Topic: NSW & SE QLD Rain, Flooding and Storms: 18-25 April 2008

[Michael Bath]

The coastal showers have been hanging around NSW coastal locations the past couple of days, but the wet weather looks set to increase as a strong high pressure system becomes established over Tasmania and the Southern Tasman Sea. Models are forecasting an upper level trough and/or cold pool to persist over eastern NSW for several days. This will create instability and probably lead to rain periods and some embedded thunderstorms - particularly in coastal areas - with strong winds too.

[Matt Pearce]

Yeah...it certainly looks interesting. I was toying with the idea about putting out a media release about it, but then chickened out a bit when this afternoon's model runs dropped the totals back and held most of the heaviest rain offshore. There should still be some 100mm+ totals along the northern NSW coast, though, which will bump a few locations into record April monthly total contention.

[Steven]

Looks nice, although coastal showers aren't welcomed. Any chance Brisbane's dams scoring 50+ mm from this?

[Richary]

According to 9 news weather tonight, only 5mm over Warragamba in the last week, despite suburbs closer to the coast getting a lot more (about 30mm here for the week). And ones on the coast got a lot more. Standard for Sydney though.

[Michael Bath]

Last night's Brisbane sounding shows a marked increase in moisture since yesterday morning and a deep SE flow has become established. 40mm at my location in 23 hours to 8am, and 42mm at Rodney's - check AWS updates from these pages:

http://australiasevereweather.com/video/webcam.htm

http://australiasevereweather.com/links/richmond_hill/aws.html

Steven - I'd be surprised if the Brisbane catchment does not receive at least 50mm over the next several days, though the setup does very much favour coastal locations at this stage.

[Michael Bath]

At least two cumulonimbus amongst the showers this morning - one west of Byron Bay and the other around Coraki - could see the tops of that and the lightning tracker picked up a couple of bolts.

Ballina AP is up to 377mm for the month. The record at that site is 456mm in 2003 but the site only started in 1992. The old Ballina site had 657mm in 1988 - one I remember as I was living there at the time. Prolonging major flooding of the Lower Richmond River occurred.

The old Lismore (Centre Street) site had two consequent wet Aprils in the late 1980s: 529mm in 1988 and 514mm in 1989. 2nd April 1989 saw the biggest flood in Lismore since 1974. Another downpour later in the month gave a moderate flood peak of the Wilsons River in Lismore.

edit: Highest rainfalls 24 hours to 9am 18 April

Upper Springbrook 46mm
Goonengerry 60mm
Repentence 60mm
Nashua 52mm

[Jason(pato)]

I received a welcome 46.5mm up till 9am this morning. On top of that I've received another 11mm since 9am, with the majority of that falling in the last hour from a sustained moderate to heavy shower. Looks like its going to be a wet few days ahead, so will be interesting to see much will fall. Hope it gets to where its needed most

[Harley Pearman]

Hello

Between 11 am and 1 pm today I was observing a narrow band of showers moving across southern and south central areas of Sydney similar to a train effect echo.

Similar to a series of train cars moving past one station, the showers were moving across one particular area of Sydney in succession. This was an ongoing effect for a few hours. Suburbs on either side of the shower band had light falls but those suburbs underneath the showers received some reasonable cumulative rainfall totals approaching 20 mm from 9 am to around 2 pm 18/4/2008.

The showers developed just off the coast, moved onshore in a NW direction in succession eventually affecting Auburn (where I work), Lidcombe including Strathfield and nearby areas bringing contrasting rainfalls ie 12 mm at Sydney Olympic Park, 10 mm at Parramatta but just 3 mm at Rosnay Golf Course in the SW portion of Auburn. The succession of showers passed over Parramatta and then weakened to the NW.

This is evident by the fact that just 1.5 mm of rain fell at Blacktown (NW of Parramatta) between the period 9 am to 7 pm 18/4/2008.

Harley Pearman

[Richary]

It certainly came down quite heavy at Rydalmere during this. We managed about 26mm from it all, slightly more than the bureau readings for Homebush etc. It was certainly quite a significant amount of rain at times, leading to quite a few puddles in places along Victoria Road (had to drive to West Ryde in the middle of it).

[Harley Pearman]

Hello

Rydalmere happened to be in the path of this succession of showers. I am aware that other suburbs near and along this SE to NW line had rainfall totals up around 25 mm or more for the period 9 am to 7 pm. It is truly amazing how a train effect echo of showers (Defined as a long narrow line of showers following one another) can create a large rainfall variation across Sydney. Usually the highest totals occur in a relatively narrow band a few kilometres wide.

Yet places a few kilometres either side of this will receive very light totals tapering to nothing. For a while, the same places will keep receiving shower cell after shower cell until the train effect echo collapses.

I have been reading about these this week in my weather book "Extreme Weather" by H Michael Mogil - 2007 and finally I got to observe one such effect across Sydney 18/4/2008.

Harley Pearman

[Michael Bath]

47.6mm here for the 24 hours to 9am 19th April mostly from heavy showers between 7.30pm and 11pm last night.

Several locations along the coast north of Sydney have had 50-60mm in the 24hours. The highest reported is 88mm at Blacksmiths on the Hunter Coast. I see the BoM had a severe weather warning out for the locally heavy rain there as 67mm of that fell between 9pm and midnight.

[Richary]

There was at least a small amount of lightning associated with the Hunter falls last night, as I saw a little bit off in the distance looking north about 10pm.

[Michael Bath]

Another 33mm here in the 24 hours to 9am 20th April.  Quite a few centres on the Mid North Coast and Northern Rivers have had 50-70mm, but nothing outstanding.

I see the Sydney forecast now has rain rather than showers - which matches the heavier coastal cloud developing and spreading southwards.

Some lightning off the Coffs Harbour area in the past hour too.

[Steven]

There was a small amount of lightning too. And an impressive total of 74.6mm to 9am this morning, clearly the highest total for SE QLD.

[Harley Pearman]

Hello

Currently in Sydney, showers continue to prevail. No extended rain periods. Between 1 pm and 2.30 pm 20/4/2008, showers became more scattered over Sydney's western Suburbs for a period and some moderate bursts of rain occurred. The area around Prospect, Blacktown, Kings Langley, Baulkham Hills. Bella Vista and Toongabbie scored the best falls with rainfall totals ranging from 4 to 9 mm. (Rainfall totals are from 9 am to 4 pm from BOM) and much lighter falls elsewhere.

At 12.30 this afternoon, I noted some low topped cold weather cumulonimbus clouds sitting over the lower Blue Mountains west of Sydney but judging by their behaviour, it appears that these were only dropping moderate showers. Katoomba has scored 11 mm of rain, the highest that I can see in the Sydney region so far (9 am to 4 pm for 20/4/2008 from BOM).

The central coast and mid north coast to the north are currently getting the heaviest showers but there is a significant build up of cloud to the north, mainly alto stratus, stratus and strato cumulus cloud but some cirrus clouds is becoming evident too. The satellite photo is showing more dense cloud just to the north of Sydney a likely pre curser to more rain / showers.

Harley Pearman