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Offline Colmait  
#21 Posted : Monday, 16 September 2019 8:47:34 PM(UTC)
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LOL Blink Crying Brick wall Whistle Boo hoo!

Haha. It took me so long to tap out how to interpret BoMs forecast then to grab a screen shot and try and use the apple ipad edit tools. I finally posted and just saw that Greg beat me too it with a very professional version. Wish I had that link it would have saved a lot of time. ThumpUp

Hey thanks Ken also for the summary.
Could be a bad day for fires and especially if we get a dry storm with any decent CG’s in the right spots.

I am trying to get a few over from SKI. I posted a link to here so I don’t know if any had a look today.

Edit. Welcome Greg. Great to have you here.

Edited by user Monday, 16 September 2019 8:51:34 PM(UTC)  | Reason: Not specified

Colin Maitland.
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Offline SatMan  
#22 Posted : Monday, 16 September 2019 9:35:55 PM(UTC)
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What is great (Colin and Greg) is that they both say the same thing, so it must be true!
I have learnt something this evening and I now understand their forecast percentages! BigGrin

Stunning description Ken. Thank you for the images too.

Fingers crossed to a bit of action tomorrow. I have to be in the CBD tomorrow, so I hope it makes its way north.
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Offline DelBoy  
#23 Posted : Tuesday, 17 September 2019 5:29:38 AM(UTC)
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I see BOM have now added "possibly severe" to the possible afternoon storm for Brisbane today.

50% chance for the Gold Coast and 40% chance for Brisbane.

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Offline Colmait  
#24 Posted : Tuesday, 17 September 2019 6:25:55 AM(UTC)
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I think the possible severe part is strong winds and the dangers of fire starting from lightning strikes. Very dry.
The problem with storms, although in the forecast there is a possibility of 25% chance of receiving 1mm, BoM states that there is a unpredictable factor to a certain degree to accurately forecast that total, we could receive higher amounts very quickly than what the models suggest. (Mainly for storms)

But in this case I think the wind and fire risk is the main concern. There is moisture and it would support good size hail but is there enough moisture for that to happen in this case? Large hail that is.

Hopefully Ken maybe able to a paint a clearer picture in regards to hail with this one, or even clarify what could be the severe sector of the storms.

Cheers
BC01DCFA-78D2-4262-9CBB-F419A1012F81.png

Edited by user Tuesday, 17 September 2019 6:33:00 AM(UTC)  | Reason: Not specified

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Offline crikey  
#25 Posted : Tuesday, 17 September 2019 12:04:25 PM(UTC)
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No cumulus thunder clouds to be seen here. Just a flat mass of smokey virgery sky, mixed with cumulus stratus

Just looking at the current obs' for coolongatta at 11.30am

Dew point has climbed to 15.5, humidity 64% , temp' only 22.5. wind has swung to easterly her which is no doubt bringing in some moisture.

BOM
forecast
Forecast issued at 4:50 am EST on Tuesday 17 September 2019.
Forecast for the rest of Tuesday

Summary
Max 26
Late shower, possible storm.
Chance of any rain: 50%


Gold Coast area

Mostly sunny day. Medium (50%) chance of showers late this afternoon and evening. The chance of a gusty thunderstorm late this afternoon and evening, possibly severe. Light winds becoming northwest to northeasterly 15 to 25 km/h in the late evening.

Fire Danger - Very High

.
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Offline Pabloako  
#26 Posted : Tuesday, 17 September 2019 12:08:30 PM(UTC)
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Lovely and warm up here and 29°C.
Dew Point is only 7°C though (RH 25%), so not much moisture at the surface.

This is a chart from my site, which imports SYNOP and METAR data and roughly shows where the wind change is happening.
LargeLocalWind.gif

Edited by user Tuesday, 17 September 2019 12:11:22 PM(UTC)  | Reason: Not specified

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Offline SatMan  
#27 Posted : Tuesday, 17 September 2019 12:25:19 PM(UTC)
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Great to see the cloud band reaching far inland and hopefully bringing some rain to the inland regions.
Untitled.png
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Offline Ken  
#28 Posted : Tuesday, 17 September 2019 12:59:44 PM(UTC)
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My thoughts on today's shower/thunderstorm potential haven't changed much since yesterday
i.e. good chances near, and south of the border (moreso over inland higher ground), moderate chances in southern parts of SEQ, close to 50/50 for Brisbane itself, and slight chance for northern SEQ such as the Sunshine Coast.
But as I mentioned previously, I'm always cautious about the northern end of these setups because it doesn't take much for that section to be vulnerable to downgrades.

Apart from the more obvious aspects of the setup (significant coastal capping but a bit weaker inland, dry low levels and momentum transfer of strong winds aloft leading to elevated risk of strong gusts under any storms, low rainfall/dry lightning potential, etc),
a few things that make me a bit more optimistic than I'd otherwise be for these setups include the cold midlevel air moving across which may help things a bit despite the marginal moisture and capping here and the reasonable multimodel PoP values for southern parts of SEQ (although it'd be good if the current patchy mid and high cloud in the south wasn't there), and the post-seabreeze front higher dewpoint surface air infiltrating a fair way inland in southern SEQ after it merges with the weakening approaching coastal change, as well as the seabreeze front itself.
Shear and the W to NW steering winds are also strong which would help rapidly advect any activity towards parts of the coast although it'd mean that southern coastal parts would be more favoured.

So I still think the most likely scenario will play out in this order:
1. Some high-based popcorn convection (due to marginal moisture) initiates over inland higher ground mainly in the south (near the QLD/NSW border), the northern NSW tablelands, and possibly also in western parts of SEQ/far eastern Downs where the cap is weaker.
2. This activity then rapidly moves E (then later, ESE or SE) on the strong steering winds aloft.
3. The activity may become a bit more numerous as it get closer to the coast and encounters the seabreeze front and more moisture (but the stronger cap near the coast makes this less than certain).
4. Later in the afternoon or evening, this activity may eventually reach some sections of the coast as gusty low-rainfall showers or storms but if the cap is too strong near the coast, there is the risk these storms may die before reaching there.

Timing looks a bit tricky IMO - I often find initiation tends to be delayed during dry setups but on the other hand, you have the strong steering winds which may advect any activity towards the coast earlier than expected.

I'm not certain yet if it'll play out this way though given the marginal moisture and capping around.

Above is an output using convective cold cloud depth calibrated to past lightning - if I were to manually adjust anything, it'd probably be to shrink the northern, western, and coastal margins of the higher probabilities inwards a little bit, and tone down the higher probabilities in SEQ (and also shrink the area of hail ingredients in a bit as well).
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Offline Colmait  
#29 Posted : Tuesday, 17 September 2019 2:14:37 PM(UTC)
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I have a cell starting to show just to the Northwest. It is either the Highvale cell or a very dry cell because it is a lot closer than Highvale but is not showing up for on radar at the moment. It looks nice but it is a worry when they are virga or dry cells.
Colin Maitland.
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Offline Pabloako  
#30 Posted : Tuesday, 17 September 2019 3:12:00 PM(UTC)
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It is actually starting to cloud over here in the city, from the south and clear to the north.

Here is a very quick snap from Milton. I like to think they are small mamantus clouds, but I think they are just lumpy bases.


Untitled.png

Edited by user Tuesday, 17 September 2019 3:15:43 PM(UTC)  | Reason: Not specified

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Offline crikey  
#31 Posted : Tuesday, 17 September 2019 3:13:04 PM(UTC)
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Originally Posted by: Colmait Go to Quoted Post
I have a cell starting to show just to the Northwest. It is either the Highvale cell or a very dry cell because it is a lot closer than Highvale but is not showing up for on radar at the moment. It looks nice but it is a worry when they are virga or dry cells.


There is quite a bit of clear sky to the east and north at 3 pm and heat around atm for convection. Cant see cumulus thunderclouds as such but growing stormy look to the SW of the tweed.
and
BTW l opened the freezer and cloud emerges.The freezer barometer for rain. A sultry feel in the air emerging.

Looking at radar. Looks like some incoming storm or rainband in the next hour here.




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Offline CantSpellNarangba  
#32 Posted : Tuesday, 17 September 2019 3:21:49 PM(UTC)
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Originally Posted by: Ken Go to Quoted Post

My thoughts on today's shower/thunderstorm potential haven't changed much since yesterday
i.e. good chances near, and south of the border (moreso over inland higher ground), moderate chances in southern parts of SEQ, close to 50/50 for Brisbane itself, and slight chance for northern SEQ such as the Sunshine Coast.
But as I mentioned previously, I'm always cautious about the northern end of these setups because it doesn't take much for that section to be vulnerable to downgrades.

Apart from the more obvious aspects of the setup (significant coastal capping but a bit weaker inland, dry low levels and momentum transfer of strong winds aloft leading to elevated risk of strong gusts under any storms, low rainfall/dry lightning potential, etc),
a few things that make me a bit more optimistic than I'd otherwise be for these setups include the cold midlevel air moving across which may help things a bit despite the marginal moisture and capping here and the reasonable multimodel PoP values for southern parts of SEQ (although it'd be good if the current patchy mid and high cloud in the south wasn't there), and the post-seabreeze front higher dewpoint surface air infiltrating a fair way inland in southern SEQ after it merges with the weakening approaching coastal change, as well as the seabreeze front itself.
Shear and the W to NW steering winds are also strong which would help rapidly advect any activity towards parts of the coast although it'd mean that southern coastal parts would be more favoured.

So I still think the most likely scenario will play out in this order:
1. Some high-based popcorn convection (due to marginal moisture) initiates over inland higher ground mainly in the south (near the QLD/NSW border), the northern NSW tablelands, and possibly also in western parts of SEQ/far eastern Downs where the cap is weaker.
2. This activity then rapidly moves E (then later, ESE or SE) on the strong steering winds aloft.
3. The activity may become a bit more numerous as it get closer to the coast and encounters the seabreeze front and more moisture (but the stronger cap near the coast makes this less than certain).
4. Later in the afternoon or evening, this activity may eventually reach some sections of the coast as gusty low-rainfall showers or storms but if the cap is too strong near the coast, there is the risk these storms may die before reaching there.

Timing looks a bit tricky IMO - I often find initiation tends to be delayed during dry setups but on the other hand, you have the strong steering winds which may advect any activity towards the coast earlier than expected.

I'm not certain yet if it'll play out this way though given the marginal moisture and capping around.

Above is an output using convective cold cloud depth calibrated to past lightning - if I were to manually adjust anything, it'd probably be to shrink the northern, western, and coastal margins of the higher probabilities inwards a little bit, and tone down the higher probabilities in SEQ (and also shrink the area of hail ingredients in a bit as well).



Stunning explanation Ken. Thank you for putting the effort in and explaining it to us.Applause ThumpUp



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Offline crikey  
#33 Posted : Tuesday, 17 September 2019 3:24:43 PM(UTC)
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Yes. Lightning tracker showing a line of storms from Lismore to west of Brisbane.

I think the radar rain intensity color marks their current position.

17th sept 2019 midmand NE NSW storms.jpg

Dew point still 15 here and wind calm. Note to self. Get washing in off line and shut car windows.
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Offline Pabloako  
#34 Posted : Tuesday, 17 September 2019 4:04:48 PM(UTC)
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4 drops of rain in the CBD
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Offline Greg  
#35 Posted : Tuesday, 17 September 2019 4:22:08 PM(UTC)
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Just back from a walk up to Mt Cootha. Two rumbles of thunder (just after 3:00 pm) and a very light shower while I was out. Radar looking a bit better than when I left but I don’t think much is reaching the ground.

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Offline Colmait  
#36 Posted : Tuesday, 17 September 2019 4:23:13 PM(UTC)
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Originally Posted by: Pabloako Go to Quoted Post
It is actually starting to cloud over here in the city, from the south and clear to the north.

Here is a very quick snap from Milton. I like to think they are small mamantus clouds, but I think they are just lumpy bases.


Untitled.png


Howdy Pabloako, yes 100% they are mammatus. The word mammatus Comes from a Latin word meaning mamma or udder ( like on a cow. ). I had an old bushy mate when I was growing up, an ex- soldier, ex tracker who taught me survival and weather. But he never called the clouds by their right names. He said when you see the egg shell clouds ( mammatus) know that it is very turbulent up their and a bad storm is coming, and in the 70’s and early 80’s they were nasty.

He was a great family friend and mate even though he was so much older than me.

Great photo.

Cloud over the Northside but nothing eggciting. No lightning, thunder or spots of rain as at 16:21. Everything is going the way the models suggested and the NSW border and Goldie are getting the best of it, but at the same time a lot of lightning and if it is dry, possible fire ignition points.
Colin Maitland.
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Offline crikey  
#37 Posted : Tuesday, 17 September 2019 4:25:47 PM(UTC)
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Troughy un-photogenic mess in the sky. Regular Rumbles of thunder at Tweed.I wonder if we will see some night lightning tonight. We haven't seen that for awhile.
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Offline Pabloako  
#38 Posted : Tuesday, 17 September 2019 4:27:56 PM(UTC)
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Originally Posted by: Greg Go to Quoted Post
Just back from a walk up to Mt Cootha. Two rumbles of thunder (just after 3:00 pm) and a very light shower while I was out. Radar looking a bit better than when I left but I don’t think much is reaching the ground.



Same here in the CBD. It is trying, but nothing really reaching the ground. Sad
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Offline WarwickEye2Sky  
#39 Posted : Tuesday, 17 September 2019 4:33:37 PM(UTC)
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Windy with light to moderate rain here. Even saw a CG to our W to NW about 25 min ago. Not much rain overall, but this is the most excitement we have had here in about 6 months.
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Offline crikey  
#40 Posted : Tuesday, 17 September 2019 5:11:13 PM(UTC)
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The radar is suggesting a secondary line of storms is forming from Tenterfield to Kingaroy.Should be at the Tweed in an hour if the line doesn't weaken. We have light rain here..

Weatherzome Stormtracker image inflates the activity l think. Thoze big red crosses.

But l don't know of any other storm trackers that are for free. Any links to better ones?

17th sept 2019 cluster of storms NE NSW.jpg
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