The big rain system is delivering widespread rain, but not everyone has a soak

The big weather system affecting nearly all states and territories is a classic example of how we get widespread rain in Australia.

It kicked off in the west over the weekend and early in the week. Then low pressure met up with a feed of tropical moisture pouring in from the Indian Ocean in a juicy northwest cloudband. This pushed mid-week rain across the interior, southwest Queensland, western NSW, northern Victoria and parts of eastern South Australia. 

Then the low pops out off the coast near Sydney, ensuring big rainfalls for southeast NSW to end the week, thanks to a feed of moist air from the Tasman Sea. 

This produces widespread rain, a good soak, across huge areas of the country, over the course of nearly a week. 

Not everyone sees the rain.

As always, thanks to our terrain and the path of the low pressure, there are some areas that miss out.

All coastal parts north of Newcastle in NSW have either light falls or nothing at all. The path of the low pressure means that the widespread rain is west of the ranges, and it dries up as it crosses the Divide. The opposite of what we see a lot of, where the coast gets the rain and it dries up as it heads into the west. The story is different for southeast NSW because the low takes a path near Sydney, ensuring those to the south pick up the big rainfalls once it becomes a ‘coastal’ rather than a ‘western’ system.

Once again, Melbourne and surrounds miss out.

The first part of this weather system came down from the north, with much of southern Victoria in the rain shadow. At the same time we had a front crossing Tasmania, delivering big falls there with low level snow, but the front wasn’t strong enough to do much for Victoria's south.

The second part of this weather system has the low crossing NSW. That won’t do much for southern Victoria, again on the dry side of the ranges. When the low pops out near Sydney it is too far away for much wrap around rain then too. 

When you hear long term forecasts talking about a wet Spring and Summer, keep in mind that the reason for these above average forecasts is all the moisture we have access to - from both the Indian and Pacific Oceans. But you need low pressure to turn that into rain, and while it can take a path that affects huge parts of the country, it may not make a stop at your place. 

The next big weather system affects the southwest on the weekend, and the southeast early next week. This one may take a better path for the areas in the southeast that have missed out.