Thread by @althecat

Phase one of this major Middle East #ExtremeWeather rain event commenced yesterday evening and brought rain to large areas of Eastern Central Saudi Arabia, Bahrain and Qatar starting Christmas Evening.

These four images show snapshots of rain radar measured rainfalls over night [25th 7pm, 26th 1.30am, 7am and midday].Yellow areas indicate very intense rain.

Here's a GFS3h model rainfall forecast for a 39
hour period starting yesterday. It is clear from this that rainfall forecasts for this event are already under-estimating actual rainfall. This has been a consistent pattern and not-unexpected, presumably due to historic records.

An interesting feature of this weather event is the area where airborn atmospheric rivers collide this is producing a storm over the Red Sea south East of Makkah and Jeddah which is forecast to intensify and eventually come on shore.

Here's a wider view of this interaction from yesterday,

Here we can see the primary cause of this, incoming water vapour flooding in over the Sahara towards the Middle East from: Tropical Atlantic, North Atlantic and the East African Monsoon.

This unusual weather activity is forecast to continue throughout the long range weather simulation window, which @NOAA's GFS model provides us a view of for 16 days, trough to 11th January at least.

This is the current long range regional accumulated rainfall forecast for 11/1

But for the reasons indicated above, it is possible that this is a significant underestimation of the intensity of this event in terms of rainfall.

Here is a five day IWVT forecast through to NYE which shows us where the moisture is coming from.

In my last thread on this, published Christmas Eve, I divided this unusual weather event into three phases, and what we see here is phase one, the most modest of these phases, and which started yesterday.

The phases correspond to pulses of intense water vapour transport.

Above we see PWAT (Precipititable Water) which can also be seen as a correlate for energy, as water vapour contains mass and therefore energy.

Below we see the rainfall solution for this - relatively speaking - modest intensity beginning of this event over the next five days.