Verification of a poor East Coast autumn
For the last month the cries have been loud and clear: "worst autumn ever", "we haven't had a clean swell for months", "there's no sand on the points".
While some regions of the East Coast have offered cleaner and fun waves all autumn, a lack of southerly winds (and the northward longshore drift that comes with it) have been compounded by smaller swells and persistent northerly winds across Northern NSW.
Climate data from the past month has just come in and it's confirmation that the synoptic setup during April was far from normal.
The diagram below shows the difference in Mean Sea Level Pressure (MSLP) in April from the 30 year climatological mean running from 1981 to 2010. What we can see is that there was a significant positive pressure anomaly in the Tasman Sea, up to 4hPa above the climatological average.
You can also see that south of the country there was a significant negative anomaly (-6hPa), which is linked to Victoria and South Australia's persistent run of W/SW swell through April.
But back to the East Coast, and with a high pressure anomaly, onshore easterly to north-east winds were directed into the northern NSW coast for most of the month while also blocking the formation of an any Tasman Lows.
When we grab the surface wind anomaly charts for the same month you can see the correlation: the onshore flow across south-east Queensland and northern NSW was stronger than the climatological average, while also identifying the swell-generating westerly winds south of Western Australia.
Looking back on the same data for March, and while the MSLP anomaly charts don't immediately reveal anything out of the ordinary, one look at the surface wind anomalies show the story through the Tasman and Coral Seas. Stronger than normal northerly to north-easterly winds spanning the whole ocean basin, meaning the pattern has continued since at least March.
If we look at the coming winter, and with an El Nino watch still in place (though if we reach the threshold it will only be weak and short-lived), it looks like we'll see another fairly benign swell outlook on the East Coast as discussed in this past article - El Nino and Australian swell patterns. La Nina years are more likely to bring increased swell activity, the last significant event which was 2011.
Whether this is a peek into the future regarding the new norm on the East Coast is to be seen, but let's hope the coming months buck the trend.