Swell Maps – How To Use The Swell Maps

HOW TO USE THE SWELL MAPS
The Swell Map section is an invaluable tool for every surfer chasing waves in Costa Rica, and is the very first product that has ever plotted the local offshore bathymetry as a tool to find the best waves in Costa Rica. As we know, the offshore bathymetry and continental shelf plays a huge role in focusing swell energy along the coastline and the exact same swell could have up to a 10 foot difference in wave height along only a few miles of coastline! In the Swell Maps we have plotted the most typical swell directions for the Pacific coast of Costa Rica with a long swell period of 18 seconds to show the typical scenario of how the swells will be affected by the offshore underwater bathymetry.

Swell directions above Northwest-295 degrees are blocked by the coast of Mainland Mexico from reaching Costa Rica, and swell directions below South-180 degrees are typically blocked by the coast of South America. Other long period swell directions between the West/southwest-240 and West-275 degrees are not practical from storms in the North or South Pacific, but may be rarely possible as short period swells from brief hurricanes off Mexico.

Shorter period swells – (less than 12 seconds between successive waves) are typically generated by local winds or local tropical storms, and have much less energy extending deeper below the ocean surface so they are much less affected by underwater bathymetry and the continental shelf than longer period swells. Shorter period swells are very typical for the Caribbean coast of Costa Rica so there is usually very little refraction offshore compared to the Pacific coast of Costa Rica.

Mid period swells – typically between 12-15 seconds between waves – are generated by bigger storms with strong winds extending over hundreds of miles. These swells begin to extend deeper below the ocean surface and will begin to feel the bathymetry of the ocean floor further offshore. Mid period swells may begin to be focused by the underwater bathymetry with slightly larger waves in some areas.

Long period swells – typically 16 seconds or greater between waves – are generated by much larger storms with stronger winds blowing over much greater distances, often thousands of miles of fetch. These larger storms are located further away in the North and South Pacific Ocean regions during their respective winter seasons. The longer period swells from these storms are the primary source of waves along the Pacific Coast of Costa Rica, and are also greatly affected by the offshore bathymetry of the continental shelf.

The Swell Maps compare the original offshore deepwater swell heights, to the swell heights nearshore in shallow water up to about 30 feet deep – after the affects of the swell interaction with the underwater bathymetry of the ocean floor during the transition between deep water and shallow water. Using the color legend below the charts as a reference, you can easily see where most of the swell will be hitting along the coast, and sometimes even more importantly, where it won’t be hitting. Depending on the offshore bathymetry of the specific location, the swell energy hitting the coast could be 2-3 times greater than the original deepwater swell height, or much less. The color legend displays original offshore deepwater swell heights of 3, 5, and 10 feet; and a percentage scale to be used for other swell heights. The color of the original offshore deepwater swell height will always be Yellow.

As an example, using the color legend for a 5 foot deepwater swell offshore, if the swell color nearshore along the coast is:

Yellow: then the swell has maintained its original height of 5 feet or is still 100% of its deepwater height.

Light Green: then the nearshore swell height will be 3 feet or 60% of the original deepwater swell height offshore.

Dark Purple: then the nearshore swell height will be 10 feet or 200% larger than the original deepwater swell height, usually the product of an underwater canyon or the swell focusing toward the shallower water of underwater bank or seamount.

Galapagos Wave Shadow

The Galapagos Island chain is located about 700 miles south-southwest of Costa Rica and will often interfere and partially block Southern Hemisphere swells approaching from the south-southwest between 200-225 degrees. The islands can create a virtual wave shadow over certain sections of the coastline and this shadow will shift along the coast depending on the swell direction. Areas experiencing the Galapagos wave shadow will have smaller, less consistent waves than elsewhere. As most Southern Hemisphere swells travel long distances over thousands of miles to reach Costa Rica, the swell direction range may become very focused within 5 degrees, which helps to make the wave shadow very defined along the coast. Swells with a wider range of swell direction (10-20+ degrees) will produce surf along the coast less affected by the Galapagos Islands, and these wider swells may be generated by larger storms with wider swell generating fetches, as well as from moving storms where the swell direction is always shifting.

Comments