Planetary- and Synoptic-Scale Signatures Associated with Central American Cold Surges

Motivated by outstanding issues from a previous case study of a midlatitude cold surge that affected Mexico and Central America, the climatology of Central American cold surges is examined in this paper. An independently derived listing of 177 cold-surge events is employed for which the following properties are tabulated: onset date, duration, time between cold-surge events, latitude of maximum equatorward penetration ( min ), and 48-h maximum surface temperature change at Merida, Mexico (T). These data show that 75% of the cold surges have durations of 2-6 days, the same timescale as mobile disturbances in the westerlies. Also, there does not appear to be any relationship between T and the duration of the event, although cold surges that penetrate to low latitudes ( min 7-10N) have a weak tendency to persist longer than those that do not penetrate to low latitudes ( min 15-20N). In addition, the Reding data indicate that the cold surges tend to reach their most equatorward extent where topographic features impede the progress of equatorward-moving cold air; the temperature decrease in the postsurge air (as measured by T) does not appear to be related to the most equatorward extent.