The Tehuano wind is a north to northeasterly wind which periodically blows across the Isthmus of Tehuantepec in southern Mexico. The wind is stronger than the trade winds which normally blow here. It is notable for causing a pronounced increase in upwelling of cooler, nutrient-rich waters in the Gulf of Tehuantepec on the Pacific coast which in turn supports an abundance of sea life. The wind and upwelling are together referred to as a Tehuano event.
The Tehuano is caused by a surge of cooler, drier air originating from the North American continent. Such surges are more common in the winter, but may occur at other times of the year as well. This air is denser than the tropical air mass normally present in the region, thus a strong pressure gradient is established which induces the wind. The wind is further accelerated by the funneling effect of the Chivela Pass between the Bay of Campeche and the Pacific coastlines.[1] The same conditions are the cause of the Papagayo wind off the coast of Costa Rica and the Panama wind further south.