Reason for slow-moving low pressure systems

Deep Easterly

MiNdGaM3 wrote: »

Perhaps the coming El Nino can change things for the 2nd half of summer, or even just August?

but more probably for winter!

EDIT. Very Interesting article by the UK Met Office on their blog site this morning which discusses the unusual weather pattern this summer so far and possible causes, one or two of which have already been touched upon in this thread.

http://metofficenews.wordpress.com/

(Article under title: 'The UK’s wet summer, the jet stream and climate change'.)

cherryghost

At least there's an emerging pattern for a mini heatwave in about 2 weeks :P

Deep Easterly

Very informative lecture from the Rutger University Weather & Climate Summit earlier this year which explains how changes in the Arctic Oscillation over the last 30 years has impacted in sea ice and how this impact is beginning to affect weather patterns over the Northern Hemisphere such as higher amplitude ridging, weaker troughing, slower moving synoptic scale weather patterns etc.

http://www.youtube.com/watch?v=RtRvcXUIyZg&feature=g-high-rec

I think it might be worth doing a small amateur study (using re-analysis) to see if surface pressure patterns have changed over the last 30 years or so for the NE Atlantic region and to see if any changes correspond with the overall 500 hPa anomalies over the wider north Atlantic region over the last 10 years as claimed in the video.

Capillatus

Deep Easterly wrote: »

I think it might be worth doing a small amateur study (using re-analysis) to see if surface pressure patterns have changed over the last 30 years or so for the NE Atlantic region and to see if any changes correspond with the overall 500 hPa anomalies over the wider north Atlantic region over the last 10 years as claimed in the video.

I was thinking of doing something like that. But you have to know, that you are talking about MSLP anomalies and 500mp anomalies, a.k.a. patterns. I can do this "study" but it wont really prove much, regarding the linkage with changes in the Arctic. Its a fact, that there are a lot of factors that affect weather and weather patterns. And we should first start looking at what affects the Arctic? Taking all the oceanic and atmospheric cycles and oscillations into the "equation".
And of course there are changes in the patterns, which correspond with all the changing cycles in nature. It would be almost absurd to expect more or less constant seasonal weather patterns, with little variance.

And of course the 500mb patterns have changed over Atlantic in the past 10 years, because that somewhat corresponds with the start of a warm AMO cycle.

If I will have enough free time, I will do the study you requested.

Best regards.

Sponge Bob

Just out of interest Capitallatus what long term trends do you possibly see coming out of such an analysis AND affecting your corner of Europe..eg drought or not.

Capillatus

Well, I am seriously thinking about such an analysis/reanalysis for a bit longer term.

And to answer your question.
I remember a few years ago, when Joe Bastardi was talking about, how we are slowly going back to the patterns from the past and more like it was in the 70's. I had no idea what he was talking about back then, because I had no real "weather knowledge" or access to any database. But when I began digging through data, I realized that the guy might actually have a valid point. Of course it was just my thinking. And it never changed. All the weather patterns we see, have occurred at some point in the past. Not really with exact strength and location, but the similarity is quite good. And that shows you how the patterns and the weather is just responding to all of the nature cycles. You have some people like Al Gore and his like-minded souls, who use those cycles to make profit. And if I can take this opportunity to present my opinion on AGW: The only thing man made in "weather", are the CO2 taxes that we have to pay. And even with the temperature trend being flat for more than 10 years, and even being slightly negaitve for the past 6-7, there are still people forcing the idea that we humans are to blame for the non existing warming of the planet. I could make a whole new thread on my AGW opinion.
Back on the topic: And the beauty of weather forecasting is in the fact, that when looking even slightly into the future, you can never take everything into consideration, to see exactly what is going to happen. There is just too much variables. One big chaos. We have NWP or "Numerical Weather Prediction" a.k.a. weather models, that tries to take everything into account instead of us, but as you all know, they are far from perfect, because there is too much stuff going on.

And now to really answer your question.
The way I see it, and the way weather looks to be going, is to be more favorable for weather like it was from the 50's to 70's. Basically because of the cold PDO/warm AMO setup (and yes, everything that goes along with it ). Now this is just my opinion, or thoughts, or theory.

If I make reanalysis of the winter patterns for 3 periods. 1950-1979, which was the last cold PDO/warm AMO setup, then it was 1980-1998, warm PDO/ cold AMO, and from 1999-2012, with the PDO going back to cold, and AMO going into a warm cycle. The years are not really that exact for the start of the cycles, because there is some lag present or maybe one cycle starting before or later, but its good enough for the overall idea. It might also shed a little more light on why systems are allegedly getting "slower"? I think more analyses should be made before making any final claims on that specific idea.





Before I post the reanalysis, keep this in mind: This is a composite, or a blend of winter patterns in all the years in those periods. So the anomalies are not really that strong, but when you consider how many years and patterns its in these composites, the anomalies are actually very strong and show the tendencies and how the overall thing looked like. There was of course variance within each period, but we are going to look how the average pattern looked like, when mixing all together, or which pattern was most dominant. And of course there are other things besides PDO and AMO that affect the outcome, but for this post, I will focus only on these two big cycles.
And these are only 500mb patterns, so temperature and precipitation can still vary. Especially in the reanalysis, because there was no satellite measurements before 1980, so the temp. and prec. data is less reliable. But still, the main focus here remains on the patterns.

1950-1979, Cold PDO, Warm AMO


1980-1998, Warm PDO, Cold AMO


1999-2012, Shifting to Cold PDO, Warm AMO


And an animation, for a better comparison.


EDIT: Added MSLP reanalysis.







Also worth pointing out, is the relative small sample size of the last period 99-12. The cycles are still in progress in this period, but I thing the overall tendency is already visible. Especially when compared with the last cold PDO/warm AMO period. And the 12/13 winter, will be/should be/looks like it will be in this general idea, further strengthening the overall pattern seen in the reanalysis.

Enough of my lame blabbing. And I have to say that all above is nothing more and nothing less, that just my opinion or my thoughts.

Best regards.

Sponge Bob

Thanks Capitallatus. I agree with you fully, on principle, that patterns repeat themselves and that the future can be found in the past ....in many cases.

Deep Easterly

Sponge Bob wrote: »

Thanks Capitallatus. I agree with you fully, on principle, that patterns repeat themselves and that the future can be found in the past ....in many cases.

True, but not in all cases. the run of lower than average MSLP anomalies during the summer period for this part of the world for example is without precedent.


Good post Capitallatus, well considered and a lot to be learned from it.