Flood Watch for parts of NSW

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A large part of the NSW coast is on flood watch with an east Coast Low expected to develop during Monday. Models are not consistent with the timing or placement of a possible low, or ever whether heavy rainfall will push inland much. However the BoM have issued a flood watch

FLOOD WATCH FOR MINOR TO MODERATE FLOODING ON THE PATERSON, WILLIAMS, WYONG, NEPEAN, GEORGES AND THE TIDAL ZONES OF THE COOKS AND WORONORA VALLEYS.

Issued at 12:45 pm EST on Friday 21 June 2013

Note: This Flood Watch is a "heads up" for possible future flooding along all rivers and creeks within a nominated valley and is NOT a Flood Warning [see note below].

From late Saturday night (22/6/13) through to Monday night, heavy rain is expected over coastal districts between Narooma and Seal Rocks. This rain is likely to cause local and main river flooding.

At this stage there is a greater than 70% chance of flooding along the following river valleys:-

Paterson and Williams Valleys - minor to moderate flooding

Wyong Valley - minor flooding

Georges River Valley - minor flooding

Nepean River Valley - minor to moderate flooding

Heavy rain combined with King Tides over the same periods may also expose the tidal zones of the Cooks and the Woronora Rivers to minor flooding.

This Flood Watch means that people living or working along rivers and creeks must monitor the latest weather forecasts and warnings and be ready to move to higher ground should flooding develop. Flood Warnings will be issued if Minor Flood Level is expected to be exceeded at key sites along the main rivers for which the Bureau of Meteorology provides a flood warning service. Across NSW about 75% of Flood Watches are followed by flooding within the catchment.

FloodSafe advice is available at www.ses.nsw.gov.au

For emergency assistance call the SES on telephone number 132 500.

For life threatening emergencies, call 000 immediately.

 

 

 

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  • Harley Pearman

    The rain event has started and it appears that a small area of Sydney was drenched overninght and early morning. An area roughly south of Sydney Harbour, west to Lidcombe, south to Bankstown and east towards Botany Bay received falls of anywhere between 50 mm and 80 mm. The highest total was 80 mm at La Peruse, 60 mm at Marrickville, 57 mm at the airport and 56 mm at Observatory Hill.

    Falls were much lighter outside this small area. It seems the heavy rain was concentrated into this small area for Sunday morning. Rainfall totals dropped sharply further away eg 20 to 40 mm around Parramatta, 16 to 18 mm around Blacktown and Baulkham Hills but further west barely anything fell. Penrith had 4.2 mm and just 2 mm at Windsor.

    The figures are for the 24 hours to 9 am Sunday morning 23/6/2013.

    So far, it appears the rain event is being concentrated along the most exposed coastal strip of New South Wales south of the lower North Coast all the way to Merimbula. on the South Coast.

  • Harley Pearman

    I have been watching this event and I have been fascinated to see how the coastal strip has been drenched but little rain getting too far inland. Today the rain moved south of Sydney to drench the southern Illawarra region and south coast but as I write this, the rain appears to be settling back into much of Sydney.

    Early afternoon, it appeared that a low pressure cell had passed right over Sydney with the rain bands on the southern side but clear skies to the North West. When viewing radar images and wind direction (wind barbs), winds seemed to be a westerly quarter across northern Sydney but more easterly and southerly south towards Wollongong and the south coast.

    Overnight to 9 am this morning some heavy rainfalls to report south from Newcastle but highly coastal. For example, Norah Head had 126 mm. Near Gosford, Mt Elliot had 98 mm and 63 mm fell at Gosford.

    Around Sydney rainfall patterns are amazing from only 1 mm at Windsor, 2 mm at Kurrajong and 2.2 mm at nearby Richmond to 96 mm at Dee Why on the coast. Penrith had 2 mm during the same period. This shows north west and far western Sydney has missed the event to date. Around Blacktown rainfalls increase sharply to 20 to 27 mm with 26 mm at Blacktown itself. Areas around Campbelltown received from 23 mm to 39 mm. At Parramatta, falls increase again from 34 mm to 46 mm. The heaviest falls occurred in a small pocket bounded by Dee Why to Hornsby and south to the North Shore to Manly where falls of 32 mm to 91 mm occurred including 78 mm at Terrey Hills and 83 mm near Chatswood.

    During the same period, Wollongong received variable falls of 40 mm to 86 mm including 80 mm at Darkes Forest and a very isolated fall of 104 mm at Brogers Creek south west of Kiama.

    Further south, falls averaged 50 mm to 67 mm around Jervis Bay and an isolated fall of 112 mm fell at Ulladulla. There was an isolated fall of 73 mm at Narooma during the same period.

    In all cases, the heaviest falls occurred close to the coast or in exposed coastal locations.

    Interestingly, between the period 9 am to 6 pm 24/6/2013, the heaviest falls were concentrated around Braidwood, Araluen and Moruya areas where falls of 50 mm to 71 mm occurred. The highest total was 71 mm at Bendethera and 70 mm at The Lagoon (Moruya). In this instance, the heviest falls moved slightly inland even reaching the eastern side of the Southern Tablelands.

    Additionally, the rain even penetrated as far inland as Yarrawonga and areas west of Wagga Wagga but these falls were very light within the range of 1 mm to 5 mm for the period 9 am to 6 pm 24/6/2013.

  • Harley Pearman

    For the 24 hours till 9 am 25/6/2013 some unusual weather patterns and rainfall patterns emerged as follows:-

    – Some flooding at Goulburn following 102 to 109 mm overnight.
    – A narrow rain band having a train echo effect onto the coast creating a situation where those underneath it are receiving some heavy falls while those on either side of the band are receiving little or light rainfall..
    – A case where the southern half of Sydney is wetter than the northern half where the highest rainfall occurred around Campbelltown (Up to 35 mm) while just 0.5 mm fell at Dee Why.

    In Sydney anywhere south of a line from Maroubra to Bankstown then west to Warragamba was relatively wet with totals of 10 mm to 35 mm. North of this line, falls were in the range of 1 to 9 mm. Again falls tapered towards the north west and north east and Dee Why had just 0.5 mm for the period.

    The focus of the heavy rain was was centred around Jervis Bay to Ulladulla, Araluen then even inland to Goulburn then back east towards Kiama.including Robertson. In this relatively small area, rainfall totals exceeded 100 mm at many localities including:-

    Mangarlowe – 185 mm (Highest for NSW).
    Yalwal – 178 mm.
    Point Perpendicular – 143 mm.
    Bungonia – 118 mm.
    Araluen 110 mm.
    Robertson 109 mm.
    Goulburn Water Treatment Works – 109 mm and 102 mm at the nearby airport.

    Totals tapered away outside this area but still included 83 mm at Batemans Bay (South cost) and 73 mm at Crookwell (Southern Tablelands). Beyond these areas, totals were much lighter.

    Even Canberra has received worthwhile falls from this event being on the edge of the system.

    It is understood there has been some localised flooding in low lying areas of Goulburn with some road closures cutting links between the town centre and the small suburb of Eastgrove. Reading the local paper, areas within the Mulwaree River and Wollondilly River catchments have experienced rising water levels and some local flooding.

    Today Sydney experienced further shower / rain activity but the stronger falls continued to stay just to the south. Although late morning or early afternoon, a very isolated short but heavy downpour passed over Auburn where I work.

  • Harley Pearman

    Finally the rain is beginning to ease along the New South Wales coast as the east coast low moves away from the coast.

    This morning a roof collapse on a large industrial / warehouse building occurred at Auburn (In Duck Street) which appears to have been caused by water ponding on the roof from the recent rain.

    Overnight and for the 24 hours till 9 am, south west Sydney received further heavy falls of up to 58 mm. Camden / Campbelltown had from 24 mm to 58 mm during the period. Falls were lighter elsewhere across Sydney from 9 mm to 23 mm. An area around Dee Why and Narrabeen had the lowest totals from 4.4 mm to 9.6 mm.

    A feature of this event across Sydney has been the large variation between rainfall totals over relatively short distances. Unusual for Sydney, Camden to Campbelltown and southern Sydney has had the highest rainfall totals for two days in a row.

    The heaviest falls for New South Wales for the period was focussed onto a small area around Kangaroo Valley and South West of Wollongong and adjacent regions. These include:-

    Brogers Creek (Brogers No 2) – 180 mm (Highest total in NSW).
    Fitzroy Falls – 138 mm.
    Clover Hill – 132 mm.
    Burrawang – 120 mm.

    This area is dominated by hilly terrain close to the coast and it is likely that orographic influences boosted rainfall totals in this area. Falls of 100 mm or more were common within the hilly Kangaroo Valley environs.

    There were further heavy falls north of Ulladulla including 66 mm at Nowra and falls of 62 to 86 mm around Mittagong / Bowral / Moss Vale.

    Darkes Forest had 117 mm and Mt Pleasant had 112 mm.

    In the Blue Mountains falls of 53 mm to 81 mm occurred including 81 mm at Katoomba. Falls tapered away further north and west.

    The result of the rainfall has been the spillage of water from Warragamba Dam and some minor flooding around Nowra.

    Overall, there are areas that have had cumulative totals exceeding 200 mm from this event and it is identified that the rain event mainly impacted an area of the New South Wales coast from Newcastle in the north to Narooma in the south.

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