Tropical Storm Pena weakens far south of Hawaii

Tropical Storm Pena has weakened and could dissipate as soon as today as it moves west far south of Hawaii.

As of 5 a.m. today, Pena had maximum sustained winds of about 40 mph, down from 45 mph Sunday evening, and was centered about 585 miles south-southwest of South Point on the Big Island, according to the Central Pacific Hurricane Center in Honolulu. It was moving west at about 9 mph.

Winds of tropical storm strength extend up to 45 miles from Pena’s center.

Forecasters said satellite and other data show Pena has become less organized and may have lost a well-defined center near the ocean surface. They said it is possible the storm will dissipate as soon as later today.

Little change in strength is expected over the next 48 hours. Forecasters said Pena could strengthen slightly, to about 45 mph, by Tuesday afternoon but is not forecast to strengthen after that. Some computer forecast models show it weakening and dissipating over the next couple of days.

Forecasters said it is unclear why Pena has struggled to strengthen in a generally favorable environment, and that stronger winds higher in the atmosphere and drier air later this week should allow it to weaken. They expect it to keep moving west for the next couple of days, then turn gradually toward the west-northwest and speed up.

No coastal watches or warnings are in effect, and the hurricane center listed no hazards affecting land.

The National Weather Service in Honolulu said the difference in air pressure between a high-pressure ridge to the north and Pena, passing far to the south, has kept tradewinds strong. As the ridge weakens, tradewinds should ease today and become moderate to locally breezy Tuesday. Breezy to locally windy tradewinds are expected to return Wednesday, Veterans Day, and Thursday as a new strong high-pressure system settles north of the state, with northeast winds of 15 to 30 mph in the forecast for Kauai, Oahu, Maui, Molokai and Lanai.

Forecasters said they are monitoring whether a wind advisory will be needed because gusty winds blowing downslope could approach advisory levels. Showers should stay mostly in windward and mountain areas, with a slight increase in windward showers as a band of moisture moves south across the state as early as Wednesday night through Thursday.

A small craft advisory, which means conditions are hazardous to small boats, remains in effect until 6 p.m. today for most Hawaiian waters, with winds of 15 to 25 knots (about 17 to 29 mph) and seas of 7 to 10 feet, the weather service said. It was extended until 6 p.m. Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel and waters off the Big Island’s leeward and southeast coasts.

Separately, forecasters said a much larger northwest swell, generated by a gale-force storm east of Kamchatka, could bring surf at warning level to north- and west-facing shores beginning Wednesday and peaking Wednesday night. They said surf should drop to advisory level Thursday and fall below it by Friday. Smaller swells are expected to keep surf elevated on north- and west-facing shores through Tuesday.