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chrisbell-nottheweatherman

Continued rain through to the end of the year?

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I know this is based on a lack of meteorological understanding, but I have this looming sense of dread for those in flood-hit regions (or possibly anyone who isn't near the summit of a mountain) that this horrendous, zonal winter is going to be followed by a wet spring, a 2007-esque summer and another wet autumn and winter.  With reference to this, I have a couple of questions:

 

1.)  Is it theoretically possible, without some kind of cataclysmic global event, to have a weather pattern such as that which we've had now for nearly 2 months become so embedded that it lasts for months or even years?

 

2.)  If the answer to question 1 is "yes", what would the consequences be, especially in those areas already flooded?  Could the vision of large tracts of low-lying countryside staying under multiple feet of floodwater for many months actually feasibly happen?  If so, is anyone aware if there are any contingency plans to evacuate said regions and cope with the resulting migration/refugee crisis?

 

Apologies for the "doom and gloom" nature of these questions, but, even though I'm in an area which isn't prone to flooding, reading the Model Discussion thread at present is like living through a nightmare.

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1.)  Is it theoretically possible, without some kind of cataclysmic global event, to have a weather pattern such as that which we've had now for nearly 2 months become so embedded that it lasts for months or even years?

The answer to this question in general (not focusing on the weather over the Atlantic) seems to be yes. For example, in California, they are suffering from a drought due to a semi-permanent high pressure area located directly over that area. It has been there since more than a year (with some brief intermezzo's). The complete story about this weather-event can be seen below:

 

http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2624

 

Different patterns giving equal synopsis over NW Europe

 

However, when one views the general NH pattern which directly influences our weather, the same weather pattern will never be able to exist for a very long period. To give an example, I'll compare the NH charts from 26 December 2013 and 31 January 2014.

 

Posted Image

GFS analysis on the 26th of December

 

Posted Image

GFS analysis on the 31st of January

 

When one compares the two surface and 500 hPa charts, one can clearly see the overall pattern is very different. Even though the outcome for NW Europe is the same in both situations (i.e. zonal flow with high levels of precipitation), there are many large-scale features which are located on a completely different position. 

 

What I would like to emphasize, therefore, is that weather patterns are never equal, even if it would seem to be the case on a small scale analysis. 

 

Persistent features

 

There are some features which have been very persistent in this winter. The most pronounced one for us, and most likely the main indirect reason for the weather we are experiencing now, is a persistent 500 hPa trough (as can be seen with the purple colors on the maps above) over northern Canada. The trough does seem to be associated (or entangled) with a piece of the polar vortex (at 100 hPa) which has been located over that area during almost the whole extent of this winter.

Please note that the position of the polar vortex at 100 hPa is not always associated with a 500 hPa trough. The reason why this is currently the case is currently beyond my reach of knowledge, perhaps an expert can give you that answer.

 

Also important to note is that the polar vortex (or the 500 hPa trough associated with it) has not been the direct consequence of the barrage of low pressure areas being fired toward NW Europe. The main reason is a very sharp temperature gradient (i.e. a very steep change of temperature over a small distance) associated with this feature. This has been a huge energy source for these lows to intensify rapidly. For example, look at the 850 hPa temperatures below:

 

Posted Image

GFS 850 hPa temperatures (31 January)

 

Note the very steep temperature gradient over the Atlantic and near Canada (about 20*C difference in about 2000 km). This is mainly caused by very cold air associated with the trough over Northern Canada and warm subtropical air flowing toward the north on the eastern flank of the Azores high.

 

The polar vortex will most likely be weakened severly during Spring, and therefore, the chances that the 500 hPa trough will be located over exactly the same position are not very high. (more in-depth information about this can be found in the Stratosphere thread)

 

Concluding, the weather pattern that we have had thus far has actually never been the same on the larger view. However, there is a dominant and very persisten feature (the 500 hPa trough over Canada), which is aiding in the rapid cyclogenesis of many low pressure areas. Wheather this pattern will persist for a long time or not remains to be seen. 

 

I hope this has made things a little bit more clear (from a meteorological point of view). Also don't hesitate to correct me if I'm mistaken somewhere in the analysis.

 

Sources: 

http://www.wetterzentrale.de/

http://dutch.wunderground.com/hurricane/

Edited by Vorticity0123
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1.)  Is it theoretically possible, without some kind of cataclysmic global event, to have a weather pattern such as that which we've had now for nearly 2 months become so embedded that it lasts for months or even years?

 

 

 

Hope so - I love rain, but as always we haven't had much around here. Probably end up with a 1976-style disaster....

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just a damp dry spell really.

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The answer to this question in general (not focusing on the weather over the Atlantic) seems to be yes. For example, in California, they are suffering from a drought due to a semi-permanent high pressure area located directly over that area. It has been there since more than a year (with some brief intermezzo's). The complete story about this weather-event can be seen below:

 

http://dutch.wunderground.com/blog/JeffMasters/comment.html?entrynum=2624

 

Different patterns giving equal synopsis over NW Europe

 

However, when one views the general NH pattern which directly influences our weather, the same weather pattern will never be able to exist for a very long period. To give an example, I'll compare the NH charts from 26 December 2013 and 31 January 2014.

 

Posted Image

GFS analysis on the 26th of December

 

Posted Image

GFS analysis on the 31st of January

 

When one compares the two surface and 500 hPa charts, one can clearly see the overall pattern is very different. Even though the outcome for NW Europe is the same in both situations (i.e. zonal flow with high levels of precipitation), there are many large-scale features which are located on a completely different position. 

 

What I would like to emphasize, therefore, is that weather patterns are never equal, even if it would seem to be the case on a small scale analysis. 

 

Persistent features

 

There are some features which have been very persistent in this winter. The most pronounced one for us, and most likely the main indirect reason for the weather we are experiencing now, is a persistent 500 hPa trough (as can be seen with the purple colors on the maps above) over northern Canada. The trough does seem to be associated (or entangled) with a piece of the polar vortex (at 100 hPa) which has been located over that area during almost the whole extent of this winter.

Please note that the position of the polar vortex at 100 hPa is not always associated with a 500 hPa trough. The reason why this is currently the case is currently beyond my reach of knowledge, perhaps an expert can give you that answer.

 

Also important to note is that the polar vortex (or the 500 hPa trough associated with it) has not been the direct consequence of the barrage of low pressure areas being fired toward NW Europe. The main reason is a very sharp temperature gradient (i.e. a very steep change of temperature over a small distance) associated with this feature. This has been a huge energy source for these lows to intensify rapidly. For example, look at the 850 hPa temperatures below:

 

Posted Image

GFS 850 hPa temperatures (31 January)

 

Note the very steep temperature gradient over the Atlantic and near Canada (about 20*C difference in about 2000 km). This is mainly caused by very cold air associated with the trough over Northern Canada and warm subtropical air flowing toward the north on the eastern flank of the Azores high.

 

The polar vortex will most likely be weakened severly during Spring, and therefore, the chances that the 500 hPa trough will be located over exactly the same position are not very high. (more in-depth information about this can be found in the Stratosphere thread)

 

Concluding, the weather pattern that we have had thus far has actually never been the same on the larger view. However, there is a dominant and very persisten feature (the 500 hPa trough over Canada), which is aiding in the rapid cyclogenesis of many low pressure areas. Wheather this pattern will persist for a long time or not remains to be seen. 

 

I hope this has made things a little bit more clear (from a meteorological point of view). Also don't hesitate to correct me if I'm mistaken somewhere in the analysis.

 

Sources: 

http://www.wetterzentrale.de/

http://dutch.wunderground.com/hurricane/

 

Cheers - I'm interested to find that it isn't as much the 500hPa trough that's been amplifying the Jet, but that the temperature gradient is the main causative factor (makes absolute sense though - whenever you see a steep gradient of any variable or parameter in science you know that something interesting is likely to be going-on).

 

As regards "laserguy" - I suggest that there are many for whom more rain this spring and summer isn't what they want.  Your approach seems to me to be a very "IMBY"-based one.

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