Queensland/Nth NSW  Forecast
Forecast issued: Wednesday, 1 September 2010
Sunshine Coast Gold Coast North Coast NSW Forecast issued 6.00pm Wednesday, 1 September 2010. By Ben Macartney Short Forecast Thursday SE swell 1 – 2ft max across northern NSW exposed coasts, grading to 0.5 - 1ft across the Gold Coast. WIND: WNW to NE 10 - 20 knots ahead of a late SSE change. Friday S swell 1ft+ across northern NSW south facing coasts and 0.5ft across the Gold Coast. WIND: Early inshore SW to NW 10 – 15 knots tending ENE 10 – 15 knots during the day. Saturday S groundswell 1 – 2ft northern NSW south facing coasts, increasing to 2 - 3ft later. ENE windswell increasing to 1 - 2ft across the Gold Coast. WIND: Early NNE 15 – 20 knots tending NNW later in the afternoon. Sunday: S groundswell 2 – 4ft across northern NSW, crossing over with ENE windswell at 1 – 2ft across south-eastern Queensland. WIND: WNW 15 – 25 knots, easing during the day. Monday S groundswell 2 – 3ft northern NSW south facing coasts, combining with ENE windswell at 1 – 2ft across the Gold Coast. WIND: WSW 5 – 15 knots. Tuesday Combined S swell 2 – 3ft northern NSW, and smaller NE windswell 1 - 2ft across the Gold Coast, building during the day. WIND; S 15 – 20 knots tending SSE into the afternoon. Recap A small pulse of S swell gradually wound down across the region into the middle of the week; hanging in at three feet across the most exposed south facing coasts across northern NSW on Monday before dropping a notch into Tuesday. The swell wrapped into south-eastern QLD locations at one to two feet at best and by Wednesday it was just about all over. A combination of background SE swell and tiny NE windswell hovered around half to one foot on the sets, grading to a larger one to two feet south of the border. Some longer period ESE swell moved in during the day, but this energy was still too small to have a notable impact on conditions during the afternoon. Forecast Overview The low ebb endures across the region on Thursday; a subdued phase associated with a slow moving high pressure system over the Tasman Sea coupled with an inactive Southern Ocean storm track prevailing beneath the eastern half of the continent. The Tasman high maintains slack pressure gradients across our short range swell window, and in the short term the only potential new swell source is a cold front sweeping across Bass Strait and the southern Tasman on Wednesday evening; Source BOM. A cold front sweeping across Tasmania into the southern Tasman holds minimal new swell potential for the NSW coast on Friday. Tiny levels of SE and S swell across the region on Thursday and Friday Unfortunately swell potential associated with the front has been largely downgraded since Monday’s forecast. The front isn’t overly strong; extending a weak southerly change across the NSW coast by Thursday morning while directing a broader area of 20 to 30 knot SW winds across the southern Tasman on Wednesday evening. The wind-fetch is less favourably aligned with the East Coast than what was projected in Monday’s model runs. Hence projected S swell spreading out off this system is only expected to come in at about one to two feet across northern NSW south facing beaches on Friday; grading even smaller across less exposed east facing coasts. In the wake of the change a high pressure ridge builds in across the region, setting up a moderate southerly flow across the western Tasman on Friday. This in turn should see short period S swell at one to two feet across south facing beaches throughout the day. Stronger increase in S groundswell moves in by Sunday There’s some notable improvements in the outlook heading into the weekend. A second cold front sweeping past Tasmania’s east coast on Thursday is linked to a deeper extratropical low traversing out long range S swell window; generating a broad swathe of WSW gales across the Southern Ocean beneath Tasmania. This extensive wind-fetch generates a large open ocean SW swell across the southern Tasman into the end of the week, sending a small component of high energy S groundswell up the NSW coast. Leading forerunners move in across northern NSW on Saturday at tiny levels ahead of the bulk of swell filling in by Sunday. This should see longer lines arriving at two to four feet across the most exposed northern NSW south facing coasts under a robust northerly flow developing along the coast early in the day. NE windswell on the rise into Sunday As discussed on Monday the increasing northerlies are linked to a low pressure system developing over Bass Strait this weekend. The is set to develop on a broad low pressure trough spanning the Western and South Australian interior on Thursday before tracking south-eastward across South Australia on Friday, intensifying as it goes. Source; BOM. A broad N fetch becomes established over the western Tasman as the low intensifies over Bass Strait on Saturday. The northerlies ramp up in strength as the low pushes into western Bass Strait on Saturday morning, combining with the high pressure system located over the central Tasman to establish a short range, gale force NNE fetch across the western Tasman; Source; Metervice. A gale force N fetch sets up across the Tasman on Saturday; in turn driving a steep increase in NE windswell across the southern half of the NSW by Sunday. Computer modelled projections have fallen into line regarding this system; for the most part downgrading the length and duration of the northerly fetch over the western Tasman to about 24 hours. The fetch endures as the low traverses eastward across Bass Strait throughout Saturday, but once it moves out into the southern Tasman into the early hours of Sunday morning wind vectors will swing WNW, out of alignment with the NSW coast. The key constraining factor for the region is the localised nature of the northerlies to more southern latitudes; wind speeds north of The Hunter coast are likely to be notably weaker at 20 to 25 knots, with the strongest area of gales affecting the southern Tasman south of the 33S parallel; Source; BOM. Several recent model runs indicate the full impact of the N fetch will be confined to the South Coast. Like the NE swell of Wednesday 11 August, Tasmania's east coast would receive the bulk of the resulting NE swell on Monday. This is likely to limit the peak of the resulting NE windswell to about two to three feet across the northern NSW coast on Sunday, grading smaller to one to two feet or so across south-eastern QLD. An easing trend in NE windswell follows in wake of the NW winds shift on Sunday morning; wave heights are likely to reach a peak through the middle of the day before easing back again into the afternoon. Long Range The outlook for early next week also hinges on the further evolution of the low as it traverses out of Bass Strait and across the southern Tasman. As the storm moves out towards the South Island on Sunday it will align a second wind fetch at the NSW coast from the opposite direction; briefly aiming a broad belt of SSE gales at the East Coast as it moves out across the southern Tasman later Sunday/ early Monday; Source; Metervice. Once the low shifts out across the southern Tasman it's likeliy to aim a SSE fetch at the East Coast, setting up an increase in SE swell for Tuesday/ Wednesday. Beyond that, we’re likely to see a new high setting up over the Tasman on Wednesday, establishing a blocking pattern across our swell windows. This hints at a return to tiny/ flat conditions into the second half of next week.