Typhoon Surigae, previously a tropical storm, is rapidly gaining strength and is set to intensify further over the weekend as it churns through the western Pacific Ocean. Late Saturday into Sunday, it could sideswipe the Philippines and bring gusty winds, heavy rain, and rough surf. While it will be a close call, the storm's worst conditions, equivalent to a Category 4 hurricane, should stay out to sea.
Both the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) and the Joint Typhoon Warning Center in Honolulu currently predict the storm to remain just offshore the Philippines. However, some forecast models suggest the storm, called "Bising" in the Philippines (which uses a different naming system), could track close enough to the coast to bring hazardous weather.
PAGASA, the Philippine's meteorological agency, says it may issue a signal 1 or 2 warning (on its 1 to 5 scale for wind impacts), signifying the possibility of modest to moderate wind damage from the typhoon. But it writes that if the track of the storm shifts any close to the coast "there is a possibility that some localities will be placed under higher levels of wind signal."
Presently, PAGASA is calling for moderate to heavy rain over the Eastern Visayas and Cometes islands and the possibility of "flooding (including flashfloods) and rain-induced landslides."
Surigae is the first typhoon of the season in the western North Pacific, a region known for its annual barrage of fierce storms. Super Typhoon Goni struck Catanduanes in the Philippines at Category 5 strength last October, estimated to be the most powerful storm observed anywhere globally in the previous four years.
Surigae is one of several storms to have developed in the past two weeks in the Pacific Ocean, with Cyclones Odette and Sergia swirling through Australian waters earlier in April.
Surigae was first named on Tuesday, and now stands as the equivalent of a Category 2 hurricane with maximum winds estimated at 90 mph. It was located about 150 miles north-northeast of Palau, an island nation in the west tropical Pacific, and had already passed well southwest of Guam and the Northern Mariana Islands. The island of Yap in the Federal States of Micronesia encountered gusty winds and squalls, but on Guam proper, impacts were limited to a light breeze and hazardous seas of 9 feet or greater on south- and west-facing reefs.
On satellite, Surigae appeared considerably more organized than it had even eight to 12 hours prior, exhibiting a more symmetrical form amid a circular "central dense overcast" region, or CDO. Convection, or shower and thunderstorm activity, had largely consolidated within this zone, with a few additional spiral rain bands becoming increasingly organized and feeding into the circulation as well.
Several "hot towers," or locally taller thunderstorm tops, can be seen in one arc of rain squalls northwest of the central dense overcast. Drier air is present southeast of the storm, cutting back a bit on convective activity there.
Farther to the west, the outer periphery of high-altitude outflow clouds and a few showers were affecting central and southern parts of the Philippines.
Satellite imagery also indicated some warming cloud tops towards the middle of the storm, suggestive of sinking air commensurate with the attempted formation of an eye. That's adjacent to extremely cold, tall cloud tops within a discernable eyewall. While visible satellite imagery indicates the eye hasn't fully cleared out yet, there is likely a local minimum in winds. The eye will likely improve in structure once vigorous thunderstorms fully wrap around the center.
In the coming hours and days, the Joint Typhoon Warning Center is anticipating Surigae will gain strength. Its environment is ripe for strengthening, characterized by very warm sea surface temperatures between 84 and 87 degrees and relaxed upper-level winds. Wind shear, a change of wind speed and/or direction with height, is weak; that will allow the storm to further blossom unimpeded.
Surigae is expected to make a run at 140-mph Category 4-equivalent strength by Sunday before slowly tempering some as it curves to the northwest and eventually north. The strongest winds will remain in the eyewall, which should pass well out to sea.
Depending on its track, tropical storm-force winds of 39 mph or greater may or may not scrape the east coast of the Philippines. But even if the storm center stays well offshore, bands of heavy rainfall and breezy squalls would be possible through the weekend, especially in the central Philippines.
There is an outside chance that high pressure over the western Pacific could steer Surigae closer to Luzon than initially forecast; that's something that will have to be monitored.
Thereafter, Surigae should drift out to sea and eventually weaken, potentially affecting the jet stream and influencing the upper-air weather pattern over the Pacific and even North America into May. Confidence on how that may evolve is very low.
Before Surigae became the first Pacific typhoon of the season, a tropical storm named Dujuan brought flood rain and wind gusts approaching 45 mph to the central Philippines in late February. In addition, tropical depressions formed in January and March.
South of the equator, where cyclone season is drawing to a close, it has been active one. Storms there aren't typically as strong as in the north Pacific or Atlantic, and resultantly Australia and Fiji use a different scale. One storm - Niran - attained Category 5 strength, though it would only match to a level 3 on the Saffir-Simpson scale.
On April 8, Odette and Seroja orbited one-another in a Fujiwhara dance northwest of Australia. Odette petered out while Seroja impacted northern regions of Western Australia with winds gusting up to 110 mph.
In the Atlantic, meanwhile, meteorologist are gearing up for what could be another busy hurricane season.
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