Predictions East Coast Rain Event 3-11 Feb 2020

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Bello Weather

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Models have been indicating the potential for a wet spell along the east coast, kicking off early next week and lasting for a good few days. Early days and likely to see the details change as we get closer, but good to have some wet weather to talk about. The current trough moving across far SE Aus (and bringing heatwave conditions and more poor fire weather down there) will slowly swing up across SE Aus, eventually running WNW to ESE through NE NSW / SE QLD before it gets pushed back inland as a surface trough develops along the coast. It looks like a combination of upper trough to the west / hot SSTs off the coast / high moving well to the south could bring some big totals to some areas of the east coast. There is the potential for a low to develop close to the coast as well - and if it does then areas just to the south could see some high totals in a short length of time bringing the risk of flash / river flooding.

Here's the current EC pressure / upper chart through next week:

ecmwf_z500_mslp_aus_fh72-240.gif


And here's the forecast rain totals over the next 10 days as a result from the European / American / Australian models:

ezgif.com-gif-maker (19).gif


SSTs off the coast looking more than decent:

imageserver (1).png


...so we've got the energy there, and with the surface and uppers looking like they could play ball we should be game on for some areas (and potentially quite a few areas) to see the biggest falls in some time through next week.
 

POW Hungry

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Deterministically, it's a positive outlook but the big question is; are these falls verifying?

It was pointed out in the Southern Vic/Melbourne Thread (@Vermillion @Claude Cat ) that GFS has been performing well in the tropics regions of late and I tend to agree; we're not seeing the mid-range range falls progged by EC/AXS, lately.
GFS is on the 'conservative' side of the triumvirate for the said timeframe.

EC Accum Falls to 11am tomorrow:
Screen Shot 2020-01-30 at 8.52.07 pm.png


BoM observed Falls to 7:41pm:
Screen Shot 2020-01-30 at 8.52.23 pm.png


Granted, we're a little sparse on AWS through the interior and we've still got time on our side.
Deep convection looks positive but we're a little premature to excite ourselves with an 'rain event' scenario just yet.

The talk of cut-off/wandering Tasman low is a bit of a hopecast IMO, given the zonal nature of the -'ve AAO outlook over the next week.
 

Bello Weather

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Yes, been watching that forecast of the AAO once again heading in negative territory. It's one of the key climate drivers that just keeps on giving (or should that be taking) this year. Wondering if the models will pull back a little as they absorb the changing AAO influence into their runs. The 00z run is now in and most models still give a big dump across NE NSW as a low forms within the trough and close to the coast, before deepening and making its way offshore as it moves SE. Here's the 10 day totals from EC / GFS / Canadian / Australian:

ezgif.com-gif-maker (17).gif


Interestingly the Australian models has had the Coral Sea low getting caught up with this system and then developing, not surprisingly, a pretty strong feature as it heads close to the NSW coast...suspect this is a less likely scenario however:

ezgif.com-gif-maker (18).gif


I'll try to avoid posting each run as it comes out! Can't help but get a little excited after such a dry spell... Images thanks to Weatherzone and Meteologix.
 

DaveM

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With all the humidity of recent times I’m more optimistic that we may actually end up with decent rain in the next fortnight. Hope it doesn’t dissipate as previous forecast tended to do.

But yep, more hopeful than usual, just have to get past this weekend heat, feel moisture levels then rise all next week and whinge about humidity until it actually rains.:cheers:
 

Wavey

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With all the humidity of recent times I’m more optimistic that we may actually end up with decent rain in the next fortnight. Hope it doesn’t dissipate as previous forecast tended to do.

But yep, more hopeful than usual, just have to get past this weekend heat, feel moisture levels then rise all next week and whinge about humidity until it actually rains.:cheers:

Yeah agreed and pretty understandable to whinge when dew points on the tablelands are above 20°C. Your mouse stickiness index must be at unprecendented levels at the moment :D
 
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filski

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Big big 2 week totals tonight from both GFS and EC - multiple events with onshore winds sticking around - actually surprising to see such cionsistency between them for such a dynamic event - big floods if anything like this happens:

xx_model-en-304-3_modez_2020013100_360_13008_157_m0.png

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Absolutely dreadful result if even half of those totals occur :(

The erosion and damage in the wake of the fires will be terrible
 

Auzza

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That's the problem with our climate here. It's either bone dry or it's flood after flood. I'm contemplating whether I should take Tuesday off work and drive to the Gold Coast that morning instead of Wednesday to avoid getting stuck or washed away. Seems like a smart option at the moment.
 

AshestoAshes

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EPS is looking to lock in the event from the backend of next week with a very prolonged period of easterly flow and upper low presence, perfect summer pattern. Honestly have seen an upper low sitting so far west , won't be a drought breaker but dam filler.
Also the Euro Ensembles peg a 153.2mm over a 15-day period, will need to get the grass mowed definitely it's ridiculous how much it grew in 2 weeks.
ecmwf-ens_z500aNorm_aus_fh48-240.gif
 

Bello Weather

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Oz GFS - Brisbane this one is for you ;) GFS shows the rain event further up the coast, well into SE Qld now...no certainty as to who will see the biggest falls...deep onshore flow with some disturbances within in - anyone to the south of those disturbances will see some big totals in a short time frame...should note that these totals are only out to Monday 10th Feb 1400 - GFS shows heavy falls continuing after this time period. Massive increase in the GFS totals as it starts to follow the Access G model and absorb the Coral Sea low into the trough. Huge flooding potential if that came off.

xx_model-en-304-4_modusa_2020020100_219_12880_157.png
 

MisterMxyzptlk

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I'm not hopeful of significant falls up in SEQ despite the 00z GFS. I would want to be further south in NSW. These type of set-ups often have a southward or eastward (offshore) trend. I'm not sure we'll know exactly the extent of the falls until later next week.
Agree with that- but at the same time Weather patterns are definitely changing
The on shore blob that dumped a couple hundred mls 2 weeks ago was from the North East
In all my years of weather here on the GC watching big wets arrive they have usually come from either the North West or ECLs/degraded TCs
 

Alc2110

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What does all this mean for Sydney? GFS raincast is saying >200 mm by Feb 9. I've only looked at that model, though.
 
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Alc2110

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Looks like Sydney starts to get wet from Thursday onwards
Obviously the rain is needed, but a deluge like that would cause significant flash flooding, wouldn't it? I'm no expert, but it seems like there will be lots of runoff due to how dry the soil is right now, I don't think I've ever seen it this dry. There's a hard crust in places, and kicking it sends up a huge cloud of dust. Would it soak into the ground, or simply cause erosion and runoff? I'm worried about my foundation, due to the clay soil which is susceptible to moisture changes like this.
 

Steve777

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BOM Forecast total rainfall February 3-9, mm rounded:

Sydney : 50 -140
Penrith : 65 - 165
Bathurst : 7 - 40
Newcastle : 35 - 110
Wollongong: 65 - 180

Others might wish to add their areas.

Unfortnately it's a mainly coastal event in Central and Southern NSW.

There's not much rain in the next couple of days. After possible storms tonight and tomorrow and, for the coast, a couple of dull overcast days with little or no rain, it starts in earnest on Thursday and extends well beyond the forecast period, likely the middle of the week after next.
 
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AshestoAshes

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I'll post more details soon when the model runs are up but there will be 'reasonable inland' (subjectivity on what's good for everyone) event that coincides with the coastal deluge. The presence of an upper low means that there will be an inland troughs definitely the BOM 4-day presents this, the only issue that I see is that it will often be thunderstorm activity which is patchy at best. Hopefully there may be squall lines and band type activity but hopefully more knowledgeable people may be able to pitch in.
Also the BOM i feel is lowballing forecasts for this event given the possible trajectory being put up by models even considering Ensembles, so we may see a ramp up. The upper darling region though is a clear winner when talking inland.
Screen Shot 2020-02-02 at 5.40.03 pm.png

Definitely not a drought-breaker but a step in the right direction well before ECL season steps in.

Don't think riverine flooding should be too much of an issue in my woods with some recent rain opening up the soils (indicator black soils here and weeds easy to pull out) Although on the escarpment landslides a huge risk may 1998 Illawarra proportions.
 

Bello Weather

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Yes, agree absolutely...rain along the coast looking like it's pretty much locked in....but check out the EC inland forecast :eek:

Coastal rain from GFS and EC:

xx_model-en-304-3_modusa_2020020200_240_13008_157 (1).png
xx_model-en-304-3_modez_2020020200_240_13008_157_m0.png

...but then zoom out to all of NSW and check out the EC 10 day forecast...

xx_model-en-304-3_modez_2020020200_240_1532_157 (1).png

Some huge totals forecast...now that would put a flush down the Murray Darling.
 
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jonathanc

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Yes, agree absolutely...rain along the coast looking like it's pretty much locked in....but check out the EC inland forecast :eek:

Coastal rain from GFS and EC:

xx_model-en-304-3_modusa_2020020200_240_13008_157 (1).png
xx_model-en-304-3_modez_2020020200_240_13008_157_m0.png

...but then zoom out to all of NSW and check out the EC 10 day forecast...

xx_model-en-304-3_modez_2020020200_240_1532_157 (1).png

Some huge totals forecast...now that would put a flush down the Murray Darling.
Huge drop in total precip for Canberra since the last run. Was up around 65mm for the 10 days.
 

Snowmaker7

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3mm in the can from the afternoon's storms... Basically missed out! Have only recorded just over 140mm since July 2019 here in Bowral. Places around Horsley Park received nearly one third of our 6 monthly total in 40 mins this afternoon! Nevertheless some exciting weather to look forward to this week! Interestingly, this week is going to be very cool also. 850hPa temps down to 3C in nowra and nearly 0C down south tomorrow afternoon. Quite cold for this time of year!
 

Bello Weather

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Ouch - Access G still going hard with this one...going to put it into the very-unlikely category...but geez this model has been sticking with this outcome for some runs now...suspect it will fall into line with EC soonish, but still interesting to follow:

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WATL not surprisingly upping the quantities on the 8 day outlook with most models giving good totals:

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EC still going for good falls for much of NSW, with big / damaging falls for some areas...some variances from run to run but starting to lock it in:

xx_model-en-304-4_modez_2020020212_240_1532_157.png


Interesting one to watch - trough heads north with storms, then heads south again with the big rains...
 

Ken Kato

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I posted the following in the SE QLD/NE NSW thread but it does belong in here too.

The big persistent upper troughing over the southeast interior of the continent which eventually cuts off into a huge upper low (EC scenario) causing a huge area of upmotion anywhere to its east for the whole week and into some of next week... combined with the strong SSE coastal change that surges up the SE QLD coast tomorrow morning before stalling and coming back down the coast on Wed as a coastal trough that starts digging further south, causing persistent wind convergence on its southern end... then eventually digging further south along the NSW coast and possibly forming a small low... well that to me is a great recipe for widespread heavy falls anywhere to the east of the upper feature and near the southern flank of the potential coastal trough or low. Even north of the coastal trough/wind convergence/low, there's only a small section which has a drier southerly flow... you go even just a bit further north than that, and the winds are mainly onshore.
Synoptically speaking, you'd have to think that the persistence of the overall setup for so many days would make flooding a real risk in the more favoured areas, especially given the anomalously high PWAT values.... provided of course, the setup evolves close to model suggestions.

A couple of caveats though - the EC ensemble has been favouring two focal areas for the best falls. One being further inland over the southwestern Downs/Northwest Slopes and Plains closer to the upper troughing... and the other being along the NSW coast/far SE corner of QLD due to the onshore moisture and convergence... but with a bit of a no-mans land (for example, the eastern Downs) with lower rainfall totals in between those deep inland and coastal areas.

SE QLD itself is a bit of a gamble re widespread heavy falls but even so, the general upmotion downstream of that broad upper troughing hopefully will give many sections some good falls.

1st graphic above - a regionalised (SE Australia and surrounding waters) version of the SAM for the next 2 weeks from the NCEP ensemble using 700hpa heights averaged across the domain. You can clearly see the good tight consensus in the rise over the coming days.

2nd graphic above - EC ensemble probabilities of accumulated 10-day rainfall exceeding 150mm.
 
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