Forecaster Blog: Major E swell Brewing for Late January

25 Jan 2018 3 Share

Ben Macartney

Chief Surf Forecaster

COASTALWATCH | FORECASTER BLOG

Issued Thursday, 25 January 2018

It’s about now that you might be regretting going a bit hard on the Christmas pudding – and a bit soft on the fitness over the holiday period. There’s now increasing confidence a large and powerful easterly groundswell will impact the entire East Coast over the course of next week, providing days of solid surf ranging from physically demanding to straight up life-threatening.

The prospective source of this event is a tropical low/ cyclone forecast to develop over the Coral Sea this weekend, before transitioning into a deep, sub-tropical storm over the northern Tasman early next week. These events follow the onset of the Australian monsoon across the tropical north over the past week; precipitated by the eastward migration of an MJO event over the maritime continent. As the MJO moves further eastward into the western Pacific this weekend a deepening tropical low is widely projected to drift east/ southeast, out towards New Caledonia.

Regardless of whether or not the impending E swell gets chunky or huge, there's bound to be some fine moments at the right time and place. Photo: Uploaded to CW by Dan Sinclair.

Regardless of whether or not the impending E swell gets chunky or huge, there's bound to be some fine moments at the right time and place. Photo: Uploaded to CW by Dan Sinclair.

In it’s early stages the low combines with a large, slow moving high over New Zealand to establish a strengthening easterly tradewind belt throughout our easterly swell window; broad enough to trigger a building trend in easterly swell across the entire Eastern Seaboard early next week. However, the key period in swell-production is forecast to occur early next week. Based on GFS model runs, the low will curve poleward and steadily intensify as it undergoes extratropical transition over the north-eastern Tasman Sea on Monday and Tuesday; contributing to a stronger belt of easterly gales in conjunction with the aforementioned high, now positioned just east of NZ:

All global atmospheric models, like the BOM's ACCESS model pictured here, are now picking up the developing low reaching peak intensity over the northern Tasman on Tuesday 30 January. Source: BOM.

All global atmospheric models, like the BOM's ACCESS model pictured here, are now picking up the developing low reaching peak intensity over the northern Tasman on Tuesday 30 January. Source: BOM.

If this comes to fruition, we’ll see maximum significant wave-heights peaking in the order of 30 to 35ft just east of the 160E meridian; close enough to  spawn a heavy round of E swell for the entire East Coast mid-next week:

Latest Wave Tracker runs reflect the forecast 30 to 35ft sea-state that may result as the low deepens over the Tasman early to mid next week.

Latest Wave Tracker runs reflect the forecast 30 to 35ft sea-state that may result as the low deepens over the Tasman early to mid next week.

While a building trend in E swell appears a virtual certainty, the various models differ with respect to the speed of the low’s development, it’s forecast location and projected wind-speeds through the height of its lifecycle. Given the GFS scenario above is at the most aggressive end of the scale, we may well see the forecast E swell coming down in height and period over the next few days. Then again, if the low develops closer to the coast as some models suggest, it could be bigger.

The BOM's ACCESS model is playing down the strength of the developing fetch. This would still see a large, powerful E swell arriving mid next week - just not as humungous as the scenario depicted above. Source: BOM.

The BOM's ACCESS model is playing down the strength of the developing fetch. This would still see a large, powerful E swell arriving mid next week - just not as humungous as the scenario depicted above. Source: BOM.

Southern Queensland and northern NSW
Even at this early stage, the stars are clearly aligning for the region’s points and bays next week. The swell’s arrival is projected to coincide with a firming high pressure ridge; facilitating a SSE to SE wind-regime as the bulk of the E groundswell starts to kick in on Wednesday and Thursday. This should be proceeded by a slower building trend in mid-sized E swell, but stay tuned to Friday’s detailed update for specifics.

The Wave Tracker shows peak wave period; showing the bulk of groundswell filling in across the Southern Queensland and northern NSW coasts on Thursday morning, coinciding with SSE winds to produce epic conditions across the points and bays.

The Wave Tracker shows peak wave period; showing the bulk of groundswell filling in across the Southern Queensland and northern NSW coasts on Thursday morning, coinciding with SSE winds to produce epic conditions across the points and bays.

Sydney, Newcastle and the South Coast
At this point the outlook for more southern locations isn’t so flash. The arrival of a cold front along the coast late on Tuesday is forecast to lead in a firm ridge extending from a large high over the Bight. This feature is projected to instate a moderate to strong S to SE airflow across the coast; kicking in just in time for the E swell’s arrival on Wednesday and Thursday. This of course doesn’t mean there won’t be some good or even epic conditions to be had over the course of this event, so stay tuned to the detailed forecast for what’s to come over the course of next week.

This chart shows peak wave period for Wednesday 31 January; picking up long-period E groundswell building in along the NSW coast as a shorter period S windswell builds in from the south. The end result could be stormy chaos along exposed breaks, but expect further changes to the outlook as the week progresses.

This chart shows peak wave period for Wednesday 31 January; picking up long-period E groundswell building in along the NSW coast as a shorter period S windswell builds in from the south. The end result could be stormy chaos along exposed breaks, but expect further changes to the outlook as the week progresses.


Tags: Forecaster Blog , Ben Macartney , Tropical Cyclone , E groundswell (create Alert from these tags)

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