**Central American and Caribbean precipitation associated with cold surges

During the cooler half of the year cold air from the interior of the North American continent frequently penetrates equatorward into Central America. Central American cold surges occur 12-20 times per year and exhibit considerable intraseasonal and interannual variability. Nearly 40% of cold season precipitation in Central America and the Caribbean basin occurs in conjunction with half of all cold surges. Especially heavy precipitation can arise when extended cloud plumes from the tropical eastern Pacific and associated disturbances embedded in the subtropical jetstream cross Mexico and move into the Caribbean, interacting with remnant low-level baroclinic zones left behind in the wake of previous cold surges.

A 21-season (1977-98) climatology of cold surges across Mexico and Central America, stratified by wet and dry events, will be used to help identify possible characteristic precipitation signatures. Data sources include surface land and marine observations, the Comprehensive Oceanic and Atmospheric Data Set (COADS), daily rainfall observations, and outgoing longwave radiation (OLR) measurements. The National Centers for Environmental Prediction (NCEP) reanalyses are used to identify, compare and contrast synoptic signatures associated with wet and dry cold surges events.

Initial investigation of the synoptic setting for the top quintile of surge events producing precipitation in the Caribbean showed a tropical connection via a low-level inverted trough between the surge high and the subtropical high. Tropical moisture was funneled poleward by the low-level flow associated with the inverted trough. An upper-level trough over the Gulf of Mexico with approaching jet streaks in the subtropical jetstream provided the support for enhanced rising motion in the area of significant precipitation. In contrast, this synoptic setting resulted in dry or only marginally wet surge events across eastern Mexico, since the most favorable dynamics for producing precipitation was located to the east over the Caribbean. However, wet surge events in eastern Mexico generally resulted in wet conditions across the Caribbean as the easterly flow upstream of the inverted trough over Mexico pulled moisture out of the tropics and across the Caribbean on its way to eastern Mexico. The synoptic setting for wet surge events in Central America and for dry surge events across both regions will also be presented.