Gulf of Tehuantepec Gales

The onset of winter brings frequent cold outbreaks across the central and eastern US that can often result in gale to storm force winds over the Gulf of Tehuantepec.

I first heard about the Gulf of Tehuantepec gales from my father who sailed with the United Fruit Company’s Great White Fleet during the late 1940’s and 1950’s. The Gulf of Tehuantepec gales are strong northerly winds that funnel through gaps in the Sierra Madre Mountains and spill out over the Gulf of Tehuantepec along the south coast of Mexico during the winter season.

The Sierra Madre extend southeastward through Mexico and Central America and separates the Gulf of Mexico, the Bay of Campeche´ and Caribbean Sea from the Pacific Ocean. Several mountain gaps allow air to flow across Mexico and the most prominent gap is the Chievela Pass which allows strong cold air surges to pass into the Gulf of Tehuantepec on average about 15 times each winter season with about 2 of these strong enough to reach storm force conditions.

The winds are produced when there is a strong pressure gradient between the Gulf of Mexico to the north and the eastern North Pacific to the south. Northerly winds can increase to storm or even hurricane force during the more extreme events. The first event of each cool season normally occurs in mid-October with the last event occurring in late March or early April.

At the outset of gale events, surface pressures reach a maximum value of about 1028mb at Brownsville and 1024mb at Coatzacoalcos. During storm events the pressure at Brownsville are about 4mb higher and at Coatzacoalcos about 3mb more. During Tehuantepec events, the track of the high pressure center is often more critical than the maximum pressure at the center. The path that the anticyclone takes drives the northerly fetch down the coast of Mexico and setting up the strong pressure gradient across the Isthmus of Tehuantepec.

As a practical matter, whenever the Brownsville pressure exceeds 1020mb there is a good chance that a Gulf of Tehuantepec event may occur so mariners expecting to pass across the Gulf of Tehuantepec should monitor the surface forecast charts for the Western Gulf of Mexico as an indicator.

During gale events, the center of the high could track as far north as the Tennessee and Ohio River valleys while storm events require the high center to track into Mexico or the western Gulf of Mexico. Storm events are also frequently correlated to strong 500mb upper level troughs.

Since QuickScat’s demise, one critical observation tool for monitoring the Gulf of Tehauntepec surface winds has been lost. During the last 10 years, QuckScat data was instrumental in helping meteorologists better understand the dynamics involved with this phenomena and how to forecast both the strength and extent of these outbreaks.