Monsoon trough of the summertime Asian monsoon is in its normal orientation (oriented east-southeast to west-northwest), tropical cyclones along its periphery will move with a westward motion. If it reverses its orientation, orienting southwest to northeast, tropical cyclones will move more poleward. Tropical cyclone tracks with S-shapes tend to be associated with reverse-oriented monsoon troughs. The South Pacific convergence zone and South American convergence zones are generally reverse oriented. The failure of the monsoon trough, or the ITCZ, to move south of the equator in the eastern Pacific Ocean and Atlantic Ocean during the southern hemisphere summer, is considered one of the
Rockall base. The nearest permanently inhabited settlement is 366.8 km, or 198.1 nmi, west of the headland of Aird an Rùnair, near the crofting township of Hogha Gearraidh on the island of North Uist at . North Uist is part of the "Na h-Eileanan Siar" council area of Scotland. The exact position of Rockall and the size and shape of the Rockall Bank was first charted in 1831 by Captain A. T. E. Vidal, a Royal Navy surveyor. The first scientific expedition to Rockall was led by Miller Christie in 1896 when the Royal Irish Academy sponsored a study of the