Santa Rosa storm
Encyclopedia
The Santa Rosa Storm occurs in the Southern Hemisphere
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

 up to five days earlier than or five days later than the festival of Santa Rosa of Lima
Lima
Lima is the capital and the largest city of Peru. It is located in the valleys of the Chillón, Rímac and Lurín rivers, in the central part of the country, on a desert coast overlooking the Pacific Ocean. Together with the seaport of Callao, it forms a contiguous urban area known as the Lima...

, Perú
Peru
Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

, 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
Dutch people
The Dutch people are an ethnic group native to the Netherlands. They share a common culture and speak the Dutch language. Dutch people and their descendants are found in migrant communities worldwide, notably in Suriname, Chile, Brazil, Canada, Australia, South Africa, New Zealand, and the United...

 pirates from attacking the city of Lima in 1615. However, meteorologists
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...

 attribute the storm to the clash of the first warm winds which are a product of the arrival of spring
Spring (season)
Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of the exact timing of "spring" varies according to local climate, cultures and...

 with cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...

s.

The legend is very popular in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 and Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...

, especially around the Rio de la Plata
Río de la Plata
The Río de la Plata —sometimes rendered River Plate in British English and the Commonwealth, and occasionally rendered [La] Plata River in other English-speaking countries—is the river and estuary formed by the confluence of the Uruguay River and the Paraná River on the border between Argentina and...

 area (including Buenos Aires
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...

 and Montevideo
Montevideo
Montevideo is the largest city, the capital, and the chief port of Uruguay. The settlement was established in 1726 by Bruno Mauricio de Zabala, as a strategic move amidst a Spanish-Portuguese dispute over the platine region, and as a counter to the Portuguese colony at Colonia del Sacramento...

) and the Argentinian province of Córdoba
Córdoba, Argentina
Córdoba is a city located near the geographical center of Argentina, in the foothills of the Sierras Chicas on the Suquía River, about northwest of Buenos Aires. It is the capital of Córdoba Province. Córdoba is the second-largest city in Argentina after the federal capital Buenos Aires, with...

 and the Cuyo region
Cuyo (Argentina)
Cuyo is the name given to the wine-producing, mountainous area of central-west Argentina. Historically it comprised the provinces of San Juan, San Luis and Mendoza. The term New Cuyo is a modern one, which indicates both Cuyo proper and the province of La Rioja...

, 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
Southern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...

 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
Buenos Aires
Buenos Aires is the capital and largest city of Argentina, and the second-largest metropolitan area in South America, after São Paulo. It is located on the western shore of the estuary of the Río de la Plata, on the southeastern coast of the South American continent...

(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.
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