The Great Southern Route : 2013 - 2014
WEATHER ROUTING 254 | GSR worst of the conditions occurs during the winter season, as stronger gales/storms pass off to the south, and their associated strong cold fronts approach and pass from the west. With the approach of fronts, winds veer, becoming north to northwest to west, increasing and often approaching gale force. With the passage of fronts, winds shift, becoming S-SW, and periods of gale to storm force winds often occur, especially along and near the southern African coast. These winds often last about 24-36 hours before high pressure moves in from the west and winds ease. Post-frontal passage seas are typically from the south, southwest, and west, and can be quite large, often reaching as high as 12-15 feet. Especially large seas will be found within the fast east to west moving Agulhas Current along the South African coast, and in southwest to westerly sets. Larger seas typically last for about 1-2 days at a time, abating as lighter winds (from following high pressure ridges) develop and persist. High pressure ridges moving into and across the region between cold fronts bring fairly significant breaks in the weather as winds veer becoming more easterly in direction over time. Winds can be as low as force 3-4 very near the centers or axes of these high pressure areas, and seas then turn abate, leaving mainly residual S-SW swells, which become long-period as time wears on and lighter winds continue to persist. Later in the year, during the Spring and much of the Summer, the weather becomes increasingly less volatile, in that the effects from cold fronts, while still evident, are not to the degree of winter months. Fronts only pass through the region about every four days or so during late spring and summer, often remaining south of the South African coast during the period as well. Pre and post frontal passage winds are typically below gale force, especially during late Spring and Summer, when winds usually max out at force 6-7, and are mainly confined to coastal waters of South Africa, and follow the strongest of frontal passages. Combined seas behind averaging anywhere from 0.4-0.7 knots outside of the faster current areas mentioned previously. SOUTH OF MADAGASCAR / MOZAMBIQUE CHANNEL TO SOUTH AFRICA We're looking farther south, and as the more seasoned veterans of the sea can attest to, we're looking at an area that is not without its weather dangers and bouts of adverse conditions. The During the remainder of the year (September through October), the weather is certainly active, though cold fronts tend to be somewhat weaker and less frequent than during winter. Generally speaking, one can expect a frontal passage to occur about every three to four days, with fronts extending as far north as 25S-30S, moving well into the southwest Indian Ocean before encountering ridging from high pressure farther east and slowing/weakening later on. As for our semi-permanent high pressure ridge, that particular feature is still prevalent, and during this period generally extends as far north as 15S. As with winter months, the ridge will be reinforced and intensify some as transitory high pressure ridges farther west move into the Indian Ocean and eventually merge with the semi-permanent ridge, again, inducing surges of higher E-SE trade winds across the region. However, the greatest weather dangers occur as fronts approach and pass farther to the south, particularly in and near Mozambique Channel and much of Madagascar. Post frontal passage S-SW winds can still reach as high as gale force, especially within Mozambique Channel, partly due to local funneling of winds in the area, and as stronger fronts pass. The faster north to south currents also aid in bringing larger post-frontal passage S-SW seas, with such seas reaching as high as 10-12 feet as S'ly sets run against the faster currents across the area. Outside of Mozambique Channel, currents across the area generally run from east to west, and northeast to southwest on the north and northwest sides of the South Equatorial Current. By and large, slower currents are found, Figure 2 -- Typical winter patterns across the Southwest Indian Ocean, including stronger, more frequent cold fronts and passage of transitory highs (symbolized with blue H's).
2010 - 2011