Mid-Central Coast NSW  Forecast
Forecast issued: Wednesday, 1 September 2010
Mid Coast Forecast issued 3.40pm, Wednesday, 1 September 2010. By Ben Macartney Short Forecast Thursday New S swell 1 - 2ft south facing coasts, potentially building to 2 – 3ft into the afternoon and to 2ft+ open beaches. WIND: NW to SW 5 – 15 knots tending SW to SE into the afternoon. Friday SSE swell 2 - 3ft south facing coasts, 2ft open beaches. WIND: SW 10 – 20 knots tending ESE, then ENE during the afternoon. Saturday New S groundswell 2 - 4ft south facing beaches. NE windswell increasing to a wind affected 2 – 3ft+ across open beaches into the afternoon. WIND: NE 15 - 25 knots tending NNE 20 – 30 knots during the day, then NNW in the evening. Sunday: NE swell 2 – 4ft open beaches grading to 3 – 5ft+ across the South Coast, easing into the afternoon. WIND: Early WNW 15 – 25 knots, easing throughout the day. Monday ENE swell 2 – 3ft across the Mid North Coast and new swell 2 - 4ft south facing beaches from The Hunter south. WIND: WSW 10 – 15 knots, tending light SE during the afternoon. Tuesday SSE swell 2 – 3ft south facing beaches, potentially building to 3 – 4ft during the day. WIND: SW 10 – 20 knots tending S, then SE 10 – 15 knots during the afternoon. Recap The tail end of last weekend’s S swell dwindled away into the middle of the week. By Tuesday there were still one to two foot waves trundling in across exposed coasts out of the SE, but by Wednesday it was all over; background SE swell and tiny NE windswell were hovering around one foot on the sets. Although some longer period ESE swell moved in during the afternoon, 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 Thursday. Minor levels of 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 NSW 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 south facing beaches on Thursday; grading even smaller across less exposed east facing coasts. The Bureau of Meteorology have issued a gale warning for waters south-east of Tasmania on Wednesday night; given wind speeds are sustained at 30 to 40 knots into Thursday morning we may see a building trend in S swell during the afternoon, pushing wave heights up into the two to three foot range across south 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 two feet plus across south facing beaches throughout the day. Stronger increase in S groundswell moves in by Saturday 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 on Saturday. Leading forerunners move in on Friday at tiny levels ahead of the bulk of swell filling in by Saturday morning. This should see longer lines arriving at two to four feet across south facing coasts under a robust NNE 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 other constraining factor is the localised nature of the northerlies; wind speeds north of Seal Rocks 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 impacdt 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 plus across Sydney and surrounds on Sunday morning, grading a foot or so larger across South Coast locations better exposed to the swell source. A rapid easing trend in NE swell 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 NSW 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.