On the col structure associated with winter traveling disturbances across the Caribbean and its effect over northern South America

It is well known that winter traveling disturbances across the Caribbean can produce great economic loss as, for instance, the “Superstorm 93” also named, “The storm of the century”. These disturbances often affect the Northern South America with heavy precipitation.

It is shown in this work how an extra-tropical disturbance interacts with the Tropics, through a col structure which develops in the Caribbean, especially during the boreal winter. This col structure is configured by: the low following the extra-tropical disturbance; The eastern Atlantic anticyclone, the anticyclonic circulation that occupies the Eastern Pacific-Central America and Western Caribbean; and the cyclonic curved trade winds over Northern South America, whose curvature is not yet completely understood.

The col structure is responsible for the strengthening of the trade winds and rains in Central America, Northern South America and adjacent Caribbean. This col structure is simulated with the MM5 model and based on the col center prediction the development of a new forecasting approach is suggested.

It is also shown, through Reanalysis data that the cyclonic curvature of the trade winds bordering Northern South America, is due to the combined action of the equatorial low belt and a low pressure system emerging at this time from the tropical South American Continent. However, other factors such as the approaching Central America anticyclonic circulation, and the topographic barrier of the Andes Mountain Range against the trade wind, may as well contribute to this curvature.

Due to the predictive potential of the col structure, its analysis may be useful for improving weather forecasting in Central America, Northern South America and adjacent Caribbean.