World's greatest 1-minute Precipitation Record
Last June I blogged about the world-record rainfall for one minute
reportedly set at Unionville, Maryland on July 4, 1956. In that blog I dismissed the purported 1.50” in one minute at Barot, Guadeloupe (that has been written up in various sources) as lacking evidence. An obscure old French scientific document has recently come to my attention that seems to confirm the validity of the Barot measurement (actually 38 mm/1.496”) in one minute on November 26, 1970. Details herein.Guadeloupe is a large Caribbean Island featuring a rugged landscape the tallest point of which is the volcano La Soufriere at 1,467 m (4,841’).
Photo from tourist web site, photographer not identified.
A paper published in the official journal of the “Office de la Recherche Scientifique et Techninque Outre-mer” (translated as Office of Scientific and Technical Research for Overseas”), a French government agency responsible for scientific and technical research projects outside of France (and now called the “Institute of Research for Development” (IRD), appeared in Vol. 8, No. 2 of the ORSTUM hydrology journal issue of 1971 and was authored by a B.C. Klein, Senior Researcher, Hydrological Service, L’O.R.S.T.O.M. The title of this report was Intensite Extraordinaire de la Precipitation du 26 Novembre 1970 dans la region des Grands-Fonds de Guadeloupe
(“Extraordinary Rainfall of November 26, 1970 in the Grands-Fonds region of Guadeloupe”).
The 12-page document contains a detailed analysis of the rainfall event that affected a narrow strip of the eastern portion of the Caribbean island of Guadeloupe.Map of Guadeloupe in relation to the Caribbean region (top) and a topographical map of the island (bottom). The intense rainfall of November 1970 occurred in the interior of the ‘Grande-Terre’ portion of the island about halfway between Point-a-Pitre and Sainte-Anne.
According to Klein’s report a line of very intense but short-lived rain showers developed during the late morning of November 26, 1970 over a small area of the Grande-Terre portion (eastern) of Guadeloupe. The heaviest band of showers was along a southwest to northeast axis about 20 kilometers long and 10 kilometers wide. Within this area three automated recording rain gauges were in operation. The area of flooding rain was so small that little notice was paid at the time to the event aside from a single flood victim whose body was found washed down a creek some miles from her home in the village of Boisvin. In one ravine in the area three-quarters of the vegetation was swept away. There were three gauges that had been installed by the Guadeloupe Departmental l’Equipment in 1968 and 1969 to monitor rainfall in the area. The gauges were said to be “CERF tipping buckets, type R 205 A of the ‘National Weather Service’ “ (not clear whether not this refers to the U.S. NWS or not) with drums and paper charts and three clock movements capable of recording one minute measurement gradations.
The instruments were tested after the event for accuracy and deemed satisfactory. Below is the pluviograph for the site named ‘Barot’:
The other two sites, aside from Barot, measuring intense rainfall are named Port-Blanc and Masselas. Below is a map of the location of thee three sites (as well as others on Grande-Terre). The event was short-lived as evidenced by the graphs on the illustration below with storm total precipitation being 75 mm (2.95”) for Barot, 55.5 m (2.19”) for Port-Blanc, and 49.5 mm (1.91”) for Masselas.
It is interesting to see that the other two sites also measured incredible short-duration rainfalls almost equal to Barot’s over the respective storm period.Details of the rainfall, its time of occurrence, and amounts measured during the event of November 26, 1970.
Here are the figures in inches for the three sites:
The report cited some other heavy 15-minute rainfalls measured at other locations in Guadeloupe and Martinique for comparison purposes (these all occurred during tropical storms unlike the 1970 event):CONCLUSION:
It would appear that a thorough investigation has been made of the Barot event, in many ways just as thorough as in the Unionville, Maryland case of 1956, and so this record should most likely be accepted official being well documented and verified by scientific experts as well as anecdotal evidence (local flooding and local populace reports).REFERENCE:
For those whose French is adequate, the entire Klein report may be viewed here.
This was Volume 8 issue number 2 of the ORSTOM issue in 1971. The Google English translation is very rough.
Christopher C. Burt