A study on Super Typhoon Yutu had to reach back 56 years ago just to find something to compare it with.
A joint study done by the National Weather Service-Guam and the University of Guam concluded that Super Typhoon Yutu came extremely close in magnitude and intensity to Guam’s Super Typhoon Karen, which left 95 percent of Guam in ruins back in 1962.
According to a joint statement from the National Weather Service in Guam and the University of Guam, Chip Guard of NWS and Dr. Mark Lander of UOG did an assessment on the southern one-third of Saipan on Nov. 13, a similar assessment on Tinian on Nov. 14, and the final assessment for the northern two-thirds of Saipan on Nov. 15 to determine the scope of damage and the intensity of the storm.
The study concluded that Super Typhoon Yutu is, by far, one of the strongest typhoons to make landfall (eye passage) in the CNMI and rivals Super Typhoon Jean that devastated Saipan in April 1968 and Super Typhoon Karen that devastated Guam in November 1962.
Super Typhoon Karen flattened Guam back in 1962 with maximum sustained winds of 175 miles per hour and gusts of over 200.
In the final analysis, Guard and Lander also concluded that Yutu’s maximum wind intensity while crossing Saipan and Tinian was at 170 mph, with gusts of up to 200 mph.
The Yutu assessment also depended on an evaluation of the damage to structures and vegetation, on the measurement of coastal inundation, and on individual interviews to determine exactly where the eye passed.
The assessment team found that the worst damage to vegetation appeared to be on northern Tinian. The power distribution systems on both Tinian and the southern half of Saipan were severely damaged, with hundreds of power poles toppled, hundreds of transformers destroyed, and hundreds of miles of downed power distribution lines.
They also found that hundreds of homes were severely damaged, and most wood and tin roofs were destroyed, even those anchored to concrete structures. Concrete structures with concrete roofs fared relatively well, despite reports of many metal storm shutters being ripped from buildings. The maximum coastal inundation was measured at around 30 feet above sea level at Long Beach on the east coast of Tinian. Water levels of 20 to 25 feet were measured at Tank Beach on eastern Saipan and Ladder Beach on southern Saipan.
Lander was on Saipan during the passage of the typhoon and set up a rain gauge and a barometer at his location in San Vicente. All official ground-based instrumentation failed on Tinian and Saipan as the winds surged well above 100mph. The minimum pressure in San Vicente dropped to 921.7 millibars (mb), according to Lander’s findings.
After necessary adjustments, the pressure was used to estimate the minimum central surface pressure of Yutu, which was found to be somewhere in the range of 905-910 mb. His rain gauge recorded about 10 inches of rainfall during the storm, which was used to supplement the 2.66 inches of rainfall recorded up to midnight at the Francisco C. Ada/Saipan International Airport.
A Saipan resident measured a peak wind speed of 168 mph at his residence on Wireless Ridge (722 feet above sea level), and an anemometer located at the Pacific Amusement Office on Middle Road in Gualo Rai recorded a peak wind speed of 133 mph. These wind measurements provided important information about the distribution of winds across Saipan.
Yutu began as a disturbance in the western Marshall Islands around Oct. 19 and headed toward the Marianas over the next week at an average speed around 12 mph.
Yutu passed directly over the island of Tinian on the night of Oct. 24 through the early morning hours of Oct. 25.
The impacts to Tinian and the southern half of Saipan were catastrophic. Yutu’s satellite intensity estimate peaked at 155 knots (178 mph and category 5) just prior to landfall over Tinian and the southern half of Saipan. That value seems to establish the upper limit of the maximum intensity while over the islands.
In comparison, the Joint Typhoon Warning Center measured Typhoon Soudelor at 180 mph, making it a category 5-equivalent super typhoon.