X-Sender: disarm at braenet.com.au (Unverified) X-Mailer: Windows Eudora Pro Version 3.0 (32) Date: Fri, 19 May 2000 15:11:00 +1000 To: aussie-weather at world.std.com From: Matthew Smith Subject: aus-wx: warm front Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Latest (well ok, 5 hours old) synoptic chart by the BoM has a warm front *just* south of Tazzy for those interested. http://www.bom.gov.au/weather/national/charts/synoptic.shtml Matt Smith +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ From: "Lyle Pakula" To: Subject: Re: aus-wx: National Climate Centre predicts warm and dry winter for South Eastern Australia Date: Fri, 19 May 2000 19:04:17 +1000 X-Mailer: Microsoft Outlook Express 5.00.2615.200 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Blair, Just a comment on the position of the high's - From memory fo the past three years, I can't remember the ridge's actually remaining as north as they currently are for this period of time - the period I refer to is the past week or two. Before anyone jumps the gun, I know there not actually that far North but being above the Prom is a good enough sign for me. Hell, Melbourne had westerlies in the last high! Although the avg temps and rain is disapointing, I'm sure the snow people among us will take anything as a good sign to wax their equipment :) Cheers, Lyle. - - ---==( lyle_pakula at hotmail.com )==--- - - . / \ . /~~~\/ \ " No Friends On A Powder Day " / \ \ / \ \ ----- Original Message ----- From: Blair Trewin To: Sent: Thursday, May 18, 2000 11:22 AM Subject: Re: aus-wx: National Climate Centre predicts warm and dry winter for South Eastern Australia > > > > The National Climate Centre has predicted a fairly strong chance of dry and > > warm conditions over the next 3 months ( June - August). I cannot understand > > how this prediction is made. We are not entering an El-Nino phase but rather > > a decaying La Nina and I would have thought this would have caused the dry > > conditions to be around Eastern and Northern Australia. The prediction of > > dry conditions for SE Australia is particularly surprising and alarming > > given the fact that SE Australia has not had a decent winter for years and > > currently many areas are having record dry 36 month period. Surely we are > > due for a boomer wet Winter! > > > > Martin > > A few points here: > > 1. The seasonal forecast is based on sea-surface temperature patterns > in both the Pacific and Indian Oceans - it's not just a simple ENSO- > based system. The Pacific, averaged over the year and country as a > whole, has more influence than the Indian, but there are certain > seasons and regions where the Indian Ocean is the more significant of > the two. > > 2. There is very limited forecast skill arising from ENSO at this > time of year. In essence, this is because marked deviations from > neutral conditions characteristically begin and end in the southern > autumn, and hence near-normal SSTs in the eastern Pacific in April > (the current situation) don't imply the likelihood of near-normal > conditions several months down the track, in the way that they would > later in the year - near-normal conditions in April could mean the > start of an El Nino/La Nina, the end of an El Nino/La Nina, or a > prolonged period of near-normal conditions, and at that time of year > it's hard for a forecast scheme to tell which is which. This is > known as the 'autumn predictability barrier'. > > 3. As a result of the lack of persistence in ENSO in autumn, whilst > there are strong simultaneous correlations between tropical Pacific > temperatures and eastern Australian winter rainfall (and minimum > temperature), the lag correlations (which is what you need for a > forecast, because you don't have the winter SSTs to hand when you're > trying to make a winter forecast) are weak to non-existent. This > means that at this time of year the forecast skill in SE Australia is > limited (and what there is comes mainly from the Indian Ocean). The > ENSO influence on the forecast picks up considerably from July onwards. > > One of the problems we face in making seasonal forecasts is that, in > any given season, there will be parts (sometimes large parts) of the > country where we have little forecast skill, but we don't have the > option of just leaving those bits of the map blank. You'll notice > references to skill (or lack thereof) in some of the media releases, > but that sort of subtlety rarely makes it into the media (except > perhaps for the specialist rural papers). > > The current drought is extremely localised by normal standards > (although I suspect it would be far more widespread if we had capacity > to measure rainfall over the oceans south of Victoria); it is > essentially confined to Tasmania, southern Victoria and south-eastern > SA. It has also persisted through just about every possible state of > ENSO. The main synoptic driving force behind it is that the high- > pressure belt has been persistently south of its normal position for > three years now, but it is far from clear why this is happening. > > Blair Trewin > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com > with "unsubscribe aussie-weather your_email_address" in the body of your > message. > -----------------------jacob at iinet.net.au------------------------------ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------ Date: Fri, 19 May 2000 19:30:57 +1000 From: Anthony Cornelius X-Mailer: Mozilla 4.72 [en] (Win98; I) X-Accept-Language: en To: aussie-weather at world.std.com Subject: Re: aus-wx: National Climate Centre predicts warm and dry winter for South Eastern Australia Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Lyle, I actually thought the Baric Ridge has been further south than usual. Normally during winter, the Baric Ridge will sit somewhere around the 30S mark. This gives Brisbane the more characteristic (and dreaded), SW'lies (and it's not unusual to have them at gale force). If the Baric Ridge were to sit at this level, I would have thought it'd mean a much more fun winter for the SE Australian's - as it'd allow the passage of fronts, and also allow cyclongensis to occur more frequently down near Victoria and Tasmania. This isn't an attempt to jump the gun - so don't worry :-) My 2c worth. Lyle Pakula wrote: > > Hi Blair, > > Just a comment on the position of the high's - From memory fo the past three > years, I can't remember the ridge's actually remaining as north as they > currently are for this period of time - the period I refer to is the past > week or two. Before anyone jumps the gun, I know there not actually that far > North but being above the Prom is a good enough sign for me. Hell, Melbourne > had westerlies in the last high! Although the avg temps and rain is > disapointing, I'm sure the snow people among us will take anything as a > good sign to wax their equipment :) > > Cheers, Lyle. > -- Anthony Cornelius Queensland Coordinator of the Australian Severe Weather Association (ASWA) (07) 3390 4812 14 Kinsella St Belmont, Brisbane QLD, 4153 Please report severe thunderstorms on our Queensland severe thunderstorm reporting line on (07) 3390 4218 or by going to our homepage at http://www.severeweather.asn.au +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ To unsubscribe from aussie-weather send e-mail to:majordomo at world.std.com with "unsubscribe aussie-weather your_email_address" in the body of your message. -----------------------jacob at iinet.net.au------------------------------