West Side

Today: Sunny early in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 79 to 87. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 71 to 78. Northeast winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 20 percent.

Sunday: Breezy. Partly sunny with isolated showers in the morning, then cloudy with numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 79 to 87. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 60 percent.

South Side

Today: Sunny early in the morning then becoming mostly sunny. Breezy. Highs around 88. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Lows 72 to 81. Northeast winds 10 to 15 mph.

Sunday: Mostly cloudy. Scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 88. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

North Shore

Today: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 67 to 72 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 74 near the shore to around 59 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 82 near the shore to 68 to 73 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Sunny early in the morning then becoming mostly sunny. Breezy. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy after midnight. Lows around 74. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Sunday: Mostly cloudy. Breezy. Isolated showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 81 to 88. Northeast winds 10 to 20 mph. Chance of rain 60 percent.

Upcountry

Today: Partly cloudy early in the morning then becoming partly sunny. Scattered showers early in the morning, then isolated showers in the afternoon. Highs 65 to 82. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 56 at the visitor center to around 50 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 71 at the visitor center to around 60 at the summit. East winds up to 15 mph. Chance of rain 70 percent.

East Maui

Today: Breezy. Mostly cloudy with scattered showers. Highs around 82 near the shore to 67 to 72 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 74 near the shore to around 59 near 5000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 82 near the shore to 68 to 73 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Sunny early in the morning then becoming mostly sunny. Breezy. Highs 78 to 84. Northeast winds 15 to 25 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows 69 to 74. Northeast winds 10 to 25 mph.

Sunday: Mostly cloudy. Breezy. Numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 78 to 85. Northeast winds 10 to 20 mph decreasing to up to 15 mph in the afternoon. Chance of rain 60 percent.

Kaunakakai

Today: Sunny early in the morning then becoming mostly sunny. Breezy. Highs 76 to 89. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Lows 64 to 77. Northeast winds 10 to 20 mph.

Sunday: Breezy. Partly sunny with isolated showers in the morning, then cloudy with numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 77 to 90. Northeast winds 10 to 20 mph. Chance of rain 60 percent.

Detailed Forecast

Synopsis

Breezy trade winds continue through the weekend with clouds and showers focused windward and mauka. Hurricane Lowell is forecast to move close to Kauai County Monday night as a category 2 to 3 hurricane. Impacts such as high surf and heavy rain are forecast to extend hundreds of miles from the center of Hurricane Lowell, potentially impacting any of the islands.

Discussion

Breezy trade winds will continue through the weekend. Radar and infrared satellite show partly cloudy skies and scattered trade showers this morning. Clouds and showers will gradually increase through the weekend as trade winds push in a bit more upstream moisture. Focus of the showers will be windward and mauka and occur mostly during the overnight and early morning hours through Sunday.
Our attention will then turn to Hurricane Lowell, now a category 4 on the Saffir-Simpson scale (155 mph maximum sustained winds), and impacts to Hawaii. Lowell is about 625 miles south southwest of Kauai still tracking slowly to the west. Lowell is expected continue westward today and then turn north Sunday. Lowell is expected to make its closest approach to the main Hawaiian Islands Monday night as a category 2 to 3 hurricane, and any deviation eastward from its forecast track could bring more severe wind impacts especially to Kauai County. It is currently too early for tropical watches and warnings this morning, but will be discussed and determined soon. If a watch is issued, we will move to alternative schedule of for this forecast disscussion, zone, state and coastal water forecast to coincide with our production of the Hurricane Local Statement and the National Hurricane Center advisory.
As far as expected impacts, there remains a risk for high surf, strong winds, and heavy rainfall for all islands. A south swell has already elevated surf across south facing shores and will become extra large out of the southwest Sunday night/Monday as Lowell approaches. High surf will have the greatest coverage across the state as the swell moves from the storm, so confidence is highest with the surf and surge impacts.
Winds will shift southward and deep tropical moisture will advect across all islands late Sunday through Tuesday, producing warm and humid weather conditions. Heavy rainfall is likely to impact most islands at some point during Lowell's passage.
High pressure builds back over the islands from Tuesday afternoon onward as a wet trade wind pattern with periods of passing showers sets up across the state into the end of next week. A moist area left from the remains of Karina is now modeled to move through the area Wednesday afternoon through Wednesday night, possibly providing an especially wet period.

Aviation

Breezy trade winds will gradually decrease in strength through Sunday as the ridge north of the islands weakens. Hurricane Lowell roughly 600 miles south of Kauai continues to journey westward. Bands of unsettled clouds are developing in the trade winds just northeast of the Hawaiian Islands. Expect increasing cloud and shower trends bringing a few passing MVFR conditions over windward mountain areas lasting into the early morning hours with the potential for an AIRMET Sierra issuance for mountain obscurations.
AIRMET Tango remains in effect for low level mod turb over and south through west of all island mountains.

Marine

A surface high persists north of the Hawaiian Islands and will slowly drift east through the weekend. Currently, Hurricane Lowell is around 550 nm south-southwest of the islands as it continues to track west. The trade winds are beginning to ease slightly as Lowell gains a bit of distance from the island chain, and the Small Craft Advisory (SCA) has been trimmed back to only the windier waters and channels around Maui County and the Big Island through this afternoon. Lowell is expected to turn northward on Sunday, which will cause winds to veer to the southeast to south with the strongest winds over the western end of the state.
Confidence has grown with the latest updates from the National Hurricane Center for the potential for hurricane conditions in the offshore waters west of 160W Sunday night through Tuesday. While confidence is increasing in the track forecast of the cyclone, a deviation in track of 50 nm west or east from the current predicted path will have significant differences in impact for the coastal waters around Kauai County. As for Hurricane Karina, it is expected to weaken and pass northeast of the state.
Southerly swell generated by Hurricane Lowell will keep surf along south facing shores at High Surf Advisory criteria today. As Lowell begins to turn north on Sunday, its swell will gradually veer from south to southwest and begin a rapid upward trend. Very large surf exceeding warning criteria appears increasingly likely for south and west facing shores on Monday. Coinciding also with monthly high tides, this will create the potential for impacts to harbor entrances, channels, as well as coastal properties and infrastructure including roadways. Surf will then rapidly decrease on Tuesday after the hurricane passes north of the island chain. A pulse of northwesterly swell could then bring a bump to north shore surf on Tuesday and fade through Thursday.
East facing shores will see continued advisory level surf from a large, medium-period east swell generated by Hurricane Karina to the east of the islands. This swell will gradually fade early next week as Karina weakens into a tropical storm. Late next week, surf along east facing shores could be bolstered by some medium-period swell generated by Hurricane Marie in the East Pacific. Otherwise, expect choppy conditions from easterly trade wind swell through the week.

Fire weather

Periods of passing showers will mainly impact windward and mountain slopes through early Sunday. Considerably more showers are likely over most areas from Sunday afternoon into early next week. The temperatures inversion heights near Maui and the Big Island will range from 6,000 to 7,000 feet elevation today.

Hydrology

NBM guidance initially brings heavy rain across south slopes of Maui and Big Island as early as Sunday evening followed by the rest of Maui County and Oahu Monday morning, and Kauai Monday afternoon. Initial storm total rainfall estimates range from 2 to 8 inches statewide. With a significant period of south to southeast winds forecast, we expect locally higher amounts (around 10 inches) along south and southeast slopes. A Flood Watch will be considered for all or portions of the state.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Sunday for Niihau, Kauai Leeward, Waianae Coast, Olomana, Kahoolawe, Maui Leeward West, Kona, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Molokai Windward, Molokai Southeast, Molokai West, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov