Tehuantepecer, or Tehuano wind, is a violent

mountain-gap wind A mountain-gap wind, gap wind or gap flow is a local wind blowing through a gap between mountains. Gap winds are low-level winds and can be associated with strong winds of 20-40 knots and on occasion exceeding 50 knots. Gap winds are generally st ...

that travels through the

Chivela Pass The Chivela Pass is a narrow mountain pass in the Sierra Madre Mountains that funnels cooler, drier air from the North American continent, through southern Mexico, into the Pacific. These northeasterly winds, specifically the Tehuano wind, which ...

in southern

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

, across the

Isthmus of Tehuantepec The Isthmus of Tehuantepec () is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean. Before the opening of the Panama Canal, it was a major overland transport route known simply as the Te ...

. It is most common between October and February, with a summer minimum in July. It originates from eastern Mexico and the

Bay of Campeche The Bay of Campeche ( es, Bahía de Campeche), or Campeche Sound, is a bight (geography), bight in the southern area of the Gulf of Mexico, forming the north side of the Isthmus of Tehuantepec. It is surrounded on three sides by the Mexico, Mexic ...

as a post-frontal northerly wind, accelerated southward by

cold air damming Cold air damming, or CAD, is a meteorology, meteorological phenomenon that involves a high-pressure area, high-pressure system (anticyclone) accelerating equatorward east of a north-south oriented mountain range due to the formation of a barrier je ...

, that crosses the isthmus and blows through the gap between the Mexican and Guatemalan mountains. The term dates back to at least 1929. This wind can reach gale, storm, even hurricane force. The leading edge of its outflow (or

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Norther ...

) may form rope cloud over the

Gulf of Tehuantepec Gulf of Tehuantepec () is a large body of water on the Pacific coast of the Isthmus of Tehuantepec, southeastern Mexico, at . Many (but not all) Pacific hurricanes form in or near this body of water. A strong, gale-force wind called the Tehuan ...

. These winds can be observed on satellite pictures such as

scatterometer A scatterometer or diffusionmeter is a scientific instrument to measure the return of a beam of light or radar waves scattered by diffusion in a medium such as air. Diffusionmeters using visible light are found in airports or along roads to measur ...

wind measurements, they influence waves which then propagate as swell and are sometimes observed away (such as in the Galapagos Islands). These strong winds bring cooler sub-surface waters to the surface of the tropical eastern Pacific Ocean and may last from a few hours to 6 days.

Climatology

The synoptic condition is associated with the formation of

high-pressure system A high-pressure area, high, or anticyclone, is an area near the surface of a planet where the atmospheric pressure is greater than the pressure in the surrounding regions. Highs are middle-scale meteorological features that result from interpl ...

s in

Sierra Madre Sierra Madre (Spanish, 'mother mountain range') may refer to: Places and mountains Mexico *Sierra Madre Occidental, a mountain range in northwestern Mexico and southern Arizona *Sierra Madre Oriental, a mountain range in northeastern Mexico *S ...

in the wake of an advancing cold front. Tehuantepecers primarily occur during the cold season months for the region in the wake of cold fronts, between October and February, with a summer minimum in July caused by the westward extension of the Azores-Bermuda high pressure system. Wind magnitude is greater during

El Niño El Niño (; ; ) is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date L ...

years than during

La Niña La Niña (; ) is an oceanic and atmospheric phenomenon that is the colder counterpart of as part of the broader El Niño–Southern Oscillation (ENSO) climate pattern. The name ''La Niña'' originates from Spanish for "the girl", by an ...

years, due to the more frequent cold frontal incursions during El Niño winters. Tehuantepec winds reach to , and on rare occasions . The wind's direction is from the north to north-northeast. It leads to a localized acceleration of the

trade wind The trade winds or easterlies are the permanent east-to-west prevailing winds that flow in the Earth's equatorial region. The trade winds blow mainly from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisph ...

s in the region, and can enhance

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...

activity when it interacts with the

Intertropical Convergence Zone The Intertropical Convergence Zone (ITCZ ), known by sailors as the doldrums or the calms because of its monotonous windless weather, is the area where the northeast and the southeast trade winds converge. It encircles Earth near the thermal e ...

. The effects can last from a few hours to six days.

As seen by weather satellites

Its leading edge shows up as a rope cloud within the visible and infrared channels of weather satellite images, and since it lies at the leading edge of a density (

temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...

and

dew point The dew point is the temperature to which air must be cooled to become saturated with water vapor, assuming constant air pressure and water content. When cooled below the dew point, moisture capacity is reduced and airborne water vapor will cond ...

) discontinuity, its leading edge by definition it is a cold front, though it has also been described as a

squall line A squall line, or more accurately a quasi-linear convective system (QLCS), is a line of thunderstorms, often forming along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front (which often are accompa ...

, with embedded rain squalls sometimes seen. Within polar orbiting imagery, a corridor of strong low-level winds show up this feature within scatterometer data retrievals, with its leading edge at the south to southwest edge of the wind surge.

Ocean impact

Tehuantepecers can be felt up to out to sea in the tropical eastern Pacific Ocean. Sustained winds at sea have been recorded as high as , with gusts as high as , with a wind event in February 1974 which sandblasted the ship which took the observation. These winds cause waves which then propagate as swell and are sometimes observed away (e.g., in the Galapagos Islands). Its effects can appear similar to a tropical cyclone, though the sky is usually clear. The surface wind can also change local ocean currents during an event. These strong winds

upwell __NOTOC__ Upwell is a village and civil parish in the English county of Norfolk. Upwell village is on the A1101 road, as is Outwell, its conjoined village at the north. The nearest towns are Wisbech to the north-west and Downham Market to the ...

sub-surface waters, cooling the tropical eastern Pacific Ocean by as much as 14 °F (9 °C), and may last 4–7 days.

References

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Climatology

As seen by weather satellites

Ocean impact

References

Other reading