Hurricane Hugo, Puerto Rico, the Virgin Islands, and Charleston, South Carolina, September 17-22, 1989 (1994) / Chapter Skim
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Hydrology
Hydrology
Pages 48-62
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From page 48... ...
The maximum rainfall amounts for durations of 6 through 48 hours are primarily associated with hurricanes and tropical storms, and on some occasions with cold fronts and easterly waves (U.Se Weather Bureau, 1961~. The maximum 24-hour rainfall is 24 inches on the north side of the mountains of Puerto Rico associated with the San Ciriaco Hurricane of August 1899.
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From page 49... ...
PRECIPITATION Radar observations from the NWS lO-cm WSR-74S at San Juan, Puerto Rico, provide a general overview of the sequence of precipitation events over Puerto Rico and the Virgin Islands. For most of the Virgin Islands, it is the only record of the precipitation events from Hurricane Hugo, since only a few rain gages remained in' _ I 67.0 66.5 66.0 65.5 FIGURE 2-1 Rivers on Puerto Rico and relation to topography.
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From page 50... ...
Moreover, many observers in the Virgin Islands had to abandon their observation posts before Hurricane Hugo arrived. Radar was the primary too} used to examine the precipitation over the Virgin Islands.
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From page 51... ...
John and St. Thomas Hurricane Hugo's first major rainband moved across the British Virgin Islands about 1830 AST on September 17 and over St.
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From page 52... ...
John Cancel Bay Plantation 0.00 8.50 0.58 9.08 Catherineburg 0.27 4.90 0.45 5.62 Coral Bay 3.00 6.60 0.06 9.66 East End 0.02 6.24 1.11 7.37 Cruz Bay 0.36 6.46 059 7.41 St. Thomas Water Isle 0.02 5.24 0.15 5.41 estimated daily amount estimates of the daily totals were made from other daily rain gages and the recording rain gage at Cancel Bay that functioned throughout Hurricane Hugo.
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From page 53... ...
Bay Plantation -- ' ~ 1 1 olo Time 1 8 (AST)
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From page 54... ...
Throughout the time that Hurricane Hugo moved from St. Crow to north of Puerto Rico, there was little evidence of convective precipitation in the two rear quadrants of the hurricane, and the recording rain gage data on Puerto Rico and St.
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From page 55... ...
I.lla ~) Caribbean Sea 7.5 67.0 66.5 66.0 65.S FIGURE 2-4 Hurricane Hugo rainfall (inches)
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From page 56... ...
However, the actual rainfall catch at San Juan Airport was corrected by local NWS officials to compensate for the effects of the winds. From this secondary maximum a general maximum runs west with a tight gradient of rainfall amounts along the southern slopes of mountains that run eastwest across central Puerto Rico.
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From page 57... ...
In the Virgin Islands, there was flash flooding, and sheet flow must have existed over many of the roads because of the intense rainfall for at least 12 hours over the area. However, no major flooding was noted.
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From page 58... ...
a~rr~ A, ~E S~ · · f San to'.n~o 3 8 14umacaq,2 SSE Cav v I E (taval- Carn. i, dSlorna Allo ~C ~v ~ \ ~/ ~ Caribbean Sea ~ b~ I NNE Uaunabo · · Palilles Se.te ~o 0 10 ~j'eS 1 1 67.5 67.0 66.5 66,0 65.5 FIGURE 2-6 Return frequencies of 12-hour precipitation from Hurricane Hugo.
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From page 59... ...
In addition, E} Carra~zo dam on the Rio Grande de Loiza, which impounds water for the San Juan water supply, was overtopped. Figure 2-7 shows some of the erosion that was sustained at this dam In San Juan there was Booding In low-ly~ng parts of the urban area These are the same areas that frequency Good In any intense r~nfaD.
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From page 60... ...
Major hydraulic structures need to be better prepared to sustain the intense rains of a hurricane. During Hurricane Hugo, the dam on the Rio Grande de Loiza could not operate its floodgates because of a lack of emergency power and, subsequent to the hurricane, it had no spare pumps to provide fresh water to San Juan.
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From page 61... ...
In those regions where there is the potential for extensive loss of life, the hydraulic structures should be checked to ensure that they can sustain a probable maximum precipitation event. Rainfall frequency and probable maximum precipitation data have not been updated over Puerto Rico and the Virgin Islands since 1961.
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From page 62... ...
1961. Generalized Estimates of Probable Maximum Precipitation and Rainfall Frequengy Data for Puerto Rico and Virgin Islands.
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