Heavy Orographic Rainfall - Cwym Dyli Raingauge Nant Ffrancon Valley, Snowdonia

[nuts]

In 7 hours to 1100 BST Tue 19 Sept, this gauge reported 59.6mm rainfall.

My understanding for the requirement for heavy orographic rainfall is:

a frontal system in the area, allowing a great vertical depth of cloud,

a strong wind at summit height

cloud present at the summit, for raindrops falling from medium level cloud to 'scour' the moisture droplets, adding to the rainfall total at ground level.

The event is not over at the time of posting!

[Wetterfrosch]

45 minutes ago, nuts said:

In 7 hours to 1100 BST Tue 19 Sept, this gauge reported 59.6mm rainfall.

My understanding for the requirement for heavy orographic rainfall is:

a frontal system in the area, allowing a great vertical depth of cloud,

a strong wind at summit height

cloud present at the summit, for raindrops falling from medium level cloud to 'scour' the moisture droplets, adding to the rainfall total at ground level.

The event is not over at the time of posting!

Thank you very much for that contribution and a very warm welcome to this forum!!! In simple words, where moist air hits a mountain range and is forced to rise any rainfall will be enhanced. The higher the mountain and the stronger the wind the effect will then also be stronger. I happen to live between the western slope of Yr Wyddfa (Snowdon) and the Irish Sea coast which already accounts for about 1600 mm rain a year (just over 2000 mm in 2008!). Right on top we are told up to 5000 mm can be expected. There used to be an AWS once but didn't last too long in those harsh conditions.

Btw, is there a live upload from that rain gauge that you know of? Would be very interesting to follow it, especially now entering the wettest period of the year.

Diolch/thanks!!

[nuts]

Cwm Dyli raingauge - River levels, rainfall and sea data

RIVERS-AND-SEAS.NATURALRESOURCES.WALES

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We publish the information about river levels so people living in flood risk areas are better informed and can decide what actions to take as the water levels change. Anglers and boaters will also be able to use this...

 

[Wetterfrosch]

Brilliant - thanks for the link!!👍

[Metwatch]