAO+ event transiting into an NAO− event, the SBL is generally stronger because of the NAO being positive (Luo et al. 2007). It is found from Fig. 4b that during the NAO+ to NAO− transition the SBL strength is positive between lag −10 and lag +12, indicating a tendency to increase before lag 0 and then decrease until lag +4. A rapid reintensification of the SBL pattern is again seen after lag +4, followed by the beginning of its decay at about lag +7, after which it becomes negative at lag +12. Thus, the transition from an NAO+ to an NAO− event is closely related to a change in the SBL (Scandinavian Blocking) strength. Moreover, it is seen that the occurrence of the SBL precedes the formation of an NAO− event during the NAO+ transition (solid line in Fig. 4b). This is because the NAO− event arises from the retrograde displacement of the SBL (Scandinavian Blocking) pattern. Feldstein (2003) found that European blocks retrograde before an NAO− event forms. More recently, Sung et al. (2011) suggested that NAO− events tend to be preceded by a blocking ridge in the vicinity of northern Europe. Cassou (2008) noted that an enhanced SBL and NAO−, associated with the Madden–Julian oscillation (MJO), can be interpreted as being the consequence of the previous NAO+excitation. However, we see here that the reintensification of the SBL (Scandinavian Blocking) pattern is crucial for the NAO+ to NAO− transition


Also see

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1256/qj.02.76?casa_token=qNmP7R8p9AYAAAAA:CsevTy9aIC0waYxRuOU0UFDPHVUhGVsW2V4fg0qZusYT3VV-kIEta7Ztu641gCuJlodkafAX8dFFAcw


https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2010JD015006


https://idp.nature.com/authorize/casa?redirect_uri=https://www.nature.com/articles/nature07286&casa_token=MeTwFkjjovUAAAAA:Fc9BuCbX5G3xULHwII3ZZML9qVRql5ktM90-q9jL5rK9670BKKCBjZ5NVi0eggY259ToVAHzZk_tLi_6
 
Webberweather53 said:
That's not how this works. A blocking ridge (or trough) that moves from west to east is definitely not "retrograding" because it's in the same direction as the background flow (which is also west to east), that would be actually be a "prograde" motion. What's far more likely happen to develop a -NAO from +NAO is the blocking high over the Barents Sea & Scandinavia would retrograde westward w/ time if the N Atlantic storm track is sufficiently excited by a slow moving, West Pacific MJO event that migrates into the western hemisphere.

See for example:

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0289.1.xml

On the other hand, for the NAO+ to NAO− transition events during P2, a comparison between Figs. 8b and 9b shows that the transition events coincide with the NAO− (NAO+) anomaly being markedly enhanced (weakened). A comparison between Figs. 8b and 9b also shows for the NAO+ to NAO− transition events that the SBL (Scandinavian Blocking) is enhanced and exhibits a westward-displaced position. The strengthening and westward-displaced position of the SBL (Scandinavian Blocking) within P2 takes place with the intensification of the NAO− anomaly. Thus, the NAO+ to NAO− transition appears to be connected to the excitation of the enhanced SBL (Scandinavian Blocking) pattern. These results suggest that the enhancement of the SBL (Scandinavian Blocking) pattern plays a role for the NAO+ to NAO−transition events. Thus, the NAO+ to NAO− transition event is likely to coincide with an increase in the amplitude and the westward-displaced position of the SBL (Scandinavian Blocking) pattern. As noted by Cassou (2008), a greater frequency of occurrence of the SBL (Scandinavian Blocking) can lead to an NAO+ to SBL (Scandinavian Blocking) to NAO− transition.


From Part II of this study

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0290.1.xml?tab_body=fulltext-display

"It is found that the NAO+ to NAO− transition is more likely to occur when the SBL (Scandinavian Blocking) is enhanced, with the route NAO+ to SBL to NAO− taking place."

An analogous result is found for NAO+ to NAO− transition events when the SBL is strong (Fig. 3b). The difference of the composite NAO index between the weak and strong SBL (Scandinavian Blocking) strengths is statistically significant at the 90% confidence level with a Monte Carlo test. This result indicates that an enhanced SBL (Scandinavian Blocking) pattern favors the transition from the NAO+ to the NAO− event.


Prior to the NAO+ event transiting into an NAO− event, the SBL is generally stronger because of the NAO being positive (Luo et al. 2007). It is found from Fig. 4b that during the NAO+ to NAO− transition the SBL strength is positive between lag −10 and lag +12, indicating a tendency to increase before lag 0 and then decrease until lag +4. A rapid reintensification of the SBL pattern is again seen after lag +4, followed by the beginning of its decay at about lag +7, after which it becomes negative at lag +12. Thus, the transition from an NAO+ to an NAO− event is closely related to a change in the SBL (Scandinavian Blocking) strength. Moreover, it is seen that the occurrence of the SBL precedes the formation of an NAO− event during the NAO+ transition (solid line in Fig. 4b). This is because the NAO− event arises from the retrograde displacement of the SBL (Scandinavian Blocking) pattern. Feldstein (2003) found that European blocks retrograde before an NAO− event forms. More recently, Sung et al. (2011) suggested that NAO− events tend to be preceded by a blocking ridge in the vicinity of northern Europe. Cassou (2008) noted that an enhanced SBL and NAO−, associated with the Madden–Julian oscillation (MJO), can be interpreted as being the consequence of the previous NAO+excitation. However, we see here that the reintensification of the SBL (Scandinavian Blocking) pattern is crucial for the NAO+ to NAO− transition


Also see

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1256/qj.02.76?casa_token=qNmP7R8p9AYAAAAA:CsevTy9aIC0waYxRuOU0UFDPHVUhGVsW2V4fg0qZusYT3VV-kIEta7Ztu641gCuJlodkafAX8dFFAcw


https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2010JD015006


https://idp.nature.com/authorize/casa?redirect_uri=https://www.nature.com/articles/nature07286&casa_token=MeTwFkjjovUAAAAA:Fc9BuCbX5G3xULHwII3ZZML9qVRql5ktM90-q9jL5rK9670BKKCBjZ5NVi0eggY259ToVAHzZk_tLi_6
Click to expand...

And the master continues to school to grasshopper...
 
Webberweather53 said:
That's not how this works. A blocking ridge (or trough) that moves from west to east is definitely not "retrograding" because it's in the same direction as the background flow (which is also west to east), that would be actually be a "prograde" motion. What's far more likely happen to develop a -NAO from +NAO is the blocking high over the Barents Sea & Scandinavia would retrograde westward w/ time if the N Atlantic storm track is sufficiently excited by a slow moving, West Pacific MJO event that migrates into the western hemisphere.

See for example:

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0289.1.xml

On the other hand, for the NAO+ to NAO− transition events during P2, a comparison between Figs. 8b and 9b shows that the transition events coincide with the NAO− (NAO+) anomaly being markedly enhanced (weakened). A comparison between Figs. 8b and 9b also shows for the NAO+ to NAO− transition events that the SBL (Scandinavian Blocking) is enhanced and exhibits a westward-displaced position. The strengthening and westward-displaced position of the SBL (Scandinavian Blocking) within P2 takes place with the intensification of the NAO− anomaly. Thus, the NAO+ to NAO− transition appears to be connected to the excitation of the enhanced SBL (Scandinavian Blocking) pattern. These results suggest that the enhancement of the SBL (Scandinavian Blocking) pattern plays a role for the NAO+ to NAO−transition events. Thus, the NAO+ to NAO− transition event is likely to coincide with an increase in the amplitude and the westward-displaced position of the SBL (Scandinavian Blocking) pattern. As noted by Cassou (2008), a greater frequency of occurrence of the SBL (Scandinavian Blocking) can lead to an NAO+ to SBL (Scandinavian Blocking) to NAO− transition.


From Part II of this study

https://journals.ametsoc.org/view/journals/atsc/69/8/jas-d-11-0290.1.xml?tab_body=fulltext-display

"It is found that the NAO+ to NAO− transition is more likely to occur when the SBL (Scandinavian Blocking) is enhanced, with the route NAO+ to SBL to NAO− taking place."

An analogous result is found for NAO+ to NAO− transition events when the SBL is strong (Fig. 3b). The difference of the composite NAO index between the weak and strong SBL (Scandinavian Blocking) strengths is statistically significant at the 90% confidence level with a Monte Carlo test. This result indicates that an enhanced SBL (Scandinavian Blocking) pattern favors the transition from the NAO+ to the NAO− event.


Prior to the NAO+ event transiting into an NAO− event, the SBL is generally stronger because of the NAO being positive (Luo et al. 2007). It is found from Fig. 4b that during the NAO+ to NAO− transition the SBL strength is positive between lag −10 and lag +12, indicating a tendency to increase before lag 0 and then decrease until lag +4. A rapid reintensification of the SBL pattern is again seen after lag +4, followed by the beginning of its decay at about lag +7, after which it becomes negative at lag +12. Thus, the transition from an NAO+ to an NAO− event is closely related to a change in the SBL (Scandinavian Blocking) strength. Moreover, it is seen that the occurrence of the SBL precedes the formation of an NAO− event during the NAO+ transition (solid line in Fig. 4b). This is because the NAO− event arises from the retrograde displacement of the SBL (Scandinavian Blocking) pattern. Feldstein (2003) found that European blocks retrograde before an NAO− event forms. More recently, Sung et al. (2011) suggested that NAO− events tend to be preceded by a blocking ridge in the vicinity of northern Europe. Cassou (2008) noted that an enhanced SBL and NAO−, associated with the Madden–Julian oscillation (MJO), can be interpreted as being the consequence of the previous NAO+excitation. However, we see here that the reintensification of the SBL (Scandinavian Blocking) pattern is crucial for the NAO+ to NAO− transition


Also see

https://rmets.onlinelibrary.wiley.com/doi/abs/10.1256/qj.02.76?casa_token=qNmP7R8p9AYAAAAA:CsevTy9aIC0waYxRuOU0UFDPHVUhGVsW2V4fg0qZusYT3VV-kIEta7Ztu641gCuJlodkafAX8dFFAcw


https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2010JD015006


https://idp.nature.com/authorize/casa?redirect_uri=https://www.nature.com/articles/nature07286&casa_token=MeTwFkjjovUAAAAA:Fc9BuCbX5G3xULHwII3ZZML9qVRql5ktM90-q9jL5rK9670BKKCBjZ5NVi0eggY259ToVAHzZk_tLi_6
Click to expand...

Look no further for real time proof of this than last month, when a blocking high developed over Scandinavia and the Ural Mountains, which when coinciding w/ favorable tropical forcing caused the upstream waves to slow down, break, and divert the N Atlantic storm track south of the blocking high. Coupled w/ tendency for high-latitude, large-scale, & strong Rossby Waves to retrograde westward (via beta advection), eventually this led to -NAO.





Then we got this a few weeks later.
1637080079271.png
 
To sun up what Webber said into my own words, it’s gonna be a top down approach with regards to the thermals. Gonna blast the heat then blast the cold. No step down process or sloshing but rather a top down approach that will be delayed but not denied. It’s yet to be determined how much of winter will be deleted but imo we could be waiting till January 15th at minimum for even a chance of significant winter weather east of the mtns.
 
Goal posts could use some researching. January 15th, February 5th, February 20th and March 10th. Would be nice to see what science and climo can help us pinpoint when to punt and forecast advance winter weather dates for the public. Instead of cramming everything into a seasonal broad forecast I believe there is room to focus the communication on if anyone cares to listen.
 
Myfrotho704_ said:
This is one of the warmest starts to dec for the US from what I can see on wxbell from 1981-2021View attachment 96909
The only years that compare to this so far is 1995, 1998, and 2012 from what I saw
Click to expand...

What a trio!!!

giphy.gif
 
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