(from U.S Climate Prediction Center)
NCEP Tropical Hazards global map shows the reasonable strength MJO min Phases 4-5 north of Australia in the Maritime Continent. Due to seasonality, the MJO influence doesn’t penetrate into the Australian region and instead, maintains its presence along the equator and further into the Northern Hemisphere.
A look back to mid-March 2021 at the seasonal forecast issued for Apr-Jun showed a wet signal very for the top end, based on the warm Arafura Sea and Ningaloo Region off the WA coast. The BOM model hosed down expectations with a neutral forecast for all other areas, which was pretty close. The IRI model was picking up activity in eastern NSW as was the European CS3 group of models, which did occur in a few pockets. None of the predictions picked up the broad-scale decile 2-3 rainfall across 50% of the continent, although temperatures were reasonably close to what was predicted. None of the models really nailed it through this period but this also highlights the difficulties when the climate drivers are finding their feet. The trophies stay in the cabinet again this month!
Apr-Jun rain (LHS) and temp (RHS) deciles
A survey of 12 international models condensed in the below charts (top both and bottom LHS) shows the outlook for late winter early spring rain sitting in the upper level of probabilities. The BOMs ACCESS model is showing “Anthony Mundine” like confidence in its predictions for some eastern locations, whereas the group of European multi-model is more conservative. With more certainty on the path of key drivers: IOD and Modoki this month, those who have decisions to make in the spring should be running this very wet scenario in their businesses. No extreme temperatures predicted is a salient point, as we know heat can undo an erratic wet forecast coming into spring.
See the bottom chart for the IRIs refreshed early spring outlook!
Order of Figures clockwise from top left: ACCESS-S tercile forecast, CS3 multi-model tercile (ECMWF, UK, France, Italy, US, Japan), 5x North American models combined on the bottom showing rainfall (LHS) and temperature (RHS). IRIs extended outlook at the bottom.
IRIs winter precip and temp forecasts
IRI’s early spring forecast refreshed this week.
(from U.S Climate Prediction Center)
NCEP Tropical Hazards global map is not picking up any major events through the Australian region that make the UPPER THIRD Tercile (i.e. wettest 33%) of weekly conditions over the next fortnight. Rainfall and convection showing in the eastern pole of the IOD box is the only notable feature.
A look back to mid-February 2021 at the seasonal forecast issued for Mar-May showed a wet signal virtually split between three model sources between southern, central and northern parts of eastern Australia. The observations for that period (top chart, below) shows a reasonable representation of the models over the period with a few exceptions: the Vic Mallee was hammered with decile 1-3, not picked up and Eastern Qld was on the leaner end of rainfall. The CMCC European model probably did the best of the three and also picked up the central-Australian rainfall extending across from moisture off the WA coast. No clear winner this Autumn among any of the temp or rainfall predictions, again validates the difficulty during this time of year.
A survey of 12 international models condensed in the below charts (top both and bottom LHS) shows the outlook for winter rain sitting in the mid-tercile range for the BOM and other EU multi-system, whereas the IRI North American ensemble is more bullish on higher precipitation. Temperature predictions (bottom RHS) show a similar theme with no signal for cooler or warmer conditions. This is not unusual given most indicators are quite close to neutral. The longer-range charts do favour a wet Indian Ocean Dipole developing along with a wet Modoki phase, influencing our spring. SST predictions also favour warm waters through the Arafura Sea and Ningaloo Reef which could well be flowing through model outputs for the mid-latitudes.
See bottom chart for the IRIs refreshed early spring outlook!
Order of Figures clockwise from top left: ACCESS-S tercile forecast, CS3 multi-model tercile (ECMWF, UK, France, Italy, US, Japan), 5x North American models combined on the bottom showing rainfall (LHS) and temperature (RHS). IRIs extended outlook at the bottom.
IRIs winter precip and temp forecasts
IRI’s early spring forecast refreshed this week.
(from U.S Climate Prediction Center)
NCEP TC watch is showing very little going on in the Australian region out to 26 May. This time of year the MJOs impact tends to be more Northern Hemisphere-based, as shown by heavy rainfall around and north of the equator. Dry weather across the Western Indian Ocean shows the MJO has moved eastwards at least. With the monsoon and MJO losing its influence on rainfall, this TC Hazards section will go to the sidelines next week.
A look back to mid-January 2021 at the seasonal forecast issued for Feb-Apr showed a broad wet signal for NSW and SE Qld areas. The observations for that period (top chart, below) shows a reasonable representation of the models over the period with a few exceptions: the Vic Mallee was hammered with decile 1-3, not picked up and SE Qld was on the leaner end of rainfall. However, the WA and NSW areas were definitely smiling after the wet predictions came to fruition in a period where model skill is perceived to be lesser than during the winter and spring. The BOMs ACCESS-S model was not far off and took the honours with ECMWF not far behind in 2nd place. Models fared much better during this period than the 3-months before when the trophies never left the shop.
(from U.S Climate Prediction Center)
NCEP TC watch is showing very little going on in the Australian region out to 18 May, consistent with MJO Phase being in 2 and 3 - over the Indian Ocean while multi-week models calling for fine weather over much of the continent in at least the next couple of weeks. A useful model to see how quickly and where the MJO is predicted to be in the coming fortnight in terms of broad-scale convection.
What is an analogue year? This is a “like” or “similar” year when the ocean and air pressure conditions are almost the same. A study by CSIROs Jaci Brown et. al. (2018) found a combined GCM analogue year approach can be useful in decision making for winter cropping in eastern Australia. Here’s what we know;
One floated analogue by Accu Weather Climatologist, Jason Nicholls (US) is 1989. A look at this 1989 year shows neutral ENSO, neutral/wet IOD and neutral/wet Modoki index. This is the only year that sticks out since 1980 that ticks these boxes in line with global forecasts. Check your rainfall records for that year for May-October. (1989 rain decile map bottom).
The GCM outputs reviewed last week showed average rainfall and temperatures for the next 3-months. Most models showing decile 4-6 rain, with the exception of the IRI model, which favour decile 7 for NSW. Longer-term IRI prediction favour a wet spring. (top chart with yellow border, below).
The subtle difference between 1989 obs. and the forecast is that in 1989 the Modoki index was in wet phase for winter, then faded to neutral. The outlook in 2021 is for Modoki and possible IOD to strengthen from neutral to wet phases, which is worth keeping an eye on. ENSO looks to be neutral, consistent with 1989/2021.
Jaci Brown’s paper here: https://doi.org/10.1016/j.agrformet.2018.06.001
A survey of 12 international models condensed in the below charts (top both and bottom LHS) shows optimism for winter rain diminished somewhat compared to a month ago, although a hint of a wet winter from the IRI ensemble. Temperature predictions (bottom RHS) show a similar theme with no signal for cooler or warmer conditions. This is not unusual given most indicators are quite close to neutral. The longer-range charts do favour a wet Indian Ocean Dipole developing and influencing our spring with wetter than normal conditions favoured. More on that next week.
Order of Figures clockwise from top left: ACCESS-S tercile forecast, CS3 multi-model tercile (ECMWF, UK, France, Italy, US, Japan), 5x North American models combined on the bottom showing rainfall (LHS) and temperature (RHS).
(from U.S Climate Prediction Center)
NCEP TC watch is showing very little going on in the Australian region out to 4 May, consistent with MJO Phase being in 8 and 1 - over Africa while multi-week models calling for fine weather over much of the continent thru May.
A look back to mid-December 2020 at the seasonal forecast issued for Jan-Mar showed a broad wet signal for NSW and Qld areas. The observations for that period (top chart, below) shows a contrast between NSW and inland Qld areas, not really captured too well by any of the models (bottom charts). The IRI multi-model ensemble did pick a dry tercile in NT, however, also went for a wet SE Qld which never eventuated. The ECWF was close, but no wet signal predicted for central Australia. The degree of difficulty through the summer monsoon is quite high when one or two intense events can shape the outlook one way or the other. Hence no prizes for 1st place this week, with all models about on par with each other.
(from U.S Climate Prediction Center)
NCEP TC watch is showing very little going on in the Australian region out to 20 April, consistent with multi-week models calling for fine weather over much of the continent this month.
(from U.S NOAA website: https://psl.noaa.gov/map/images/fnl/slp_07a.fnl.html )
The chart below shows an anomalous ridge of high pressure camped right over the centre of Australia.
The interesting feature is the vast area of low air pressure surrounding our continent.
Models are showing this pattern persisting through April at this stage.
(from U.S Climate Prediction Center)
NCEP TC watch is showing activity in the NW of Australia in week 2 with the anticipated arrival of the MJO into the region north of Australia and potential TC formation and rain in the top end.
The SST anomaly for this week (bottom) shows water warming right around Australia’s perimeter, not unlike a traditional La Nina at its peak. Looks like good potential for Autumn rain on that basis. Chart courtesy: https://www.tropicaltidbits.com/analysis/ocean/
Still a reasonably optimistic Apr-Jun period, although watered down a little from last month. Warm waters from the La Nina appear slow to decay to Australia’s north, so looks like the top end could be in for a slightly longer wet season. The US (IRI) predictions are particularly bullish for NSW, with moisture streaming down from the NW and warm waters extending up from the Ningaloo Reef. No red flags in terms of temperature at this stage.
Order of Figures clockwise from top left: ACCESS-S tercile forecast, CS3 multi-model tercile (ECMWF, UK, France, Italy, US, Japan), 5x North American models combined on the bottom showing rainfall (LHS) and temperature (RHS).
(from U.S Climate Prediction Center)
NCEP TC watch is showing activity in the NW of Australia in week 1 and potential TC activity in the same region with the addition of the Gulf.
The MJO signal is weak and not near the Australian region. The outlook is a fairly general reflection of the SSTs (bottom figure) and broad-scale mean sea level pressure anomaly posted in “climate in brief”. Drier in FN Qld and more tropical activity in NW Australia and the eastern Australian mid-latitudes.
2020-2021 Summer season saw the La Niña signal convert to good rainfall and cooler temps in NSW, but the decile 1-2 rain in SE Qld was less telegraphed and completely missed by the majority of models. A prudent reminder that expert commentary on analogue or “like” years should remain a key part of due diligence and risk management, despite statistical methods falling out of favour among some scientists.
Reflection and key learnings: The 2020 La Niña was slow to arrive and patchy when it did. All but one GCM (US IRI) model got completely sidetracked by the warm SSTs and traditional La Niña precipitation projections. In this 2020-21 event, the atmospheric conditions were slow to align with the warm SST signal, not occurring until around mid-December. International commentators Jason Nicholls (@jnmet) and Ben Noll (@BenNollWeather) predicted the rainfall and convection to be more in-line with 1988-89 with NSW the main beneficiary (mid-panel text). The cooler-than-normal southern Coral Sea, based on research may well have reduced available convection and moisture for rainfall events and this was picked up by the IRI (US) model. This region appears to be warming up now at a rapid rate, so hopefully, those farmers get their turn this Autumn.
(from U.S Climate Prediction Center)
NCEP TC watch is showing activity in the NW of Australia in week 1 and the Coral Sea region for both 7-day outlooks.
The MJO signal is weak and not near the Australian region. The outlook is for the tropical convective activity to move into the Coral Sea region, with the sea surface temps (SSTs) there finally warming up (bottom chart). The Gulf and Arafura Sea drier outlook mirrors the average/cool SSTs.
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