LOOKING AT THE END OF 2021 AND JANUARY 2022.

SUMMARY

The last of the dry heat for the nation is coming to a close as we now move into a wetter phase with the monsoonal flow lurking north of the nation from Christmas leading to an increase in rainfall for the tropics. But as mentioned throughout the week, this monsoonal flow will draw moisture through the nation, whether it be via a deep tropical low/cyclone moving southeast over the nation or the seeding of troughs with moisture from the north....or both.


While we figure out what is happening with the north in the medium term, the SAM is heading back to a positive phase and likely to remain positive for a good chunk of the end of the year into January, leading to moist easterly winds and showers increasing. The showers could be heavy at times as early as Christmas and then through New Years and be with the eastern portions of QLD and NSW through a large period of January.


The south remaining seasonal, the ridging could get stuck through southern WA and SA and oscillate north and south through this area, but the impact is the same with fairly settled weather to develop.


The north and east of the nation is where you will continue to find the above average rainfall chances and below average temperatures (even after this heatwave) and the south and southwest, is where you find the seasonal rainfall odds and above average temperatures, though depending on ridging, the west coast of WA may be below average.


The unusually cool Spring has taken a break through this week with the heatwave over the nation, but the cooler weather may resume once again to end the year.

FORECAST

CLIMATE DASHBOARD

No change in the climate guide moving through the next 6 weeks The IOD is now resolved. It has contributed to the heavy spring rainfall and early build up over the tropics as well. The SSTs in the Coral Sea suggest that the La Nina has been underway for some time and the monsoonal flow has arrived out east of the nation (thank goodness) with TC Ruby running through the Coral Sea.. The SAM is currently neutral for the coming 4-5 days but is expected to turn positive through until mid January at this time and some signals that may persist through to Australia Day.

TROPICAL WEATHER

December 16 2021 -January 16 2022

The MJO has moved into the Coral Sea and Pacific Ocean and that resulted in TC Ruby emerging. That system is on by The weather is expected to turn wetter as we go along in the medium term, with daily rainfall increasing. Signals of a tropical wave passing through northern Australia with that feature likely to bring down a northwest flow aloft by years End increasing rainfall chances and the developing monsoon. The MJO throughout the the period is expected to dance in the Western Pacific in the shorter term but longer term will roll through Africa and then come back into the Indian Ocean by mid January and over Australia once again, that could be a very wet phase and nationally, pay attention to the forecasts as the rainfall may be with us for 4-6 weeks!

DATA - Refer to video for more on these sets of data


FORECAST

Rainfall Outlook - Next 6 Weeks - December 17th 2021 - January 31st 2022

% chance of exceeding the median rainfall for the coming 6 weeks

Rainfall is increasing in line with the emergence of the a pseudo monsoonal flow coming through next week, but the monsoon proper may develop through early January, leading to elevated rainfall chances for much of the north and east and along the path of any landfalling tropical low/cyclone through interior parts of the nation. Persistent easterly winds are expected to develop with high chances of rainfall developing for the east coast of QLD and NSW and this extending inland. Moisture feeding a near stationary inland trough from QLD through to NSW, will lead to widespread rainfall through may areas of the nation. But over the southern and western portions of Australia, a ridge that is likely to dominate this part of the world, sinking air motion will lead to drier weather for most of this region, BUT that does not mean some of the tropical weather won't bring periods of humid and thundery weather, the higher frequency is likely further east and north.

Temperature Outlook Next 6 Weeks - December 17th 2021 - January 31st 2022

% chance of exceeding the median temperatures for the coming 6 weeks

The temperatures near and north of ridging over southern Australia may trend above normal for the period, but where the rainfall and cloud cover remains is where the weather will be cooler than normal. Much of eastern and northern Australia is expected to be cloudy and cool for this period, so Summer fans looking for heat will have to head inland and west from the east coast and south from the northern tropics.

Humidity Outlook - Next 6 Weeks - December 17th 2021 - January 31st 2022

% chance of exceeding the median humidity for the coming 6 weeks

Thankfully the major monsoonal burst that was being modelled over the nation is expected to remain out in the Coral Sea but the monsoon will return in January. The east under persistent easterly winds are expected to combine with warmer weather to make it feel very tropical in the eastern inland extending back to central Australia. With the La Nina building conditions are expected to become more humid as we go through this period for northern and eastern Australia. The west seeing a drier 6 weeks but the values will continue to increase as we move through Summer as the monsoonal weather moves southwards across the country.

Disease Outlook - Next 6 Weeks - December 17th 2021 - January 31st 2022

The wet weather, and now a shift to hotter weather with high humidity increases the risk of fungal diseases to many crops, even as we enter a quieter week nationally. This signal does not change over the coming 4 weeks. The west may be dry for now, but there will be an increase in humidity returning through this period and with the higher temperatures this could see prolonged periods of above average humidity values as the monsoon deepens and that will have a high impact on crops and produce in the southeast and east of the nation for the end of December into January.

Riverine and Flash Flood Risk January 2022

The fact we have ongoing flooding for much of December as a flow on effect from the high rainfall, additional rainfall will continue to exacerbate this risk through until early 2022. Many inland rivers could be flooded right through Summer 2022. The risk will return for outback areas once the monsoon starts so the back half of the month into early January which will see new areas come under flood risk.

Riverine Flood Risk Summer 2021/22

The flood risk is ongoing and continues through the remainder of December and January, and with the wet signal peaking in February, the flooding is here for a while. Keep up to date with the medium term forecasts in the east as rainfall could return next week and persist again.. The monsoonal weather expected from this week, thankfully has landed east of the nation but the tropics rebound in activity towards Christmas and beyond so that will be of concern to the flood zones over the east and southeast as that moisture moves southeast. Flooding over the west and central parts of the nation will be connected to the tropical lows/cyclones that move around the north.

RAINFALL

Euro Rainfall Accumulation Ensemble Data - Next 6 Weeks - December 17th 2021 - January 31st 2022

The models remain unchanged, for the wet signal to build further over northern Australia during this period and over the eastern seaboard. The early monsoonal burst is expected to develop north of Australia and spread over the northern states by Christmas and persist into January.. The east is expecting further rainfall and flooding issues as we go through the latter part of this month but more likely in January in line with the monsoon returning and the bulk of the nation looks to record at least seasonal to above seasonal rainfall values, ridging over southern and southwest Australia will keep the rainfall frequency down for the period, with stable sinking air close by.

Euro Rainfall Accumulation Control Data - Next 6 Weeks - December 17th 2021 - January 31st 2022

The heavy rainfall guide continues for the southeast, east and northern parts of the nation with flooding being renewed through January over inland NSW and QLD. Northern Australia will get a good monsoonal burst later this month and as expected rainfall chances to increase nationwide, not just the east. Some areas can expect flooding to develop in areas that have been spared so far, especially over eastern inland areas and through central interior locations, and that will be associated with landfalling tropical features. The far south may see seasonal conditions.

Euro Rainfall Anomalies - Next 6 Weeks - December 17th 2021 - January 31st 2022

The numbers over the south and east remain elevated. But now we see the strengthening of the monsoonal signal from later this month through January and that will likely sweep south and east through the nation with increasing rainfall and humidity.

You can see the impact of tropical features on rainfall over the north of the nation and the persistent easterly winds. The driest parts of the nation looks to be the southern and southwest areas at this time, but the wild card feature is the developing tropical weather over the north spreading south and southeast into these forecast dry areas.

GFS Rainfall Accumulation - Next 5 Weeks - December 17th 2021 -January 20th 2022

Has finally shifted into line with the other models, picking up the monsoonal burst and widespread rainfall developing from next week over northern Australia and this then spreading throughout the north of the nation. The east wet, easterly winds looks a good forecast for most of this period with a few breaks, so if you are living out east, I hope you like humid unsettled weather. For the remainder, mixed odds in rainfall forecasts and that is thanks to the thundery weather with troughs passing through from time to time.

GFS Rainfall Anomalies - Next 5 Weeks - December 17th 2021 -January 20th 2022

Northern tropics are tending wetter and the moisture over the northeast and east via onshore winds will lead to widespread showers and persistent cloud cover and cooler weather. Drier weather, likely for the west but not that dry.

CMC Rainfall Accumulation - Next 4 Weeks - December 17th 2021 - January 19th 2022

This is suggesting a very robust monsoonal burst over northern Australia and this translates southwards through the nation and then impacting the east of the nation, combining with onshore winds to bring large rain and thunderstorm outbreaks, starting from as early from next week. The west is expected to remain quite changeable, but not as wet and that will extend into SA and southwest VIC. That weather is expected to remain flip and flop according to the SAM phase for southern parts of the nation.

CMC Rainfall Anomalies - Next 4 Weeks - December 17th 2021 - January 19th 2022

The models are really starting to suggest the monsoon is now set to pounce on the north and influence rainfall over eastern and southeast areas of the nation. Mixed rainfall odds for the south and is dependent upon the path of tropical features. But I am calling it more seasonal for southern SA and through to southern WA at this time.

TEMPERATURES

Euro Temperature Anomalies - Next 6 Weeks - December 17th 2021 -January 31st 2022

This is probably the closest to post still, we have seen a warmer shift over the southern inland of Australia with the cooler bias over the east and seasonal weather elsewhere. The weather while dry over the southwest of WA, it may be devoid of high heat, with persistent ridging, so a mild summer for the west may be a fair forecast, which may be good for those fire impacted areas.

GFS Temperature Anomalies - Next 5 Weeks - December 17th 2021 -January 20th 2022

This is probably too warm considering the development of monsoonal weather and rainfall increasing across the nation.

CMC Temperature Anomalies - Next 4 Weeks - December 17th 2021 -January 20th 2022

This is likely too cold.

SUMMER REVIEW - A REMINDER THAT MODELLING CAN BE OUT FOR TROPICAL RAINFALL EXPECTIONS AS PER THE BELOW. THESE WERE UPDATED ON 1ST DECEMBER.


January 2022 - Rainfall Anomalies

The model has turned a bit drier for January which I am not totally convinced about, the shorter and medium term forecasts support a deepening of the low pressure over the north of the nation, but for now calling it seasonal for the north and west, with drier spots here and there over the outback and possibly through the south, wetter over the east.

February 2022 - Rainfall Anomalies - May be more reflective of what we see in January.

The wet signal increases over the tropics which is in line with the La Nina in place and the impacts of that being felt from late January into February. The nation as a whole responding to that, with a very wet end to Summer possible.

SEASONAL

Summer - Rainfall Anomalies

But looking at the Euro, the impact of La Nina is evident. I would not read too much into that brown shading over WA as it takes one system from the tropics to see that drier bias disappear. The wet Summer continues for the east and north.

I will have an update from Darwin in the new week on this product and being in the monsoon and seeing it for myself I am able to forecast the impact and spread of Summer rainfall a lot more readily.



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