According the The Age, a very large wave washed 6 people into Acapulco Bay, Mexico on Monday, after sweeping across the resort city's coastal road.

The article goes onto to say that the wave "occurred on a sunny, hot day with no storm in sight, and its source was not clear". While this had Associated Press scratching for answers as to where the wave came from, it was very clear to those who had been scanning weather charts the previous week. 

An extremely large and intense low pressure system with a central pressure of 953hPa formed over the South Pacific early last week and produced a very broad region of 50-65kt+ winds on Tuesday April 3rd. The low can be seen on the pressure chart for the Pacific (above), but perhaps more impressive is the regional map displaying satellite derived winds (below). This enormous fetch - the area that the winds blow over - stood out as one of the most significant swell generating systems for the Pacific Coast of Mexico since June last year, when the Rip Curl Pro was held in epic waves a La Jolla. 

Last year's swell also affected coastal roads, with the army called in to clean up the mess at the popular surf town of Puerto Escondido. Restaurants that line the beach were also damaged by the huge swell. A clip of this event can be seen here (although you may want to turn down the sound!).

Both swells were very impressive due to the fact that they were generated thousands of miles away from Mexico in the Southern Hemisphere. Acapulco lies at approximately 19 degrees north of the equator, while the low pressure system responsible for this week's swell formed at 55 degrees south of the equator. The distance between the low and Acapulco was approximately 4700 nautical miles (8695km).

The low pressure system formed last Tuesday, so it took 6 days for the swell to reach the Mexican Coast, which means that it was travelling at approximately 60km/h. From this we can also deduce that the wave period was in excess of 20 seconds, as wave period has a direct relationship with the speed of the swell in deep water. This fits in with the initial wind observations around the storm, which were in the range (55-60kts+) required for wave periods in excess of 20 seconds. Long period swells such as these hold their energy better than shorter period swells, which helps to explain how such large waves can traverse significant portions of the globe.

While reports of wave heights from Mexico have been hard to come by, it is likely that Puerto Escondido had sets of at least 15-20ft. Swellnet got in contact with legendary bodyboarder Mike Stewart from Science bodyboards, who was in Hawaii at the time. "I spoke with some friends in California, and they said it was the biggest south they have ever seen at a few breaks," said Mike.

These reports were confirmed by Swellnet contact Tim Lewis in Newport Beach, California, who told us that this week's swell delivered some of the best waves he's ever seen at his local break. Despite the epic swell, the lineup was empty at several beaches due to two tragic events. "A surfer broke his neck - he fell on the take off and went head first into the rocks," said Tim. "The next day, a couple got swept off the rocks. The authorities still haven't found the bodies, so it was pretty eerie out there."

There is a great story on the web of Mike chasing a large southern hemisphere swell all the way from Tahiti to Alaska - check this article (also check out his site at http://www.mikestewart.com/).