Thread by @althecat

Thread....

It appears the very wet Northern Hemisphere, and accompanying peculiar weather phenomena may finally be coming to an end.

The focus on extreme weather will now move to the Southern Hemisphere for the next 6-8 months.

It's not quite over yet, but the forecasts appear to be in agreement that the unusually intense tropical storm activity around the planet is about to stop - and the forecast arrival of a La Nina ENSO condition is a big part of this >> cpc.ncep.noaa.gov/products/analy…

Moving east to west this thread will survey the tropical belt beginning here in West Pacific, which is not quite finished yet, as you can see.

As we move west, in the direction of the flow of the tropical atmospheric mega-river, this thread will provide first a 24 snapshot of current conditions plus a 10-day model forecast of what's expected to follow. In the West Pacific that includes quite a lot more rain.

In the above forecast we see a dramatic reduction in the strength of the tropical monsoon over 10 days. One which will be I expect welcome in a region that has born the brunt of extreme weather over the course of the year.

Here we see the Indian Ocean over the past 12 hours.

The Indian Ocean plays a role as a valve on the intensity of the tropical mega-river, when it is running hot the monsoon spreads north west and excess moisture is transits SW over the Middle East as well as NE over the Himalayas into central and East Asia.

In the above forecast we see the next SEA/Pacific powered monsoon burst over the Bay of Bengal and India quickly suppressed by dry air coming in from the north west.

And this may finally signal the end of the Horn of Africa Rainy Season.

Here's a 10 day forecast for ME and HoA region, whilst history suggests there's still a possibility of cyclones spinning up in the Arabian Sea through December, the picture we see here is likely to finally bring fairly clear skies over Ethiopia.

In North Africa the southward migration of the ITCZ Intertropical Convergence Zone (i.e. monsoon) is now very obvious in areas west of Chad.

This sector has another interesting feature a jet heading north from East Africa carrying moisture into the Levant.

Here's a forecast from the rain positive KMA forecast for the impact of this late season monsoon jet's impact in the Levant.

And here's a 10 day forecast for the horn of Africa, beyond the next five days there's not a lot of rain forecast for western and highland areas. And Tigray is clear for the full period.

When we look at North Africa the migration south of the ITCZ (Intratropical Convergence Zone = Monsoon) southwards is particularly obvious with the Sahel now mostly clear of clouds except in the East.

And here we see what may be a final set of Sahel rain storms moving west across the continent over the next 10 days.

Moving further west we see two active storms in the West Atlantic, one of which is a hurricane that is set to make landfall in Mexico and head towards Texas. We also continuation of the turbulent weather in the North Atlantic.

But with an end to fresh fuel coming in from the West African Monsoon this zone is also forecast to become a little calmer on the airborn moisture front.

For now Europe remains a cauldron of storm activity, the persistent nearly stationary storm which has been over Italy and the Adriatic has finally moved East and is probably contributing to the rain forecast over the Levant.

And finally to complete the picture we have Eurasia, the great land mass from Eastern Europe through Central Asia to the northern West Pacific coast. For now its still pretty busy.

But with winter heading in from the North West there is not a lot of additional moisture forecast from here on, especially in the Eastern half, just a growing mass of dark cold dry air.

The final animation shows the forecast atmospheric configuration for the Southern Hemisphere for then next 16 days. And here we can see a fair bit of moisture headed NZ and Australia's way.

However if the ENSO predictions are correct and a La Nina is setting in for a few months, that should bring some relief as soon as the tropical moisture massed over South East Asia clears.

/ENDS

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