Indian Ocean has warmed of NW Australia and cooled off East Africa in the last 7 days. Interesting change and one to watch in the next 2 weeks relating to the IOD.
Attachments
SST change Indian Ocean last 7 days.jpg (108.94 KiB) Viewed 17849 times
Encouraging signs taking place in the Indian Ocean now, with warming to our N/W and cooling over towards Africa. Rainfall prospects should continue to improve if this development continues.
Geoff wrote: ↑Mon Aug 07, 2017 7:18 pm
Encouraging signs taking place in the Indian Ocean now, with warming to our N/W and cooling over towards Africa. Rainfall prospects should continue to improve if this development continues.
Good pick up Geoff. Interesting signs also on the eastern side of the Pacific.... looks a little La Nina-ish
I wonder what period the 31 August outlook will apply to given the 17 August forecast is for Sept-Nov?
Yes, Gordon. Well spotted. They have got August wrong now 2 years in a row. Last year they said the IOD was weakening and then KABOOM within 2 weeks. This year they underestimated the westerly conveyor belt. They should stick to 14 days forecasts until climate modelling becomes more accurate IMO.
Didjman wrote: ↑Mon Aug 28, 2017 7:48 pm
So JS, could that translate into a good storm season here?
Peter
Yes Peter, If the atmosphere aligns with the ocean temps in the next month, I think it will be double the storms of the last couple of years for eastern and south east Australia. NSW and QLD especially but Victoria definitely increased. The coral sea is unusually warm, so an early start to cyclone season has potential as well.
One for Jasmine, hillybilly or any other experts that care to venture an opinion please?
During late spring/and through summer in La Nina years, there is an almost unbelievably sharp rainfall 'line' that forms between just west of Port Phillip, angling up roughly through Bendigo and on up into the northern Mallee. West of this line, there is little rain or thunderstorm activity; east of it and the heavens open! In this setup (and about half a dozen times this summer) I often watch castellus or young cumulus clouds form up overhead, but only produce rain once they've travelled across the line.
The December 2017 rainfall map shows this rather neatly:
Any thoughts on what causes this divide? Is it something to do with the topography of the ocean wedge between Cape Otway and Wilson's Prom? Or are other factors at play?
Gordon wrote: ↑Tue Jan 09, 2018 2:42 pm
One for Jasmine, hillybilly or any other experts that care to venture an opinion please?
During late spring/and through summer in La Nina years, there is an almost unbelievably sharp rainfall 'line' that forms between just west of Port Phillip, angling up roughly through Bendigo and on up into the northern Mallee. West of this line, there is little rain or thunderstorm activity; east of it and the heavens open! In this setup (and about half a dozen times this summer) I often watch castellus or young cumulus clouds form up overhead, but only produce rain once they've travelled across the line.
The December 2017 rainfall map shows this rather neatly:
Any thoughts on what causes this divide? Is it something to do with the topography of the ocean wedge between Cape Otway and Wilson's Prom? Or are other factors at play?
Interesting question Gordon... I'm not sure I have an exact answer but the placement of the high pressure ridge's during this La Nina may have something to do with it. It's been quite a north easterly flow and no real big easterly dip so far. I think, that once the coral sea starts seeing tropical depressions from the monsoon trough, troughs will move west with an associated inland low / easterly dip. Here is the position of the 2011 trough that dropped around 260mm around here in early January when the monsoon trough pushed down. time will tell
This is going to go big, once the monsoon trough arrives in February off the east coast. These Sea surface temps are starting to look nuclear for a synoptic scale attack. 26c tropical cyclone SST line has dropped south off the Northern NSW coast.
Attachments
SST Jan 17th 2018.jpg (336.36 KiB) Viewed 16566 times
Thanks JS. No guarantees, but at least the trend is towards a negative IOD rather than the dreaded positive IOD.
The one reliable rain forecaster of any use to us here (far west central VIc) is a negative IOD - without fail it brings us average to above average winter/spring rain. (Unlike useless (for us) La Nina!)