Back to: Wave Hazard Assessment for Selected Sites on the West Coast of Dominica, West Indies |
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The events most likely to generate significant waves for the study site are tropical cyclones. As of 1996, the US National Center for Atmospheric Research has 110 years of reliable, standardized weather data for the region. The HURSTAT program, developed by Charles Watson in conjunction with CDMP, extracted statistics for Dominica, using the latitude and longitude of a point near the center of the west side of the island.
The storms are sorted by category of intensity, according to the Saffir/ Simpson hurricane scale. HURSTAT gives the storm category according to the pressure and wind strength at the longitude and latitude chosen. Many of these historical storms had higher intensities at their centers, but the centers did not pass over the chosen location, and HURSTAT compensates for that.
Category | Pressure (millibars) |
Winds (km/hr) |
Storm Surge (meters) |
Damage |
0 Tropical storm | > = 995 | 61 - 119 | 0.5 - 1.2 | Some |
1 Hurricane | 980 - 995 | 119 - 153 | 1.2 - 1.5 | Minimal |
2 " | 965 - 979 | 154 - 177 | 1.6 - 2.4 | Moderate |
3 " | 945 - 964 | 178 - 209 | 2.5 - 3.6 | Extensive |
4 " | 920 - 944 | 210 - 250 | 3.7 - 5.4 | Extreme |
5 " | < 920 | > 250 | > 5.4 | Catastrophic |
Number of storms | 61 |
Years with storms | 45 |
Years with multiple storms | 13 |
Years with multiple hurricanes | 1 |
Category 0, tropical storms | 40 |
Category 1, hurricanes | 13 |
Category 2 " | 3 |
Category 3 " | 3 |
Category 4 " | 2 |
Category 5 " | 0 |
Intervals Found | 35 |
Average Interval | 2.885714 years |
Maximum Interval | 12 years |
Minimum Interval | 1 year |
Interval between storms (years) | Number of occurrences of interval |
1 | 15 |
2 | 10 |
3 | 1 |
4 | 2 |
5 | 1 |
6 | 2 |
7 | 1 |
8 | 1 |
11 | 1 |
12 | 1 |
Intervals Found | 17 |
Average Interval | 5.764706 years |
Maximum Interval | 20 years |
Minimum Interval | 1 year |
Interval between storms (years) | Number of occurrences of interval |
1 | 3 |
2 | 5 |
4 | 2 |
5 | 1 |
7 | 1 |
10 | 2 |
12 | 1 |
13 | 1 |
20 | 1 |
Intervals Found | 7 |
Average Interval | 13.57143 years |
Maximum Interval | 34 years |
Minimum Interval | 2 years |
Interval between storms (years) | Number of occurrences of interval |
2 | 2 |
8 | 1 |
10 | 1 |
13 | 1 |
26 | 1 |
34 | 1 |
Intervals Found | 4 |
Average Interval | 23.75 years |
Maximum Interval | 70 years |
Minimum Interval | 2 years |
Interval between storms (years) | Number of occurrences of interval |
2 | 1 |
10 | 1 |
13 | 1 |
70 | 1 |
Intervals Found | 1 |
Average Interval | 15 years |
Maximum Interval | 15 years |
Minimum Interval | 15 years |
Interval between storms (years) | Number of occurrences of interval |
15 | 1 |
Warning: With only two C4 hurricanes, interval analysis is doubtful. |
The numbers in the tables above need to be used with caution. For instance, Table 3 indicates that there would be an interval of nearly three years (2.88 years) between storms, on the average. But, looked at in another way, the Table 3 says that there are 15 chances out of 35 that any given interval will last only a year, and 25 chances out of 35 that it will last two years or less.
In order to relate these statistics to personal experience, it is useful to remember that Hurricane Marilyn of 1995 was a strong Category 1, and that Hurricane David of 1979 was a strong Category 4 hurricane.
Personal experience offers only limited help in assessing the risk of severe storms, however. Table 4 shows that there was one interval when Dominica did not have a hurricane for twenty years. People who grew up during that calm period may have felt complacent about hurricanes, based on their experience, but they were wrong to do so.