HailMan06 Posted January 27, 2013 Share Posted January 27, 2013 Stratosphere appears to be cooling. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 27, 2013 Share Posted January 27, 2013 Bump Any updates? From the changes in the Arctic Oscillation, I believe it is now more likely than not that the stratospheric warming event was the result of the sustained block that ended in early January. If correct, the warming event was a bottom up response to earlier blocking, not a top-down one that would lead to strong blocking. While such blocking can't be ruled out at some point in February, such blocking probably would not be a response to the stratospheric warming event. Link to comment Share on other sites More sharing options...
cbmclean Posted January 27, 2013 Share Posted January 27, 2013 From the changes in the Arctic Oscillation, I believe it is now more likely than not that the stratospheric warming event was the result of the sustained block that ended in early January. If correct, the warming event was a bottom up response to earlier blocking, not a top-down one that would lead to strong blocking. While such blocking can't be ruled out at some point in February, such blocking probably would not be a response to the stratospheric warming event. Don, I try to be a well-behaved weather weenie and never expect that Mets want to spend all of their time educating me. However, I wonder if you are interested in commenting on a question which I am sure many interested laypeople have: "what exactly 'causes' blocking"? Link to comment Share on other sites More sharing options...
wxmx Posted January 28, 2013 Share Posted January 28, 2013 From the changes in the Arctic Oscillation, I believe it is now more likely than not that the stratospheric warming event was the result of the sustained block that ended in early January. If correct, the warming event was a bottom up response to earlier blocking, not a top-down one that would lead to strong blocking. While such blocking can't be ruled out at some point in February, such blocking probably would not be a response to the stratospheric warming event. I disrespectfully disagree Don. Top/Down and Bottom/Up events are both originated in the troposphere, though the Top/Down events have their genesis in the tropics/subtropics via mountain and/or tropical forcing. The late Nov/early Dec event was a classic bottom/up event, and the early Jan one was a classic top/down warming. In the above figure you can see the first event, and it's repercussions in the stratosphere...well short of a very distinct and dramatic top down event, shown below Blocking is not continuous, not even on the greatest events, they come in waves, but overall the "normal" state is for high latitude ridging. Ie. 1985: We might have a slightly positive AO in the short term, but it will probably be short lived (figure 2 it's showing +heights anomalies propagating down as we speak). Even models are adjusting their forecasts in the mid term Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 30, 2013 Share Posted January 30, 2013 Basically, the polar vortex weakens and/or retrogrades. Stratospheric warming events can lead to a weakening or splitting of the polar vortex. The strength and location of the polar vortex can also be a function of SSTAs and snowcover trends (possible link to the build up of autumnal Eurasian snowcover). Unfortunately, It remains difficult to predict blocking with a good degree of accuracy beyond two weeks or so. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 30, 2013 Share Posted January 30, 2013 I disrespectfully disagree Don. Top/Down and Bottom/Up events are both originated in the troposphere, though the Top/Down events have their genesis in the tropics/subtropics via mountain and/or tropical forcing. The late Nov/early Dec event was a classic bottom/up event, and the early Jan one was a classic top/down warming. In the above figure you can see the first event, and it's repercussions in the stratosphere...well short of a very distinct and dramatic top down event, shown below Blocking is not continuous, not even on the greatest events, they come in waves, but overall the "normal" state is for high latitude ridging. Ie. 1985: We might have a slightly positive AO in the short term, but it will probably be short lived (figure 2 it's showing +heights anomalies propagating down as we speak). Even models are adjusting their forecasts in the mid term Jorge, I haven't ruled out the top-down outcome (and I'm using the term not to refer to the progression of the warming, but whether it was a response to earlier blocking or driver of future blocking; I should be clearer in the future). My point is that I believe the likelihood that the stratospheric warming event was a response to the recent blocking (late November-early January block) appears greater. I'll wait to see how things turn out down the road. I do believe there could be a blocky period in February, but that might occur during the second half of the month and perhaps beyond the timeframe one typically associates with precursor stratospheric warming events. Of course, I could be wrong and it is difficult to reliably forecast blocking more than 2 weeks into the future (with some exceptions e.g., certain candidates for long-duration blocking regimes as commenced in late November 2012). Link to comment Share on other sites More sharing options...
wxmx Posted January 30, 2013 Share Posted January 30, 2013 Jorge, I haven't ruled out the top-down outcome (and I'm using the term not to refer to the progression of the warming, but whether it was a response to earlier blocking or driver of future blocking; I should be clearer in the future). My point is that I believe the likelihood that the stratospheric warming event was a response to the recent blocking (late November-early January block) appears greater. I'll wait to see how things turn out down the road. I do believe there could be a blocky period in February, but that might occur during the second half of the month and perhaps beyond the timeframe one typically associates with precursor stratospheric warming events. Of course, I could be wrong and it is difficult to reliably forecast blocking more than 2 weeks into the future (with some exceptions e.g., certain candidates for long-duration blocking regimes as commenced in late November 2012). Gotcha Don! It appears from the graphics that the period of blocking centered around 8-10 days ago was a consequence of stratospheric warming, at least partly. It's not uncommon for stratospheric warming related blocking periods to last 4-8 weeks from central day of warming... see the 1985 warming which lasted for about 6 weeks. The 2009 warming wasn't as a good propagator, but still one can see strat warming blocking related (at least partially) lasting almost 8 weeks. There are better propagators than others, this event looks like it will be average on that respect. Link to comment Share on other sites More sharing options...
nzucker Posted January 31, 2013 Share Posted January 31, 2013 This never really developed into a solid blocking event, despite all the excitement. -NAO has been lacking all winter, hence the low snowfall on the East Coast. Link to comment Share on other sites More sharing options...
donsutherland1 Posted January 31, 2013 Share Posted January 31, 2013 Gotcha Don! It appears from the graphics that the period of blocking centered around 8-10 days ago was a consequence of stratospheric warming, at least partly. It's not uncommon for stratospheric warming related blocking periods to last 4-8 weeks from central day of warming... see the 1985 warming which lasted for about 6 weeks. The 2009 warming wasn't as a good propagator, but still one can see strat warming blocking related (at least partially) lasting almost 8 weeks. There are better propagators than others, this event looks like it will be average on that respect. We are in agreement that certain stratospheric warming events are better than others at driving blocking. It will certainly be interesting to see how things play out over the next several weeks. Link to comment Share on other sites More sharing options...
wxmx Posted January 31, 2013 Share Posted January 31, 2013 We are in agreement that certain stratospheric warming events are better than others at driving blocking. It will certainly be interesting to see how things play out over the next several weeks. Lower stratosphere is still warm, but we'll need to wait to see what happens after this current bout of +AO Link to comment Share on other sites More sharing options...
calm_days Posted March 12, 2013 Share Posted March 12, 2013 There is still currently or was recently a big SSW over Asia, I thought I saw it in this topic, but it must have been in one of the forecasting topics. This may have been a direct or indirect result of the warming: I'm not sure though. Link to comment Share on other sites More sharing options...
calm_days Posted March 12, 2013 Share Posted March 12, 2013 I found it. This is from andyhb in the mid-range forecast topic. Not sure if this has been mentioned or not, but another SSW episode looks to be in progress over E Asia... Link to comment Share on other sites More sharing options...
am19psu Posted March 12, 2013 Share Posted March 12, 2013 It's not an SSW. Link to comment Share on other sites More sharing options...
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