UPDATE: Sunday 11 p.m.

Tropical Storm Calvin continued to rapidly decline in strength Sunday night as it approaches the Central Pacific on a track that would bring it near or over Hawaii island by Wednesday.

Before 11 p.m. Sunday, the National Hurricane Center said Calvin had maximum sustained winds of 50 mph, and was 1,030 miles east of Hilo moving west at 18 mph. Tropical storm-force winds extend up to 90 miles from the center.

Calvin started the day as a strong tropical storm with 70 mph sustained winds, but has weakened significantly as it moves over cooler water.

Calvin is still forecast to be a weak tropical storm, with maximum sustained winds of 40 mph on Wednesday when it is expected to be near or over the Big Island, forecasters said.

Despite its weakened state, officials say, Calvin still threatens to deliver heavy rain and dangerous, “life-threatening” surf to the islands.

RELATED STORY: Hawaii officials urge vigilance, preparation as Calvin threatens

“From Tuesday night into Thursday, storm total rainfall amounts of 4-7 inches are possible along windward areas of the Big Island of Hawaii, with lower amounts (1-4 inches) expected elsewhere in the state,” the hurricane center said. “This rainfall could lead to localized flash flooding and mudslides.”

In addition, swells generated by Calvin are expected to begin reach the islands over the next couple of days. “These swells are likely to cause life-threatening surf and rip currents,” forecasters said earlier Sunday.

After passing the Big Island, Calvin is expected to continue on a path south of the other islands as a tropical depression with 35 mph sustained winds, then dissipate as it moves west away from the state late this week.

The storm is expected to enter the Central Pacific overnight, and forecasters with the Central Pacific Hurricane Center in Honolulu will take over monitoring the storm from the Miami-bases NHC on Monday.

A tropical storm watch could be issued for portions of the main Hawaiian islands Monday, officials said.

A tropical storm watch for Hawaii island’s windward waters was issued late Sunday.

The National Weather Service said northeast to east winds of 30 to 40 knots, and 12 to 18 foot seas are expected. “Tropical storm force winds could begin as early as Tuesday afternoon. Seas will build rapidly late Tuesday afternoon, then peak Tuesday night,” forecasters said.

They said strong winds will cause hazardous seas that could capsize or damage vessels, and reduce visibility.

5:45 p.m.

Tropical Storm Calvin continues to slowly weaken, but is still forecast for either a direct hit or near-miss for Hawaii island by Wednesday, bringing with it the risk of heavy rainfall, dangerous surf and rip current conditions.

As of 5 p.m., Tropical Storm Calvin was packing maximum sustained winds of 60 mph, with higher guests, and was centered 1,150 miles east of Hilo, moving west at 17 mph. Tropical storm-force winds extend up to 90 miles from the center, according to the National Hurricane Center in Miami.

According to a forecast of the current five-day track, Calvin will enter “the central Pacific basin soon, and move near or over the (Hawaii island) early Wednesday. It should then continue westward, becoming post-tropical on Thursday before dissipating.”

There are no coastal watches or warnings in effect, but a tropical storm watch may be required for portions of the main Hawaiian islands tonight, forecasters said.

Calvin’s latest five-day forecast track has the storm near or over the Big Island Wednesday as a minimal tropical storm with 40 mph maximum sustained winds, then passing south of the other islands as a tropical depression and dissipating late in the week after it moves west away from the state.

NHC forecasters, in a 5 p.m. update, said that the official track forecast was basically unchanged from the 11 a.m. advisory.

They added that rainfall of 4 to 7 inches is possible along windward areas of Hawaii island from Tuesday night into Thursday, with lower amounts, about 1 to 4 inches, expected in other parts of the state. Forecasters said that “this rainfall could lead to localized flash flooding and mudslides.”

“While the exact storm track near Hawaii is still uncertain,” forecasters said, “there is potential for portions of the state to experience some heavy rainfall, dangerous surf and rip current conditions, along with minor wind impacts from Calvin.”

The National Weather Service said that before Calvin arrives Tuesday night through Wednesday night, the islands will see moderate to breezy trade winds and some showers in windward areas. Trade winds will resume after Calvin, or its remnants, passes the state Thursday.

12:30 p.m.

The center of Tropical Storm Calvin is forecast to move into the central Pacific basin late tonight or early Monday and approach the Hawaiian Islands on Tuesday and early Wednesday.

As of 11 a.m., Tropical Storm Calvin was packing maximum sustained winds of 65 mph, centered 1,260 miles east of Hilo moving west at 16 mph. Tropical storm-force winds extend up to 90 miles from the center, according to the National Hurricane Center in Miami.

The current five-day track “shows the center of Calvin passing near or over (Hawaii island) early Wednesday, then continuing westward and becoming post-tropical on Thursday before dissipating.”

Forecasters said Calvin’s approach, includes the potential for “heavy rainfall and dangerous surf and rip current conditions.”

There are no coastal watches or warnings in effect, but a Tropical Storm Watch may be required for portions of the main Hawaiian islands later today, forecasters said.

Forecasters said this afternoon that the satellite presentation of Calvin has not changed much since the morning advisory, but that satellite intensity estimates continue to fall. The next complete advisory from the National Hurricane Center is slated for release at 5 p.m. today.

NHC forecasters said this afternoon that Calvin is expected to continue weakening over the next few days as it moves into a “drier, more stable environment during the next couple of days.”

Forecasters said this afternoon that Calvin’s exact storm track near Hawaii is still uncertain, but said, ” there is potential for portions of the state to experience some heavy rainfall, dangerous surf and rip current conditions, and minor wind impacts from Calvin.”

Swells generated by Calvin are expected to reach the islands over the next couple of days. “These swells are likely to cause life-threatening surf and rip current conditions,” forecasters said this afternoon.

They added that rainfall of four to six inches is possible along windward areas of Hawaii island on Wednesday and Thursday, with lower amounts, approximately one to three inches, expected in other parts of the state.

PREVIOUS COVERAGE

Hurricane Calvin was downgraded overnight to a tropical storm as it approaches the Central Pacific but is still on track to pass near or over Hawaii island later this week, forecaster said this morning.

“Tropical Storm Calvin is expected to move close to, or over, the islands from Tuesday night through Wednesday night, bringing the potential for a period of locally strong winds, heavy rain, and high surf,” the National Weather Service in Honolulu said this morning. “Stay tuned for forecast updates that will provide greater forecast detail.”

Swells generated by Calvin are expected to reach the islands over the next couple of days. “These swells are likely to cause life-threatening surf and rip current conditions,” forecasters said.

As of 5 a.m., Tropical Storm Calvin was packing maximum sustained winds of 70 mph, centered 1,355 miles east of Hilo moving west-northwest at 16 mph. Tropical storm-force winds extend up to 105 miles from the center, according to the National Hurricane Center in Miami.

There are no coastal watches or warnings in effect, but a Tropical Storm Watch may be required for portions of the main Hawaiian islands later today, forecasters said.

“On the forecast track, the center of Calvin will move into the Central Pacific basin late tonight or early Monday morning and approach the Hawaiian islands on Tuesday,” the hurricane center said this morning.

Calvin is expected to continue weakening over the next few days as it moves over cooler water and encounters wind shear in the Central Pacific.

The current five-day track has Calvin reaching the Big Island early Wednesday as a weak tropical storm with maximum sustained winds of 40 mph, then traveling just south of the rest of the state as a “post-tropical remnant low” with winds of 35 mph. The storm is expected to dissipate by Friday after it passes the islands to the south, according to the latest NHC forecast.

Before Calvin reaches Hawaii, forecasters said, the islands will see moderate to breezy trade winds, bringing some showers to windward areas, especially during nights and mornings.