Large Long period swell on the way for WA, SA, Vic and Indo.
By Coastalwatch meteorologist Jeff Callaghan.
A large long period swell is currently still developing southwest of Australia in the Kerguelen Island region. In Figure 1 the low pressure system responsible for the swell can be seen intensifying as it moved towards Kerguelen Island last Sunday (20 September). Yesterday (21 September) an enormous zone of 50 to 60 knot winds developed north and northwest of the centre (Figure 2).
As a result of these unique conditions a very large swell can be seen to develop in the region (Figure 3) with analysed heights exceeding 48 feet. The heights in the swell zone should peak today (22 September) and gradually ease thereafter as it moves towards Australia and Indonesia. However the period of these swells has been increasing and is expected to increase over the next few days as energy is transferred to the longer period end of the wave spectrum. In Figure 4 the peak energy wave analyses and forecasts show the peak energy period of the wave front increase and is forecast to reach 20 seconds as it approaches Australia and Indonesia.
Large long period swells should reach Western and Southern Australia as well as Indonesia.
Figure 1. Quikscat winds and US high resolution mean sea level pressure distribution for 0000UTC 20 September 2009 top frame (10am EST 20th) and 1200 UTC 20 September 2009 lower frame (10pm EST 20th). “L’ denotes the position of the mean sea level low centre.
Figure 2. Quikscat winds and US high resolution mean sea level pressure distribution for 0000UTC 21 September 2009 top frame (10am EST 21st) and 1200 UTC 21 September 2009 lower frame (10pm EST 21st). “L’ denotes the position of the mean sea level low centre.
Figure 3. Swell height analyses showing the development of the large swell near Kerguelen Island.”L” denotes the position of the low pressure system.