Characterizing the December 2013 extreme rainfall event over the Eastern Caribbean

During the period December 23rd-25th, 2013 an uncharacteristic lower tropospheric low pressure trough moved across the Eastern Caribbean producing an unprecedented amount of rainfall within 24 hrs., and causing widespread flooding and landslides in the islands of Dominica, St. Lucia and St Vincent and the Grenadines. The structural damages inflicted on those islands, particularly St Lucia and St Vincent were massive with an accompanying loss of 18 lives. The evolution of this event caught regional meteorological services by surprise and the governments and peoples of those islands, especially St Lucia and St Vincent, were generally in a state of unpreparedness prior to the onset of the torrential rains that accompanied the system. In this paper, we provide a review of the evolution of the low pressure trough and the associated atmospheric features which facilitated development of a scenario somewhat akin to a “perfect storm” in the Eastern Caribbean. The analysis is based largely on a detailed examination of the Global Forecast System's reanalysis data for the period during which the trough affected this sub-region of the Caribbean. Our analysis suggests that this intense rainfall event was not attributable simply to the presence of the low level trough itself, but rather to a unique combination of atmospheric forces that happened to coincide at the time.