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ARTICLES >> Environment Weather Watch

Weather Watch - June 2011

Posted by Bestprac on Jun 02 2011

by Susan Carn

First a quick snapshot of the Carn farm! It’s cold and wintery and the grazing country is still looking really good after a good start to the year. Consequently we had the best lambing percentage in many years. However, our May rainfall was disappointing and we have only recently had enough rain to get started on some cropping. But should we be sowing? Read on!

Last week I was invited to the South Australian Bureau of Meteorology in Adelaide, where I took part in reviewing some new web page designs for the Seasonal Outlook Service. Darren Ray, Senior Meteorologist/ Climatologist and Manager of Climate Services, conducted the interview. The BOM are keen to make this service as useful and user friendly as possible.

The Seasonal Outlook Service is updated every month and gives an indication of rainfall, for the next three months, across the country. Although I am excited by a lot of their new ideas, the changes may not happen for a while, as the reviewing process is Australia wide.

While I was there, I took the opportunity to ask how the Bureau of Meteorology sees the rest of 2011 turning out. A strong message from Darren Ray was that we were definitely not going to have a wet spring and summer like last year. He said that the 2010/11 La Nina was probably a 1 in 50 year event.

I asked if my lack of autumn rainfall could be attributed to any one climate driver and, it seems, that there is a very concerning trend towards dryer autumns, over the last 15 to 20 years. Scientists believe the reason for this is the strengthening of the subtropical ridge.

The position of the subtropical ridge influences the rainfall patterns in Australia. The following examples show the position of the ridge during a day in summer and a day in winter.

So ideally the further north a high sits, the more chance there is of low pressure systems bringing rain northwards.

The week in late May when I did get some “opening” rain, the way was clear for a low pressure system to come up. Now, however, we are back into a huge blocking high situation again, and it looks set to stay that way for at least a week. So in effect the subtropical ridge is still in its summer position.

A good way to watch the predicted movements of high and low pressure systems for the next 7 days can be found on the BOM Interactive Weather and Wave Forecast Maps.

Another interesting website, especially for croppers, is the NSW government, “Crop Mate”. Here you can key in your location (in NSW, SA, VIC or QLD) and get access to, not only cropping decision tools, but a huge range of weather information and climate forecasting tools.

This site is well worth having a play around with. For example, under “Climate Averages”, you will be able to quickly access old rainfall records of your area, and make comparisons, and get a graph of your 5 year rolling average.

Under “Climate Outlook”, you can access graphs of the Southern Oscillation Index (SOI), Indian Ocean Dipole (IOD) and links to other information, such as an easy explanation, with diagrams, of the subtropical ridge and its different seasonal positions.

Looking at the latest climate indicators, this year is shaping up to be neutral, at best, for the SOI and IOD. So, even though we have more sub-soil moisture than last year, we have decided to only sow a conservative acreage.

Last changed: Feb 09 2012



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