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Vorticity0123

Memorable summer storm in the Netherlands

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Today has been a memorable day for the Netherlands, with the strongest storm in July ever seen since the start of measurements in 1901 leaving the country towards Denmark and Scandinavia. In fact, IJmuiden (near the west coast) measured a sustained 10 beaufort for over an hour, making this storm the only one ever in July to achieve this. The KNMI (Dutch equivalent of MetOffice) even issued a code red, the highest category of warnings possible for the Netherlands. In this post I will cover the synopsis of the storm as well as some notable features and damage reports.

 

An unusual autumn-like synopsis

 

The low pressure area seen today was able to develop in a rather autumn-like synopsis. Below is 18UTC satellite imagery of yesterday, showing the general pattern:

 

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18 UTC 24-07 Water Vapor satellite imagery and 500 hPa heights (lines). (Courtesy: Eumetsat)

 

As can be seen from the image, a 500 hPa trough extended from Great Britain all the way down to western France. The low pressure area at the surface (denoted by the red L) already had quite well-developed frontal characteristics (one could clearly discern a cold front over Eastern France, and a possible warm front somewhere north of the Netherlands), and was located just ahead of the 500 hPa trough.

 

At the given time, the low pressure area was located about right below a southwest-to-northeast orientated part of the jet stream (this can be seen by the position where geopotential heights are very close together). This aided in the rapid cyclogenesis of the system.

 

If one follows the 500 hPa heights to the west of the UK, one can see that these run about east-west, and that they are located very close together. This all is indicative of a very active jet stream for the time of the year.

 

If one goes 24 hours ahead in time, one can see that the low has developed further:

 

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18 UTC 25-07 Water Vapor satellite imagery and 500 hPa heights (lines). (Courtesy: Eumetsat)

 

The 500 hPa trough has moved through the Netherlands towards Denmark. Furthermore, the low pressure area at the surface (red L) has moved directly underneath the 500 hPa trough.

 

Another visible satellite image of 16 UTC this afternoon/evening nicely shows the frontal structure of the system, with the center over northwestern Germany:

 

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16 UTC 25-07 Visible satellite imagery.

 

The warm front is denoted in red, the cold front in blue and the occluded part in purple. This pattern is a characteristic of a classic low pressure area.

 

Unprecedented strong winds for July

 

As mentioned before, the wind speeds measured today were unprecedented for July. Below is a map of the maximum wind gusts measured today:

 

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Peak measured wind gusts in km/h as of 25-07 (Courtesy: Buienradar)

 

IJmuiden measured a peak wind gust of 120 kilometres per hour, while a couple of stations along the coast also reached wind gusts exceeding 100 km/h. Even further inland, wind gusts still exceeded 80 km/h at quite some places.

 

The maximum sustained winds of the day were probably even more impressive:

 

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Peak measured sustained winds in Beaufort as of 25-07 (Courtesy: Buienradar)

 

As can be seen here, IJmuiden had top sustained winds of 10 Bft, which is unprecedented for the Netherlands in July. Quite some stations near the North Sea actually had storm force winds, and the whole country experienced force 6 at some moment today.

The question why the sustained winds are more impressive for this time of the year than the wind gusts can be explained by the fact that during summer, often very strong wind gusts are experienced near heavy thunderstorms. Only very few thunderstorms were present in this occasion, and these did not cause such significant wind gusts. The most impressive is that a baroclinic low itself caused these wind speeds.

 

Next to the strong winds, also a lot of precipitation fell, thereby alleviating the drought which plagued the country during the past few months:

 

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Rainfall totals over the past 24 hours as of 21:10 LT 25-07 (Courtesy: Buienradar)

Except for the extreme southeast, most places experienced rainfall totals over 10 mm, with some places in the north even exceeding 30 mm. This rain has been very welcome for many locations, though.

 

Extensive damage due to trees full in leaf

 

The damage potential of the storm of today was enhanced because most trees are currently in full leaf. Therefore, the storm caused lots of fallen trees, blocking some main roads and disrupting public transport on many places. Unfortunately, one casualty and a few injuries were reported due to a falling tree. Furthermore, aviation was greatly hindered with many flights being cancelled. Finally, a number of events, including the Rotterdam Summer Carnaval were cancelled as well.

 

More in store for next week?

 

The models are hinting that another storm may hit the country on Tuesday. Both the GFS and the ECMWF show a sub-1000 hPa low pressure area moving just north of the Netherlands. In this case, strong westerly winds would again hit the country. Below is the GFS output for Tuesday 06Z:

 

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GFS 12Z MSLP + 500 hPa heights, T+60h. (Courtesy: Wetterzentrale)

 

Of course this is just a scenario out of many possibilities, but given that this low is modelled for only 2,5 days away, it appears that the Netherlands may again have to prepare for another round of strong winds. Looking in some more detail shows that the GFS shows a force 8 just missing the coast, but for this timeframe details yet have to be pinpointed.

 

Summary

 

It has been a day to remember for the Netherlands, as the country got hit by a severe summer storm. The system was a very interesting one to track as well. Unfortunately, this low pressure area also caused quite some damage and even one casualty. Probably next Tuesday will show another storm, so this may not be the last wind event this summer.

 

Sources:

http://www.weerplaza.nl/

http://buienradar.nl/

http://www.knmi.nl/

http://www.netweather.tv/index.cgi?action=jetstream;sess=

http://eumetrain.org/eport/euro_00.php?width=1366&height=768&date=2015072500&region=euro

http://www.wetterzentrale.de/topkarten/fsavneur.html

http://www.nu.nl/binnenland/4095312/schade-en-slachtoffers-zomerstorm.html
http://www1.wetter3.de/animation.html

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Thanks for that vorticity, goes to prove its not just us suffering this summer !!.

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Thanks for that vorticity, goes to prove its not just us suffering this summer !!.

 

Yep Misery Loves Company

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Very interesting read Vorticity. thanks. I see this morning's ECM isn't making too much of Tuesday with around 40kts for the gusts.

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Looks like the UK had a lucky escape in this instance. Sad to read of a casualty in the Netherlands.

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Yesterdays storm also made landing tricky at Schiphol

 

Mlllaaa...that's usually reserved for LBA on a bad day, and it feels as bad as it looks!

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Yesterdays storm also made landing tricky at Schiphol

 

 

It's on days like that, that pilots really earn their money. Could you stick that in the Aviation thread  please?

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It's on days like that, that pilots really earn their money. Could you stick that in the Aviation thread  please?

 

Posted in the Aviation thread

 

:)

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