Santa Rosa storm

The Santa Rosa Storm occurs in the Southern Hemisphere up to five days earlier than or five days later than the festival of Santa Rosa of Lima, Perú, celebrated on August 30 each year.

Legend has it that Isabel Flores de Oliva, a.k.a. Rosa de Lima, caused a mighty storm which prevented Dutch pirates from attacking the city of Lima in 1615. However, meteorologists attribute the storm to the clash of the first warm winds which are a product of the arrival of spring with cold fronts.

The legend is very popular in Argentina and Uruguay, especially around the Rio de la Plata area (including Buenos Aires and Montevideo) and the Argentinian province of Córdoba and the Cuyo region, west of Buenos Aires.

Myth and reality

 Accumulated rainfall
for the Santa Rosa storm period (August 20 to September 20 approx.)
1861 - 2003
Year Period Rainfall
(mm)
1870 08/30 28
1876 08/29 to 08/30 73
1822 08/29 to 09/01 80
1923 08/27 to 09/03 80
1942 08/31 to 09/02 98
1956 08/29 to 08/31 97
1959 08/30 to 09/01 55
1983 08/26 to 08/31 60
1986 08/29 to 09/03 68
1992 08/29 to 09/02 54
1993 08/30 to 09/01 49
1994 08/31 to 09/02 39
1996 08/25 to 08/26 22
2001 08/26 to 08/27 59
2002 08/28 13
2003 09/03 to 09/07 88
Source: Metsul

Climate data show that the storm is one of the first to form at the end of Southern winter, some 10 days before August 20 and September 20.

In popular belief, the Santa Rosa storm is one of the most violent of the year. However, reality is different. For the City of Buenos Aires (according to the Villa Ortúzar SMN Observatory), the storm has only appeared five days before or after the 30 August on sixteen occasions since 1861. However, showers are frequent in this period, which helps keep the myth alive.

Of the sixteen storms, seven have occurred since 1992, probably owing to global warming.

References

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