Hilo

Tonight: Cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 66 to 73 near the shore to 58 to 63 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Saturday: Cloudy and breezy. Occasional showers in the morning, then frequent showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 78 to 86 near the shore to around 66 at 4000 feet. North winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Saturday Night: Breezy. Frequent showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 67 to 74 near the shore to 59 to 65 at 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Kona

Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 76 near the shore to 52 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Saturday: Tropical storm conditions possible. Mostly sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 84 to 91 near the shore to around 72 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Saturday Night: Tropical storm conditions possible. Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows around 76 near the shore to 54 to 59 near 5000 feet. South winds up to 15 mph shifting to the east after midnight. Gusts up to 35 mph increasing to 40 mph after midnight. Chance of rain 70 percent.

Waimea

Tonight: Windy. Mostly cloudy with scattered showers. Lows 66 to 74 near the shore to 59 to 66 near 3000 feet. East winds 10 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Saturday: Tropical storm conditions possible. Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 63 to 85. East winds 10 to 40 mph. Gusts up to 60 mph increasing to 70 mph in the afternoon. Chance of rain 70 percent.

Saturday Night: Tropical storm conditions expected. Cloudy with frequent showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 67 to 74 near the shore to 60 to 67 near 3000 feet. East winds 15 to 40 mph with gusts to 70 mph decreasing to 10 to 30 mph after midnight. Chance of rain 90 percent.

Kohala

Tonight: Windy. Mostly cloudy with scattered showers. Lows 66 to 74 near the shore to 59 to 66 near 3000 feet. East winds 10 to 30 mph with gusts to 50 mph. Chance of rain 50 percent.

Saturday: Tropical storm conditions possible. Mostly cloudy. Scattered showers in the morning, then numerous showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 63 to 85. East winds 10 to 40 mph. Gusts up to 60 mph increasing to 70 mph in the afternoon. Chance of rain 70 percent.

Saturday Night: Tropical storm conditions expected. Cloudy with frequent showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 67 to 74 near the shore to 60 to 67 near 3000 feet. East winds 15 to 40 mph with gusts to 70 mph decreasing to 10 to 30 mph after midnight. Chance of rain 90 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 76 near the shore to around 56 near 5000 feet. Northeast winds up to 20 mph shifting to the north up to 10 mph after midnight. Chance of rain 20 percent.

Saturday: Tropical storm conditions possible. Mostly sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 88 near the shore to around 73 near 5000 feet. East winds up to 30 mph. Gusts up to 50 mph in the afternoon. Chance of rain 40 percent.

Saturday Night: Tropical storm conditions expected. Cloudy. Numerous showers and isolated thunderstorms in the evening, then frequent showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows around 76 near the shore to around 57 near 5000 feet. East winds up to 40 mph increasing to 20 to 40 mph after midnight. Gusts up to 60 mph. Chance of rain 80 percent.

Puna

Tonight: Cloudy. Numerous showers in the evening, then occasional showers after midnight. Lows 66 to 73 near the shore to 58 to 63 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Saturday: Cloudy and breezy. Occasional showers in the morning, then frequent showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 78 to 86 near the shore to around 66 at 4000 feet. North winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon. Chance of rain 90 percent.

Saturday Night: Breezy. Frequent showers and isolated thunderstorms. Locally heavy rainfall possible. Lows 67 to 74 near the shore to 59 to 65 at 4000 feet. East winds 10 to 20 mph. Chance of rain near 100 percent.

Waikoloa

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 77 near the shore to around 58 above 4000 feet. Southeast winds up to 20 mph. Chance of rain 20 percent.

Saturday: Tropical storm conditions possible. Mostly sunny in the morning, then partly sunny with isolated showers and thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 82 to 93 near the shore to 69 to 75 above 4000 feet. Northeast winds up to 40 mph with gusts to 65 mph. Chance of rain 20 percent.

Saturday Night: Tropical storm conditions expected. Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then numerous showers and isolated thunderstorms after midnight. Locally heavy rainfall possible. Lows around 78 near the shore to around 61 above 4000 feet. East winds up to 40 mph with gusts to 65 mph decreasing to up to 15 mph with gusts to 45 mph after midnight. Chance of rain 70 percent.

Detailed Forecast

Synopsis

Breezy trade winds will continue through tonight, with showers favoring windward and mauka locations. The Central Pacific Hurricane Center continues to closely monitor Tropical Storm Hone far east-southeast of the Big Island moving westward. On its current track, Hone is expected to pass near or south of the Big Island Saturday night into early Sunday bringing the potential for heavy rainfall, damaging winds, and large surf. Expect strong and gusty easterly winds to continue Sunday into Monday as Hone passes south of the smaller islands. A brief return of moderate to breezy trade winds is expected late Monday through Wednesday of next week as Hone tracks away from the state and Tropical Cyclone Gilma approaches the region from the east.

Discussion

Breezy trade wind conditions will continue through tonight as strong high pressure remains well north of the state. Showers will predominantly affect windward and mauka areas, with some occasionally reaching leeward sections during the overnight hours.
Our attention then turns to Tropical Storm Hone. The latest Central Pacific Hurricane Center forecast shows Tropical Storm Hone briefly becoming a hurricane Sunday night as it passes south of the smaller islands. Forecast confidence in Hone impacting our local weather continue to increase, regardless of its exact development and track.
Guidance continues to show winds across the state increasing on Saturday as the gradient tightens ahead of Hone. Strong downslope winds are likely across the smaller islands Saturday morning through Sunday night, with gusts to 45 mph possible, so a Wind Advisory has been issued for these areas.
Drier air is also expected to filter in across the state on Saturday ahead of Hone. The combination of the dry air mass and strong downslope winds will bring elevated fire weather concerns to leeward portions of the islands. Afternoon relative humidity remains marginal tomorrow, but given past events with passing tropical systems a Red Flag Warning was issued for leeward areas Saturday afternoon. The threat of elevated fire weather concerns decrease late Saturday as moisture from Hone starts to move into the state.
Based on the current forecast track for Hone, strong and gusty winds associated with Hone will begin to impact the Big Island Saturday evening, with widespread gusts up to 50 mph likely late Saturday through early Sunday. The strongest gusts are expected around South Point/Ka Lae, as well as downslope from Mauna Kea, Mauna Loa, the Kohala Mountains, and the Humuula Saddle, which could see gusts as high as 60 mph. The Central Pacific Hurricane Center has upgraded the Tropical Storm Watch for the Big Island to a Tropical Storm Warning. Now is the time to finalize your emergency plans and supplies and take the necessary actions to protect your family and secure your home or business.
Deep tropical moisture will move in from the east on Saturday into Sunday increasing the potential for heavy rainfall across windward and southeast areas of the Big Island. As rainbands associated with Tropical Storm Hone move in late Saturday into Sunday, heavy showers and thunderstorms will increase the potential for localized flash flooding. A Flood Watch remains in effect for the Big Island starting Saturday afternoon. Shower coverage then expands up the island chain Sunday into early next week as Hone passes to the south.
A brief return of moderate to breezy trade winds is expected late Monday through Wednesday of next week as Hone tracks away from the state and Tropical Cyclone Gilma approaches the region from the east. Forecast confidence, with regards to impacts to our local weather, remains very low late next week due to significant differences shown between the various sources of guidance as Gilma approaches the region.
For further details on Hone's development, please refer to the latest forecast issued by the Central Pacific Hurricane Center at www.hurricanes.gov.
Note that public and marine forecasts from WFO Honolulu will be updated on a modified schedule, in conjunction with the latest CPHC forecast issued at 5 AM/PM and 11 AM/PM HST.

Aviation

This afternoon, breezy to windy trade winds are prevailing across the island chain. Low clouds and showers embedded within these trades continue moving into N through SE sections of the islands, producing MVFR ceilings and visibilities for these areas. As a result, AIRMET Sierra for tempo mountain obscuration remains in effect. Additionally, AIRMET Tango remains in effect for moderate low-level turbulence below 8,000 feet downwind of island terrain, and this AIRMET will likely be needed through the weekend and into next week.
Heading into the weekend, the forecast will be primarily driven by Tropical Storm Hone, which is expected to move on a westward track and pass near the Big Island Saturday night and Sunday. Hone is then expected to continue moving west-northwest and away from the islands Monday and Tuesday. As rain bands associated with Tropical Storm Hone move in Saturday and Sunday, heavy showers, thunderstorms, reduced visibilities, and strong winds will be possible at times, particularly over the eastern end of the state. A Tropical Storm Warning is now in effect for the Big Island and its adjacent waters to account for expected impacts from Hone. Additionally, a Flood Watch for flash flooding potential will also be in effect for the Big Island beginning midday on Saturday. Elsewhere, a Tropical Storm Watch is in effect for the leeward waters of Maui County and Oahu, including the channels. Wind advisories are also posted for portions of the smaller islands outside of the tropical storm watches and warnings. Over the next couple of days, expect that additional AIRMETs may need to be issued to account for sustained 30kt winds over portions of the area, as well as potential IFR conditions as rain bands move through. As Tropical Storm Hone approaches the islands, aviation interests should also closely monitor updates to TC SIGMET Whiskey series this weekend.

Marine

Locally strong trades prevail today then ramp up to tropical storm force in some areas in response to the approach of TS Hone. The Small Craft Advisory remains in effect for the windier waters and channels of Oahu, Maui County, and the Big Island. The Tropical Storm Watch has been upgraded to a warning around the Big Island. Meanwhile, the watch has been expanded northwestward to include channels and leeward waters of Maui County and Oahu. Rain bands from TS Hone will also result in occasional heavy rain, low visibility, and the possibility of thunderstorms Saturday afternoon through late Sunday night, especially for the southeastern portion of the coastal waters. Marine interests should monitor updates to the forecast, watches, or warnings over the weekend.
Existing small NW swell will slowly decline through early Saturday. Surf along north facing shores will then return to typical summertime flat levels over the weekend through the middle of next week, aside from some trade wind swell wrap. Surf along south facing shores will remain small today, near or slightly below the summertime average.
Meanwhile, observations indicate surf is elevated for the southeast-facing shores of the Big Island. Short period swell associated with TS Hone will continue building and will maintain hazardous surf for east and southeast facing shores of the Big Island through the weekend. A High Surf Advisory has been issued accordingly. The potential for expansion of the advisory to include east- facing shores of some or all of the smaller islands will be evaluated in subsequent forecast packages.

Fire weather

Drier air is expected to filter in across the state on Saturday ahead of Hone. This drier air mass will arrive as winds start to increase, with strong downslope winds expected Saturday. The combination of dry conditions ahead of Hone and the uptick in winds will bring elevated fire weather concerns to leeward portions of the islands. Afternoon relative humidity over leeward areas remain marginal tomorrow, around 45-55%, but given past events with passing tropical systems a Red Flag Warning was issued for leeward areas for Saturday afternoon as the driest air moves over the area. The threat of elevated fire weather concerns decrease late Saturday as moisture from Hone starts to move into the state.

HFO Watches/Warnings/Advisories

Wind Advisory from 6 AM Saturday to 6 AM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Leeward West, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Leeward, Molokai West, Molokai Leeward South, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, South Maui/Upcountry, South Haleakala.
Red Flag Warning from 10 AM to 6 PM HST Saturday for HIZ301, HIZ304, HIZ305, HIZ307, HIZ308, HIZ309, HIZ310, HIZ311, HIZ313, HIZ315, HIZ316, HIZ320, HIZ321, HIZ323, HIZ324, HIZ325, HIZ326, HIZ328, HIZ329, HIZ330, HIZ333, HIZ334, HIZ337, HIZ341, HIZ342.
Tropical Storm Warning for Big Island,
Flood Watch from Saturday afternoon through Monday evening for Big Island,
High Surf Advisory until 6 AM HST Sunday for Big Island Southeast, Big Island East, Big Island North.
Tropical Storm Warning for Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Tropical Storm Watch for Kauai Channel, Oahu Leeward Waters, Kaiwi Channel, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel.
Small Craft Advisory until 6 PM HST Saturday for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov