Thread by @althecat

North Africa, Ethiopia and Middle East long range rainfall forecast bulletin:

The interaction between the two greatest Equatorial forests is having a massive impact on weather (see quoted thread for more).

This bulletin begins with a look at Ethiopia where rains over the #HornOfAfrica have been steadily building in April (img: today). A strong big rainy season is indicated by this, notwithstanding a strong La Nina which is typically associated with droughts (see quoted thread ^^).

We can see a glimpse of the GERD today - Easter Sunday in the Western Church - through the clouds (Rosieres Top Right - GERD Bottom Left). Satellite images of the dam - which this year will have its 2nd filling - may be increasingly hard to get with increasing cloud.

This image from April 13tt shows the GERD and Rosieres (Dam) as well as Lake Tana, the pride of Gondar and source of the Abbay aka the Blue Nile which provides roughly 60% of the flow of the mighty Nile river.

Last year the 2nd GERD filling was completed on July 19th-21st. Just three weeks into the big rainy season - as a result of high levels of rain. The year before, 2020, the 1st filling was completed on July 20th. God willing there will be another early filling this year.

These 10 & 12 day accumulated rain forecast maps for rain in the #HornOfAfrica are from yesterday. They show rain in #Ethiopia (incl Tigray, Afar and Somali regions) as well as #Eritrea #Somalia and #Sudan. The first two are from the KMA model (10 & 12 days).

These three plots, from today, show estimated total rain over the next three days. The forecast rain is remarkably widespread. Rain will likely be particularly welcome in the dryer and drought effected areas in the East of the Horn - Somalia and Ethiopia's Somali region.

This animation - also from yesterday shows the atmospheric weather picture over Ethiopia over 10 days - ECM model - there are multiple sources of the water which will bring this rain - which I will discuss later in this bulletin.

^^ There is a significant regional (ME+HOA "flooding of the zone" PWAT (Precipitable Water) event beginning April 19th-20th, driven by convection in the Indian Ocean which is responsible for much of this rain. The red areas you see in the animation show a glimpse of this.

We will now move to the Middle East.

The regional "flooding the zone" event is already underway - and is forecast to intensify this coming week. This animation shows storms in Saudi Arabia yesterday.

This animation begins on the 13th and ends on 14th of April.

. @Arab_Storms remains the best source of eyewitness reports of the consequences of storms on the Arabian Peninsula. Here are a few of his recent tweets.

This one is from Oman.

But what is really extraordinary is what is yet to come in the Middle East, especially when you bear in mind that model rainfall forecasts for the Arabian Peninsula tend to under-estimate the intensity of rains.

Here are four 10 day model forecasts for rainfall in the Mddle East (yesterday's runs)

These three day forecasts cover the period before the significant rains arrive.

This animation shows the broader picture. Rain falling on the mountains in the South West of the peninsula today are higher than forecast - and they are being fed from the North, by a Saharan water transport event - which is indicative of what we are seeing more generally.

This PWAT (Precipitable Water) animation 16-days shows the "Flooding the zone" ME rain event through to early May.

These are yesterday's long range rainfall forecasts - 12, 15 and 16 day accumulated rain forecasts for the region. In the 12 months I have been following this - I have never seen anything remotely like this.

While April is Saudi Arabia's wettest month. Historically that typically means 1-5 days of rain - in most places the average is closer to 1. This forecast shows rain every day over Saudi Arabia - over large areas of desert.

Next up we are going to look at North Africa - beginning with an PWAT animation of all of Africa. In this animation you can see (at the beginning) a cyclonic event over Madagascar (another one) which is contributing to this.

This animation shows PWAT anomlay over the entire African continent. And what is startling in this is the consistent anomaly over the Sahel - which has been there for weeks now.

This animation shows the source of the water stream which is bringing rain to in Jinzan Mountains today in West Africa.

The WMA (West African Monsoon) is one of two sources of water causing the current and forecast sources of water over the Middle East. The other is the Amazon.

This animation from the 11th-12th April shows the interaction of the two monsoons more clearly. There is a flow of water westerly from the WMA into the Amazon. And just north of it a return path, carrying water from the Northern Amazon over Western Sahara.

This animation is from tonight. It shows a new atmospheric river, not yet that intense, originating in the north of the Amazon.

This closeup animation - 24 hours shows the source of this atmospheric river more clearly.

A16 day animation shows how this atmospheric river is expected to evolve and intensify. A messy picture as the dominant water flow is to the west, but the direction of the red "lip" we see here definitely indicates a North Easterly atmospheric river strengthening.

This broader view shows simplifies the picture -as within the atmospheric column water can flow in different directions in large quantities. Intense convection projects water into jet streams which carry water massive distances at high speed. And in this case over the Sahara.

This animation is from the Canadian CMC model and it illustrates the "flooding the zone" hypothesis very clearly. The amount of atmospheric water we see here over Sudan and Chad, is seriously anomalous for this time of year.

Which brings us to the consequences in rainfall. The CMC model is an outlier here. But all models even the conservative ECMWF are showing a very intense WMA for this time of year - and significant rains across the #Sahel & in the #HOA and #MiddleEast.

Here we have longer range forecasts, respectively 12 (KMA), 16 (GFS) and 15 (EPS) days.

Finally because its interesting, its important to understand that the Europe is also affected by all this. This from today shows the impact of the West African Monsoon sourced atmospheric river over the Eastern Mediterranean.

Over the next 16 days Europe's Zone is also expected to be flooded.

BONUS images:

Rainfall forecasts for:
1. All of Africa
2. North Indian Ocean and SEA
3. Eurasia
4. Europe.

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