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Discussion in 'Daily & Chat' started by Jellybeans, Jul 4, 2019.
Synoptic systems don’t seem to have much influence either
@Rainbow Serpant errr how do you figure that? Synoptic systems are THE main influence at those types of latitudes. Big frequent cold fronts sweeping across southwestern WA are the very reason why they've gotten so much rain. Have a look at the chart archives. Cold fronts are synoptic systems.
And synoptic systems such as persistent ridging up the coast are also the main reason why they've been preventing much rain for eastern QLD because of their effects on La Nina while widespread wetter than normal conditions developed over large sections of the interior in recent months.
Post made back in September:
@Rainbow Serpant ahh that old chestnut again. I'm not sure if you actually read what others have posted here that answered your very question. You even replied to a post about how La Ninas don't cause above average rain in the exact same areas each time. And here's another post I made elsewhere recently about it:
" For those who keep going on about how the predictions for a La Nina happening were supposedly "wrong", please READ the posts - by very definition, a La Nina officially is, and ALWAYS has been an ocean phenomenon where eastern central Pacific waters near the equator temporarily become cooler than normal, which then often causes its own atmospheric circulation - it is NOT, and NEVER EVER has been decided by whether an area gets lots of rain or not.
For examples of official definitions of La Nina from national weather agencies, refer to http://www.bom.gov.au/climate/enso/lnlist/ and https://w1.weather.gov/glossary/index.php?letter=l
La Nina and El Nino are terms that originated from Peruvian fishermen to describe the periodic dramatic cooling and warming of waters off their coast that has a big effect on their fishing industry. El Nino is Spanish for “the boy” or boy child and its effects there typically tend to be most pronounced around Christmas time. La Nina translates to “the girl” or girl child and is the opposite to El Nino.
While the majority of past La Ninas have historically caused widespread above average rainfall in sections of central, northern and eastern Australia and therefore shift the odds in favour of flooding rain in these areas, they don't and never have caused this rain in the exact same areas every time, nor at the same time of the year, nor with the same intensity.
We've said this time and time again over the years in ENSO-related posts... and in fact, we did a post dedicated to this very thing back in September even before the La Nina really ramped up where we even put a big red exclamation mark at the very start of the post to highlight this!
Have a look at these historical rainfall patterns from past La Ninas to see how the affected areas are often different each time: http://www.bom.gov.au/climate/enso/lnlist/
The predictions for a La Nina DID end up being correct because not only was the pre-determined La Nina criteria (which has never been based on rainfall amounts) met back in September, they've also been sustained ever since. In Australia, these criteria are a minimum of at least three of the following:
1. Sea surface temperature: Temperatures in the NINO3 or NINO3.4 regions (eastern central Pacific Ocean) are 0.8 °C cooler than average.
2. Winds: Trade winds have been stronger than average in the western or central equatorial Pacific Ocean during any three of the last four months.
3. SOI: The three-month average SOI is +7 or higher (not the daily or monthly average).
4. Models: A majority of surveyed climate models show sustained cooling to at least 0.8 °C below average in the NINO3 or NINO3.4 regions of the Pacific Ocean until the end of the year.
It also pays to look beyond one's own backyard whenever a weather or climate phenomenon affects a region or country – SEQ, or eastern QLD in general for that matter is NOT all of Australia. As also posted so many times already, in the case of the current La Nina, above average rainfall affected huge sections of the deep interior of Australia and parts of SE Australia over the last few months. "
La Nina has NOTHING to do with what you believe or don't believe. It's not opinion. Nor has it EVER been measured by how much or little rain falls in a given area.
Widespread above-average rain is one of the common end-effects of La Nina but that end-effect has never decided whether a La Nina exists, and the geographical positioning and timing of that rain is also different from La Nina to La Nina.
The article I linked above talked about that:
One of the reasons for this has been unusually strong upper-level ridges near southeastern Australia, which have prevented cold fronts from moving up over the eastern half of the country. Instead, these rain-bearing fronts have been hitting the southwest and then dropping down into the Southern Ocean.
The result of this abnormal synoptic pattern has been prolific rain in southwestern Australia and not much rain elsewhere.
Perth is already having its wettest November in records dating back to 1876, with 84mm in the gauge so far this month.
Basically, WA has benefited from our suffering.
Ferny Grove Weather
Date: 20 Nov 2020
Time: 9:10 AM
Min Temp since 9am yesterday: 15.5 C
Max Temp since 9am yesterday: 28.3 C
Min Ground Temp: 13 C
Rain since 9am yesterday: 0 mm
Temperature: 26.1 C
Relative Humidity: 56 %
Dew Point: 16.6 C
MSL Pressure: 1021.8 hPa
Wind Speed: 11 kph - light breeze
Wind Direction: ESE
Present Weather: State of sky generally unchanged during preceding hour
Visibility: 20km to 39km - Very Good Visibility
Cloud Cover: 2/8
Ground State: Ground dry
Notes of yesterday weather -
19/11/20: Partly cloudy with Cu and Sc clouds. Smoke haze. Warm early in the day with the temperature stable during the early hours, became near average in the morning and was slightly cool from the late afternoon becoming near average in the evening. Variable temperature from the mid morning to the mid afternoon and rose a little slowly later in the morning to the maximum temperature in the early afternoon. Early in the day the dew point fell slowly, rose slowly in the morning close to average before falling from the mid afternoon, rose slowly in the early evening before falling later in the evening while remaining close to average. Relative humidity fell slowly early in the day slightly below average, fell from the early morning and returned to near average. Early in the evening the relative humidity became slightly below average before returning to near average later in the evening. Light S to SW winds in the early hours and early in the morning, backed during the morning to S to SE in the mid afternoon, SSE to ESE later in the morning, followed by E to SE winds in the afternoon and early evening before calm winds later in the evening.
Today: The temperature have been near average today that fell steadily in the early hours and warmed quickly this mornnig. The dew point was stable and near average in the early hours, rose in the early morning before becoming generally stable while remaining close to average. Relative humidity was near average early in the day while rising slowly, then fell quickly this morning and became moderately low while falling quite quickly. Calm winds early before SSW to WSW winds in the early morning and followed by E to SE winds.
There is a La Nina in place. That is an objective fact. The term "La Nina" is not synonymous with above average rainfall over eastern Australia; it refers to a state in which the SSTs (sea surface temperatures) in the central and eastern equatorial Pacific Ocean are cooler than normal, which is typically associated with anomalously high MSLP in the Central Equatorial Pacific and anomalously low MSLP over the maritime continent and northern Australia, along with stronger than normal trade winds across the Pacific.
As such La Nina increases the likelihood of, but does not guarantee, above median rainfall over eastern Australia. La Nina tends to increase the inflow of moisture laden air into the maritime continent and northern Australia region, but whether or not this enhanced moisture actually advects southward into non tropical eastern Australia and is activated - i.e. made to condense into liquid droplets to form clouds and rain - depends on the local synoptic patterns, and while La Nina also tends to increase the likelihood of synoptic patterns which are favourable to rainfall in both tropical and non tropical eastern Australia, there are other important factors that, as Ken put it in a recent post, may either reinforce or counter the influence of La Nina on these synoptic weather patterns and therefore on rainfall over eastern Australia. To cut a long story short, ENSO influences, but does not determine, rainfall over eastern Australia; La Nina increases the likelihood of, but does not guarantee, above average rainfall over eastern Australia.
This La Nina event was a late starter. Whereas La Nina events typically commence in autumn, the current La Nina started (reached La Nina thresholds) in September of this year (2020). Thus last month (October 2020) has thus far been the only full month since early 2018 in which ENSO has been in a La Nina state. And October did see above average rainfall averaged over eastern Australia as a whole; 45.60 mm as compared with a mean of 37.4 mm for all Octobers during the 30 year period from 1961 to 1990.
A considerable proportion of SE Queensland received above median rainfall last month, including in the Rockhampton region.
It is true that it has been very dry lately in Rockhampton; the last year which saw above median rainfall for the Rockhampton region was 2017, and like much of SE Queensland, Rockhampton's annual rainfall was very low in both 2018 and 2019. As a result the ground in Rockhampton was undoubtedly very dry by the beginning of last month, and virtually all of the water which fell as rain in the month would simply have been soaked up by the soil, and therefore not run off into creeks, rivers or dams etc. Furthermore, the rain which fell on SE Queensland last month was mainly due to thunderstorm activity, and as a result, there would have been considerable variability in October 2020 rainfall between different locations in SE Queensland. So it is quite possible, for all I know, that you had the misfortune of receiving low (below median) rainfall at your place in October. And Rockhampton airport has recorded no rainfall so far this month (November 2020) as at two thirds of the way through this month. So it is unfortunate, but hardly surprising, that conditions are currently so dry on your property - even if you did receive above median rainfall last month.
Regarding the possible factors which may be causing the low rainfall so far this month in eastern Australia, despite the presence of La Nina, I suggest that you read some of the posts on this thread, as a large proportion of them discuss possible factors which are responsible for rainfall over eastern Australia being so low so far this month. In particular, I believe you will find some answers to your questions at this site originally linked to by Mezo.
I'm going to assume that you were engaging in hyperbole when you said that this dry weather would never end, as there is obviously no way to be certain whether or not any given future period will see above or below median rainfall during any given future period. Sooner or later, a big rain will come; it's just a matter of when.
I hope this helps; and I hope your rain comes sooner rather than later. GOOD LUCK!
The sky to my South-west is looking really good atm, Solid looking updraft.
If I didn't have sciatica problems I would take a drive, so hoping these storms make it toward the coast.
This is why it’s so dry
Here in Yeppoon we have had water fall from the sky but it's light showers that come over for about 15 secs then stop . Around 1mm in it . Not much.
I can't remember if it's normal for this time of year but the wind has gone straight Easterly and it's comfortable, sure it's humid but it's windy it's not a super warm wind. 26 deg now feels like 24 deg.
If you look at the Meteye it has feels like temps in the mid 20's until about Tuesday then winds NW/N then NE in the afternoon and feels like temps around 28-30deg
Then Thursday back to Easterly winds and feels like temp around 25-26 in the afternoon.
It's nice when at this time of year the temperature feels cooler rather than hotter than it is. Sooner or later maybe in a month or two for a few weeks you know it's going to get nasty with humidity in the new year like it always does.
That's not why. It's just a map that confirms, yes, it's been dry.
I often wonder if the huge amount of land clearing and the subsequent degradation of the soil and the soils ability to hold moisture without trees/plants has a contributing effect on how dry things are. Water being drawn out the the river systems creating dry creek beds that usually had some water in them (like Rainbow Serpant mentioned). The sheer amount of land that has been cleared out SW of Brisbane in the new suburbs is massive. When we were kids thats where the storms used to roll across then march on towards Brisbane now they just seem to die or have freak 13cm hailstones.
Didn't they clear a million acres a year in the 70's in SW WA or near the Wheatbelt? I remember seeing a video on it about 15 years ago.
Surely that is one factor behind the drying climate down there.
By the way in Cairns 40 percent humidity dew point 15.9 deg 31 deg feels like 27 deg, that's not too bad for November on the comfort scale !
@Vinny the drying climate there and SE Australia as far as winter/early spring rainfall goes is because of the distinct longer term southward contraction of the midlatitude lows and cold fronts, associated with the southward contraction of the southern polar vortex.
It’s been extensively analysed and documented, and has also been in line with longer term projections.
But future warm season rainfall has more uncertainty.
If the SAM is trending more positive, shouldn't that mean an increase in trade winds and more rainfall?
@Stumer1 only in some parts of eastern Australia and only at certain times of the year. Also, it’s not much use even for our area having positive SAM if we’re also getting more frequent broad areas of high pressure which extend ridging up over us all the time. We need high pressure and accompanying ridges to stay much further south at the right time of the year so we get an onshore flow with a good moist easterly fetch onto our coast.
The longer term increase in positive SAM has had a big detrimental effect on cool season rainfall in the southern half of Australia because of less cold fronts and lows being able to reach as far north.
As below....Note the Manly West is still much cooler than the Wynnum North site, with identical equipment at both sites...So far this month Manly West average max 0.8C less than Wynnum North, Manly West average min 0.7C less than Wynnum North.
I could be wrong, but my understanding has been that a positive SAM means that the synoptic weather systems are further south than normal for the time of year, and that in the warm season this means that there is less ridging
and lower pressure up the eastern coast of Australia, allowing, among other things, rain bearing tropical systems to move further southward. Thus I would have thought that "having positive SAM" would tend to reduce the frequency of "broad areas of high pressure which extend ridging up over us all the time". Is there something wrong in my understanding?
Nah that's correct. But that's given all things equal. If there's something else either related or not related to SAM changes that's causing so much stubborn high pressure to ridge up our coast so much, it doesn't matter that much how positive SAM gets, we won't get a good onshore flow to help enhance our rainfall because that ridginess will prevent a good fetch of easterlies. Instead we get southeasterlies and subsidence aloft which discourages good widespread rain, especially if that ridginess extends through the midlevels as well.
Q. Any intel on a light aircraft doing laps over Brisbane ATM. Fairly regular every couple of days and there for several hours. Fairly high circa 10000' I would estimate. High wing, single engine. Training or aerial photography? Doesn't seem to have ADSB. Just curious.
BOM's state forecast is talking about an upper low in central Queensland at the end of the week.
Hmm, isnt that good for us?
On the subject of trees, if every tree on this planet is chopped down, what will happen?
Get my drift?
We will no longer exist.
We need tree herders
But not near houses or infrastructure, for every tree felled, at least 5 or even more must be planted elsewhere away from population.
i have always found, when WA is wet, QLD coastal area's are dry ,especially in the cooler months
Yeah that's often because longwave troughing is in place over WA longitudes when that happens but the typical wavelengths mean that when that occurs, we're under the influence of the downstream longwave ridging or on the backside of longwave troughing just to our east.
Thunderstorms on the eastern slopes of the ranges spread their anvil cloud over the coast around here late this afternoon / evening.
So far this spring, it hasn't got any warmer than 31.8°C at Kempsey Airport (22-23kms inland), 31.3°C at Coffs Harbour Airport (1km inland), and 32.2°C at Port Macquarie Airport (5-6kms inland). Those temps at all three places occurred on September 22nd.
Kempsey and Coffs are forecast on Monday to reach 35 and 33 degrees, respectively. So they might better what they have recorded so far this spring.
Thank you for your reply, Ken.
It seems then that my understanding was not so much wrong, as incomplete. That raises a few questions:
Does a positive SAM tend to favour lower atmospheric pressures along the eastern Australian coast in the middle and/or upper levels of the troposphere as well as at and near the surface?
Is the positioning of the LWT(s) in and near Australian longitudes one of those other factors (in addition to SAM) which can affect the degree of high pressure ridginess up the eastern Australian coast?
According to this article, the Antarctic polar vortex is unusually strong for this time of year (November), which "will promote a positive Southern Annular Mode (SAM) as we head into summer". Does that also have the potential to influence those "other factors" to which I alluded in question 2?
The temperature was close to average during the day and was a little variable from the mid morning to the mid afternoon. Tonight the temperature have remained close to average while falling steadily. The dew point was generally stable in the morning, rose slowly in the afternoon before falling slowly tonight while remaining close to average.
Relative humidity eased to slightly below average in the mid morning and to near average later in the morning as the relative humidity fell more slowly from the mid morning. Near average relative humidity in the afternoon and tonight. Light E to SE winds were followed by SE to NE winds from the mid morning, ESE to ENE winds in the afternoon, E to NE later in the afternoon and early tonight before calm winds during the rest of tonight.
Last 24 hours:
In answer to your first question, the way the SAM's measured actually uses the midlevels themselves i.e. it's also known as the antarctic oscillation index and uses the height of the 700hpa level then compares it against climatology for that height using a loading pattern. But I can't recall whether positive SAM would favour lower pressures at the surface or mid/upper levels along the east coast and it'd also depend on the season. It'd also depend on not only the high pressure belt being further south (which would normally lower surface pressures over our part of the coast) but whether highs become broader as well (which would counteract those lower surface pressures) or stay the same. The key for us as far as rainfall's concerned during positive SAM phases isn't the absolute value of pressures themselves - it's whether the north-south distribution of those surface pressures causes a moist onshore flow for us, and whether the distribution of the midlevel heights cause upper troughing just to our west or not.
And a southward shift of those highs may or may not be necessarily reflected by lower heights in the mid and upper levels compared to climatology. If you leave climatology out of it, a southward contraction of the midlatitude cyclonic belt and the high pressure belt just to its north would generally mean higher mid/upper level heights if all other things remained equal because heights generally increase the further you move towards the tropics. There should be some papers online somewhere which answer the part of your question about the effects on pressures and midlevel heights in our local area.
To answer your second question, in a way, yes. A stagnant longwave pattern featuring a LWT over WA or SA longitudes is usually accompanied by downstream longwave ridging closer to eastern Australia. Highs like to sit in areas near, or a bit to the east of longwave ridging. So if you get a longwave pattern that favours highs sitting in the Tasman Sea, those highs will often extend a stubborn ridge up the coast. Even longwave patterns that favour highs out in the eastern Tasman can cause them to extend stubborn ridges all the back up the coast.
As for your third question, it'd have an effect on longwave patterns in general - a contraction and tightening up of the polar vortex generally leads to a less meridional longwave pattern and La Nina may enhance the positive SAM phases even more. But it's uncertain how much of an effect it'll have on the actual positions of the LWT's themselves this season. They have preferred positions (not to the extent of the northern hemisphere though) but they can shift depending on how mobile or not the longwave pattern is and how many waves there are in the pattern at any given time which also affects how changeable or unchangeable the overall pattern is.
WYNNUM NORTH ( 27.4S 153.2E ) - WEATHER
( DATA FROM 0900 PREVIOUS DAY TO 0900 CURRENT DAY )
21 NOVEMBER 2020
CURRENT DEW POINT.......18C
CURRENT WIND.........E 3Kph
CURRENT CLOUD.....1/8 Cu
CURRENT WEATHER...No significant weather
RAIN SINCE 0900 FRIDAY...0.0mm
SUMMARY LAST 24 HOURS
YESTERDAYS MAX TEMP..........29.1C
THIS MORNING'S MIN ..........17.1C
PAST 24 HOURS TEMP ANOMALY...0.00C
THIS MORNING'S GRASS MIN.....15.4C
AVERAGE 24 HOUR DEW POINT......18C
AVERAGE 24 HOUR PRESSURE...1020.5Hpa
PAST 24 HOURS MAX WIND.....NE 24Kph 1550
PAST 24 HOURS SIG.WEATHER..No significant weather.
NOVEMBER RAINFALL TO DATE.............18.0mm
NOVEMBER AVERAGE RAINFALL............105.0mm
2020 RAINFALL TO DATE...............1188.0mm
AVERAGE ANNUAL RAIN TO END OF NOV...1026.4mm
Wow from a national perspective next Saturday 28/11 - Monday 30/11 looks like an historic heat event for large parts of the continent. Looks like 46 degrees for example in Mildura Victoria which would threaten records
Time to plan for a fire event this season again, repeat of 2019. Comments are short and sweet, otherwise people will get annoyed
7 months until snow season, days are counting...
Thank you for your Answer, Ken. It seems that the more I learn about meteorology, the more intricate and complicated the weather system seems. Just one question: what do you mean by the phrase "a less meridional longwave pattern"?
No worries Brett. Meridional = very wavy with big northwards and southwards excursions. Less meridional (zonal) = straighter west to east pattern. But even with a more zonal pattern, you'll still get waves in the pattern as well as individual synoptic systems arcing up and down as they pass through LWT's and LWR's.
Next weekend is shaping up to be nasty for fires especially in sth aust and Vic with temps getting up into the mid to high 40,s with gusty winds.This will migrate into nsw late weekend.This weekend may well go into record books.And SE Qld will also cop this heat not as extreme but hot enough.
I think people including myself get annoyed because of comments from some people whose only interest always seems to be trying to ridicule declarations of phenomena (despite how many times it's been pointed out what the criteria actually is), without any interest in the meteorology behind it or even trying to understand the basics of it. And I'm not referring to highly technical talk that only a few may understand either, nor just good day to day banter.
It's starting to resemble facebook rather than a weather forum. Fortunately though, the majority of people on here are still good.
The reason why I've never had facebook
Ferny Grove Weather
Date: 21 Nov 2020
Time: 11:50 AM
Min Temp since 9am yesterday: 16.7 C
Max Temp since 9am yesterday: 29.8 C
Min Ground Temp: 13.9 C
Rain since 9am yesterday: 0 mm
Temperature: 29.6 C
Relative Humidity: 48 %
Dew Point: 17.4 C
MSL Pressure: 1020.1 hPa
Wind Speed: 9 kph - light breeze
Wind Direction: E
Present Weather: Clouds generally dissolving or becoming less developed during the preceding hour
Visibility: 20km to 39km - Very Good Visibility
Cloud Cover: 1/8
Ground State: Ground dry
Notes of yesterday weather - 20/11/20: Mostly sunny with Cu and Sc clouds. The temperature was a little variable from the mid morning to the mid afternoon. Dew point was near average over the entire day, which was stable early in the day, rose in the early morning became stable in the morning, slowly rose in the afternoon before falling slowly in the evening. Relative humidity was near average early in the day while slowly rising, fell quickly in the morning and became moderately low, then eased during the morning returning to near average in the late morning as the relative humidity fell more slowly before near average relative humidity during the remainder of the day. Calm winds early, then SSW to WSW winds in the early morning tended E to SE that became SE to NE from the mid morning, ESE to ENE in the afternoon, E to NE later in the afternoon and early evening before calm winds during the rest of the evening.
Today: Near average temperature in the early hours before rising fast this morning and became slightly above average in the early to mid morning. Since the mid morning the temperature have rose more slowly but is rising steadily whilst returning to near average. Early in the day the dew point was stable and close to average, rose in the early to mid morning before generally stable but a little variable dew point since the mid morning while remaining close to average. Relative humidity was near average early in the day while rising slowly, then fell quickly in the early to mid morning and became moderately low. Since the mid morning the fall in the relative humidity has slowed and returned to near average. Calm winds early, then light WSW to SSW winds in the early morning, then SE to NE winds with some N to NE winds earlier this morning and some S to SE winds later this morning.
Is it wrong to associate a La Niña event with increased chances of rainfall? I’m guessing it is by some of the posts preceding. Therefore it’s also wrong to be asking questions and posting observations that are perpendicular to the consensus surrounding a La Niña.
The BOM state on their climate updates and I quote that La Niña “typically increases the chance of above average rainfall across much of Australia during spring, and across eastern Australia during summer”. So with a few earlier posts eluding to this being an atypical La Niña by ways of below average rainfall only to get responded with ridiculous green ticks and red crosses or discounted as Facebook talk. I’d like to ask why looking at the effects or the tangible elements we can all see and experience make a small few of you go a little cranky?
Im not sure about the rest of you but weather is something I like to see/feel/hear. Sitting on a computer looking a a temperature change of 0.5D in the middle of the Pacific 5000km away does nothing for me unless it correlates to something real or physical that I can touch or feel locally. I don’t live on the internet. I have a house in Rockhampton and a small property at Cawarral with now only 3 cattle and one horse. I had 60 heathy cattle on average from 2008-2019 and 3 horses. So what falls from the sky is important to me, so please don’t try tell me La Niña is only about SSTs, Trade Winds, or SOI etc. I, like so many others want to see it produce something that can be a benefit, rain.
I have spoken!
Nothing wrong involving the mention of what you’re experiencing weather wise. However, you have consistently mentioned through multiple forums that there simply is, no La Niña, over and over again. Well there is - simple as that. Science shows it, observed weather in many other regions nationally and internationally show it.
May I rephrase. I’m yet to see any on the ground results of a La Niña. Without looking at a sat temp pic of the central pacific I would call what I’m seeing locally as El Niño. Feed has become expensive, let’s call it a Moduki La Nada thus far
@Rainbow Serpant No it is not wrong to associate a La Nina with increased chances of rainfall. Has anyone stated otherwise? But increased CHANCES is exactly what it is. How does increased chances translate to "a La Nina causes increased rainfall in the same areas each time"? Big difference between the two. Therefore it IS wrong to assume that just because a region doesn't get increased rainfall in a particular La Nina, then it musn't be a La Nina.
You say, "I’d like to ask why looking at the effects or the tangible elements we can all see and experience make a small few of you go a little cranky?". But that's not what you did? No-one said there's anything wrong with that in itself. But what you did was then use that to keep ridiculing the meteorological reasoning behind the existence of a La Nina, even after the definition of a La Nina was spelled out a number of times.
You also said "sitting on a computer looking a a temperature change of 0.5D in the middle of the Pacific 5000km away does nothing for me unless it correlates to something real or physical that I can touch or feel locally... so please don’t try tell me La Niña is only about SSTs, Trade Winds, or SOI etc".
Sitting on a computer looking at a temperature change of MORE than 0.5 degrees (not 0.5 degrees at all and furthermore, the cooling encompasses a huge chunk of the eastern central equatorial region of the Pacific if you read the posts) in the middle of the Pacific 5000km away is the ONLY way you can get any idea of what's happening on a much broader scale in the atmosphere and ocean which is what La Nina is.
And as has also been posted, it's not just the huge tongue of much cooler than normal waters extending across the eastern central Pacific. It's also most of the other key components of La Nina such as the much stronger than normal trade wind flow that developed across the tropical Pacific back in late winter (almost reaching damaging strength in some parts of the far north tropical coast of QLD on a number of occasions), the much higher than normal moisture levels that kept getting advected across the tropics then down through central and SE Australia, decreased cloudiness near the international date line, etc etc. All those are classic components of La Nina. That's what a La Nina is, and always has been.
How does simply going by what you can touch or feel locally give you any idea of how the rest of the ocean and atmosphere's behaving across many thousands of km, let alone give you any idea of whether there's been lots of rain in other states, or even on the other side of the same state in which you live?
As has also already been posted about many times, the observed rainfall maps above for the Aug to Oct period (not including the current dry break this month) are great examples of how it should never be assumed that just because it’s been dry in eastern QLD in recent months, then it must have been like that everywhere else in Australia as well. There's a lot more to Australia than just eastern QLD in general for that matter.
Many locations in those areas also received their best rain in many years after years of very low rainfall, particularly over the deep interior.
Areas like southern parts of the Murray Darling basin did particularly well with many of the water storages having experienced inflows even greater than the amounts they were able to release.
The bottom line:
It's never had anything to do with opinion, who's right or wrong, whether you should agree to a certain line of thinking or not, etc.
This is what the official criteria is: http://www.bom.gov.au/climate/enso/outlook/#tabs=Criteria
It's not just a matter of ticking a few boxes for the sake of it either. Those criteria are there to clearly distinguish a La Nina from other ENSO states, and they also reflect the key behaviours of the atmospheric response when a La Nina occurs and couples with the atmosphere.
La Ninas have ALWAYS been an ocean phenomenon that’s often accompanied by an atmospheric circulation which also often manifests itself through the SOI, trade winds, etc. Hence why the term originated from Peruvian fishermen.
Widespread areas of above average rain are just one of the common end-effects of La Ninas compared to non La Nina years but whether a given area gets above average rain has never defined what a La Nina is.
Furthermore the same areas most certainly aren’t affected every time either, nor at the same times of the year, and nor at the same intensity because of the modulating effects from other climate drivers on rainfall.
It's like having a particular disease but "only" experiencing 3/4 of its common symptoms (the end-effects) of that disease..... and therefore ridiculing all the years of proven medical science that identify the disease and concluding you don't have it, even though blood test results, biopsies, or microscopic examination of tissue samples clearly show that you do. In La Nina's case, rain is just one of the common symptoms - it is not the disease itself, nor does the absence of that particular symptom mean that you don't have the disease.
Nice post Ken.
It's also worth noting that many of those positive anomalies across the Top End were in fact record breaking in the context of all years, La Nina or El Nino. Having travelled much of the north over the past couple months I can assure you that many places in the NT are in fact much wetter than I've seen in many, many years and if one were to look at these regions in isolation it would be easy to make the assumption that this event is already on a par with some historically wet years, though obviously this not how we assess these events as a whole.
BoM seemed to have locked Tuesday in as a storm day. Hopefully it's not too localised. Would love a classic line coming in from the west that gives everyone a drop.
This contraction of the southern polar vortex, is it something that is likely to revert in our lifetimes? Or is it something that happens over a long period of time?
That's what no-one's certain about yet Cirrusfibratus because there's two competing factors.
One is the increasing greenhouse gas concentrations that's been making part of the stratosphere increasingly colder (extra carbon dioxide molecules up at that height tend to have greater efficiency in sending heat energy from that level up and out into space, as opposed to the molecules lower down in the much denser troposphere which tend to trap more of the warmth in there and warm up sections of it... and that also prevents more of that heat energy from coming up into the stratosphere and warming it). The coldness of the stratosphere over the polar region and the vertical temp gradient it causes is what maintains the polar vortex's strength. A colder stratosphere causes the polar vortex to strengthen but also contract further south. It also allows more polar stratospheric clouds such as Mother of Pearl clouds to form because they can only form below about -77C in the stratosphere - these clouds chemically react with ozone molecules and deplete their concentrations. It's also been manifested in various ways such as on the ground and satellite analyses of increasing wind speeds over sub Antarctic oceans and islands, increasing storminess at those latitudes, etc.
The other opposing influence is the continuing ozone hole recovery. Recovering ozone levels in the stratosphere = more ozone molecules to warm up the stratosphere when incoming solar radiation hits them = encourages the polar vortex to expand further north.
If this influence wins out (and no-one's sure if it will) and the polar vortex expands back further north, it's likely to do a lot of it within our lifetime. But even if it does do that, it'll depend on how quick the ozone hole continues to recover and if that recovery won't be intefered with. It also doesn't necessarily mean more frequent colder outbreaks because it depends on the season (e.g. strongly negative SAM in late spring can cause extreme fire weather, heat and dryness in areas like NSW and QLD) and also because the overall increase in longer term temps regardless of SAM is likely to modulate the effects as well.
But it's important to remember that the observed increasing trend in positive SAM phases mainly only applies to summer and not all the year round. So even if the polar vortex expands back further north or keeps contracting further south, it's likely that any trends won't be evident all year round. Or it could just stay within the current range of natural variability if the two opposing factors cancel each other out.
Either way, it's one of the more fascinating interplays of chemical reactions and physics which ultimately have a big effect on the weather at the surface.
A warm day around Perseverance Dam and Peachy state forest.
Temp about 31c.
Amazing blue sky
Unfortunately cannot climb the fire tower.
All steps and ladders removed.
It's a wireless camera site now, looking for bush fire out breaks.
25 deg now but with a constant 30 something km breeze all day and night it actually feels comfortable inside and out. Feels like about 22 deg which for sleeping isn't too bad despite 60-70 percent humidity.
Interesting weeks ahead on the cards, & I always find the Bom's 28 day forcast's interesting regarding the 'Hemispheric-Long-Wave-Patterns'.
Bom's Notes are as follows below & I have underlined one section which looks pretty suspicious of an El-Nina encouraged events which should increase rain totals for some, , wide spread showers with pockets of some rather enhanced wet-downs in areas,,, that said, not possible to predict where exactly but for the most part, likely be in central & southern areas, again.
Can only hope the Ridgy-Didge could be obsolete by then for the east coast ?
Bom's Notes: _______
The hemispheric long wave pattern has remained stable in recent weeks. There are seven main troughs. Currently the most significant troughs are near the longitudes of South Africa, the southwest Indian Ocean, the Indian Ocean, Western Australia, New Zealand, the south Pacific, and South America.
Over southern and eastern Australia the cold front events with potential to bring widespread rain are now expected about 28 November to 2 December, 10 December to 14 December, and 22 December to 26 December.
Rain events originating in the tropics and moving south are possible about 30 November to 4 December, 7 December to 11 December, and 11 December to 15 December.
Over Western Australia the strongest cold fronts should occur about 28 November to 2 December, 10 December to 14 December, and 22 December to 26 December.