Australian Severe Weather Forum

Gday All,

After watching the models for a few days now it now appears that a significant rainfall event is going to unfold. GFS accumulated precipitation has been bouncing some very juicy totals up and down the NENSW/SEQLD coast for the past few days now. Both GFS and EC are both agreeing on a deep E-NE flow onto the coast and in combination with a developing upper trough/cold pool this event looks to be a near certainty now. GFS places the cold pool west of Gympie on Friday morning. Also of interest is the LI's which are in negative figures, varying between -2 to -4 between Gympie and Lismore. I'd assume that this will aid in development of rain bearing clouds (someone with a bit more expertise may want to confirm this). I think I've only scratched the surface of the forecast and I welcome others to have their input and views. Feel free to correct or add valuable information as I am still learning the art of forecasting rain events.

Btw here is the latest 00z forecast accumulated precipitation from BSCH



As you can see this looks fairly substantial and I'm sure those in and around the Coffs Harbour district are hoping this event stays well north of them.

Cheers Jason

Interestingly if you run the prediction for the next 4 days only that large amount of rainfall around/west of Coffs Harbour isn't there, only the Brisbane one.

Then days 4-6 are when Coffs gets it, 500+mm over 48 hours. So Thursday and Friday could be interesting up the coast. The models also show the bulk of the Brisbane rain happening on Wednesday.

The overnight GFS run has again focused the heaviest falls near the QLD/NSW border with over 700mm for Lismore. Most of the rain will commence Tuesday night with all models on board. EC does keep rainfall totals lower than GFS but still major flood potential.

As regards the rain event for NE NSW and SEQ, BOM has issued this latest severe weather alert at 5.35 pm Monday the 18th May. It states:

TOP PRIORITY FOR IMMEDIATE BROADCAST
SEVERE WEATHER WARNING
for Flash Flooding
For people in the Southeast Coast District and the Wide Bay and Burnett district
south of Sandy Cape
Issued at 5:35 pm on Monday 18 May 2009

Synoptic Situation:
A strong upper low will move across southern Queensland during the next few
days. As it moves eastward, this system will generate a strong surface trough
about the southern coast.   

Areas of heavy rain are expected to develop about the Southeast Coast district
and the Wide Bay and Burnett district south of Sandy Cape from Tuesday night and
extending into Wednesday and Thursday. Some localised flash flooding is possible
associated with the heavier falls.

Winds around the southern coast are expected to increase from about mid week.

The State Emergency Service advises that people in the affected area should:

· avoid driving, walking or riding through flood waters

Contact the SES on 132 500 for emergency assistance if required.


The next warning is due to be issued by 11:00 pm

We have had constant rain all night in Brisbane and surrounding areas. at 8.00 am this morning, the Brisbane airport has registered 77mm of rain since 9am yesterday with most of that occurring through the night.

Brisbane 52mm
Beerburrum 74mm
Beaudesert AWS 62.4mm
Coolangatta 46mm
Archerfield 43mm
Upper Springbrook AL 140mm
Clearview TM *  105mm
Tallebudgera Ck Dam AL *124mm
Mt Tamborine AL *135mm
Maclean Bridge AL * 87mm
Toombul(Nudgee Rd) AL *92mm

There will be road closures due to flash flooding as the rain continues. There is still a current weather warning issued for SEQ as the system continues to move east. 

The Brisbane radar 24 hour rainfall accumulation shows the extent of falls well:



One site in the Tweed Valley managed to reach 100mm overnight with most parts of the Tweed and Brunswick over 50mm. The latest charts suggest the rain will focus in NE NSW after today, with the peak rainfall max again around the Bellingen Valley.

Some excellent rainfall stats for those areas.  Has this season  been beneficial for the catchment areas and dams?   We don't get to see a lot of info re the dam levels media wise - unless you tune into the Weather Channel - but there's some significant areas of very high cloud tops shown in the GFS graphic!

Not the main Brisbane ones yet Mike - though that may change in the next 24 hours.

BoM have issued a severe weather warning and flood watch for most of Northeast NSW - and also a media release

Thanks for the update, Michael.  An interesting low pressure system indeed.  Amazing how so much rainfall can come from such a stationary system but at least it is active which is the main focus of interest.

Brisbane Rainfall - 19 May 2009

The Bureau of Meteorology network of rain gauges throughout Brisbane highlights how much rain fell across the city from 9 am 18/5/2009 to 9 am 19/5/2009.

Generally, the further inland the less rain that fell.

The highest rainfalls across Brisbane city in this period are:-

Gordon Park Alert - 91 mm.
Lytton Alert - 92 mm.
Nudgee Road Alert at Toombul - 99 mm.

Although not shown in the plot below, regions just west of the Gold Coast just to the south of Brisbane received higher totals during the same period including:-

Tomerwin Alert and Hotham Creek Alert - 104 mm each.
Clearview - 105 mm.
Benobble Alert - 107 mm.
Tallebudgera Creek Dam - 124 mm.
Lushcombe Alert - 125 mm.
Mt Tamborine (2 rain gauges) - 135 and 136 mm respectively.
Upper Springbrook Alert - 140 mm (Highest total for the period).

Totals were also relatively high just south of the state border in New South Wales around Tweed Heads and nearby areas but falls tapered away further south.

It is noted that substantial rainfall is occurring across Northern Brisbane suburbs and the Sunshine Coast from 9 am 19/5/09 to present which is likely to continue for a while.

In Sydney some light shower activity has occurred and the showers only reached Sydney's western suburbs around Blacktown after 6.30 pm although falls are light.

The Brisbane rainfall plot below is sourced from the Bureau of Meteorology "Water and the Land" site at http://www.bom.gov.au/hydro/flood/qld/

Harley Pearman

this is a really severe weather event that is occurring in SEQ and heading south. I have not seen this much rain for years and heavy. It has been torrential causing widespread flooding and damage. The wind is picking up and the threat is expected to last another day or so then easing to showers. It cant come quick enough, I will probably be offline for a few days due to our office flooding, due to the tile roof not been able to take the amount of rain and wind, therefore I am just about to move everything out. Be interesting to see the stats when I get back. 
 Col

Thanks for the report Col - hope you are able to protect things.

Been some major flooding in the Greater Brisbane area today with some very significant totals including falls of close to 200mm in 5 hours from 9am today (20th May).

The rain has spread into the Northern Rivers, mostly the Tweed Valley with a flood warning there too now.

Brisbane rainfall for 20 May 2009

Some substantial rainfalls across Brisbane. I have looked at the Water and the Land site at the Bureau of Meteorology for the rainfall figures. The figures are for the 24 hours from 9 am 19/5/2009 to 9 am 20/5/2009.

Wamuran Alert - 268 mm (This station is to the NNW of Brisbane).
Mt Glorious Alert - 253 mm.
Baxters Creek Alert - 227 mm.
Strathpine - 206 mm.

The plot below from the "Water and the Land" http://www.bom.gov.au/hydro/flood/qld/ show the rainfall for the city. Northern Brisbane received the heaviest falls, generally over 100 mm while southern Brisbane received between 62 mm and 99 mm and the Ipswich area to the south west receiving lighter falls of between 35 and 60 mm.

The heaviest falls for the period were confined to areas just north of Brisbane. The heaviest falls that I can find are:-

Goodwin Beach - 332 mm.
Beerburrum - 302 mm.
Warmuran Alert - 286 mm (As previously mentioned).
Burpengary (Rowley Road) - 261 mm.

Since 9 am 20/5/09, Brisbane has received further extensive rainfalls and some falls are considerable. From 9 am to 7.50 pm, Mt Coot Tha Alert has received 236 mm.

The extensive rainfalls have now moved into the north east corner of New South Wales.

Sydney rainfalls 20/5/09

Of interest small portions of the Sydney Basin received some reasonable falls from 9 am 19/5/09 to 9 am 20/5/09 being Cronulla South - 73 mm, Bellambi AWS - 61 mm, Audley Weir - 56 mm and Woronora Dam - 50 mm. These were the highest falls outside the far north east corner of New South Wales.

Blacktown where I live received 20 mm for the same period.

Harley Pearman

Getting more serious for Lismore now though it does require a lot more rain before there will be major impacts.   99mm here since 9am yesterday.   

It got VERY windy this morning with gusts exceeding 130km/h at Cape Byron several times.


MODERATE FLOOD WARNING
FOR THE WILSONS RIVER AT LISMORE
Issued at 7:56 AM on Thursday the 21st of May 2009

Flood Warning Number: 2


Average of 115 millimetres of rain has fallen during the past 24 hours to 6 am
today. Rainfall intensity has increased the past 3 hours with 40 millimetres
falling during this period. Further heavy rain in the order of 65 millimetres
is forecast for the next 12 hours.

Moderate flooding is expected at Lismore late tonight.

Further heavy rainfall is expected over the next 24 to 48 hours which could
produce further river rises. The situation is being closely monitored and
revised predictions will be issued if necessary.

At this stage it is not possible to predict the flood peak because of
uncertainty over how much more rain will fall.



Predicted River Heights/Flows:

Lismore - exceed minor flood level (4.2 metres AHD) around noon (21/05/09)
- exceed moderate flood level (7.2 metres AHD) around midnight (21/05/09)
- with forecast rainfall possibly exceed 9.0 metres AHD
around 9 am (22/05/09) with moderate flooding

Warwick Qld Severe Storms. 20th May.

Got a break in the rain late yesterday afternoon. The rain has been phenomenal to say the least. I had read about severe wind down the coast during the day but we didn't receive it them till 5pm when I go this set. The sky cleared and showed the fronts associated with the severe weather we have been receiving and I was fast running out of light. There was no lightning just ferocious freezing cold wind.






Had trouble with attachments. Would only allow one and I hosted the two above.
Regards,
Chris.