La Niña, where the bloody hell are ya?
So many questions, and all wanting the same answers.
Over the last month I've fielded a few queries along the lines of: "Where are the cyclone swells?" and "Where's La Niña gone?".
While here at Swellnet, we're always quick to point out that cyclones aren't necessarily favourable swell producers, as discussed here, the lack of cyclones (for now) is still a good talking point.
Climate teleconnections (links between climate patterns across large distances) such as the El Niño/La Niña Oscillation (ENSO) and the Indian Ocean Dipole (IOD) don't just play out over weeks, but we see them evolve and influence the climate and weather patterns over months and across seasons. In regards to ENSO, the current La Niña signal, which reached a peak through the central Pacific Ocean around November, is still strong, but closer to us around the Date Line (180 degrees of longitude) the cool sea surface temperature anomalies are only just reaching a peak.
As a result, most climate models have La Niña persisting through March, with a 65% chance that it'll hang through until May. That's another four months away so there's still a long way to go in regards to how this will play out over the coming months. Add in the lag of warmer Coral Sea water feeding south with the East Australian Current and the effects should be felt well into winter.
Now, while this La Niña hasn't been a typical one per se, with starts and stutters, what we should be keeping our eye on is the wave of tropical activity that helps activate and nurture tropical activity across our region. This is known as the Madden Julian Oscillation (MJO) and it last passed through during December, bringing the large rainfall totals to most of the country while also feeding the deep costal trough that brought the large storm surf to south-east Queensland/northern NSW and also spawning Tropical Cyclones Yasa (severe) and Zazu in the western Pacific Ocean.
The chart below shows where the MJO has been around the Earth (at tropical latitudes) through December (green) and January (dark blue). The perspective is that of looking from the North Pole with the MJO peaking just east of us mid-December, leading to the formation of Tropical Cyclones Yasa and Zazu, weakening before then popping back up in the Indian Ocean.
While south-east Queensland and northern NSW have offered fun, persistent levels of easterly trade-swell along with favourable winds the past couple of weeks, there hasn't been any significant developments since the coastal trough in December.
This can be largely put down to the MJO weakening and moving back across the Indian Ocean as shown above. Looking ahead though, the MJO is currently strengthening across the Indian Ocean and this will lead to the formation of a cyclone or two which will track west towards Madagascar through next week.
Over the coming fortnight this strengthening MJO signal is forecast to move east towards us and this will bring that injection of tropical instability to the region. With this we'll hopefully see the trade-pattern kick back in late in the month/February and depending on the strength of the MJO, likely a cyclone or two.
So sit tight and work around the coming southerly swell episode due next week across the eastern seaboard, with trade-swell likely to follow.