Cross the Gulf of Tehuantepec

Pay attention to the weather and other marine traffic, and getting across the once-feared T-peck doesn’t have to be nerve-wracking.

Scary legends about the gulf of Tehuantepec persist from the 1960s, before the world had GPS and accurate weather reporting. These days it’s much safer and easier for recreational boats to cross the gulf. Doing so requires a competent skipper in a reasonably well-equipped cruising boat. On a boat that has GPS, radar, a depthsounder and some method to monitor weather forecasts, crossing the gulf is a breeze. You just have to pay attention.

Tehuantepec’s north shoreline curves 250 nautical miles from the resort port of Huatulco, on the east end, around to Puerto Chiapas on the southwest end. Sheltered marinas in both of these small ports are comfortable spots where dozens of recreational boat crews monitor the weather reports, waiting for a weather window that allows them to scoot across.

Salina Cruz is a small commercial port at the head of the gulf where recreational boaters avoid ships in the vessel traffic separation lanes. However, along most of this north shore boaters find calm seas in the lee of the land — even while a gale is blowing south across the isthmus.

The narrow Isthmus of Tehuantepec is so low it allows certain winds in the southern Gulf of Mexico to funnel south and amplify in a Venturi effect, the source of the Tehuantepec gale. When a gale does blow, it can blast 100 miles offshore and fan out, so it’s impossible to outflank it by going farther south. Boats that get caught too far offshore when a gale begins find it difficult to bash back north into the calm lee of the land. So you have to pay attention.

 

 

Weather Reports

From Acapulco south, the Tehuantepec weather report is what all southbound boaters boaters are paying attention to. It’s the primary topic in the marinas, anchorages and on all the cruisers nets and internet groups. All the port captains broadcast it daily on local VHF radio and post the reports on their office door. (Look at the “T-peck WX” sidebar for other weather resources.)

There’s a way to predict the start of a T-peck gale. In advance of a cold front moving southeast into the Gulf of Mexico, prevailing east winds in that area will shift southeast and east. Then as that cold front passes, high pressure fills in behind it. When that high moves over Texas, any wind in the Gulf of Mexico clocks around to blow from the north, lines up with the Isthmus of Tehuantepec and funnels strongly south into the Pacific.

 

 

Crossing Routes

It’s rare, but when we received a reliable prediction for a large enough window in the past, we opted to run straight across the gulf from Huatulco to Puerto Chiapas. This “straight across” route is 220 miles — a 30-mile shortcut — and can bypass the shrimping boats that may be working close to shore. But it carries the risk of getting caught too far offshore if a T-peck gale arises. What if you foul a prop?

Even during a T-peck gale, my husband and I have many times crossed the Gulf of Tehuantepec by running in a manner known as “one foot on the beach.” We run nonstop in about 30 feet of water for 25 hours straight, constantly hand steering. The benefit is that wind waves remain small this close to shore, no big seas can build up and we can keep moving.

Doing it is draining on all crewmembers, who have to stand watch around the clock, but we were professional mariners delivering yachts for a living, under pressure to maintain a schedule. Now that we boat purely for pleasure, I recommend a variation of this plan for pleasureboaters.

 

One Foot “Off” The Beach

Top off in Huatulco and wait for your required no-gale weather window. Use the radar vigorously to coast about three miles off the scalloped western side of the gulf. As you approach Salina Cruz, track all ship traffic (AIS, radar, VHF) and avoid any ships that pop out of the lighted break waters. Just past Salina Cruz, angle northeast across Bahia Ventosa toward the low, sandy shore of the eastern gulf and run about two and a half miles off the beach, staying in about 45 feet of water.

At two places along this eastern shore, be prepared to jog three and a half miles off the beach due to seasonal shoals: Boca de San Francisco and Boca de Tonala. After clearing each shoal, jog back to about two and a half miles off the beach in about 45 feet of water, continuing to Puerto Chiapas.

This slightly farther offshore method still requires careful navigation by radar — course needs to constantly be adjusted to accommodate the gently curving coastline — and by depthsounder to avoid drifting too far offshore. If a gale suddenly comes up, you’re still close enough to turn closer to shore or anchor in the lee of the beach until things calm down.

T-peck WX Resources
The closest and clearest SSB weather reports and predictions for the Gulf of Tehuantepec come from New Orleans, via the Coast Guard’s SSB station NMG (November Mike Golf) on Khz frequencies 4317.9, 8503.9, 12789.9, 17146.4. The most recent schedule is broadcast at 2025 Zulu, and as we go to press, the “Tehuantepec Forecasts” start at 0000Z, 0600Z, 1200Z and 1800Z.
The five NMG WX-fax charts (TIF and GIF) of most importance are:
• 00Z and 12Z, Sea State Analysis for the areas 0°N to 31°N and 35°W to 100°W.
• 00Z and 12Z, 24-Hour Wind/wave Forecast for 0°N to 31°N and 35°W to 100°W.
• 12Z, 36-Hr Wind/wave Forecast for 0°N to 31°N and 35°W to 100°W.
• 00Z and 12Z, 48-Hr Wind/wave Forecast for 0°N to 31°N and 35°W to 100°W.
• 00Z and 12Z, 72-Hr Wind/wave Forecast for 0°N to 31°N and 35°W to 100°W.

Windy.com is an excellent resource while you have good cellphone or internet connections. Download the Windy.com app, which delivers constantly updated global weather, then zero in on the Gulf of Tehuantepec and use the prediction mode at the bottom.

Saildocs.com is a free service from Eric “Sarana.” He provides grib files (graphic weather presentations) via HF email, cellphone or satellite phone. To initiate contact, send a blank email to gribinfo@saildocs.com and in the subject line write Tehuantepec Forecast.

WWV at 5, 10 and 15 megs broadcasts at 10 minutes after every hour and announces any WX warnings across all the Pacific, including one specifically for the Gulf of Tehuantepec.

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