Why is Portugal so wet this winter?

[maria]

The first of many questions from me haha!!

I have live all my life in south west Portugal - 27 years. I have never seen so much rain as there has been this winter, I would like an explanation to what is causing this? The rain this winter has been persistent, slow moving and incredibly heavy. It is very unlike our normal winter weather which is usually brief heavy downpours.

There has been flooding in Morocco, Algeria and Spain too.

 

[oldseadog]

The jet stream, think of it as a path for the low pressure systems to follow and as a rule of thumb they are guided by this river of air way up in the troposphere but not always. This particularly jet stream in question is the polar jet which is primary driver of weather for our part of the world.

There is a persistent blocking high over northeastern Europe where temperatures have been frigid for weeks. The jet stream is being pushed south because of this block and to make it more interesting, the temperature gradient is quite extreme with frigid temperatures over eastern north America, this fuels up the jet stream making it more powerful over the north Atlantic.

It's a very amplified jet stream at the moment which tends to make for stormier weather patterns, usually the jet stream is a little more flat (zonal).

Normally the polar jet is to the north of Iberia. The rain is also being boosted by warmer than normal sea surface temperatures over the north Atlantic. In some cases by 3c which may not seem a lot, but it's enough to feed moisture for these low pressure systems which are stalling and meandering dumping rain over your region because of the block over north eastern Europe.

There is imagery from water vapour satellite, where you can see Leonardo drawing moisture from down in the Caribbean.

I have attached the sst anomaly from Feb 4th showing the warmer than average temperatures.

 

[maria]

Thank you Oldseadog, that was a good explanation