textproduct: Honolulu

SYNOPSIS

Breezy east-northeast trade winds will gradually veer to the east and then east-southeast over the next couple of days as Hurricane Lowell approaches the western islands from the southwest. Lowell is forecast to pass west of Kauai's coastal waters Monday night. A Tropical Storm Warning is in effect for Kauai, Niihau and the surrounding coastal waters as a result. Impacts such as high surf and heavy rain could impact all of the islands.

DISCUSSION

Hurricane Lowell is about 550 miles south-southwest of Kauai this morning. Lowell is expected to move northward, and pass west of the Kauai coastal waters late Monday through Monday night. Tropical Storm force winds are expected to reach Kauai and Niihau at the the closet approach, and thus a Tropical Storm Warning is in effect for Kauai County and the surrounding coastal waters. Additional impacts from Lowell are expected statewide, and a few headlines are in effect as a result. A High Surf Advisory is in effect for south and east facing shores. The south swell is from Lowell, and the east swells are from Tropical Storm Karina, which is about 1000 miles east of Kauai this morning. Karina is expected to dissipate within the next 48 hours when its a few hundred miles east-northeast of Kauai.

Showers have already been focused over the windward sides of the islands in the trade wind flow. As the winds shift to the southeast tonight, showers will spread to additional areas of the islands. The interaction of the terrain with moisture spreading over the islands could lead to heavy rainfall which could cause some flooding. Thus a Flood Watch is in effect for all islands starting at noon today, and persisting through Tuesday afternoon. With Kauai and Niihau being the closest to Lowell, rainfall totals are expected to be highest there, but due to the terrain influence on the Big Island, isolated areas could receive significant rain. Due to an unstable airmass moving over the islands, thunderstorms are possible starting tonight and persisting statewide through tomorrow. These thunderstorms could produce heavy rainfall which could also lead to some flooding. Stay alert for the issuance of any flood advisories or warnings.

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. These 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.

For surf and other marine impacts, please see the marine section of the discussion below.

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 with a drier and more stable airmass.

AVIATION

Tropical moisture will deepen over the next 24 hours as wind directions aloft shift from a more southerly direction in response to Hurricane Lowell's northward track passing just west of Kauai. This unstable tropical air mass will produce increasing clouds and showers across the state with the highest chances for MVFR conditions in low cloud ceilings and showers expected from later this afternoon into Tuesday.

Surface winds will continue to blow from a more easterly direction for most areas with stronger wind gusts near heavy rain shower bands and thunderstorms forecast through Monday night. Winds are expected to begin strengthening and start veering to an ESE direction overnight, especially over the western half of the state.

Tropical Storm force winds are possible near Niihau and Kauai from Monday into Tuesday. MVFR/IFR conditions and wind impacts for Kauai County will depend on subtle deviations in the northward track of Hurricane Lowell. Please closely monitor weather conditions for this time period as weather impacts are likely to evolve over time as Lowell continues its northward journey.

AIRMET Sierra for mountain obscuration continues for Kauai Oahu Molokai Maui and the Big Island for the foreseeable future. This AIRMET will likely be expanded to cover other areas and islands as shower coverage increases with time. AIRMET Tango may be necessary for moderate turbulence downwind of terrain once winds start to ramp up with Hurricane Lowell's approach.

MARINE

A surface high north of the Hawaiian Islands will persist through the forecast period. Meanwhile, Hurricane Lowell is around 500 nm south- southwest of Kauai, now tracking north-northwest. Lowell will continue to turn north today and as it approaches the island chain winds will begin to increase. Therefore, a Small Craft Advisory (SCA) is now in effect for the windier waters and channels around Maui County and the Big Island. Winds will increasingly veer to the southeast to south as Lowell continues to approach, bringing the strongest winds to the western end of the state. Winds and seas will likely exceed small craft criteria across all coastal waters on Monday, which will necessitate an expansion of the SCA. Where winds are expected to be strongest around Kauai County, a Tropical Storm Warning is in effect.

Hurricane conditions are expected in the offshore waters west of 159W Sunday night through Tuesday as the center of the hurricane tracks west of Niihau. While confidence is increasing in the track forecast of the cyclone, any slight deviation in the track to the west or east from the current predicted path will have significant differences in impact for the coastal waters around Kauai County. As for Tropical Storm Karina, it is expected to weaken and dissipate as it moves northeast of the state. by Monday.

Southerly swell generated by Hurricane Lowell will keep surf along south facing shores at High Surf Advisory criteria through at least Monday night. As Lowell begins to turn more north, its swell will gradually veer from south to southwest and begin a rapid upward trend by Monday. Very large surf exceeding warning criteria is likely for south and west facing shores of Oahu and Kauai, and surf may also reach warning levels for the west facing shores of the Big Island, including the Kohala coast on Monday. Coinciding also with monthly high tides, this will create the potential for impacts to harbor entrances, channels, as well as vulnerable 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 minor 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 Tropical Storm Karina to the east of the islands. This swell will gradually fade early this week as Karina weakens. 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

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 tonight and tomorrow due to the unstable airmass moving overhead. Temperature inversion heights are currently near 11,000 ft from Maui to the Big Island, and are expected to remain elevated during the next few days.

HYDROLOGY

Heavy rain is possible tonight through Tuesday afternoon, and as a result, a Flood Watch is in effect for the entire state. Hurricane Lowell is expected to produce rainfall totals of 6 to 10 inches for Kauai, with maximum totals of 14 inches possible. For the Big Island, 4 to 8 inches of rain is expected with isolated totals of 12 inches possible, due to the terrain influence with the southeast flow. Across the remaining islands, rainfall of 2 to 4 inches of rain is expected, with Maui having isolated maximum totals of 8 inches possible. This rainfall may produce significant flash flooding and mudslides, especially across Kauai County and portions of the Big Island.

HFO WATCHES/WARNINGS/ADVISORIES

High Surf Advisory until 6 AM HST Tuesday for Big Island East- Big Island North-Big Island South-Big Island Southeast-East Honolulu-Ewa Plain-Honolulu Metro-Kahoolawe-Kauai East-Kauai South-Kauai Southwest-Kipahulu-Kona-Koolau Windward-Lanai Leeward-Lanai South-Maui Central Valley South-Maui Leeward West- Molokai Leeward South-Molokai Southeast-Molokai West-Molokai Windward-Niihau-Olomana-South Haleakala-South Maui/Upcountry- Waianae Coast-Windward Haleakala.

Tropical Storm Warning for Kauai East-Kauai Mountains-Kauai North-Kauai South-Kauai Southwest-Niihau.

Flood Watch through Tuesday afternoon for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Central Oahu-East Honolulu-Ewa Plain-Haleakala Summit-Honolulu Metro-Kahoolawe-Kauai East-Kauai Mountains-Kauai North-Kauai South-Kauai Southwest-Kipahulu- Kohala-Kona-Koolau Leeward-Koolau Windward-Lanai Leeward-Lanai Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui Central Valley South-Maui Leeward West-Maui Windward West- Molokai Leeward South-Molokai North-Molokai Southeast-Molokai West-Molokai Windward-Niihau-Oahu North Shore-Olomana-South Haleakala-South Maui/Upcountry-Waianae Coast-Waianae Mountains- Windward Haleakala.

Tropical Storm Warning for Kauai Channel-Kauai Leeward Waters- Kauai Northwest Waters-Kauai Windward Waters.

Small Craft Advisory until 6 PM HST Monday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.