Tasmania - Fast Break
Welcome to your Fast Break newsletter
You are reading the 6th Fast Break for Tasmania
Volume 1 | Issue 6 | Tasmania | Published: 02 Oct 2018
Welcome to our sixth “Fast Break” newsletter for the Tasmanian grains industry. Our team has been preparing this monthly newsletter for 12 years in Victoria and with GRDC support we are now able to present it for Tasmania. If you like it, please consider passing it on through your networks and subscribing.
Still no sign of an El Niño and yet the majority of models predict one will occur in late spring/summer. The Pacific Ocean surface is still neutral, the SOI is vaguely interested, the cloud patterns aren’t remotely keen, the deep sea is warm to depth, but only in the western and central Pacific. The major change this month is the easterly trade winds have shown some El Niño like behaviour, with at least two, one-week long reversals of significant strength from PNG to half way across. This is likely to force the warmer water to depth further to the east, and warm the surface in the middle of the Pacific. All this is likely to take months which will just about see out the growing season before it occurs. Historically, summer El Niño’s have been hit and miss for Tasmania.
The Coral Sea is still warmer which is most unlike a “classic” El Niño.
All action has been in the Indian Ocean for some months. In the last weeks the Dipole Mode Index (DMI) measurement of the IOD has gone positive. Despite predictions from models for its occurrence all season, it has only just happened. We have had +IOD like cooling in the Timor Sea for many months but the current +IOD condition is being caused by the rapid warming off the African coast. Trade wind patterns are not consistent with a proper +IOD, but the lack of cloud off Sumatra is. Certainly, the lack of NW moisture feed for much of the season had something to do with the Indian Ocean not playing ball. If the +IOD hangs around for two months it will be called an event, but it would normally die in late October early November when the tropical wet season fires up. Historically around 50-60 of springs in +IOD years have been in the driest third of records.
Pressure patterns, which were favourable in August, have deteriorated in September by increasing in pressure and position over the SE mainland and chasing rainfall triggers further south of Tasmania. Such behaviour is classic +IOD induced.
The SAM which had been behaving itself in winter (particularly for the west of Tasmania) will cease to be a major driver in spring. Connections to tropical moisture will be more important than weak fronts.
The models surveyed are predicting drier/average conditions for spring with average/warmer temperatures.
It would be prudent to plan for the possibility of a shorter spring.
Model consensus forecast for the next six months
Current outlook (28 September)
Previous outlook (27 August)
El Niño (Modoki)
El Niño (Modoki)
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