There can be some confusion about the role of the Indian Ocean Dipole and when it "should" be in full flight, with many having unrealistic expectations vs the time of year they are looking at the driver.
We are in a time of year when the IOD is in development phase and from this time on is where we start to see the impacts emerge whether it be in negative or positive phase.
Latest Analysis - Sea Surface Temperature Anomalies - AREAS TO WATCH!
Classic Indian Ocean Temperature Spread representing the negative phase unfolding. The anomalous warmer waters surrounding Australia are way up there in comparison to previous negative IOD events and that is lingering impacts of the weak La Nina/Cool Neutral Pacific. It is clear that the warmer waters caused by both events will merge through the Spring and this will lead to elevated rainfall and cloud coverage throughout the remainder of July onwards, starting I believe from later this month and increasing through August based off the current synoptic scale. Further to this, the area near Indonesia is the area to watch over the coming month or two. In recent weeks there has been a slight cooling of the subsurface but that is neither here nor there when the SSTs are sitting at near 3C above normal offshore Indo. The cooler waters are expanding closer to Africa which is resulting in drought conditions and famine issues (see at the end of the page) we are seeing that as a direct result to the cooler waters offshore the east and south coasts.
MOISTURE IS BUILDING OVER THE BASIN ONCE AGAIN AFTER A PERIOD OF STRONG EASTERLY WINDS AND UPPER RIDGING.
Note that the moisture will eventually be pulled into frontal weather as the wind pattern in the mid and upper levels shift into the west and northwest. And the moisture over Indonesia is on the increase and note how that gets drawn southeast into the upper-level northwesterly winds over WA. We will see a gradual increase in rainfall via the cold fronts first and then cloud bands developing through the interior as the frontal passages begin to rise. But that is dependent on the Southern Annular Mode being in a more favorable phase.
MOISTURE IS LIMITED BUT NOTE THE IMPACT OF THE WARMER WATERS OFFSHORE THE NORTH AND NORTHWEST OF THE NATION SURGING INTO LOW PRESSURE.
The drier air over Australia is thanks to high pressure however this is a great example of when the moisture is in phase with low pressure, cloud bands form. And this will be repeated time and time again through the weeks and months ahead while waters remain very warm north and northwest of the nation.
A GOOD VIEW ON THE MECHANICS OF THE INDIAN OCEAN DIPOLE AND LOOK FURTHER AFIELD TO OTHER AREAS IMPACTED TO SEE IF THE INDIAN OCEAN DIPOLE IS UNFOLDING AS PLANNED.
NEGATIVE IOD IMPACTS AND GENERAL TIMING GLOBALLY!
Comparing with the current data above, you can see that we are on track with the SSTs for the unfolding negative IOD and this will continue to become more apparent as we get into August through Spring. The impacts of the IOD can be seen in the polygons outlined around the globe.
POSITIVE IOD IMPACTS AND GENERAL TIMING GLOBALLY!
We are set to see a positive IOD from next year if not the year after at this time, with that likely to combine with an El Nino phase during 2023/24 which is the most likely time we will see the drier bias return to Australia and the rainfall return to the drought impacted Africa.
WE WERE DUE FOR A PROLONGED PERIOD OF NEGATIVE IOD ACTIVITY BASED OFF THE PAST IOD HISTORY.
Remember the past significant negative IOD impacts were felt back in 2016 and that caused significant Spring flooding that came on fast after incremental rainfall over the interior that kept catchments wet. We are in a similar situation through NSW and QLD, not so much in VIC at this time, but be prepared for the impacts to be similar over NSW. The Newell Highway was raised following part of it being washed away in 2016. So that gives you some idea of when all the ingredients come together, rainfall can be excessive, and we are starting down that once again this year. Not one event is ever the same, but certainly it is fair to forecast a very wet Spring.
GLOBAL MODELLING ON THE INDIAN OCEAN FOR THE REMAINDER OF THIS YEAR.
Climate Forecast System
Look for the bold red line for the most likely outcome.
Look for the bold grey line for the most likely outcome.
Global Environmental Multiscale Model
Look for the bold purple line for the most likely outcome.
Geophysical Fluid Dynamics Laboratory Research Model
Look for the bold orange line for the most likely outcome.
National Centre for Atmospheric Research Model
Follow the bold green line for the likely outcome.
The North American Multi Model Ensemble Members.
Follow the dark blue line for the most likely outcome for the Indian Ocean.
A CLOSER LOOK AT THE DATA TOGETHER - NOT TOO MANY ARE SUGGESTING NEUTRAL CONDITION OVER THE INDIAN OCEAN THROUGH SPRING AND EARLY SUMMER
PREVIOUS 9 MONTHS OF FORECASTS FROM THE INTERNATIONAL MODELS
You can clearly see from earlier this year the signal for a negative IOD has been strong but as we have approached the event unfolding, the guidance shifts. That is because we see the modelling take real time data rather than hypotheticals, and this is what helps the modelling refine as we go along. This proves there is only SO MUCH computers and data/algorithms and mathematical equations can do, and human intervention and interpretation of the data and review of analogues is critical to producing more reliable and accurate forecasts and analysis. The latest June outlook from this plume modelling is going for the strongest Indian Ocean Negative phase than other models have suggested in the Autumn. So that could create headaches and a problematic harvest ahead.
IMPACTS ARE AS NASTY OVER THE OTHER SIDE OF THE INDIAN OCEAN WHERE DROUGHT IS LIKELY TO CAUSE A WIDESPREAD FAMINE IN THE MONTHS AND POSSIBLY YEAR AHEAD.
While we will likely be dealing with our own weather problems related to too much rainfall, over the other side of the ocean, Africa is heading to their 3rd year of well below average rainfall with some areas on the Horn of Africa expected to move into famine territory and this may spread westwards through next year if the IOD does not resolve through the Summer. We have seen plenty of evidence that the warmer waters nearer Australia may continue through Summer and cooler waters will remain nearer Africa through Summer. This is very similar to the 1970s for the eastern countries which then spread through the central countries. Many areas have also seen failed wet seasons as well along the equator.
RAINFALL AND TEMPERATURE IMPACTS FOR AUSTRALIA ACROSS THE COMING MONTHS
RAINFALL OUTLOOK WINTER INTO SPRING 2022
Noting the very high rainfall bias over northern and central Australia, extends into much of NSW and QLD with the risk of flooding increasing through August and September. The wet bias extends south into VIC and SA but it is not as aggressive so be aware, the further north and east you go, the wetter you will be through the nation, similar to the guide last year! So while you see official forecasts GREEN! it is not a sure thing, and weather patterns have to allow for moisture to meet low pressure leading to widespread rainfall.
TEMPERATURE OUTLOOK WINTER INTO SPRING 2022
The warmer bias over northern Australia will increase over the coming weeks with the peak of the dry season currently being experienced. Noting the east coast warmer than normal thanks to higher moisture content and easterly winds developing. The interior, becoming cooler than normal, especially north of the SWLD of WA where cloud bands and higher rainfall activity forms. That spreads gradually east as the IOD peaks in the late Spring.
RAINFALL OUTLOOK SPRING 2022
Very high chance of flooding rainfall for Spring, with the peak of coverage forecast during October to December to last year, so use that as a guide where we will likely see areas to the west of the divide through QLD, NSW and north of the divide through VIC and much of interior SA, NT and the tropical NW of WA dealing with excessive rainfall and high humidity. The SWLD may be drier but that is conditional upon the SSTs becoming below average. There are signals that the SSTs will be warmer than normal offshore SW WA so this forecast is of low confidence there. The IOD playing a huge part in this forecast.
TEMPERATURE OUTLOOK SPRING 2022
With the excessive rainfall chances, thicker cloud cover and higher humidity, temperatures will drop off for large areas of the nation, not freezing, but cooler for sure, with the lack of solar hours. Warmer and more humid over northern Australia with a particularly nasty build up.
More coming up on the Spring Outlook 2022 through Friday. Make sure you take a look at that.