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A study of cold fronts in Australia

I will collect information and observations

2019

Forecast for 532 thickness for Tasmania 6 days into Autumn. which can bring low level snow

low level snow tasmania 6th march 2019

dynamic jetstream AAO negative 4_3_2019

ABOVE

Nothing like a wavy sub polar jet associated with a negative dip in the AAO/ SAM since —early February 2019, to produce dynamic wavy jetstreams at the 200hpa stratosphere.

and satellite picture BELOW ……………………….

is the cold pool in the Bight 5th March 2019. The day before it travails over Tasmania.

The cold pool sits within the bulge of the sub polar jet but at the surface layer

The cold air is transported north into NSW  by the southern  and eastern flank of the

Mid -latitude High

5_3_2019. cold pool ijn the bight

SOURCE. BOM

http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=mslp-thick&tz=AEDT&area=Au&model=CG&chartSubmit=Refresh+View

__________________________________________________________

Temperatures got down to 9.8 deg in Hobart and light splatter of snow on Mount Wellington

Mount Baw baw in Gippsland Victoria also had a light dusting of snow with temps down to 0 deg c for most of the day

NEWS article

Mount Mawson 6th March 2019

quote from Ben ” 6th March 2019

Today’s taste of wintry weather comes less than a week after the state endured a day of record-breaking March heat.

Dover’s 40.1 degrees on Sunday was the first time on record any location in Tasmania has exceeded 40 degrees during March.

Eight other weather stations, including Hobart (39.1C), also beat Tasmania’s previous March maximum temperature record of 38.0 degrees on Sunday.

Impressively, Hobart’s 39.1 degrees on Sunday was also hotter than any day in the city during summer. Last season’s highest temperature was 37.9 degrees.

Sunday’s heat now seems like a distant memory, as much colder southwesterly winds flow over the state today.

Hobart was only sitting on 13 degrees at 10am, although wind chill was making it feel more like eight degrees.”

16 comments on “A study of cold fronts in Australia

  1. The cold snap made it to the NSW alps
    http://www.weatherzone.com.au/news/autumn-bites-back-in-nsw-alps/529380

    Ben Domensino, Thursday March 7, 2019 – 16:03 EDT

    Perisher Valley registered Australia’s lowest March temperature in ten years on Thursday morning.

    A pool of cold air passing over southeastern Australia behind a strong front sent the mercury plummeting on Wednesday. The wintry blast caused snow to settle in Tasmania and Victoria.
    By the early hours of Thursday morning, the temperature at Perisher Valley had dropped to a numbing minus 5.9 degrees. This is the lowest temperature measured anywhere in Australia during March since 2009.

    This cold weather comes after an unusually warm start to autumn in southeastern Australia.

    On Sunday, Hobart experienced its hottest March day on record after reaching 39.1 degrees. Dover’s 40.1 degrees on the same day was the first time in recorded history any Tasmanian location has exceeded 40 degrees during March.

    Perisher Valley managed to reach 23.6 degrees on Monday afternoon, almost 30 degrees warmer than it was on Thursday morning.

    Australia’s lowest March temperature on record was -7.2 degrees at Kiandra Chalet in NSW during 1964.

  2. 29th 30th march. intense cold pool beings low level snow and overnight tmps’ not seen since 2008 apparently. News said coldest march morning in 15 years
    Sydney coldest march night in 11 years (news)
    forum comments
    http://forum.weatherzone.com.au/ubbthreads.php/topics/1496806/55

    wave rider”To get an idea of true coldness I have compared data at Thredbo Top Station where it got down to -4.2°C this morning which is the coldest March temp since 2001 (-5.0 on the 28th). It’s also interesting to note Feb 29th 2008 got down to -5.7°C so if it wasn’t a leap year it would have been 1st March.”

    steve777″It’s quite chilly around Sydney this morning with a few sub-10 minima about, probably the coldest March morning for a decade or more at most / many Sydney sites, e.g:

    Sydney OH: 12.5, coldest in March since 2005 (when 12.1)
    Bankstown: 9.3, coldest in March and first sub 10 in March since 2008 (when 8.3)”

    waverider..”2008 comes up again in terms of records, 31st March 2008 was the coldest March morning on record for Albion Park getting down to 5.0°C. Bellambi’s previous coldest night was also on that date, but the 10.9°C there this morning was a record. Shows just how rare strong cold fronts are in March. Nice to see cold records can still be broken and this is not even related to inversions or anything like that, just almost unprecedented March cold.”
    balir trewin’
    No records at Sydney or Brisbane, although both had their lowest March minimum temperatures for more than a decade (since 2008 in Brisbane, 2005 in Sydney).

    There were a lot of March record low maximum temperatures on Saturday, but most were at short-term stations. Those at longer-term sites (30 years or more) were mostly clustered in northeast Victoria (8.6 at Omeo was one notable) and central west NSW.
    http://forum.weatherzone.com.au/ubbthreads.php/topics/1496872/Re_Vic_first_grunty_cold_front#Post1496872

  3. Following on from above
    crikey >>>>seabreeze
    http://forum.weatherzone.com.au/ubbthreads.php/topics/1496919#Post1496919

    Certainly noticed the coolness this morning, so not surprising to see last night was the second coldest March minimum temp on record at Smoky Cape (temperature records since 1957):

    11.0°C, 24th Mar 1998
    12.6°C, 31st Mar 2019
    12.8°C, 20th Mar 1970
    12.9°C, 28th Mar 1984
    13.4°C, 13th Mar 1994
    __________
    1998
    1984
    1994
    2019
    all years of solar minimum
    not sure about 1970

    I believe the cold pool was produced by a sharp decline in the AAO . Maybe this doesn’t happen very often in March?
    Interesting for me because it links solar to the antartic oscillation on a simple correlation quite well
    No sunspots or more likely some other solar variable makes the westerly belt go slower causing perturbations and cut off cold pools?
    You would need to check how often AAO declines sharply in the month of march.

    30th March 2019. Cold front reaching latitude 29s
    AAO had sharp decline from the 17th March +2.0 to the 26th March +0.3

    http://www.bom.gov.au/cgi-bin/charts/charts.browse.pl

  4. Thanks to Ken Kato . senior meteorologist posting on weatherzone.
    this information on identifying a cold front.

    “Basically just like anywhere else. Typically, winds suddenly shift from mild or warm northwesterlies to colder southwesterlies (in the southern hemisphere) when the front passes through with decreasing pressure ahead of it and suddenly rising pressure behind it. Often the fronts are dry but occasionally they’re accompanied by a rather narrow (usually) cloudband and precipitation.
    Often, cold fronts are also accompanied by an upper trough which is usually their upper level component and which can form a cloudband that’s a lot bigger than what would be caused by just the surface front itself.

    You can identify them using a combo of satpics (for the fronts that are accompanied by cloud), radar, models (these days there’s also various specialised products that automatically attempt to plot fronts which can be a useful first guess), together with the surface obs fields of temps, dewpoints, winds, pressure, etc.

    In other words, you’re basically looking for a distinct boundary separating two airmasses with contrasting temps (the core definition of a weather front) where winds suddenly shift direction which is also often accompanied by the aspects mentioned above.
    As for what criteria to use in terms of exactly how much temperature difference there has to be between the airmasses and how sharp that gradient is, I think it’s pretty subjective but anything more than a few degrees across a sharp boundary would be fair game in my view, especially if it’s accompanied by some or all of the other classic frontal signatures.

    Above is a past example of a cold front that went through this area which might help illustrate this.

  5. 9th_10th May 2019 Cold pool , cold front. From south SA into NSW and reaching possibly into SE QLD.
    The sub polar jet forms a tight bend for the surface low to form but the cold pool sits on the SE flank of the incoming high. Note also the tropical storm in the coral sea for May
    This synoptic from ACC g (BOM) is a forecast. I will do a follow up here of what happened as the event progresses.


    http://www.bom.gov.au/australia/charts/viewer/index.shtml?type=mslp-thick&tz=AEDT&area=Au&model=CG&chartSubmit=Refresh+View
    ___________________________
    The diagrams below show how an intense low sits behind the cold pool and an intense high pressure cell extends a ridge right down to the polar Antarctic.
    The cold polar air pool is driven northward into the mid latitudes. Right up to 30s
    actually.
    AAO is pos’ neutral and polar belt has just transitioned from a 5 low node symmetric belt into an un-organised state here.
    It is also noted that the 500hpa winter jet stream extends to 30s . Not the 200hpa
    Also of note is the reason for the moisture with this cold pool.
    Track the NW/SE tropical conveyor belt down into the polar low and also across the southern flank of the incoming high

    —————————-
    Real time data now. Here is satellite pic’ 8th may as cold pool and cold fromt approach SA coast lone. Notice the cold pool being projected northward

    result

    ———
    10th May 2019 4.20pm
    Wind change starting to arrive at Armidale NSW. It has been windy ahead of the change with NNW in the 30’s and gust as high as 59 km/hr with WNW.
    The cold pool has started to move in there.16deg c at 2pm and 11.6 deg c at 3.30pm.
    So that’s a drop of 4.4 degrees in one and a half hours.Feels like 4.9deg c there currently
    http://www.bom.gov.au/products/IDN60801/IDN60801.95773.shtml
    We have a thin pre-frontal cloud band west of the divide currently.4pm obs’to mark the in coming cold front interface.
    Northern tip of cold front looks to be around the latitude of Emerald QLD currently , so that’s an impressive incursion of the southerly cold pool
    I will say l saw some mid layer cloud coming from the NE this morning . So there must be some moisture feeding into this front.
    Quite a bit of patchy cloud around today as well, Off the coast, on the coast at the TWEED and over the hinterlands a tad of cumulus

    Stationary storm over cape Patterson, Gippsland coast , Victoria
    left a blanket of hail on beach and coast.

    http://www.weatherzone.com.au/news/long-lived-severe-storm-hits-victorias-gippsland/529697

    http://www.weatherzone.com.au/news/cape-paterson-hailstorm-blankets-gippsland-beach-as-wet-weather-sweeps-across-victoria/529695


    ——-
    Cold front made it right up to 23.5 deg latitude , thats Emerald Queensland latitude


    thanks to Ken Kato weatherzone forum for this capture

  6. A positive AAO in june 2019
    Stratospheric warming in the SH in JUNE and into Julyhttps://weathercycles.wordpress.com/2019/07/01/stratospheric-warming-in-the-southern-hemisphere-2019-and-onward/
    Cold fronts and associated sub polar troughing peaking in SW WA. Bad for ski fields
    Would love to know what determines the peaking longitude position of these high amplitude troughs?
    The picture below shows a high amplitude trough peaking in SW WA on 4th July 2019.Of note is the northerly extent of its reach. It will dip to the SE in the coming days just giving Victoria some of the dregs’

  7. Late evening 10th July 2019..
    Northern flank of deep low pressure system encroached on Victoria. Here is rhe radar captured by ski.forum member ‘kletterer’
    https://www.ski.com.au/xf/threads/observations-7th-to-15th-july.85125/page-4#post-3958880

    showing this intense wind mixing pattern. Many calls
    in frankston for the SES l heard on the news.

    https://ski-forum.imgix.net/2019/07/124312_65453c8a8a013307f1be9de49d3ae183.png?w=1600&q=85&fit=max&auto=format

    Thanks to ‘gregah’ for posting this snap of radat at 10pm the 10th July showing a strong rain band and storms in the northern flank of this strong low.
    Hobart mslp was 991hpa in the early evening

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