The Great Southern Route : 2010 - 2011
094 | GSR trough. The winds are stronger in the winter with these highs shifting farther north over Australia during this time of year. Farther south, a thermal trough of low pressure is usually found along the western Australian coast south of approximately 20S. The movement and strength of the trough will affect the winds and seas along the coast. The approach and passage of any cold fronts and the eventual approach and passage of any following areas of high pressure will result in an offshore progression and weakening of the thermal trough. As a result, southeast winds along the western Australian coast become light and sometimes variable (Beaufort Force 4 or less) along the trough axis. Swells generally lower to southwest 4-7ft with the highest sets farther south during these events. On the other hand, an inland progression and strengthening of the trough can be expected in the wake of these following high pressure areas, as the semi-permanent high pressure ridge builds farther east. This will increase southeast winds to approximately Beaufort Force 4-6 and southwest swells of 6-10ft (the highest conditions occurring farthest south along the western coast of Australia). Cold fronts are more frequent and stronger summer months (December through February). However, these winds increase during the winter months (June through August) out of the east and southeast of Beaufort Force 4-6 and swells 6-10ft. The reason for the higher conditions in the winter is due to the ridge of high pressure situated farther north this time of year and interacting with the equatorial trough. Closer to the equatorial trough axis (between 5S and 10S), winds are generally out of the east approximately 1-2 Beaufort Force lower, with swells 2-3ft lower. Outside of any squalls, trade winds and swells are similar across the Java and Banda Seas as described near the equatorial trough across the southeastern Indian Ocean. Winds generally funnel from Torres Strait through the Gulf of Carpentaria and Arafura Sea especially during the winter months. During the summer months, winds are out of the east to southeast Beaufort Force 4-5 (though force 6 to, at times, 7 are more likely near and in Torres Strait). Swells are usually out of the east to southeast of 6-10ft (highest just west of Torres Strait). By winter, east to southeast winds will increase 1-2 Beaufort Force higher with swells building 2-3ft higher across these regions. These surges occur when a ridge of high pressure builds across Australia and interacts with the equatorial THE FIRST IS the equatorial trough that extends from the equator southward to 10S and from 50E eastward along Indonesia and New Guinea. Scattered showers and squalls associated with the equatorial trough generally move westward and are more numerous from January through March. This feature changes little in strength and is quasi-stationary throughout the year. However, over the southeastern Indian Ocean, the equatorial trough can shift farther south a few degrees during the summer and north during the winter. A ridge of high pressure is a semi-permanent feature across much of the Southeast Indian Ocean. From November through March, the west to east oriented axis of the ridge is found along 32S to 35S and from approximately 50E eastward to 105E. This ridge shifts farther north in June through October along approximately 29S to 32S. At times, portions of this ridge will "break away" and move eastward across Australia during June through August or further south across the Great Australian Bight from December through February. Winds across the southeastern Indian Ocean from 10S to 20S are generally east to southeast of Beaufort Force 3-5 and swells 5-8ft during the General Weather Conditions Eastern Indian Ocean WEATHER ROUTING From the Southeastern Indian Ocean and Indonesia to Northern and Western Australia: Two semi-permanent weather features can be found across the southeastern Indian Ocean and near Indonesia. By Amanda Delaney, Mark Neiswender and Brian Whitley of Weather Routing, Inc.
2008 - 2009
2013 - 2014