INTRODUCTION
rains, and in some areas, high storm surge. The storm caused several deaths and widespread devastation across the Caribbean islands and southeastern continental United States. Irma formed near Cape Verde on August 30, 2017, and moved south and west, fluctuating between Categories 2 and 3 from September 1 to September 4, 2017 (Figure 1-1, top). The hurricane reached its maximum intensity of 178 miles per hour (mph) (287 kilometers per hour [kph]) sustained winds on September 5 about 80 miles (130 kilometers) east- Table 1-1: The Saffir-Simpson Hurricane southeast of Barbuda. On September 6, 2017, Irma made Wind Scale its first landfall on Barbuda as a Category 5 hurricane with maximum wind speeds of 178 mph (287 kph), making Wind Speed landfall next on St. Martin and Virgin Gorda. Irma’s eye Category mph kph passed 58 miles (93 kilometers) north of Puerto Rico’s capital, San Juan (and less than 30 miles [48 kilometers]) from Culebra) over September 6-7, 2017, before temporarily 1 74–95 119–153 weakening to Category 4. Irma made landfall on Little Inagua in the Bahamas on September 8, 2017, and in Cuba 2 96–110 154–177 on September 9, 2017, as a Category 5 hurricane with 167 mph (269 kph) winds, after which its interaction with land 3 111–129 178–208 caused it to quickly weaken to Category 2. Over the warm waters of the Straits of Florida, the storm re-intensified to a 4 130–156 209–251 Category 4 before making its sixth landfall on Cudjoe Key with winds of 130 mph (215 kph) on September 10. Later 5 ≥ 157 ≥ 252 that day, Irma made its seventh landfall on Marco Island in Florida as a Category 3 hurricane. Finally, the system The Saffir-Simpson hurricane wind scale degraded into a remnant low over Alabama and dissipated classifies hurricanes according to their peak over Missouri on September 13, 2017, (Cangialosi, Latto 1-minute wind speed at 33 feet (10 meters) above ground level over unobstructed terrain. and Berg 2018). Hurricane Irma passed less than 30 miles (48 kilometers) from Culebra as a Category 5 hurricane with wind speeds estimated to be greater than 160 mph (257 kph). The highest wind speed recorded in the Commonwealth was 58 mph (93 kph) sustained, with a gust of 89 mph (143 kph), on the island of Culebrita. On the island of Puerto Rico, the highest recorded sustained wind speed was 55 mph (89 kph), with a gust of 74 mph (118 kph), in San Juan Bay. Irma’s eye passed about 57 miles (92 kilometers) north of San Juan on September 6 (Cangialosi, Latto and Berg 2018). The peak wind gust map (Figure 1-2) depicts the high winds experienced in eastern Puerto Rico during Irma, with the highest wind speeds on the islands of Culebra and Vieques and along the northeastern coast of the island of Puerto Rico. Figure 1-2 shows estimated 3-second wind gust speeds at 33 feet (10 meters) above ground level for open terrain (ASCE Exposure Category C) for comparison with ASCE 7 design wind speeds. In contrast, Figure 1-3 shows maximum measured sustained and gust wind speeds. Note that these observations may have been made at exposure conditions or elevations above ground that differ from those modeled in Figure 1-2. Irma also caused storm surge flooding in a few areas on the north coast (Figure 1-4). The deepest inundation was 1–3 feet (0.3–0.9 meters) above ground level near Arecibo and west of San Juan in Bayamón and Dorado.
HURRICANES IRMA AND MARIA IN PUERTO RICO
MITIGATION ASSESSMENT TEAM REPORT
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