Thread by @althecat

Extreme weather in the Nth Hemisphere due to high levels of atmospheric water in 2021 look set to be maintained into 2022. Atmospheric river activity continues to have significant consequences now, and in the forecasts.

New #OurChangingClimate thread.

The satellite animation above shows the weather system that produced the devastating tornadoes on Friday and Saturday in the United States.

This 16 day simulation shows a @NOAA GFS PWAT (atmospheric river) forecast beginning 12th December, which shows extreme is far from over.

The consequences of this ongoing collision between tropical moisture and winter is set to bring much more precipitation through to New Year, and a very white Christmas in the North East US.

In the forecast above there is also a lot of rainfall in the south. This plot (which shows the Cape Index) suggests conditions may persist for extreme weather, thunderstorms/tornadoes for a bit longer, especially in Texas.

This animation shows the atmospheric river which produced the tornadoes in Kentucky arriving in Europe over night.

This view shows the next 16 days in the North East Atlantic, the inclement weather in the UK and Ireland (which has led to transport, flooding & power outages) looks set to continue.

If we zoom out we can see the underlying cause persistent tropical atmospheric rivers, some of which are colossal through to the beginning of 2022 at least.

Here we can see what is likely part of the cause, sea surface temperature anomalies [Src. ospo.noaa.gov/Products/ocean…] compared to climate trends) in the North Atlantic, North Pacific and South Pacific (affecting NZ) are already very high, not withstanding a significant La Nina.

The ENSO oscillation reports from @NOAA provide all the details of current expert thinking on where this is likely to go >> [cpc.ncep.noaa.gov/products/analy…], but so far, the usual impact in Australasia/Oceania are not yet remotely drought like, though this may come.

What this ^^ forecast tells us is that by July 2022 ENSO is expected to be back to neutral for the northern hemisphere spring - likely followed by an (wet) El Nino (same pattern as in 2021).

The remainder of this thread looks at current weather and forecasts in:
- Sth Pacific (NZ and Australia) - Cyclone Ruby
- W. Pacific - Cyclone Ria (with more to come)
- Pacific NW (lots of early snow)
- Madagascar (where it's raining)
- ME & Sahara

It's cyclone season in the Pacific, and it has started. Cyclone Ruby has formed and is heading south now, thankfully missing NZ, but the flooding threat to NZ broadly appears to be increasingly serious.

Here's a 16 day PWAT forecast for the South Pacific.

Large scale atmospheric moisture simulations are remarkably accurate over fairly long periods as shown in this rain forecast (Dec. 8) which warned about flooding which is now underway in NZ's North. You can also see a version of what is now Cyclone Ruby.

This is Cyclone Ruby.

Historically, cyclones very rarely maintain cyclonic strength by the time they reach NZ, but with high SSTs, this early cyclone, & the large low pressure storm in the previous PWAT forecast, one wonders if this can be seen as a forerunner for change.

Ruby has weakened a lot after running directly over New Caledonia, and is not currently forecast to strengthen again, but we shall see. nzherald.co.nz/nz/tropical-cy…

This view of Cyclone Ruby shows how it is embedded in a massive area of tropical moisture. Because its a cyclone it is now strengthening this atmospheric water flow with its outflows.

Here's a 16 day MLSP model run from the GFS model, the multiple low systems complex over NZ (caused by the atmospheric river/lake) appears here to absorb Ruby. But Kiwis need to watch the two more tropical low systems forming before NY.

Finally in this part of the thread, here's a 10 day rainfall forecast for NZ. The impact of Ruby can be seen at the beginning in the Bay of Plenty, but this shows flood risk level rainfall in several other places including Canterbury.

The next part of this thread looks at the West Pacific and Cyclone Rai, which appears to be just the first of several very late season cyclones/typhoons in East Asia.

Here we see Ria. Like Ruby, Ria is embedded in a massive area of atmospheric moisture providing her with fuel.

Here we have a 16 day long range simulation forecast for the West Pacific, it shows two major storms Ria - a very late South China Sea Cyclone crossing the Philippines, followed by the formation of a second storm which heads north towards Japan and then dissipates.

[For a bit of additional background, last week' thread last week looked at the West Pacific here >> ]

The NE Pacific (Pacific North West of the US) was also addressed in last week's thread and as we saw earlier the North Pacific is also still very warm, and producing lots of atmospheric water.

The persistent pattern reported on last time has broken, but what remains is still very wet, and quite similar to what we can see in the North Atlantic.

To cut to the chase, the result of this is a lot of snow settling in the North West, as well as the North East. The first image shows North American snow depth as of today, while the second one shows it as of December 30th.

And here we see just the North West, today and in 16 days time. The third image shows the depth of North Western US snow on Christmas Eve. Early travel to ski resorts may be advisable.

I have two views of the atmospheric moisture/energy dynamics that deliver all this snow. Firstly a view of the North American Continent as a whole.

Our second view gives us a view of the the Tropical Eastern Pacific, where the ENSO originates. Here we can also see several atmospheric rivers sweeping the West Coast. The last one is the strongest and delivers a lot of moisture to most of California.

Threadfix...

We now move to Southern Africa for another update on a weather pattern which was forecast to bring rain to drought stricken Madagascar.

This is the full EU produced graphic which shows the worst affected area in the South. The next few tweets show the satellite presentation of the arrival of the forecast rains, first forecast here on November 29th.

December 9th-10th

December 10th-11th

December 11th-12th [there was a bit of break in the pattern on the morning of the 11th]

December 12th-13th

And finally December 13th-14th. Making that five days of rain - mostly in the form of thunderstorms - in some of of the most drought affected areas of Madagascar.

Again here we have two forward looking views of the water/energy dynamics which have been producing these much needed rains - and which suggest it will continue, even as the weather pattern changes for a bit. Here we see the West African monsoon helping.

And here we see a full disc view of the South Indian Ocean which contains quite a few cyclones. The storms so far have been caused by the Easterly winds which are driven by high pressure systems in the south of the Ocean.

This high pressure feature appears to be fairly resilient as you can see here in a view of the Sea Level Pressure data for the same period.

If we add all this together we get a 10 day rainfall forecast through to Christmas for the Island which forecasts the rain continuing, albeit with lighter rain in the most southerly and most extreme drought affected areas.

Which brings us to our final segment, which looks at the Middle East and the Sahara water transport feature we noticed a week ago, which suggested the possibility of some more #DesertRain in the Middle East.

This Amazon to Middle East water transport feature has persisted now for several weeks, and according to @meteoblue's satellite rainfall radar is producing rainfall in the heart of the Sahara and the Northern Gulf.

Here's an updated 24 hour animation of this persistent pattern.

A 16 day forecast of Middle Eastern Rain from the @NOAA GFS model. This forecast shows minor amounts of rain in Israel, Iraq, Jordan and the Red Sea/Med Coasts as well as more significant quantities of rain/snow in Lebanon, Turkey and Iran. And even a bit of rain in Ethiopia.

Here's a water/energy PWAT simulation of this which varies at a details level from the GFS version of the same phenomena which follows.

Here's the GFS version, which is also six days longer, and provides an indication atmospheric water over the ME may linger for a while.

Here we have three 10 day rainfall forecasts for the area. The rainfall here in Iraq is insufficient to have any real impact, but if it continues, it would be very welcome as the drought in the southern Euphrates area is very acute.

And here are the two longer range model forecasts. The GFS (left) 16 days and the KMA (right) 12-days