QUICK LOOK - NEXT 6 WEEKS OF WEATHER. THE TROPICS TO DRIVE SUMMER RAINFALL AND LA NINA PEAKS.

The west and south of the nation may remain drier and more stable for the period ahead, but there may be bursts of showers and storms in these regions too, so there is not one part of the nation that is looking at drought conditions developing under the current guide.


The opposite can be said, with tropical lows/cyclone activity over northern Australia, persistent easterly winds developing over the east and southeast leading to more rain and thunderstorms about as we kick off 2022.


The risk of flooding is remaining high through this period as well for northern and eastern Australia. Thankfully, some of the river systems have started to recede and dry out after the significant Spring rainfall, but the Summer rainfall looks to rival this period of flooding so the risk is not over for QLD, NSW and VIC as well as parts of the Outback with tropical moisture streaming south.


Lets take a look


FORECAST

Rainfall Outlook - Next 6 Weeks - December 21st 2021 - February 4th 2022

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

Rainfall is expected to increase over the coming week for northern Australia and persist for about 2 weeks before contracting eastwards and the weather tending monsoonal break. For the south and east of the nation, I am expecting there to be more humidity and thundery outbreaks developing in the warm and soupy airmass as we move into the end of the year and into 2022 in response to the monsoonal burst up north. Any tropical low could result in widespread heavy rainfall moving deeper south into the nation so that is a wild card to watch. Otherwise seasonal expectations for southern and western areas of the nation where the weather is drier this time of year.

Temperature Outlook Next 6 Weeks - December 21st 2021 - February 4th 2022

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

No change in the guidance which is great, 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 21st 2021 - February 4th 2022

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

The monsoonal burst is now expected to visit the north of the nation later this week into the weekend and will lend itself to sending a large pulse of moisture south and east through the nation, with a tropical low and or cyclone possibly leading for weather turning wetter over inland areas, but it is what you would expect seasonally for the north. 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, a low pressure system may develop in the easterly flow from time to time which could increase rainfall totals for coastal QLD and NSW. 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.

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.

CLIMATE DASHBOARD

The drivers stay persistent for the coming 2-6 weeks.

TROPICAL WEATHER

December 21 2021 -January 20 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, especially early and again later in the period for northern Australia.

SOUTHERN ANNULAR MODE

Next 2 Weeks

The SAM remains positive for the coming 7-10 days before it settles again towards neutral, but there is no negative phase anticipated at this time for the coming 2-4 weeks, leading to enhanced rainfall chances and cooler temperatures over eastern Australia.

RAINFALL

Euro Rainfall Accumulation Ensemble Data - Next 6 Weeks - December 21st 2021 - February 4th 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 21st 2021 - February 4th 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 21st 2021 - February 4th 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.

TEMPERATURES

Euro Temperature Anomalies - Next 6 Weeks - December 21st 2021 -J February 4th 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 21st 2021 -January 27th 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.

Next Update on this product will be Friday morning.


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