In Hawai'i the prevailing ENE wind, called Moa'e or A'eloa, is generated by a high pressure system that is generally located to the N or NE of the islands. Hawai'i is situated toward the bottom edge of this system (called the North Pacific High), where the clockwise winds are blowing easterly. These so-called trade winds average about 14 knots, but may gust well over gale force, particularly when they are funneled through channels or mountain gaps. Wind strength is determined by (1) the strength of the high pressure; and (2) the steepness of the pressure gradient (the closer together the isobar lines are, the steeper the pressure gradient). The greater the pressure and the steeper the pressure gradient, the stronger the winds. The trade winds are the steadiest during the summer months, from May to September; during the winter months, the high pressure systems moves farther to the east, and the trade winds weaken, from October to April; however, migratory highs can bring strong and gusty easterlies during these months: "Winter months have the strongest trade wind episodes because of the passages north of the Islands by these highs but the average wind speeds do not reflect this-the average wind speed in summer is higher than that of winter in Hawaiian waters" (Haraguchi 12). When the high is centered directly over the islands, winds become light and variable. "The area under the center has light winds and low-height clouds with little precipitation outward to within about 300 miles of the center" (Haraguchi 12).