Super Typhoon Mawar poised to slam Guam with ‘catastrophic’ effects

Mawar – an extremely intense typhoon in the tropical Pacific Ocean centered about 5,800 miles west of San Francisco – is on a dangerous collision course with the U.S. territory of Guam. The super typhoon, packing maximum sustained winds of 155 mph, is predicted to slam into the island between Wednesday morning and afternoon local time. Forecasters expect the storm to unleash a “triple threat” of destructive winds, a dangerous ocean surge and excessive rainfall that will cause flooding.

“The community is advised to SEEK IMMEDIATE SHELTER, if you have not done so already,” Guam’s Office of Civil Defense wrote in a statement. “There is a potential of a catastrophic and devastating event.”

The rapidly strengthening storm reached the equivalent of a high-end Category 4 hurricane Tuesday afternoon on approach to the island. Its peak winds of 155 mph are just a few ticks shy of top-tier Category 5 strength and qualify it as “super typhoon,” meaning it has maximum winds of at least 150 mph. Tropical storms with winds of at least 74 mph in the western Pacific Ocean are called typhoons, but they are no different than hurricanes in the Atlantic Ocean with respect to how they form and their effects.

Conditions began to deteriorate Tuesday night over Guam as gusty rain squalls moved in, with progressively more violent storminess anticipated into Wednesday.

Ahead of the storm, President Biden approved an emergency declaration that orders federal assistance in response to the typhoon. In addition to civil concerns, the island is home to Andersen Air Force Base and other U.S. military assets.

Winds of 130 to 150 mph or higher are likely to lead to widespread power outages in Guam, as well as the potential for cars to be overturned, poorly constructed buildings ripped apart and foliage stripped from trees, among other effects.

Rainfall of 10 to 15 inches or more is also possible. The National Weather Service forecast office serving Guam notes the potential of up to 7 inches of rain in one hour as the eyewall – the ring of intense storms around the typhoon’s calm center – passes. Serious flooding and landslides are likely. Alex Lamers, a meteorologist with the National Weather Service, noted on Twitter that the storm is progressing at an unusually slow speed of just 7 mph, which will prolong heavy rainfall and increase the flood threat.

Gov. Lou Leon Guerrero ordered mandatory evacuations of low-lying coastal locations of the island early Tuesday. Southern villages of Inalahan, Ipan, Talofofo, Malesso, Hagat and Humatak were under particular threat from a severe ocean surge in addition to destructive winds.

“The northern eyewall could bring storm surge up to 15 feet above the normal high tide,” the Weather Service office in Guam wrote.

The storm surge is a bit like a weather-induced tsunami and can bring severe inundation of water to low-lying areas near the coast. It is historically one of the main causes of death and destruction from tropical cyclones, especially where battering waves are also added at the shore.

More than a dozen storm shelters have been opened in schools across the island, for those who live in particularly unsafe homes or regions. As of Tuesday evening local time, about 20 percent of the roughly 4,500 spaces were filled in shelters that remained below capacity.

Although the international airport was open Tuesday, most flights were canceled.

Rota, a lightly populated island north of Guam in the Mariana Islands, is also under threat from Mawar. Winds there are expected to reach lower-end typhoon levels around 80 mph, in addition to high seas, lots of rainfall and pounding waves.

According to a recent advisory from the Joint Typhoon Warning Center, Typhoon Mawar was continuing “to undergo rapid intensification, supported by very favorable upper-level conditions and a warm sea surface.”

Rapid intensification usually refers to a 35 mph increase in sustained wind speeds over the course of 24 hours. In the case of Mawar, it strengthened 50 mph in 24 hours when its maximum sustained winds leaped from 105 mph to 155 mph between Monday and Tuesday.

Such explosive maturation of a powerful cyclone requires warm ocean temperatures and favorable high-altitude winds. Scientists have found that instances of rapid intensification have become more frequent because of rising ocean temperatures spurred by human-caused climate change.

As Mawar bears down on Guam, some fluctuations in intensity are possible. The storm may be undergoing an eyewall replacement in which heavy storms around its center give way to a surrounding ring of storms. This can cause the storm to temporarily weaken before regaining strength if environmental conditions remain favorable.

Regardless of any small shifts in intensity, Mawar is likely to be one of the strongest typhoons on record to strike Guam, and the strongest since Category 5 Pongsona passed just east of the island in 2002. The last time a Category 4 or 5 made landfall on the island was in 1992 when Typhoon Omar struck.

Mawar may also become one of the strongest early-season typhoons in the region on record.

After passing Guam, Mawar is expected to continue to charge west and northwest largely unimpeded. It seems likely to remain a very powerful storm, and it will be a few hundred miles off the northern Philippines and southern Taiwan by Sunday. From there, the track is less certain as the storm slows down and begins to get pushed around by the mid-latitude winds from the west.