ENSO - Updates & Theory

22.10.2011 12:30 (zuletzt bearbeitet: 22.10.2011 12:37)
avatar  Karli
#1 RE: La Nina - Storm season in central Europe

Hello Andrej,

Thank you once more for your work! I appreciate this LaNina Thesis very much and it gives me a good understanding of the "big" processes running in earths climate and so influencing our weather situation. I must admit I will have to read it twice or more to gain full understanding of all facts.

What now would be interesting, as you mention in the last paragraphs, would be to bring together some facts about the european storm season 2001, and then compare the oncoming season 2012 to that once it's over. I'll look for some Websites and reports, and will probably post them in this topic once there's enough of them in my collection ;)).

I also have one more question, just to make sure I didn't misunderstand something:
-A weak LaNina current during the storm season makes us have more severe weather or not?

Stay tuned! :)


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11.09.2011 15:11 (zuletzt bearbeitet: 28.10.2011 00:22)
#2 ENSO - Updates & Theory

A new topic was created for ENSO updates and for everything that is related to its effect on the storm season (analyses, forecasts,...), so it would not be mixed with the thesis.

This is an ENSO update, as I promised. :)

First, here is a map of ENSO regions. Events like La Nina or El Nino, are occurring in the ENSO 3.4 region.

Current conditions across the ENSO 3.4 region, indicate, that a La Nina has already formed, and is expected to further strengthen through the 2011/2012 winter.

Here are some graphics, showing the current conditions.

The SST (Sea Surface Temperature) anomaly animation for the last month, where we can clearly see the easterly winds causing water upwelling. The water also has a bit of a NW motion, because of the process called, the Ekman transport. On a general look, we can see that maybe there is less cold water on the left side of the ENSO region, but a lot more upwelling was present over the right part (ENSO 3), which I will show later on.
Another important feature to watch is the PDO area.

Further on, when we look at actual SST values, we can clearly see the water upwelling and the wave-like shape in the ENSO region (equatorial Pacific), because of the easterly winds. Notice the very cold SST in the ENSO 1+2 regions. All of the upwelling and the cold waters will slowly expand even more to the west, deeper into the ENSO region.

This is the chart for the ENSO 3 region, which I mentioned had more upwelling present. A clear drop, that will likely continue, with occasional "ups", when the easterly wind briefly calm down.

ENSO 3.4. Even thou the 3. region had quite a drop, the 4. region was a bit warmer when the easterly winds briefly weakened. Once the easterlies start blowing on full in the 4. region, the whole ENSO 3.4 will drop quite fast.

A few late September analysis charts (I will post the October analysis in November):

Obvious easterly winds, that are affecting the surface currents, and the Ekman transport process can be seen just N and S of the equator line, in the ENSO region.
Below we can also see the anomalies for the currents and the temperature. Especially in the ENSO and the PDO region, we can see negative SST anomalies that correspond with the current anomalies and upwelling.

Speaking of winds, here we can see the "non anomalous" SE trade winds, that were blowing in the East ENSO region, and strong eastern winds in the "heart" of the ENSO region.

The water upwelling is very obvious, and signifies the early stages of a La Nina. The most intense upwelling is present between 160W and 100W equatorial latitude, which corresponds with the winds and currents direction and anomalies.

A bit less important is another upwelling chart, showing the rising of the 20°C isotherm in the same latitude I mentioned before, and so corresponding with the upwelling and the cooling of the surface temperatures.

I will finish it off with some model forecasts. In general, models are in favour of a La Nina, and taking it into the spring. This La Nina however, won’t be the same as the last one, because it will be less intense (weaker), and more "standard-like", unlike the king La Nina of the 2010/2011, which defied some of the La Nina standards.

This ECMWF forecast is really down to earth, and logical. This is how I also personally see the development.

The UK Met Office model is also in favor of La Nina, But on a bit weaker scale.

NCEP model is quite interesting. The normal ensembles are taking the La Nina in a very intense mode, especially the latest ensembles, but there is a fault with this system.

This is an improved, or PDF-corrected version. The main difference is, that this version takes past events into consideration, so it makes a "forecast" based also on past La Nina/El Nino events and their development, in combination with the regular ensemble forecast.

And here is the Version 2, of the non corrected model, which has less ensemble members, and has an improved coding and less extreme starting values.

This is a plot of many dynamical and statistical models. Some go up, some go down, so this is used just for a comparison.

Here are the past forecasts for statistical models, compared with actual conditions.

This is a very interesting graphic, showing a combination of all past dynamical and statistical models forecasts, combined with actual conditions. It is interesting to see, that most models have a hard time trying to figure out, how strong will the SST anomaly drop, but they are quite accurate about the rising/normalisation of the SST (sea surface temperatures).

A probability forecast, based on past events and statistics.

Last but not least, this is a chart, that shows current conditions, compared with past similar events. This years event, has a tendency of going down into a LaNina, and then leveling off to neutral in spring/summer, similar to 00/01, with the difference, that this La Nina will be stronger than the one in 00-01.

This brings us to the question: If this ENSO event will be similar as 00/01, can the weather pattern of 2001 repeat as well? Since there are more factors in play than just the ENSO, it is hard to say at this point without looking at other factors too, but as last year showed, it is totally possible. And we also have to keep in mind, that changes in weather patterns because of the ENSO, are not instant, so there is some lag effect present, roughly around 1-3 months.

A lot of people are wondering like: "What do I even care about all of this?". Well, to be honest, stuff like this is the first thing that you have to consider, especially as a storm spotter/chaser! Factors like ENSO have HUGE impact on the quality of the storm season in USA and also in EU, and so including Austria and Slovenia. :)

This was just an overview/update on the current ENSO status. I am planning to post some more in the future, about the expected effects on the storm season, comparisons with past ENSO events and past storm seasons, weather pattern similarities with repeated ENSO events, and so on... :)

All of the images, graphics and charts are from public websites, so their publishing is permitted. All of the text is my own writing, based on my knowledge and experience, so there is no copy-paste from any other external source.
Writing my own text allows me to write user-friendly explanations, even for those who are maybe not so familiar with this aspect of the weather, ;)

I have spent hours writing this post, and making it look decent, but for an awesome community like Stormhunters Austria, I do not regret a single second. :) You have accepted me kindly, so this is a sign of my appreciation, and I will try my best to write a lot of educational posts, and share as much knowledge as I can with the whole community.

Thank you all, and enjoy the weather.

P.S.: Feel free to share your thoughts about this topic, and stay tuned for updates in the coming weeks.


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