Blocking High Over UK Is Responsible For Devastating Floods In Spain, Sicily, Italy But Change Is Coming!

While conditions have been pleasantly tranquil across Northern Europe, it’s been turbulent across a broad swathe of the Mediterranean of late. A strong blocking high has re-dirtected the typical storm track south and when you’ve got cold core lows coming off a colder than normal Atlantic into a warm, humid sub-tropical region where a large body of water has SST’s of 25C+, the atmosphere becomes extremely unstable and turbulent and the result is usually severe weather and flash floods.

Red warnings were hoisted as infrared lit up with a monstrous cumulonimbus towering to 50,000ft over Sicily and Italy, producing -77C cloud tops!

Credit: METJEFFUK ‏@metjeffuk

Credit: METJEFFUK ‏@metjeffuk

Visible view of this huge storm from space!

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It doesn’t take much for incredible lapse rates (temperature difference with height) to drive astonishing lift and therefore extreme rainfall. SST’s around Sicily and southern Italy are at 26-28C adding fuel from below.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

These waters are running about 1-2C above normal.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

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The very same system running underneath the sprawling blocking high to the north generated devastating floods to Almeria region of Spain late weekend into Monday. Several provinces including Valencia, Alicante, and Granada were issued with weather alerts by Spain’s Civil Protection Service. Almeria alone has received 56 emergency calls. Benidorm was also greatly affected.

The huge MCS (mesoscale convective system) sat over Sicily and the boot heel of Italy yesterday releasing tremendous rains causing major, even devastating flooding to the island along with hail, gusty wind and frequent lightning strikes.

Up to 4 inches of rain fell on the mountainous island of Sicily yesterday.

Credit: Tyler Roys

Credit: Tyler Roys

This was the result.

Credit: Weather Sicily

Credit: Weather Sicily

Credit: Weather Sicily

Credit: Weather Sicily

Here’s the surface setup. Note the storm over southern Italy while a large high dominates to the north, keeping Ireland and the UK largely fine and dry with a sun, cloud mix.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

The high is shielding the UK and had this not been here, the system which crossed Spain and Italy would have likely crossed the UK but not with the same devastating results. Why? Warmer and more humid sea and air enhances rainfall and storminess and you only have to look at how cool our surrounding waters are!

The Atlantic frontal system eventually reaches the UK this weekend while the system crossing the Med fills over Greece and western Turkey with a reversal in the height field once again.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

This weekend and next week isn’t a washout but more a return to the summer pattern with one system pushing in after the next but spaced apart enough that we’ve decent weather in between.

I remain somewhat optimistic that high pressure and more settled conditions may a return by the end of September into early Oct.

GFS ensemble still has positive heights rebuilding towards the end of the month.

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

Credit: AccuWeather Pro

See this afternoon’s video for more.

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