SAIPAN — Tropical Depression 08W stalled roughly 75 miles east of the Saipan airport Tuesday morning and showed signs of strengthening, a National Weather Service lead forecaster said, raising the possibility that tropical storm warnings could be issued for Saipan and Tinian depending on how the system behaves over the following hours.
Speaking by phone on Good Morning Marianas, lead forecaster Patrick Doll said the system, which had been expected to track just north of Saipan, instead slowed dramatically and became nearly stationary. Doll said radar placed it about 75 miles east of the Saipan airport and that visible satellite and radar imagery showed it trying to organize.
Doll said the National Weather Service was in active coordination with the CNMI government Tuesday morning while it watched the system. He said it was not out of the realm of possibility that tropical storm warnings could be hoisted for both Saipan and Tinian, though he stressed that outcome was highly dependent on what the depression did over the next several hours. When a system stalls, he said, it does not always strengthen, but a stall can be a precursor to it.
The forecaster said a recent observation from Saipan measured winds of about 33 miles per hour gusting to 46, driven by a combination of heavy showers and the system itself beginning to strengthen. He said part of the gustiness was what forecasters call convectively aided wind gusts, produced by thunderstorms and heavy showers, and part was the depression organizing.
Doll said that even in a worst case, residents should expect sustained winds near 30 miles per hour at the system’s peak with gusts to about 55 miles per hour, with higher gusts possible at elevated locations such as Wireless Ridge. He said a tropical storm begins at sustained winds of 39 miles per hour and a strong tropical storm at 58 miles per hour. If the system remained stationary and continued to organize, he said, it could reach the mid to upper range of a tropical storm.
The forecaster emphasized the system did not pose a threat on the scale of Super Typhoon Sinlaku and said he doubted it would cause significant power problems unless it sat in place for a full day and kept strengthening. The greater concern with a slow-moving system, he said, was duration rather than peak strength, particularly for residents who had recently completed or partially completed repairs.
Doll said rain would come in frequent showers with breaks in between rather than falling all day, but that downpours would be heavy when they arrived, and he said residents should expect to be in the thick of the weather for the next 12 to 24 hours. He said the strongest winds were on the north and northeast flank of the system, and that forecasters expected the center to pass just south of Tinian, placing Tinian and Saipan in the strongest wind corridor.
Doll said none of the forecast models the agency runs had shown the system stalling, including the European model ensembles, the American Global Forecast System and Google’s DeepMind model, which he said had been the best-performing model of the year. He attributed part of the uncertainty to the broader pattern, saying the region was transitioning toward what could become a strong or even record El Niño, a condition that warms equatorial sea surface temperatures and can give developing storms more fuel to intensify quickly.
Doll said the National Weather Service would coordinate frequently with the CNMI government through the day and send hourly updates, including tropical cyclone updates combining radar and satellite location fixes whenever the system was in radar range. He said the agency would dedicate a staff member to social media to answer public questions and keep Saipan and Tinian residents informed, citing the islands’ ongoing recovery from Sinlaku.
