Category 5 Super Typhoon Yutu Pounding U.S. Northern Mariana Islands

October 24, 2018, 9:23 AM EDT

Above: Infrared Himawari image of Super Typhoon Yutu at 10:10 am EDT October 24, 2018. At the time, Yutu was a Category 5 storm with 180 mph winds, and its northern eyewall was affecting Tinian Island in the Northern Marianas. Image credit: NOAA/RAMMB.

Earth's strongest storm of 2018, Super Typhoon Yutu, was pounding the U.S. Northern Mariana Islands late Wednesday morning (U.S. EDT) with sustained winds of 180 mph, according to the Joint Typhoon Warning Center (JTWC). At 10 am EDT, the northern eyewall of Yutu was over Tinian Island, which will likely experience catastrophic damage. Yutu is Earth’s tenth Category 5 storm of 2018, an astonishing total that has only been exceeded only once on record (twelve, in 1997). Yutu is tied with Super Typhoon Mangkhut, which also had 180 mph winds, as the strongest storm of 2018.

The U.S. Northern Mariana Islands is a U.S. commonwealth, separate from the U.S. territory of Guam. Close to two-thirds of residents of the Northern Marianas are U.S. citizens, according to a 2015 report from the commonwealth government. The three main islands are:

Saipan: population 52,263 (2017 estimate)
Tinian: population 3,136 (2010 estimate)

Rota: population 2,477 (2010 estimate)

At 10:32 am EDT Wednesday, Saipan reported sustained winds of 68 mph, gusting to 95 mph. The airport on Tinian stopped transmitting data 13 hours previous to that. The radar on Guam has been sending data only intermittently, due to an overheated-fan issue. Although Guam and Rota are on the storm’s weaker left-hand (south) side, they could still experience high wind and heavy squalls, especially Rota.

Yutu is a large typhoon, with typhoon-force winds that extent out up to 85 miles from the center, and tropical storm-force winds that extend out up to 240 miles.

Yutu radar
Figure 1. Last frame from the Guam radar of Super Typhoon Yutu before a fan failure occurred.

Catastrophic impacts expected on Saipan and Tinian

Tinian will experience a full landfall, including the eyewall winds of Yutu and catastrophic damage; Saipan lies a bit farther to the north, and may experience lower Category 4 winds, although the eyewall may affect southern Saipan. Here is the damage one can expect in Category 5 winds, according to the National Hurricane Center (note that construction in the Mariana Islands is typically built to high standards due to the frequent typhoons they get, so damage may not be this extreme):

·       High percentage of framed homes destroyed, with total roof failure and wall collapse.

·       Fallen trees and power poles will isolate residential areas.

·       Power outages will last for weeks to possibly months.

·       Most of the area will be uninhabitable for weeks or months.

NWS-Guam is forecasting seas to increase to 30 to 40 feet near the center of Yutu as it passes, with high surf and rip currents throughout the Marianas through at least Thursday. They predict the following peak storm surge inundations:

·       Saipan and Tinian: Up to 15 to 20 feet on windward sides as Yutu approaches; after the storm passes west of the island, 5 to 7 feet along west-facing shorelines

·       Rota: Up to 2 to 4 feet on windward sides

·       Guam: Up to 2 to 4 feet on windward sides

Here are the expected rainfall totals from Yutu through Thursday:

·       Saipan and Tinian: 10 to 15 inches

·       Rota: 6 to 8 inches

·       Guam: 4 to 6 inches

This rainfall is likely to trigger dangerous flash flooding and dangerous landslides in higher terrain. A flash flood watch has been issued in the islands through late Thursday night.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.

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Dr. Jeff Masters

Dr. Jeff Masters co-founded Weather Underground in 1995, and flew with the NOAA Hurricane Hunters from 1986-1990.

jeff.masters@weather.com

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