Papagayo Jet

The Papagayo Jet, also referred to as the Papagayo Wind or the Papagayo Wind Jet, is strong intermittent winds that blow approximately 70 km north of the Gulf of Papagayo, after which they are named. The jet winds travel southwest from the Caribbean and the Gulf of Mexico to the Pacific Ocean through a pass in the Cordillera mountains at Lake Nicaragua. The jet follows the same path as the northeast trade winds in this region; however, due to a unique combination of synoptic scale meteorology and orographic phenomena, the jet winds can reach much greater speeds than their trade wind counterparts. That is to say, the winds occur when cold high-pressure systems from the North American continent meet warm moist air over the Caribbean and Gulf of Mexico, generating winds that are then funneled through a mountain pass in the Cordillera. The Papagayo Jet is also not unique to this region. There are two other breaks in the Cordillera where this same phenomenon occurs, one at the Chivela Pass in Mexico and another at the Panama Canal, producing the Tehuano (Tehuantepecer) and the Panama jets respectively. The Papagayo Jet also induces mesoscale meteorology phenomena that influence the pacific waters hundreds of kilometers off the Nicaraguan and Costa Rican shores. When the jet wind surges, it creates cyclonic and anticyclonic eddies, Ekman transport, and upwelling that contribute to the creation of the Costa Rica Dome off the western coast of Central America in the Western Hemisphere Warm Pool (WHWP). The relatively cold, nutrient-rich waters of the dome, in comparison to the surrounding WHWP, create an ideal habitat for a number of species making the Papagayo Wind Jet important for biodiversity in the Eastern Tropical Pacific.

Formation In North and Central America, during the Northern Hemisphere winter, high-pressure systems are created between the equator and 35th parallels north via atmospheric circulation. Air near the equator is warmed by the sun. This heated air is more buoyant than colder air so it rises and is then pushed poleward by more air rising from below. Once the air reaches northern latitudes it begins to cool and as a result it falls back towards to the Earth's surface. As the air is falling it exerts more pressure downward on the surface, creating a high-pressure system. This cold, high-pressure air mass then travels equatorward. Air masses repeatedly move in this loop, but due to the Coriolis force, this convection is not perfectly aligned south to north. In actuality, the air moves clockwise in the Northern Hemisphere, as it moves from the equator to higher latitudes and then back to the equator again.

The air travelling clockwise off the North American continent is cold and dense, with a high pressure. As it moves southwest over the Caribbean and the Gulf of Mexico, it meets warm, moist air with a comparatively low pressure. This establishes a dramatic pressure gradient, causing the cold, high-pressure air to flow quickly into the low-pressure area. This is analogous to air flowing rapidly out of a balloon when the neck of the balloon is left open. The air in the balloon has a higher pressure than the surrounding air so the air flows out of the balloon until the pressure inside and outside of the balloon is equal. If Central America were topographically flat, the air would flow uninterrupted from the Caribbean to the Pacific Ocean; however, the Cordillera mountains, which run along the west coast of Central America, block this flow. As a result, the air is funneled into a narrow mountain pass near Lake Nicaragua and the Gulf of Papagayo, creating the Papagayo Jet. Again, the balloon example serves as an analogy of how the Papagayo Jet forms; the air moving out of the balloon cannot escape all at once because there is only a small opening that allows for the release of air. The narrow opening of the balloon facilitates the creation of a wind because the air velocity increases through the balloon neck. Like the wind blowing through the balloon neck, the Papagayo winds reach high speeds as they travel through the break in the Cordillera. For context, Papagayo jet winds have mean speeds of 20 meters per second (72 km/h; 45 mph) and can reach speeds of up to 30 meters per second (110 km/h; 67 mph), in comparison with average trade wind speeds of 25 km/h. Once the Papagayo Jet winds reach the Pacific Ocean they slow considerably and merge with the trade winds. Papagayo wind jet surges can occur intermittently every few weeks and last several days during the Northern Hemisphere winter. The jet is most prominent in the winter months because the pressure gradient is largest between the two air masses during this time of the year. The greater the difference in temperature between the two air masses, the faster the air will flow from an area of high pressure into an area of low pressure. In the spring, summer, and fall months the air mass from the North American continent is much warmer so the resultant air flow is less dramatic and the wind speeds are not as high. In sum, wind speeds in the Papagayo Jet will be high through the months of November to March, peaking in February, then they will be reduced from April to August, and finally diminish completely in September.

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