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Sunshine Coast
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Gold Coast
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North Coast NSW
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Forecast updated 4.00pm Wednesday, 19 June 2013. By Ben Macartney. Thursday Mid period SSE groundswell 3 – 5ft far northern NSW exposed coasts (possibly bigger south facing breaks). Around 2 – 3ft across south-east QLD exposed breaks. WIND: SSW 15 to 20 knots, easing later.
Friday Mid period SSE groundswell 3 – 4ft far northern NSW exposed coasts, grading to 2 - 3ft across south-east QLD. WIND: Early light SW tending SE to NE 10 knots later.
Saturday New SSE groundswell 5 – 6ft+ far northern NSW exposed coasts, grading to 3 - 4ft+ across south-east QLD. WIND: Early light and variable tending S 10 to 15 knots during the afternoon.
Sunday SSE groundswell up to 4 – 5ft far northern NSW, grading to 2 – 4ft across south-east QLD. WIND: SSW 10 to 15 knots.
Monday SSE swell 3 – 4ft far northern NSW exposed coasts. Around 2ft across south-east QLD. WIND: W to SW 10 to 15 knots.
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Recap An increase in SSE swell set in across the region over the last few days, but most of this energy hit locations further south. Wednesday morning revealed surf up to three to five feet across northern NSW exposed stretches, grading to three feet or so across northern NSW and down to one to two feet across south-eastern Queensland, preceding an uptick in energy to two to three feet during the day.
Forecast Overview A slow moving East Coast Low drifting across the southern Tasman keeps on keeping on as it redevelops over New Zealand over the next few days. Through the first half of the week the storm system maintained an extensive south-easterly fetch across its southern flank, supplying the NSW coast with a consistent run of mid to large SSE swell that mostly bypassed far northern NSW and south-east QLD locations.
Strong SSE groundswell this weekend However, plenty of SSE swell penetrates the region over the next few days; initially picking up a foot or two out of the SSE on Thursday following the eastward movement of the low into our swell window during Monday and Tuesday. A drop in size follows by Friday following a gradual weakening of the system as it moved across New Zealand’s South Island over the last 48 hours, causing the fetch to weaken. However, the storm system is by no means packing up shop just yet. As discussed on Monday the low enters a new and final phase over our south-easterly swell window as it, merges with a vigorous cold front linked to an intense polar low now slipping away deep below New Zealand;
Source: BOM. A final resurgence of southerly gales across the eastern Tasman on Wednesday and Thursday sets up a strong SSE groundswell this weekend.
The combination of these two systems produces an extensive southerly fetch over the next 48 hours; elongating southward over 1,000 nautical miles from west of NZ, deep into the Southern Ocean below the 50S parallel. Although this wind-fetch lies out of direct range of the East Coast, all its key parameters (length, strength and duration) are substantial enough to generate maximum significant seas and swell of 30 feet plus west of New Zealand. A subsequent pulse of SSE groundswell spreads back our way on Friday, producing a rising trend in wave heights this weekend.
This episode is projected to build in across northern NSW late on Friday ahead of the bulk of groundswell filling in by Saturday – progressively superseding a still solid, lower period SSE swell. This should see wave heights jacking to a solid five to six feet plus across the most exposed northern NSW stretches by Saturday morning, grading to a solid three to four feet north of the border. Although this should mark a peak in size, there’s still likely to be solid surf on offer throughout Sunday ahead of drop to more modest levels by Monday. Further, this event coincides with a return of light to moderate south to south-westerly winds, so it’s shaping up as an excellent weekend across the Points and Bays.
New ECL to develop over the western Tasman Sea The outlook from Sunday onwards is compounded by the forecast development of a new East Coast Low over the western Tasman Sea this weekend, following the passage of an upper level low across the eastern interior over the next few days. Although the strong divergence among key computer models continues to lend uncertainty to the outlook, the most likely scenario is a surface trough developing off northern NSW and southern Queensland on Saturday, followed by a closed low forming on the trough by Sunday;
Source BOM. A new surface low/ trough developing offshore over the weekend holds plenty of swell potential for early next week.
Exactly how it will impact the coast remains less certain. Latest US model runs capture a strengthening ENE fetch developing east of the trough as it deepens on Sunday, followed by a gale force ESE fetch forming as the low drops off the Mid North Coast early on Monday. This dual fetch, or ‘multi fetch’ aspect is typical of a proper ECL.
However, diverging projections lend considerable uncertainty to how it will impact the region. Latest US modelling move the low swiftly south as it develops, so while we may see an initial increase in ENE swell, the second, heavier push in ESE swell would be mostly confined to the southern half of the NSW coast – perhaps resulting in a minor increase in SSE swell on Tuesday/ Wednesday.
Having said that, several other models place the low/ trough further north in a much weaker form – and this holds potential for a modest increase in ESE swell early to mid next week. The model divergence also extends to the outlook on local winds, so the outlook remains heavily contingent on the location of the low as it develops on Sunday and Monday. Stay tuned for revisions in Friday’s update.
Long Range Based on a loose consensus of latest long range projections, the ECL should weaken and drift east across the Tasman on Tuesday and Wednesday, making way for a new high pressure system extending across NSW and the Tasman mid to late next week. Extrapolating from this, an easing trend in ESE swell sets in from Tuesday onwards. Expect revisions in Friday’s update.
If you’ve got any questions or feedback drop me a line at benmac4cast@gmail.com
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