Acold drop (from the Spanish "gota fría") is a term used in Spain that has commonly come to refer to any high impact rainfall events occurring in the autumn along the Spanish Mediterranean coast.[1] In Europe, cold drops belong to the characteristics of the Mediterranean climate.[2][3] It is also termed a cut-off low.
If a sudden cut off in the stream takes place (particularly in the Atlantic Ocean), a pocket of cold air detaches from the main jet stream, penetrating to the south over the Pyrenees into the warm air in Spain, causing its most dramatic effects in the Southeast of Spain, particularly along the Spanish Mediterranean coast, especially in the Valencian Community. The torrential rain caused by cold drop can result in devastation caused by torrents and flash floods. For instance, the great Valencia flood of 1957 was the result of a 3-day-long cold drop.
This phenomenon is associated with extremely violent downpours and storms, but not always accompanied by significant rainfall. For this, high atmospheric instability in the lower air layers needs to combine with a significant amount of moisture.[4]
Cut-off lows are apparent near the Sierra Nevada de Santa Marta in the Colombian Caribbean, with peaks surpassing 5 km in altitude in close proximity to a warm sea. They can also occur elsewhere in the southern hemisphere, such as in South Africa, Namibia, South America and southern Australia. In the northern hemisphere, besides Southern Europe, they can occur in China and Siberia, North Pacific, Northeastern United States and the northeast Atlantic.
