Hurricane (Typhoon), Guam
- When
- September 10, 12:00 AM GST to September 11, 12:00 AM GST
- Where
- Guam forecast zone
- Category
- 2
- Property damage
- $7.6 million
- Crop damage
- $2.0 million
- Reported by
- NWS Storm Survey
A tropical disturbance was located over the Northern Marshall Islands on the morning of 7 Sept 2018. By the afternoon of the 7th the disturbance was classified as Tropical Depression 26W north of Kwajalein. By the morning of September 8th, 26W had intensified into Tropical Storm Mangkhut and was located 130 miles north-northeast of Enewetak. After further strengthening, Mangkhut became a typhoon by the afternoon of September 9th. The typhoon continued to move towards the Marianas and on 10 September the 21-mile-wide eye of Mangkhut passed over Rota about 30 miles to the northeast between 1700 and 1900 ChST. Despite moving away from the Marianas, Magkhut's continued intensification caused winds to decrease rather slowly over the islands. Even though it passed over Rota, the highest sustained wind and highest gust were not observed there, but over northern Guam at Andersen AFB. At Andersen, the winds reached 67 mph with a gust to 87 mph at 2101 ChST (1101Z) on the 10th. On Rota the highest wind observed was 58 mph with a gust to 82 mph between 1600 and 1700 ChST, although winds probably were higher than this over southern parts of Rota as the eye moved over that island. The remote observing system at the airport became inoperative after reporting the peak observation. The airport is located on the northern part of the island while the major population center is on the southern part of the island. There is no observing equipment there, but that location likely experienced the stronger winds. At the time of passage over Rota, Mangkhut was a Category 2 typhoon so sustained winds should have reached near 100 mph. Maximum estimated rainfall was recorded over Guam at Andersen AFB with 9 inches. Rota only measured 1.13 inches but this is in error as the recording rain gauge had no reports after 1800 ChST (08Z) as the the eye wall passed over the island. Rainfall reports in inches on Guam were: Umatic Rain Gauge (RG): 8.46 Almagosa RG near Santa Rita: 10.15 Fena RG at the Reservoir Pump Station, near Santa Rita: 9.1 Windward Hills RG near Talofofo: 7.89 Mount Chachao RG near Nimitz Hill, Piti: 7.74 Dededo RG near Dededo-Yigo boundary: 10.11 Mt. Santa Rosa RG near Pagat, Mangilao: 8.07 Geomag Observatory RG, Andersen AFB, Guam: 10.86 On Guam 1500 people had gone to the shelters, with shelters across northern Guam filled to capacity. As the storms passed over Rota, the strongest winds on Guam were over the northern half. These stronger winds destroyed or heavily damaged many of the tin and wood houses over the northern section of Guam. The typhoon temporarily knocked out 80 percent of the power on Guam, with 100 percent of the power knocked out on Rota. 662 families took to the shelters on Rota and only 76 families did the same on Tinian and Saipan. Preliminary estimates of infrastructure and repair costs were $4.3 million for Guam, and $3.3 million for Rota, Tinian, and Saipan.