Thread by @althecat

As nations of the world meet in NYC at #UNGA discusses Climate Change cooperation in advance of @COP26 there is a monster low pressure circulation/storm over Eastern parts of Europe.

And the weather forecast for the next five days looks a little hairy.

@COP26 Meanwhile a few 1000 kms to the south East rains over the Arabian Peninsula and Horn of Africa picked up again today.

@COP26 Zooming out we see that there are also multiple tropical storm candidates in the Tropical Atlantic which at a practical level make forecasting in Europe a little unpredictable as their path and intensity is very hard to predict.

There are two major factors driving this the Jet-stream level winds 11-18kms up which are moving water around, and the quantity of water in the atmosphere.

Here we see a 72 hour forecast which contains a powerful jet coming at Europe across the North Atlantic.

We also see a strong West to East flow across North Africa which will be also carrying tropical moisture, from tropical ears in the East Atlantic off the coast of Africa.

This animation shows a five day forecast of airborne Precipitable water. Both the Nth Atl. and Nth Africa atmospheric rivers can be seen. And also several cold air incursions from the north. When cold air & moist air collide we can expect rain.

Here we have a 6 day temperature forecast in 6 hourly increments. Its not freezing, but its also not particularly warm.

Finally we have a water vapour transport simulation plot which shows pressure, jets and water vapour together.

This currently shows the Canadian vapour jet pushing the low pressure system east.

And this plot shows the current rainfall solution which comes from all these inputs - this is over five days.

There is nothing hazardous in this at the moment, but it depends a lot on whether the Canadian Jet dislodges the low pressure system.

It was a circulation like this, with northerly (arctic) and South Western (atlantic) inputs which led to the devastating flooding in July.