Home > analysis, weather > UK Winter 2013/2014 storms

UK Winter 2013/2014 storms

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Figure 1

Figure 1 (click for larger) is showing surface level air movement from weather GCM. The stuck cold air mass over North America is part of a lack of rotation of the polar air mass leading to a stuck Atlantic circulation bringing repeated storms to Northern Europe where the energy is from the ocean circa Caribbean but with a back feed from the coast of Africa. Around and around. The parallel red arrows are showing where cyclone and anti-cyclone meet, to the left there is a sharp merge of three flows, an unstable region, the shear point is where the St Jude’s day storm formed.

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Figure 2 (click for 2.3MB animation)

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Figure 3 (click for 1.44MB animation)

Two GIF animations, figure 2 for wind including figure 1, figure 3 for rain. Click to open full size and activate.

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Figure 4

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Figure 5

Figure 4 is a snapshot of the Gulf Stream. Figure 5 is generalised North Atlantic currents. Remember that wind driven currents tend to travel in a different direction dependent on the Coriolis force, so this whole thing is complex.

Jet stream

There has been a lot of talk about the jet stream as causing the storms but it is an effect not a cause, just happens to be easy to see.

Collisions of different temperature air masses causes a storm line with strongly rising air as one tries to override the other, so we get trains of cyclones. The jet stream is associated with this churning.

There are several ways to “conceive” of these air masses, with two of these being synopic and statistical, where the latter is simply averaged in time but tells nothing about the detail which led to the result. The winter situation will probably appear as having a persistent Icelandic low and Azores high, a conventional view leading to the NAO (North Atlantic Oscillation) and work of Lamb, Jones, CRU etc.

I’ll leave that as a loose end. Feel free to disagree.

Code and Data

GCM data from here
https://www.fnmoc.navy.mil/wxmap_cgi/cgi-bin/wxmap_DOD_area.cgi?area=fnmoc_atlantic&set=All

Gulf stream images from
http://en.wikipedia.org/wiki/Gulf_Stream

Downloading the image sets from a secure server was scripted and so was creating the animations via GraphicMagick. A solid white ground has to be added to transparent gif. A bit tricky so where @list.lst is a file containing a list of files to combine here is how

gm convert -delay 100 -loop 20 @list.lst -background white -extent 0×0 +matte outfile

Note

I would have preferred a better example of GCM output but I am on my own, time and resources are limited.

Put another way, could do better, make it clearer.

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Categories: analysis, weather
  1. February 23, 2014 at 21:47

    Reblogged this on CraigM350.

  1. August 10, 2014 at 01:40

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