Update, 5 p.m.

A weakening Tropical Storm Ema is passing south of Necker Island and is no longer a threat to the main Hawaiian islands. But a tropical storm watch remains in effect for portions of Papahanaumokuakea Marine National Monument from Nihoa to French Frigate Shoals to Maro Reef.

Tropical storm conditions are possible in the watch area on Sunday, mainly from Necker Island to French Frigate Shoals to Gardner Pinnacles. Heavy rainfall may affect portions of the Papahanaumokuakea Marine National Monument from Nihoa to French Frigate Shoals to Maro Reef through Sunday night.

Ema is moving northwest near 12 mph with winds near 45 mph. Steady weakening is expected and Ema is expected to dissipate by Monday.

11:08 a.m.

A tropical storm watch has been issued for portions of Papahanaumokuakea Marine National Monument as Tropical Storm Ema approaches from the southeast, the Central Pacific Hurricane Center said.

The watch is in effect for the marine monument from Nihoa to French Frigate Shoals to Maro Reef. Tropical storm conditions are possible in the watch area, within 24 to 36 hours, the center said.

Ema is about 295 miles west of Lihue and 245 miles southeast of French Frigate Shoals. The storm is moving toward the north about 13 mph and is expected to turn towards the northwest later today.

Maximum sustained winds are near 50 mph, but a gradual weakening is expected over the next two days.

Previous coverage

Tropical Storm Ema has formed far southwest of Kauai today but is expected to weaken by Sunday, according to the Central Pacific Hurricane Center.

As of 5 a.m. today, Ema was located about 300 miles west-southwest of Lihue and about 255 miles southwest of Nihoa, packing maximum sustained winds of 40 mph with higher gusts.

Ema may bring heavy rainfall and elevated surf affecting portions of the Papahanaumokuakea Marine National Monument from French Frigate Shoals to Maro Reef through Sunday night, the Central Pacific Hurricane Center said.

No coastal watches and warnings are in effect. However, a tropical storm warning is in effect for Hawaiian offshore waters beyond 40 nautical miles out to 240 nautical miles, including a portion of the Papahanaumokuakea Marine National Monument east of French Frigate Shoals, according to the National Weather Service.

“Seas given as significant wave height, which is the average height of the highest 1/3 of the waves. Individual waves may be more than twice the significant wave height,” NWS said.

Ema was moving toward the northwest near 12 mph and expected to continue in the general motion over the next couple of days.

Forecasters are predicting little change in Ema’s strength today and tonight, but the storm is expected to weaken into a post-tropical remnant low Sunday and dissipate Sunday night.

“Ema will be entering an increasingly unfavorable environment over the next couple days, with increasing west-southwesterly vertical wind shear and dry mid-level air. This should result in a more shallow system driven by the low-level boundary layer flow,” according to forecasters.

Tropical-storm-force winds extend outward up to 45 miles from the center.

“Although Tropical Storm force winds are not expected to affect the northwest Hawaiian Islands, interests in the Papahanaumokuakea Marine National Monument should continue to monitor the progress of Ema,” the forecast said.

The next update will be issued at 11 a.m. Check back for more details.