The Tehuantepec Wind Jet As in this 2-day composite average of NSCAT observations and 1-degree gridded ECMWF analyses, the axis of the Tehuantepec jet almost always turns anticyclonically toward the west. The radius of curvature of the jet axis near the coast is consistent with that of an inertial jet shown by the heavy solid line. With increasing distance from the coast, the radius of curvature of the jet axis become progressively larger than the inertial radius. This is a characteristic feature throughout the NSCAT observational period, presumably indicative of the importance of geostrophic adjustment of the jet. The Tehuantepec jet generally becomes a geostrophically balanced zonal jet along 10N. Away from the jet axis, there is strong divergent fanning in the NSCAT observations near the coast. The much weaker fanning in the ECMWF analysis is consistently found throughout the NSCAT observational period. The differences between NSCAT observations and ECMWF analyses are especially large east of the jet axis where there is little or no eastward fanning in the ECMWF analyses. This systematic difference may indicate errors in the parameterization of boundary-layer processes in the ECMWF first-guess fields in this data-sparse region of the ocean.

Winds, divergence and relative vorticity from NSCAT observations and ECMWF analyses of a Tehuantepec event. (Enlarged image size: 28.2 K)

The Panama Wind Jet As in this 2-day composite average, the Panama jet over the upper reaches of the Gulf of Panama often shows characteristics similar to the Tehuantepec jet. The axis of the jet often turns anticyclonically toward the west in a manner that is consistent with an inertial balance at the coast. Away from the coast, the radius of curvature of the jet axis is larger than the inertial radius shown by the heavy solid line. The fanning of the winds away from the jet axis is similar to that observed in the Tehuantepec jet. This divergent fanning is again much weaker in the ECMWF analyses. Because the wind speeds are low in the Panama jet, the anticyclonic turning is often disrupted by other meteorological processes unrelated to the gap flow.

Winds, divergence and relative vorticity from NSCAT observations and ECMWF analyses of Panama event. (Enlarged image size: 28.6 K)

The Papagayo Wind Jet As in this 2-day composite average, the Papagayo jet is fundamentally different from the other two jets. The axis of the Papagayo jet never turned anticyclonically during the NSCAT observational period. The inertial balance evidently plays no significant role in the dynamics of the Papagayo jet. The gap through the Nicaraguan lake district is apparently sufficiently wide that a quasigeostrophic balance is maintained as the Caribbean tradewinds blow across Central America and into the Pacific. The fanning of the wind field away from the Papagayo jet axis is generally similar to the fanning observed in the other two jets. This divergent fanning is again much weaker in the ECMWF analyses.

Winds, divergence and relative vorticity from NSCAT observations and ECMWF analyses of a Papagayo event. (Enlarged image size: 27 K)