In the last week, the upper pattern is been pretty much opposite of the summer with a blocking high across the north while low pressure has run underneath.
The system which brought the flash flooding to parts of Spain last weekend is now crossing the Mediterranean producing very active weather over Sardinia, Sicily, Italy and eventually it will push into Greece. A strong ridge further north as been slowly moving from Atlantic to Scandinavia and by the weekend, the storm track lifts back north bringing the opposite setup next week once again.
Now… high over low
While it’s been like this across much of the UK…
It’s been like this in parts of Spain!
Next week… the more traditional low over high
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The problem with this southern storm track is that lows which typically cross the UK, contain cold air aloft and as these systems dive into a warmer, more humid environment, the instability is significantly increased, also enhanced by 20-29C waters. That’s why rainfall and storms are often worse further south than in the cooler more northern locales.
Large northern displaced ‘blocking highs’ over the UK extending into Scandinavia typically brings our best weather with cloudless skies and daytime warmth, cool by night but it turns very stormy across Iberia and the Med.
We’ve some big changes coming by the weekend. As the high has track from out over the Atlantic to Scandinavia, winds have went from a chilly northerly to warm, more humid southerly and eventually the Atlantic is opened back up with a series of lows spreading in while it turns drier, sunnier and warmer again from Iberia to Italy.
The question is this, is this settled weather gone for good or does it comeback before the end of September. The good news is that it looks set to return.
GFS ensemble 5-day mean 500mb height anomaly
The GFS surface shows the return to much more unsettled, cooler weather again but note it’s got the return of ridging around and beyond the 20th.
Then here comes the ridge once again.
See video for today’s discussion.
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