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JTWC upgrades Invest 90W's chances of becoming storm

By Barbara Brown

The Joint Typhoon Warning Center has upgraded Invest 90W's potential to develop into "a significant tropical cyclone over the next 24 hours," from low to medium.

The weather system, which earlier Friday was located 163 nautical miles southwest of Pohnpei, now is 131 nautical miles southeast of Chuuk, or 686 miles southeast of Guam.

"All model solutions are in general agreement that Invest 90W will continue to track west to northwestward over the next 24 hours," according to the latest JTWC bulletin.

The bulletin also discusses the variation in the global forecast ensemble of tracking models. "Numerical model solutions generally disagree on the timing and degree of intensification," the bulletin states. "The environment is favorable for further development with warm sea surface temperatures, low to moderate vertical wind shear and divergent upper level flow aloft."

The National Weather Service has not issued any special weather statement for the Mariana Islands. However, in a special weather statement for Palau, Yap, and Chuuk, the NWS states 90W "continues to show some gradual organization.

"Latest scatterometer data shows 20 to 25 kt winds north of the center with 15 kt westerlies south of the center. Pockets of heavy showers and thunderstorms continue to flare up near the center and farther west to the south of Chuuk and to the northeast toward Pohnpei. "Models show a slow westward motion of this circulation, bringing it near or just south of Chuuk Saturday or Sunday. As this circulation approaches, gusty showers and thunderstorms will increase. Current forecasts expect more widespread showers by Saturday and continuing through the weekend. Similarly, strongest wind gusts are anticipated tonight and Saturday, and could reach up to 35 kt. Through Sunday, 4 to 6 inches of rain is possible. "Gusty winds and elevated, choppy seas will make conditions hazardous for small craft the next few days. Residents should reconsider inter-island boating this weekend. "Be alert for rapidly rising water levels at rivers and streams, and local flooding in poor drainage and low-lying areas. Residents should stay up to date with the latest information, and listen to instructions from your local Chuuk weather service office and emergency officials." - National Weather Service May 28, 2021 11:56 a.m. Special Weather Statement

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