Lets have a quick look at the November Climate and the chances of La Nina as we head into Summer 2021/22.
There has been recent shifts towards a La Nina forming in the ENSO/Pacific amongst climate models and this signal continues in some of the data sets that I have observed this past week. A full update on La Nina and the Summer Outlook will be posted here on October 17 2021.
Now lets look briefly at November
% chance of exceeding median rainfall for November 2021
The rainfall is expected to be bias over the north and east of the nation as has been the guide for the September and October so far. The bias will continue in the same regions. The rainfall distribution becoming more uneven however, as the rainfall turns thundery, and if you live on large scale properties you know the deal. The frequency of rainfall likely to peak through late October into November with the IOD resolving but also with a developing La Nina phase in the Pacific. The tropics will respond to both of these and a near 100% chance of above average rainfall is likely. For areas such as QLD, NSW and VIC, your rainfall will come in long duration bursts through troughs and inland low pressure feeding off that deep tropical moisture. That will clip SA with better rainfall over the north and far east. The remainder of the state back into WA looking seasonal, with no bias towards above or below average rainfall at this time. Flooding is a significant risk for southeast and eastern inland parts of the nation. This forecast carries a MODERATE confidence.
% chance of exceeding median temperatures for November 2021
Cool bias continues for much of southern and eastern inland parts of the nation as the increased frequency in rainfall continues. The weather is expected to remain very warm and humid over the north with that humidity coming south and southeast adding to thick cloud cover on a regular basis. You may see blue over the east, but that cooler weather may be accompanied by higher humidity so really offsetting the COLD forecast. The weather over the SWLD likely to be cooler than normal, this could be a lag in the persistent high pressure ridging in from the Indian Ocean leading to southwest winds, so it really is conditional and low confidence in that part of Australia. Moderate confidence elsewhere.
CANSIPS November Rainfall Outlook - Rainfall Anomalies.
The rainfall bias over the north of the nation carries a very high confidence with elevated moisture levels already in place through September and October leading to higher values in November. This moisture is already beginning to circulate south and east through the nation and this sets the stage for widespread falls, particularly over the southeast and east. The remainder of the nation, flip a coin at this stage despite the spread of green on this chart, so for SA and WA, it is conditional upon storm outbreaks and inland troughs.
CFS November Rainfall Outlook - Rainfall Anomalies.
Ignore the drier signals over the northern parts of the nation as that is not likely. The rainfall bias over the southeast and east of the nation carries a higher confidence, interesting that this model continues to show heavier rainfall coming through SA and back through WA with the peak of the IOD.
Euro November Rainfall Outlook - Rainfall Anomalies.
This is closest to the post with that moisture over the north of the nation rotating through the upper level winds and moving south and southeast into the eastern inland with high chance of above average rainfall through the northern and eastern states. Will keep an eye on the increasing rainfall chances for SA and back through the outback into the NT, as that has only just started to increase on the forecast charts.
CFS November Temperature Outlook - Temperature Anomalies.
I still think this is running a little cold but it is not impossible given the short and medium term forecasts already issued this morning. Persistent rainfall and cloud cover will lead to lower than average day time temperatures but you may find your night time temperatures will be above average with nature's blanket of cloud in place. The north may see some moderation in relation to the temperatures thanks to more rainfall coming back to the forecast but your humidity values up north will be excessive and this will spread south into QLD and NSW.
Euro November Temperature Outlook - Temperature Anomalies.
This is probably a little closer to the post with the bias of warmer weather over the north of the nation easing back, but I think that is too aggressive and I am leaning toward much warmer conditions over northern areas. The cooler bias over the southeast and southwest continues to hold in most updates.
CANSIPS November Temperature Outlook - Temperature Anomalies.
In good agreement with Euro but I am leaning towards above average temperatures over the north to continue and the cooler bias is expected over much of the south with that cloud cover and widespread rainfall anticipated.
ENSO DATA - LA NINA CHANCES.
The latest data plumes from some global agencies are continuing to come in and they are continuing down the path of a La Nina forming during November and persisting until about February. This will see an increase in rainfall chances (not present on rainfall forecasts here) through December and into much of January to March 2022.
The main areas of impact again northern and eastern Australia, with a focus of an enhanced monsoon, potentially an enhanced cyclone season and storm season over the east and southeast.
With more moisture about the likelihood of above average temperatures and a severe fire season remains very low nationally. There is no evidence in drought conditions developing at this time through more areas of Australia.
Global Modelling - ENSO Predictions.
The plume of models continue to show a strong shift to La Nina conditions with only a few likely to remain neutral. Some agencies are suggesting a longer La Nina vs last year, while other global models suggest a shorter event, these details will be ironed out in coming weeks and the next update.
Dynamic Modelling - ENSO Predictions.
Again a very similar spread from the dynamical models with the shift towards La Nina conditions from November onwards.
IRI/CPC Model Run - ENSO Predictions.
Follow the Red Green and Blue line and they are bringing in a modest La Nina, though NASA continues to be most robust and has not shifted from this stance and based off the observed SSTs, SOI, Trade Winds etc it may not be too far off from the truth so watch this space.
Statistical Modelling - ENSO Predictions.
Again the statistical models are favouring a run of a La Nina summer and like the dynamical modelling, good agreement on the duration perhaps being a little longer than the last event. We wait and see.
More details coming up on La Nina on October 17th when all the data sets are in and I can scope through that tranche of information on the weekend before.