Thread by @althecat

North Africa, East Africa and Middle East Long Range Rain Update Thread: 27 March-April 13.

A forecast burst in West African / Amazon Monsoon activity noted in the Equinox Weather update is now underway, and forecasts now show #DesertRain in the Sahara & Sahel.

Here's a high resolution @NASA satellite image of the bust of monsoon water moving north east across the Sahara from the equatorial Atlantic off the West African Coast.

This burst of what is set to bring rain to Ukraine shortly.

This forecast animation shows the impact of the front of this water transit event in Europe. The Saharan event is closely followed by a storm coming in from the Atlantic which will bring an end to recent very settled weather in Europe.

This weather activity is similar to what we saw last year, albeit later in the year (quoted tweet) - a month later. It's origins can be found in the north Amazon Rain Forest which is undergoing a sudden increase in convective storm activity.

This wider angle longer animation shows the full picture, where a large area of convection off the coast of Guinea is also making a significant contribution. Water sent high up into the atmosphere by thunderstorms has been picked up by upper atmosphere jet-stream winds.

The next three tweets contain animations from the @NOAA GFS3 model forecasting the path of this event building over the next 16 days. Again, whilst Sahel Cauldron like monsoon activity took place in 2020, it came later.

The forecast above shows the raw precipitable water data over 16 days. This one adds water transport direction and sea level pressure contours. The real processes are more complex as you can see in the satellite imagery with clouds moving in different directions.

Finally we see the rainfall solution forecast from this data by the GFS model.

This 240 hour forecast from 29 May 2021 shows similar activity, and provides an anecdotal comparison of a similar event albeit a full month later in the year.... though its noteworthy that there is less rain in this Sahel rain forecast than there is in today's (2nd image).

Here are yesterday's long range rain forecasts (1-3 show 10 days) for the Horn of Africa from three models. The European ECMWF, US GFS and Korean KMA models - the last image shows a 12 day KMA forecast.

The heaviest East African Monsoon rains are not due to arrive till July, but we can already see lots of cloud activity - and rains building especially further West. This image shows the picture yesterday over 24 hours.

And this animation shows the last 24 hours i.e. overnight from the 27th-28th March.

North African 10 day rainfall forecasts from yesterday from four models, the GFS, ECMWF, KMA and CMC. The later two models tend to forecast more rain over the Sahara, and often proved correct about this last year. Saharan rain is hard to forecast.

Looking back into the 2021 archives this rain event in Algeria on March 9th-14th was also fairly spectacular.

For now the Middle East rain forecasts remain modest, but there is still some precipitation expected in the north over Syria and Iraq.

This is partly due to Atlantic storms over the Mediterranean which are associated with this water transit event. The one on the right here is at the tip of plume which was generated by yesterday's storm off the Gulf of Guinea.

These four 10 day Europe model rain forecasts show expected impacts in Europe from the monsoon plume.

The rain impact on Ukraine is notable as it follows several days of warm weather and may make the ground boggy for tanks (see attached thread from 23/3).