Hilo

Tonight: Breezy. Frequent showers and isolated thunderstorms in the evening, then frequent showers after midnight. Locally heavy rainfall possible. Lows 71 to 77 near the shore to around 64 at 4000 feet. South winds up to 20 mph. Chance of rain near 100 percent.

Tuesday: Cloudy and breezy. Frequent showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 83 to 88 near the shore to 70 to 76 at 4000 feet. Southwest winds up to 20 mph shifting to the southeast in the afternoon. Chance of rain 90 percent.

Tuesday Night: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 71 to 77 near the shore to around 64 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 90 percent.

Kona

Tonight: Frequent showers and isolated thunderstorms in the evening, then frequent showers after midnight. Locally heavy rainfall possible. Lows 72 to 79 near the shore to 58 to 63 near 5000 feet. West winds up to 15 mph shifting to the southeast after midnight. Chance of rain near 100 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 86 to 93 near the shore to around 74 near 5000 feet. South winds up to 15 mph. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 72 to 78 near the shore to around 61 near 5000 feet. South winds up to 10 mph in the evening becoming light. Chance of rain 70 percent.

Waimea

Tonight: Mostly cloudy. Frequent showers and isolated thunderstorms in the evening, then numerous showers after midnight. Locally heavy rainfall possible. Lows 71 to 77 near the shore to 65 to 71 near 3000 feet. Southwest winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 85 near the shore to 74 to 83 near 3000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy with numerous showers. Lows 71 to 77 near the shore to 65 to 71 near 3000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy. Frequent showers and isolated thunderstorms in the evening, then numerous showers after midnight. Locally heavy rainfall possible. Lows 71 to 77 near the shore to 65 to 71 near 3000 feet. Southwest winds up to 15 mph. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Numerous showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 85 near the shore to 74 to 83 near 3000 feet. North winds up to 10 mph. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy with numerous showers. Lows 71 to 77 near the shore to 65 to 71 near 3000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 70 percent.

South Big Island

Tonight: Breezy. Frequent showers. Locally heavy rainfall possible. Lows around 78 near the shore to around 62 near 5000 feet. East winds up to 20 mph decreasing to up to 10 mph after midnight. Chance of rain near 100 percent.

Tuesday: Cloudy. Frequent showers in the morning, then frequent showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs around 86 near the shore to around 72 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 90 percent.

Tuesday Night: Mostly cloudy. Frequent showers in the evening, then numerous showers after midnight. Locally heavy rainfall possible in the evening. Lows around 78 near the shore to around 63 near 5000 feet. Light winds becoming east around 10 mph after midnight. Chance of rain 80 percent.

Puna

Tonight: Breezy. Frequent showers and isolated thunderstorms in the evening, then frequent showers after midnight. Locally heavy rainfall possible. Lows 71 to 77 near the shore to around 64 at 4000 feet. South winds up to 20 mph. Chance of rain near 100 percent.

Tuesday: Cloudy and breezy. Frequent showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 83 to 88 near the shore to 70 to 76 at 4000 feet. Southwest winds up to 20 mph shifting to the southeast in the afternoon. Chance of rain 90 percent.

Tuesday Night: Mostly cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 71 to 77 near the shore to around 64 at 4000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 90 percent.

Waikoloa

Tonight: Mostly cloudy. Frequent showers and isolated thunderstorms in the evening, then numerous showers after midnight. Locally heavy rainfall possible. Lows 74 to 79 near the shore to around 62 above 4000 feet. West winds up to 10 mph shifting to the east after midnight. Chance of rain 90 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 87 to 93 near the shore to 73 to 78 above 4000 feet. Northeast winds up to 15 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Tuesday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 74 to 79 near the shore to around 63 above 4000 feet. North winds up to 10 mph in the evening becoming light. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Southeast to south winds will strengthen tonight as Hurricane Lowell approaches. The core of Lowell is forecast to pass near Niihau tonight into early Tuesday. Damaging hurricane conditions are expected with numerous threats in place throughout the state. A Hurricane Warning is in effect for Kauai and Niihau and a Tropical Storm Warning is in effect for Oahu. High surf and heavy rain will impact all islands with strong winds mainly impacting the western end of the state.

Discussion

Hurricane Lowell is about 160 statute miles southwest of Kauai this afternoon moving north northeastward at 18 mph as a high end category 2 (maximum sustained winds of 110 mph). The core of Lowell is expected to pass west of Niihau, raising the possibility of hurricane force winds reaching Kauai and Niihau and Tropical Storm force winds reaching Oahu. As a result, a Hurricane Warning is in place for Niihau and Kauai and a Tropical Storm warning is in place for Oahu. On satellite imagery this afternoon, bands of moderate rain with embedded heavy rain and have been moving over Kauai, and to a lesser extent the other islands. The shower frequency and intensity is expected to increase tonight as Lowell makes its closest approach. Winds will also tend to be strongest within the heavier rain bands.
Additional impacts from Lowell are expected statewide, and a few headlines are in effect as a result. A High Surf Warning for south facing shores for the south swell generated by Lowell for all islands, along with the west facing shores of the Big Island. A High Surf Advisory remains in effect for the east swell generated by former Tropical Storm Karina, which has weakened to a post tropical low. For surf and other marine impacts, please see the marine section of the discussion below.
The Flood Watch for the state continues through Tuesday due to heavy rain brought in by Lowell and associated rain and thunderstorm bands. Terrain influence will play a big factor with isolated areas receiving significant amounts through the event. Stay alert for the issuance of any future flood advisories or warnings across the state. See hydrology section for additional information.
The threat of short-lived, fast-moving tornados/waterspouts will be present mainly near Kauai and Niihau as Lowell makes its closest approach to the islands. A tornado watch is in effect for Kauai and Niihau. Any tornadoes would likely be embedded in rainbands. The threat for tornadoes is lower near the remaining islands, but not zero. The threat for tornadoes should decrease quickly early Tuesday morning.
Any deviation in track or intensity could also change how these hazards effect the islands.
High pressure is forecast to build back in Thursday through Saturday, bringing in a more typical trade wind pattern. Moisture may take a bit longer to exit the area as well, so conditions are expected to dry out more gradually into the weekend.

Aviation

Hurricane Lowell continues its track northward, advecting unstable deep tropical moisture northward into the islands. Shower activity will continue to trend higher into Tuesday. MVFR conditions with low cloud ceilings and showers are expected statewide. Heavier showers will produce periods of IFR conditions. Surface winds will continue to strengthen today over the western half of the state, as Hurricane Lowell continues to move north.
AIRMET Sierra for mountain obscuration continues for Kauai Oahu Molokai Maui and the Big Island. This AIRMET will likely continue into Tuesday.
AIRMET Tango was issued for moderate low level turbulence affecting the island of Kauai over and SW thru NW of island mountains. A strong surface wind AIRMET was issued for Kauai and Niihau for wind speeds greater than 30 knots due to Hurricane Lowell approaching the islands.
Light icing continues in a layer between 160 and FL220 due to strengthening low level wind speeds as Lowell approaches the island.

Marine

Hurricane Lowell continues to move northward towards the islands this afternoon. Winds and seas are on the increase as the system approaches, and both are expected to peak overnight as Lowell makes it closest approach to Kauai County. A Hurricane Warning remains in effect for waters west of Kauai County, while a Tropical Storm Warning remains in effect for Kauai Channel, Kauai Windward Waters, Oahu Windward Waters and Oahu Leeward Waters. The Small Craft Advisory remains in effect for all remaining coastal waters for a combination of winds and seas through Tuesday. Winds are expected to increasingly veer to the southeast to south as Lowell approaches and the strongest winds and highest seas are expected for the western end of the state.
Hurricane conditions are expected in the western offshore waters through Tuesday as the center of Lowell tracks just west of Niihau. Any slight deviation in the track to the west or east in the next 12 to 24 hours will have significant differences in impact for the coastal waters around Kauai County. What remains of former Tropical Cyclone Karina remains to the northeast of the islands and is expected to dissipate soon.
South-southwest swell from Hurricane Lowell will continue to build rapidly, and peak tonight as it shifts out of the southwest. As a result, warning level surf along south facing shores will continue to rise, peaking overnight. Due to the track of Lowell west of the main islands, a sharp gradient in swell is expected from west to east. This will bring damaging surf to portions of Kauai County and likely Oahu, with the potential for significant damage to coastal properties and infrastructure, particularly to those areas along the coasts of Kauai and Oahu exposed to the southerly swell. The hurricane swell energy is expected to rapidly decline on Tuesday as Lowell moves away from the islands.
A moderate, long-period south swell will peak overnight and into Tuesday, but will be overwhelmed by the larger swell mentioned above from Hurricane Lowell. This swell will also fade some on Tuesday but will keep south shore surf somewhat elevated through Thursday. A large, medium-period east swell from former Tropical Storm Karina will combine with increasing east to southeast wind wave generated by Hurricane Lowell to keep advisory level surf along east facing shores through Tuesday. Surf along north facing shores will also experience a small increase on Tuesday as Lowell lifts north of the island chain and then fade through the week.

Fire weather

Fire weather risk will remain low through the forecast period due to increasing moisture moving over the islands in association with Hurricane Lowell. Thunderstorms will be possible through through tonight to the unstable airmass moving overhead. Temperature inversion heights are expected to remain elevated or non-existent during the next few days.

Hydrology

Thus far, around 6 to 10 inches of rain have fallen on Kauai, 2 to 5 inches on Oahu and Maui County, and around 2 inches on the Big Island. The potential for flooding remains through Tuesday, and a Flood Watch is in effect for the entire state. Due to the amount of rain that has fallen especially over Kauai today, any heavy showers could trigger quick flash flooding. It is possible the watch may need to be extended into Tuesday night or Wednesday depending on the lingering rain bands across the state in the wake of Lowell as guidance suggests. However, will hold off any update to the watch at this time.
Hurricane Lowell is expected to bring additional rain to the islands through Wednesday morning with 4 to 8 inches, isolated 12 inches across Kauai. Oahu and Maui County, 2 to 5 inches, isolated 10 inches. Big Island, 4 to 8 inches, isolated 12 inches. This rainfall may produce significant flash flooding and mudslides, especially across Kauai County and south and east portions of the Big Island. Its important to note that any pop up thunderstorms that develop could dramatically increase total rainfall amounts anywhere.

HFO Watches/Warnings/Advisories

Flood Watch through Tuesday afternoon for all Hawaii islands,
High Surf Warning until 6 PM HST Tuesday for Niihau, Kauai Leeward, Waianae Coast, Kahoolawe, Maui Leeward West, Kona, Kohala, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Molokai Southeast, Molokai West, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley South, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast.
Hurricane Warning for Niihau, Kauai,
Tropical Storm Warning for Oahu,
High Surf Advisory until 6 PM HST Tuesday for Olomana, Kauai East, Koolau Windward, Molokai Windward, Windward Haleakala, Big Island East, Big Island North.
Hurricane Warning for Kauai Northwest Waters, Kauai Leeward Waters.
Tropical Storm Warning for Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters.
Small Craft Advisory until 6 PM HST Tuesday for Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov