Southern Britain Prepares For Powerful Weekend Storm

Written by on October 25, 2013 in Rest of Europe, United Kingdom & Ireland with 0 Comments

We have the perfect meteorological environment and setup across the Atlantic and Europe for ‘rapidly deepening low pressure development’ SW of the UK during late Saturday through late Sunday.

Check out the feature image above of a powerful storm system currently over the North Atlantic. Models drop pressure down to at least 955 mb tonight. This system is not the low we’re concerned about, in fact it’s not yet formed. We currently have a powerhouse trans-Atlantic jet and the strongest baroclinic Atlantic low of autumn so far as a result but check out the below 850mb temperatures which show the reason for the strong jet and storm.

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Below is the GFS jet stream forecast which shows winds clocking 211mph within a speed max but note the split and dip in the jet SW of the UK. This is the incubation area where air is forced to rise rapidly as air from the mighty trans-Atlantic jet races into the bowl created SW of the UK thanks to high pressure over Europe. As the jet splits, so air is forced upwards within the void and as air franticly piles into the trough, so low pressure is formed and fast!

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Here’s the jet forecast a little further on.

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Note the jet on the east side of the dip races NE over southern Britain. That is why modelling takes this low after development quickly northeast across the UK.

The below 500mb chart off the GFS shows the monster south of Greenland, high pressure over Europe and the trough in between to the SW of the UK. That is the region where the low forms.

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By 42 hours, while the big low tracks due east, weakening as it does so, note the kink in the upper flow to the SW over the N Atlantic. Keep your eyes fixed on this.

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Now notice the model from above to below (6-hour difference) goes from a mere ‘kink’ in the jet with pressure likely over 1000mb, drops pressure to 985mb… That’s an incredible pressure fall.

gfs-0-66

The trouble with these rapidly deepening storm system’s is that they have incredible energy release, often supporting ‘sting jets’. Rapidly deepening systems often transfer upper energy downwards and by doing so, unexpectedly stronger winds can reach the surface, this occurred during the Great Storm of ’87.

By 72 hours the model has a likely sub-980mb low racing up the Bristol Channel producing storm-force winds widely across South Wales and all of Southern England. Winds of 60-70 mph can be expected widely but along exposed coasts, wind gusts may exceed 75 to 85 mph with isolated gusts topping 90 mph.

Rainfall will also produce local flooding but that flooding may be caused more by fallen leaves, branches which block drains. Damage to property, trees and power is expected and the Monday morning commute may be very challenging.

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Could this be as bad as 1987, I’m confident in saying NO, however this system will have big impacts but this is no storm of ’87 nor will it produce winds as strong. Back then we saw winds clocking 110 mph along the South Coast and 100 mph right across London. Remember that the storm of ’87 cut a path right across Britain’s most populated area and winds back then were stronger than the system we see Sunday into Monday. In saying that, this one could be one of the stronger since then but likely not exceeding the storm of January 2007.

Further updates tomorrow! Be sure to watch the video!

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