Date: Wed, 17 May 2000 00:04:29 +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: Please explain Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi John, First of all - I didn't know you were from Oxely :-) The winds at the surface are generally SE, and should remain SE with the left (and main) split high moving eastwards at a relatively low latitude to preserve our SE'ly quidge. I think that there's a large broad/long wave upper level trough just inland - it's giving us a strong NW'ly subtropical jet (100-110kn), and since it's to our west, it's given us generally NW'ly/NNW'ly winds in the upper-mid levels. But the interesting thing is, is the sudden cooling of the mid-low levels between 00z and 12z today. 500mb has remained virtually unchanged (-10C), but 550mb is -12C! Which gives an effective 500mb temp if -18C! So that shows you that the air is quite cold...that too has come on the NW'ly/NNW'ly winds...so maybe there's a little more to our west then actually analysed. (Which may not show up well on the 500mb charts). But the surface will be SE'ly and should remain that way. Might be some good showers about tomorrow (cloud pending)...can see the faithful Telstar possibly getting a work out! John Woodbridge wrote: > > Hi Anthony and all. > > Something a bit wierd seems to be happening. According to the > current MSL charts Brisbane should be in a developing SE regime, which > overnight I would expect to be tending S or SW with clear skies and > rather cool conditions, and indeed, this was the forecast on the evening > news. But at 11:30pm I find that we have cloud streaming at apparently > quite low level from the NNW, producing light showers and radar shows > precipitation clearly moving in this direction also. > > Bar is steady, so no trough developing, maybe just the result of the > large southern High splitting off a bit into the Tasman giving us a > temporary wind change?? > > John. > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > 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------------------------------ -- 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------------------------------ Date: Tue, 16 May 2000 10:20:52 -0400 From: "Leslie R. Lemon" Subject: aus-wx: SDS To: "INTERNET:aussie-weather at world.std.com" X-MIME-Autoconverted: from quoted-printable to 8bit by europe.std.com id KAA17739 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Approved? ************************ Leslie R. Lemon Radar, Severe Storms, & Research Meteorologist Tel. 816-373-3533, 816-213-3237 E-Mail: lrlemon at compuserve.com +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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------------------------------ X-Sender: johnstone at psyphw.psych.wisc.edu X-Mailer: QUALCOMM Windows Eudora Version 4.3.1 Date: Tue, 16 May 2000 11:57:36 -0500 To: aussie-weather at world.std.com From: Tom Johnstone Subject: RE: aus-wx: cold fronts and warm fronts Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Wow - I never thought there would be so many responses to my question! Thanks to all for your very informative posts. It seems that there are a few explanations of why Australian weather maps don't show warm fronts. The most common reason given was that Australia sits at lower latitudes than Europe and the USA, and that warm fronts are usually located at high latitudes, on the polar side of low pressure systems. However, when I look at the current weather map for the USA at www.weather.com, I see a warm front marked across the northern border of Texas, and another just of the east coast of Florida. The actual URL (map taken from weather.com) is: http://www.unige.ch/fapse/emotion/members/johnston/weatherMap.jpg Interestingly, it is the are just in front of this warm front that is predicted to have severe weather, as indicated on the following map (also taken from weather.com): http://www.unige.ch/fapse/emotion/members/johnston/SWMap.jpg This are was refered to this morning as the "dry line", which I remember there was a discussion about some time ago on this list (whether we had dry lines in Australia). Any comments? Tom Tom Johnstone Psychology Department University of Wisconsin-Madison johnstone at psyphw.psych.wisc.edu +1 608 263 4517 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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: Harald Richter Subject: RE: aus-wx: cold fronts and warm fronts (fwd) To: aussie-weather at world.std.com (Australian Severe Weather Association) Date: Tue, 16 May 2000 14:58:25 -0500 (CDT) X-Mailer: ELM [version 2.5 PL3] Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Tom (and other frontal geeks), Tom wrote: > Wow - I never thought there would be so many responses to my question! > Thanks to all for your very informative posts. It seems that there are a > few explanations of why Australian weather maps don't show warm fronts. The > most common reason given was that Australia sits at lower latitudes than > Europe and the USA, and that warm fronts are usually located at high > latitudes, on the polar side of low pressure systems. However, when I look > at the current weather map for the USA at www.weather.com, > I see a warm front marked across the northern border of Texas, and another > just of the east coast of Florida. The actual URL (map taken from > weather.com) is: > > http://www.unige.ch/fapse/emotion/members/johnston/weatherMap.jpg "Latitude" is part of the problem, how "meridional" the upper flow is, that is another part. Australia is lacking the topography to really perturb the mid/upper-level flow. The upper flow pattern is more zonal, hence surface cyclogenesis is more likely to occur right along the climatological baroclinic zone or storm track (40-60 S). The 16 Z Weather Channel surface analysis you mention sits under a fairly meridional flow pattern. At 500 hPa a trough is extending as far south as ~30 N setting up a SW flow across the Rocky Mountains, which in turn is associated with lee cyclogenesis over E Colorado. That forming cyclone is enhancing the S flow which is part of the advancing surface warm front over Oklahoma. > Interestingly, it is the are just in front of this warm front that is > predicted to have severe weather, as indicated on the following map (also > taken from weather.com): > > http://www.unige.ch/fapse/emotion/members/johnston/SWMap.jpg Just N of a warm front locally backed flow often leads to an improved shear profile for supercells. In this case, the air ahead of the warm front is still warm and moist, so shear and thermodynamics can work together. We *might* see an example of the "power of the backed winds" later in W Nebraska, where the capping inversion is weaker than in OK/KS. > This are was refered to this morning as the "dry line", which I remember > there was a discussion about some time ago on this list (whether we had dry > lines in Australia). The dryline is a different beast. It is currently set up in the warm sector as a N-S oriented boundary roughly extending S from the low over E Colorado. It separates drier, SW flow to the W from juicier S flow to the E. You sometimes get storms there, but today it might remain capped (I hope it won't). Australia does have drylines. The current surface obs (19 Z or 5 am Eastern time) hints at an enhanced surface moisture gradient (a pseudo-dryline) running W from Rockhampton. Only denser surface obs could convincingly resolve a sharp dewpoint gradient, hence "pseudo". Waiting under the cap in OK, Harald -- --------------------------------------------- Harald Richter National Severe Storms Laboratory 1313 Halley Circle Norman, OK 73069 ph.: (405) 366-0430 fax: (405) 579-0808 email: hrichter at enterprise.nssl.noaa.gov --------------------------------------------- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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: Wed, 17 May 2000 03:17:08 +1000 From: Don White X-Mailer: Mozilla 4.5 [en] (Win98; I) X-Accept-Language: en To: Aussie Weather Subject: aus-wx: Unusual morning in Canberra Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Throughout the night, Canberra AP has been 6 to 8 degrees warmer than Tuggeranong, in the SW suburbs of the city and only a few kilometres as the crow flies from the airport. currently of -2 at tuggeranong and + 6 at the airport. Hard to forecast?? Don W +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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: Wed, 17 May 2000 08:07:38 +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: cold fronts and warm fronts Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi Tom, Harald and all, Tom Johnstone wrote: > > Wow - I never thought there would be so many responses to my question! > Thanks to all for your very informative posts. It seems that there are a > few explanations of why Australian weather maps don't show warm fronts. The > most common reason given was that Australia sits at lower latitudes than > Europe and the USA, and that warm fronts are usually located at high > latitudes, on the polar side of low pressure systems. However, when I look > at the current weather map for the USA at www.weather.com, > I see a warm front marked across the northern border of Texas, and another > just of the east coast of Florida. The actual URL (map taken from > weather.com) is: I think you also have to take note that the US and Australia both use different methods of front analysis. I personally believe that Australia gets a few more warm fronts then the BoM MSLA's would lead us to believe. The BoM are very conservative (from my experience) in their front analysis. But the large land mass over the US means that low pressure systems can move over the land, rather than slip SE like they do here. The other reason, as Harlald mentioned (and possibly a better explanation), is the more zonal flow over Australia, compared with the meridional flow over the US. Lows like being under upper level troughs/lows. In the US, upper level troughs/lows are amplified over the Rocky Mountains (I wrote an email a couple of months ago about this, explaining the equation etc - I'll paste this at the end of the email). So they don't weaken/drift NE as much in the US. Unfortunately, there's nothing like that here. And even if we did have 5000m ranges over WA, we'd still need to be further south to 'catch' the upper level troughs in late spring/summer. Although they would certainly help! But I'd prefer them a little closer to the east coast :) > This are was refered to this morning as the "dry line", which I remember > there was a discussion about some time ago on this list (whether we had dry > lines in Australia). We certainly have dry lines in Australia. They're most prominent in central QLD, due to the high contrast of DP's - sometimes ranging up to 20C over a small distance! I'm not a big fan of dry lines in Brisbane...they seem to coincide with kata-fronts which aren't much good for us! Here's a section of the email posted around March: If only we had 4000-5000m ranges west of central Queensland, we'd really be having some fun :-) The mountains help induce an upper level trough. As air moves towards to the mountain range, the depth of the column of air is forced to be compressed, through the absolute vorticity equation (zeta + f)/D = potential vorticity Where zeta is the relative vorticity, f is the coriolis parameter that remains constant at a given latitude, and D is the depth of the column of air. The constant, and the coriolis parameter are negative (from memory), in the southern hemisphere. As D decreases, zeta must become more positive to compensate, and an anti-cyclonic curve in the air stream occurs, so an upper level ridge will sit over the first half of the mountain range, and also for a distance 'x' before it. As D increases, zeta must become more negative to compensate, and a cyclonic curve in the jet is induced. Thus, we have an upper level trough forming on the lee-side of the mountain range. This would certainly be an advantage for us :) -- 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------------------------------ From: Chris Nitsopoulos Date: Wed, 17 May 2000 08:35:43 +1000 To: Subject: RE: aus-wx: Please explain User-Agent: IMP/PHP IMAP webmail program 2.2.0-pre10 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Quoting John Woodbridge : > Hi Anthony and all. > > Something a bit wierd seems to be happening. According to the > current MSL charts Brisbane should be in a developing SE regime, which > overnight I would expect to be tending S or SW with clear skies and > rather cool conditions, and indeed, this was the forecast on the evening > > news. But at 11:30pm I find that we have cloud streaming at apparently > quite low level from the NNW, producing light showers and radar shows > precipitation clearly moving in this direction also. > > Bar is steady, so no trough developing, maybe just the result of the > large southern High splitting off a bit into the Tasman giving us a > temporary wind change?? > > John. > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > G\'day John The same type of stratus and stratocumulus cloud was seen in Townsville yesterday evening and it also appeared to be streaming in from the north west which is highly unusual considering that we also had a fresh SE change which hit us yesterday afternoon. However, this morning the cloud seemed to have slowed down but had not yet changed direction(at 6a.m.) Cheers Chris. > 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------------------------------ From: Blair Trewin Subject: Re: aus-wx: Unusual morning in Canberra To: aussie-weather at world.std.com Date: Wed, 17 May 2000 10:33:21 +1000 (EST) X-Mailer: ELM [version 2.5 PL2] Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com > > Throughout the night, Canberra AP has been 6 to 8 degrees warmer than > Tuggeranong, in the SW suburbs of the city and only a few kilometres as > the crow flies from the airport. > currently of -2 at tuggeranong and + 6 at the airport. > Hard to forecast?? > > Don W It's definitely unusual. It seems to be related to the wind; Canberra Airport was reporting light winds (4-7 knots) most of the night, whereas Tuggeranong was calm all night. The two weren't too far apart for the first part of the night, but Canberra Airport then rose from 3.5 at midnight to 6.8 at 0330, whilst Tuggeranong kept falling. (Canberra Airport did eventually fall to 1, probably sometime between 0700 and 0730 based on the half-hourly obs - which is unusually late for a minimum there). Even a comparatively light wind can break down the low-level inversions which are critical to low minimum temperatures under clear-sky conditions. This is even more true over snow cover; I've just been looking at some Scottish observations from late December 1995, when Altnaharra equalled the British record low (-27.2) - on the previous night it went from -24 to -5 and back again during the course of a few hours, all of it in darkness, in response to the commencement and cessation of a light SE wind. Perisher Valley also rose from a minimum of -18.0 to an 0900 temperature of 0.0 in similar circumstances on 29 June 1994 (the day Charlotte Pass set the Australian record of -23). In regions with reasonably homogeneous terrain and a reasonably dense station network (for example, central western NSW and interior SW WA), the upper limit of variation of daily max/min temperature anomalies between adjacent stations is around 4 degrees. (I use anomalies, rather than actual temperatures, here to take into account sites which are consistently warm or cold, e.g. town v airport sites). This number increases considerably in complex topography or near the coast. I'm currently wrestling with the issue (in my extremes verification work) of whether or not a minimum of -12.8 at Mount Hotham was reasonable when Mount Buffalo (340m lower and similarly exposed) only managed -4. Hopefully the new AWS at Dinner Plain (potentially a very cold site) will get something lower than that this winter and save us the trouble of working out whether -12.8 is really a legitimate Victorian record :-) 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------------------------------ Date: Tue, 16 May 2000 20:51:00 -0400 From: "Leslie R. Lemon" Subject: Re: aus-wx: cold fronts and warm fronts To: "INTERNET:aussie-weather at world.std.com" X-MIME-Autoconverted: from quoted-printable to 8bit by europe.std.com id UAA10044 Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Anthony and all: > I think you also have to take note that the US and Australia both use > different methods of front analysis. I personally believe that > Australia gets a few more warm fronts then the BoM MSLA's would lead us > to believe. The BoM are very conservative (from my experience) in their > front analysis. But the large land mass over the US means that low Another major difference between the states and the BoM appears to be the fact that here we use the temperature, moisture fields, and wind fields, along with pressure. Obviously much of the BoM analyses are over the ocean. But I believe that the few ship reports along with the temperature and moisture analysis would help also. Over land, there are relatively speaking, many more surface observations from which the temperature and moisture fields could prove to be very beneficial and revealing. Are there any hand analyses along with the isobar and frontal analyses available on the web? Les ************************ Leslie R. Lemon Radar, Severe Storms, & Research Meteorologist Tel. 816-373-3533, 816-213-3237 E-Mail: lrlemon at compuserve.com +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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------------------------------ X-Sender: jdeguara at pop.ihug.com.au X-Mailer: QUALCOMM Windows Eudora Pro Version 4.2.2 Date: Wed, 17 May 2000 17:24:06 +1000 To: aussie-weather at world.std.com From: Jimmy Deguara Subject: Re: aus-wx: Please explain Sender: aussie-weather-approval at world.std.com Reply-To: aussie-weather at world.std.com Hi John and Anothony, If you look at the water vapour imagery, you will find that the mid-level band of moisture shows well on this. We also had a surprising bit of convection yesterday and it was one of the these bands of mid-level water vapour bands or jet as Anthony calls it. Jimmy Deguara At 00:04 17/05/00 +1000, you wrote: >Hi John, > >First of all - I didn't know you were from Oxely :-) > >The winds at the surface are generally SE, and should remain SE with the >left (and main) split high moving eastwards at a relatively low latitude >to preserve our SE'ly quidge. > >I think that there's a large broad/long wave upper level trough just >inland - it's giving us a strong NW'ly subtropical jet (100-110kn), and >since it's to our west, it's given us generally NW'ly/NNW'ly winds in >the upper-mid levels. But the interesting thing is, is the sudden >cooling of the mid-low levels between 00z and 12z today. 500mb has >remained virtually unchanged (-10C), but 550mb is -12C! Which gives an >effective 500mb temp if -18C! So that shows you that the air is quite >cold...that too has come on the NW'ly/NNW'ly winds...so maybe there's a >little more to our west then actually analysed. (Which may not show up >well on the 500mb charts). But the surface will be SE'ly and should >remain that way. > >Might be some good showers about tomorrow (cloud pending)...can see the >faithful Telstar possibly getting a work out! > >John Woodbridge wrote: > > > > Hi Anthony and all. > > > > Something a bit wierd seems to be happening. According to the > > current MSL charts Brisbane should be in a developing SE regime, which > > overnight I would expect to be tending S or SW with clear skies and > > rather cool conditions, and indeed, this was the forecast on the evening > > news. But at 11:30pm I find that we have cloud streaming at apparently > > quite low level from the NNW, producing light showers and radar shows > > precipitation clearly moving in this direction also. > > > > Bar is steady, so no trough developing, maybe just the result of the > > large southern High splitting off a bit into the Tasman giving us a > > temporary wind change?? > > > > John. > > > > +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ > > 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------------------------------ > >-- >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------------------------------ ---------------------------------------------------------------------------- --------------- Jimmy Deguara from Schofields, Sydney President of Australian Severe Weather Association Inc. (ASWA) http://severeweather.asn.au e-mail: jdeguara at ihug.com.au homepage with Michael Bath note new URL http://australiasevereweather.com/ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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------------------------------