July 29th: Where is the snow? And why is it raining north of the ranges?
A quick update to explain why we’ve entered this new weather pattern.
There are two ‘climate drivers’ that have changed phase - and we are seeing their effects in our day to day weather.
SOUTHERN ANNULAR MODE
The first is called the Southern Annular Mode (SAM). This is a driver that can last for a few weeks at a time.
When its negative, cold fronts are able to push further north into southern Australia. The fronts are “stronger”.
When its positive, cold fronts are squashed down to our south, and high pressure ‘gets in the way’. But that can lead to low pressure troughs or lows “wandering'“ through the inland.
That is occurring now, with an area of rain crossing northern VIC and southern NSW on Monday (with 5 to 15 mm). Then high pressure sits over the southeast, pushing rain onto the east coast of NSW and QLD for a stretch of days. See Your Forecast for hour by hour details for any spot in Australia.
The chart does align quite well with how the snow season has turned out. It was negative for the big snowfalls just before opening weekend (late May).
Then it went positive for a long stretch, and we struggled to get any snow… before plunging negative again in early July. That’s when the next big snowfalls arrived.
Its now positive again - and the snow systems have dried up. For the latest update see: Snow Forecasts and click through to your resort for hour by hour details.
Looking ahead… the SAM forecast shows we could plunge negative again by mid-August - so that will hopefully lead to more snow systems. But… there’s the Indian Ocean to consider too…
INDIAN OCEAN DIPOLE
The next climate driver has effects that last for months at a time.
Most are familiar with the Pacific Ocean and its negative state “La Nina” (encouraging rain in Australia), and its positive state “El Nino” (limiting rain in Australia).
The Pacific Ocean has now entered a neutral phase, and won’t affect us either way.
But the Indian Ocean has a similar driver, where a negative state encourages rain here, and a positive state limits it - and we’ve entered positive.
A positive Indian Ocean should last for the rest of the year.
All the climate drivers are detailed on the Seasonal Forecast page, and for an armchair view see my monthly update video, thanks to Rural Bank: