West Kaua’i

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 76 near the shore to around 66 above 3000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs 87 to 94 near the shore to around 79 above 3000 feet. East winds up to 25 mph. Chance of rain 40 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Scattered showers in the evening, then showers likely after midnight. Locally heavy rainfall possible after midnight. Lows around 77 near the shore to around 67 above 3000 feet. Northeast winds up to 30 mph. Chance of rain 70 percent.

South Kaua’i

Tonight: Breezy. Mostly clear with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 73 to 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Saturday: Windy. Partly sunny with scattered showers. Highs 80 to 91. Northeast winds 15 to 30 mph. Chance of rain 50 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Scattered showers in the evening, then showers after midnight. Locally heavy rainfall possible after midnight. Lows around 76. Northeast winds 20 to 30 mph. Gusts up to 50 mph after midnight. Chance of rain 90 percent.

Kaua’i Mountains

Tonight: Breezy. Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows around 71 in the valleys to around 64 above 4000 feet. East winds up to 25 mph. Chance of rain 50 percent.

Saturday: Mostly cloudy. Windy. Scattered showers in the morning, then showers likely in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 71 to 84. Northeast winds up to 25 mph increasing to 10 to 30 mph in the afternoon. Chance of rain 70 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Numerous showers in the evening, then showers after midnight. Locally heavy rainfall possible. Lows around 72 in the valleys to around 64 above 4000 feet. Northeast winds 10 to 35 mph. Chance of rain 90 percent.

North Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 66 to 76. East winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly cloudy with scattered showers. Highs 71 to 88. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Numerous showers in the evening, then showers after midnight. Locally heavy rainfall possible. Lows 67 to 77. East winds 10 to 25 mph shifting to the northeast 10 to 35 mph after midnight. Chance of rain 80 percent.

East Kaua’i

Tonight: Partly cloudy with isolated showers in the evening, then mostly cloudy with scattered showers after midnight. Lows 69 to 78. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly cloudy with scattered showers. Highs 79 to 87. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Numerous showers in the evening, then showers after midnight. Locally heavy rainfall possible. Lows 71 to 78. Northeast winds 15 to 30 mph. Gusts up to 50 mph after midnight. Chance of rain 90 percent.

Detailed Forecast

Synopsis

Tropical Storm Lala will move over or just south of the islands this weekend but wind, rain and surf impacts will be felt statewide. A Hurricane Warning is in effect for Big Island and a Tropical Storm Warning is in effect for the rest of the state.

Discussion

The main forecast concern for the next few days will be potential impacts from Tropical Storm Lala. As of 5 PM HST, Tropical Storm Lala was located near and moving west northwest around 14 mph. Based on the latest forecast from the National Hurricane Center, Lala is expected to move near the southern end of the Big Island Saturday, then continue moving to the west northwest, with the center of circulation remaining south of the smaller islands. Remember impacts can occur well outside the center of the storm. Please stay up to date on the latest forecasts, and prepare for the potential impacts described below.
STRONG AND GUSTY WINDS…Damaging tropical storm force winds (39 mph to 73 mph) may begin as early as tonight across parts of the Big Island, Maui County as early as Saturday morning, Oahu as early as Saturday afternoon, and Kauai as early as Saturday night. A Hurricane Warning is in effect for the Big Island and surrounding waters due to a non-negligable chance of hurricane force winds (74 mph or greater). A Tropical Storm Warning is in effect for the rest of the state and surrounding waters. Localized areas of highly enhanced and damaging winds are possible over and downwind of the mountainous terrain, even well away from the tropical cyclone center. These localized strong winds and gusts will also be felt in advance of the arrival of Lala (i.e. tonight and Saturday morning) and should be kept in mind as last minute preparations are being made.
HEAVY RAINFALL…Periods of heavy rainfall are expected starting with the Big Island tonight, reaching Maui County on Saturday, and Oahu and Kauai later Saturday and Sunday. Orographic enhancement will result in locally higher rainfall totals where moist tropical flow interacts with island terrain. If heavier rainfall persists over the same locations, flash flooding and rapidly rising streams are possible. The location of heaviest rain currently favors the Big Island and parts of Maui. The current forecast has 10 to 15 inches of rain, with locally higher amounts across windward Big Island. Rainfall totals of 8 to 12 inches are possible on windward Maui and up 8 inches of rainfall could occur across the remainder of the island chain. While the highest rainfall amounts will be focused over windward areas, leeward areas will also have a significant flood risk. Heavy rain could persist into Monday for some areas. A Flood Watch has been issued for the Big Island and Maui County from tonight through late Saturday night, and for Oahu, Kauai, and Niihau from Saturday evening to early Monday morning.
LARGE AND ROUGH SURF…Lala is expected to generate a large easterly swell as it moves northwestward. Surf may build along exposed east and southeast facing shores from east to west as the system approaches. A High Surf Warning is posted for east facing shores of Big Island, Maui, Molokai and Oahu, and a High Surf Advisory is posted for east facing shores of Kauai. Very large and extremely rough seas are expected to rapidly increase Saturday and Sunday on exposed southeast and east shores and may produce damaging surf, significant beach erosion, and overwash across vulnerable coastal infrastructure, mainly on the Big Island of Hawaii. Highest storm surge up to 3 feet is forecast for the eastern side of the Big Island.
In anticipation of critical new updates with each of the advisory packages issued by the National Hurricane Center (NHC), the NWS Honolulu will continue delaying the issuance of our typical forecast package products (AFD, SFT, PFM, ZFP, SPF, CWF, etc.) until after the release of NHC's suite of products, to incorporate the latest and most up-to-date information on Tropical Storm Lala.
Trade winds will resume through the middle of next week in the wake of Lala's departure.

Aviation

Winds will increase tonight and Saturday and conditions will deteriorate from east to west as Lala moves into the area. Threats will include all of the following: low visibility, low ceilings, heavy rain, isolated thunderstorms, and very strong winds. Widespread MVFR to IFR conditions are likely. Winds at Kona Saturday will be especially tricky as strong north winds suddenly become strong south winds sometime in the late afternoon once Lala gets west of the Big Island.
AIRMET SIERRA is currently in effect for north through east sections of Molokai, Lanai, Maui, and Big Island above 2500 feet due to low clouds and scattered showers.
AIRMET TANGO for moderate turbulence remains in effect immediately south and west of mountains due to low-level winds and will likely continue for the next couple of days. As wind speeds strengthen tonight into Saturday, an AIRMET for strong winds greater than 30 kt will likely be needed.

Marine

NE winds will strengthen areawide this afternoon through Saturday as Tropical Storm Lala passes over or immediately south of the Big Island. The strongest winds are anticipated Saturday evening into Saturday night for the waters surrounding the Big Island and Maui. Winds peak for the waters surrounding Kauai and Oahu during Sunday. Hurricane Warnings, Tropical Storm Warnings, and Tropical Storm Watches are in effect. Expect dangerous conditions including torrential rainfall, a few thunderstorms, and high surf. Lala will track WNW through the weekend, clearing the western islands by Monday. Tuesday into the rest of the week, a return to easterly trades is expected.
Surf initially trends slowly upward for E shores in response to strengthening trades, but will quickly build tonight as Lala approaches. The High Surf Warning remains in effect for E facing shores of the Big Island and Maui as well as the SE facing coasts of the Puna and Ka'u Districts where surf will be maximized. Surf is also forecast to reach low end warning critiera for E facing shores of Oahu and the advisory threshold for Kauai. Accordingly, the High Surf Warning has been expanded to include Oahu and a High Surf Advisory has been issued for E facing shores of Kauai.
For N shores, anticipate choppy conditions with swell energy wrapping from the east through the weekend. For S shores, surf will remain below the advisory threshold and will slowly diminish until another long period south swell arrives late Sunday into Monday providing a small boost to existing surf.

Fire weather

Increasing humidity and rainfall with Lala will remove fire weather concerns from Saturday into at least early next week. Temperature inversion will go away tonight across the Big Island and spread westward Saturday.

HFO Watches/Warnings/Advisories

Tropical Storm Warning for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala.
Flood Watch from Saturday evening through late Sunday night for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward.
High Surf Warning from 6 AM Saturday to 6 AM HST Sunday for Olomana, Koolau Windward, Molokai Windward, Molokai Southeast.
Flood Watch through late Saturday night for Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Big Island Summits, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
High Surf Warning until 6 AM HST Sunday for Maui Windward West, Windward Haleakala, Kipahulu, South Haleakala, Big Island Southeast, Big Island East, Big Island North.
Hurricane Warning for Big Island,
High Surf Advisory from 6 AM Saturday to 6 AM HST Sunday for Kauai East, Kauai South.
Tropical Storm Warning for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel.
Hurricane Warning for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Saturday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters.
Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel.
Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov