Topic: Rain event SE Qld and NE NSW: 19 - 25 August 2007

[Jimmy Deguara]

Hi,

Given the existence of a northwest cloud band over Queensland and moving into northeast New South Wales and southeast Queensland, a separate thread I thought would be appropriate. I have not looked further into models given time constraints but even just looking at the increasing development of the cloud band itself and its orientation, and the existence of a low pressure system, it provides an interesting scenario and potential for some much needed rainfall for the region.

Regards,

Jimmy Deguara

[Michael Bath]

All the models are now in agreeance for a good rainfall event. Some locations should end up with around 100mm for the Sunday into Tuesday period (hopefully me too!)  GFS 12z run is now also forecasting the trough to persist along the QLD coast and a coastal low to develop mid week.

The high should end up in a good cradling position for decent rainfalls.

[Steven]

Sounds good, already overcast here, must have set in last night. I also hear of weak thunderstorms in this system, is this true?

[Michael Bath]

Yes, quite possible but I don't think you'll see much unless it's from clearing storms along the coast.

LAPS differs from GFS a bit this arvo with the Australian model suggesting a low will form off the Northern Rivers and direct the better falls into the Mid North Coast and Hunter. The US model has the high a little stronger keeping any coastal low formation a bit further north - which is certainly more favourable for heavy falls in the Northern Rivers and Southeast QLD.

BoM have upgraded the NR and MNC forecasts to include the possibility of heavy falls later Sunday and into Monday.

[Jimmy Deguara]

Michael and Steven,

The clear start evolved into a chaotic sky with stratocumulus and altocumulus as well as the cirrus streaming from the NNW. I certainly hope that a low does not bomb all of the activity out to see. I do anticipate some showers or rain here (Sydney region) over the next few days.

Regards,

Jimmy Deguara

[Steven]

Now BOM has rain tipped for Tuesday at least, then it's showers onwards.

[Steven]

Well, we seem to have missed most of the rain, presumably because the band moves E/SE wards, as a result some drizzle and strong winds, oh and cold too.

[Michael Bath]

Yes, quite cool under all this cloud. Max of 15 today. 8mm to 9am and 7mm since then. BoM have just issued a severe weather warning for here tipping a low to form off the NSW/QLD border.  Will certainly become more interesting if that eventuates.


NSW SEVERE WEATHER WARNING
for Flash Flooding
For people in
Northern Rivers, Midnorth Coast

Issued at 4:20 pm on Sunday 19 August 2007

Synoptic Situation: 3:00 pm EST Sunday
A low pressure trough is expected to deepen off the northern NSW/southern Queensland coast within the next 24 hours. Rainfall is expected to increase overnight tonight and through Monday in the
northern Mid North Coast and Northern Rivers districts.

Very heavy rain may cause local flash flooding on Monday.


Been a LONG time since I've seen this sort of forecast for here (Northern Rivers):

Forecast for Sunday evening
Rain periods with some moderate to heavy falls developing. Moderate to fresh southeast wind, becoming strong and gusty on the coast.

Forecast for Monday
Rain periods with moderate to heavy falls and local flash flooding. Fresh to strong and gusty east to southeast winds.

[Jimmy Deguara]

Michael,

We have had intermittent showers and rain periods today which has also kept things cool. Sometimes the rain has been steady.

Regards,

Jimmy Deguara

[Steven]

I remember a low pressure system, in March 2004, did quite some damage to our garden. I suppose the strong winds has got to do with the fact a low is forming, am I correct?

[Jimmy Deguara]

Hi,

We had whopping 66.6mm of rain over the past 24 hours which is pretty impressive for here. The ground looks saturated and I think I would require alternative routes across South Creek this morning.

Michael how did you go up there - my assumption pretty impressive given the forecast.

Regards,

Jimmy Deguara

[Michael Bath]

Sydney and the Central Coast have certainly copped the best falls so far. Best around the Northern Rivers are in the 60 to 70mm range in the 24 hours to 9am.

I measured 7.6mm to 9am Sunday, and 57.4mm to 9am today. This is my highest 24 hour rainfall since 57.6mm on 11/9/2006 and interestingly 72.6mm on 30/8/2006 - another August rain event just last year.

Brisbane radar derived rainfall for the 24 hours to 9am 20th August - these figures are a very good indication of the totals within radar range.



Some of the rainfall maps showing totals to 9am 20th August

[Steven]

We measured 27mm to 9am from the light rain last night that went on constantly, add another 0.6mm to that.

[Jimmy Deguara]

Light rain persists with an overcast nimbostratus layer as well as stratus from the southeast. I found it difficult to determine where the rain was streaming on from but I suspect from the northeast in the mid levels. Quite cool today as well as one would anticipate.

Regards,

Jimmy Deguara


ED: Same BoM rain map is already displayed in previous post

[Michael Bath]

Best falls today are certainly on the Mid North Coast. 9am to 3pm figures include 70mm Coffs Harbour, 54mm Forster, 51mm Kempsey. Also on the flood warning page 105mm at Taylors Arm, and a 119mm at a location in the Coffs area (in 6 hours)
http://www.bom.gov.au/hydro/flood/nsw/midnorth.shtml

28mm here since 9am.

LAPS seemed to forecast the rainfall areas better than GFS for this system - so far.