FXHW60 PHFO 241524 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 524 AM HST Sat Aug 24 2024 .SYNOPSIS... Stronger winds remain in the forecast today as The Central Pacific Hurricane Center continues to closely monitors Tropical Storm Hone east-southeast of the Big Island moving westward. On its current track, Hone will brush past the southern slopes of the Big Island from tonight into Sunday morning; bringing the potential for heavy rainfall, damaging winds, and large surf. Expect strong and gusty easterly winds and periods of heavy showers 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 continues on it's westward journey moving away from the island chain. Tropical Cyclone Gilma far east of the state will weaken as it approaches the Hawaii Region by the end of next week, possibly bringing more rainfall to the islands. && .DISCUSSION... A high pressure system far north of the Hawaiian Islands and Tropical Storm Hone passing near the southern slopes of the Big Island this weekend will keep strong and gusty winds in the forecast into Monday. Cloud bands moving in ahead of Tropical Storm Hone will continue to produce periods of showers mainly over windward and mountain areas today, these showers will favor the overnight to early morning hours. The latest Central Pacific Hurricane Center forecast shows Tropical Storm Hone briefly becoming a hurricane by Sunday as it passes south of the smaller islands. Forecast confidence in Hone impacting our local weather remains high. The latest forecast guidance continues to show winds across the state increasing today as the Tropical Storm approaches the islands. Strong downslope winds are possible over the leeward mountain slopes of all islands through Sunday night. Wind gusts to 50 mph are possible and a Wind Advisory has been issued for these areas on the leeward slopes of island terrain. Drier air is also expected to filter in briefly across the state today ahead of Hone. The combination of the drier air and strong downslope winds will bring elevated fire weather concerns to leeward portions of the islands. Afternoon relative humidity levels remain marginal for a few hours today, however given past events with passing tropical systems a Red Flag Warning remains in effect for leeward sections of all islands today. The threat of elevated fire weather concerns decrease by this evening as moisture from Hone starts to move into the state. Based on the current forecast track for Hone, strong and gusty winds associated with the system will begin to impact the Big Island later today, with widespread gusts up to 50 mph likely from this evening 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 localized gusts as high as 60 mph. The Central Pacific Hurricane Center keeps the Tropical Storm Warning in effect for the Big Island. 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 is beginning to surge into the windward slopes of the Big Island this morning and moisture levels are forecast to rise like the tide through tonight. This tropical moisture will then sweep westward to all islands tonight through Sunday, increasing the potential for heavy rainfall statewide. As rainbands associated with Tropical Storm Hone move into each island, heavy showers and thunderstorms will increase the threat for localized flash flooding. A Flood Watch remains in effect for the Big Island starting this afternoon. Shower coverage then expands down the island chain from Sunday into early next week as Hone passes to the south of the state. Storm total rainfall estimates for the Big Island will range from 5 to 10 inches with locally higher amounts possible. Smaller islands should see rainfall amounts from 2 to 4 inches. The higher amounts in these ranges will fall along windward mountain slopes of each island. 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 by the end of next week. 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... The forecast here on out will primarily be driven by Tropical Storm Hone. Currently on a westward track and is expected to pass to the south of the Big Island later tonight into Sunday. As rain bands associated with Hone move in expect +RA, TSTMs, reduced vsbys and strong winds particularly over the eastern end of the state. On the western end of the state breezy to windy trades will continue and strengthen as Hone continues its westward track. Low cigs and SHRA should favor windward and mauka locations with some spillover into leeward areas. MVFR conds are to be expected. As Hone continues moving east expect conds to deteriorate. AIRMET Sierra remains in effect for mtn obsc for all islands. AIRMET Tango remains in effect for mod low-level turb blw 080 downwind of island terrain. This AIRMET will most likely be needed into early next week. Over the next couple of days, additional AIRMETs may be issued to account for sustained 30kt winds over portions of the area, as well as potential IFR conds as rain bands move through. As Tropical Storm Hone approaches the islands, aviation interests should closely monitor updates to TC SIGMET Whiskey. && .MARINE... An area of surface high pressure north of the islands will allow locally strong trades to prevail today. A Small Craft Advisory has been expanded to include all waters, with the exception of those off Big Island windward. By late this afternoon, winds across the waters surrounding the Big Island will ramp up to tropical storm force in response to the approach of Tropical Storm Hone. A Tropical Storm Warning is in effect for these areas, while a Tropical Storm Watch continues for the channels and leeward waters of Maui County and Oahu. These Watches may be upgraded to a warning today, which will depend highly on the track of the tropical cyclone. TS Hone will also bring occasional heavy rain, low visibility, and the possibility of thunderstorms this 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. Short period swell associated with Tropical Storm Hone will continue to build today and maintain hazardous surf for east and southeast facing shores of the Big Island through at least Sunday. A High Surf Advisory remains in effect. Strong winds from Hone will generate elevated and choppy surf along all east facing shores and the High Surf Advisory may need to expanded to account for this. Existing small NW swell will slowly decline this morning. Surf along north facing shores is expected to remain flat to tiny over the next several days, aside from some trade wind swell wrap. Surf along south facing shores will remain small today, near or slightly below the summertime average. The passing of Tropical Storm Hone south of the island chain late this weekend could generate a short period southerly swell from early Monday through Tuesday. && .FIRE WEATHER... Drier air is expected to filter in across portions of the state later today ahead Tropical Storm Hone. This drier air combined with stronger winds will bring elevated fire weather concerns to areas along the leeward slopes of island terrain. Afternoon relative humidity levels over these leeward areas remain marginal tomorrow around 40-50 percent, however due to strong drying trends ahead of these passing tropical systems a Red Flag Warning remains in effect today between the late morning to afternoon hours. The threat for elevated fire weather concerns decreases by this evening as humidity levels recover, and deeper tropical moisture sweeps across the island chain. .HFO WATCHES/WARNINGS/ADVISORIES... Tropical Storm Warning for Big Island- 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. Hurricane Watch for Big Island Leeward Waters-Big Island Southeast Waters. Flood Watch from noon HST today through Monday evening for Big Island- Red Flag Warning from 10 AM this morning to 6 PM HST for most areas leeward of all island mountains. Wind Advisory until 6 AM HST Monday for portions of all Hawaiian Islands. High Surf Advisory until 6 AM HST Sunday for Big Island Southeast-Big Island East-Big Island North. Small Craft Advisory until 5 PM HST Monday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Oahu Windward Waters-Maui County Windward Waters. Small Craft Advisory until 6 AM HST Sunday for Kauai Channel- Oahu Leeward Waters. Small Craft Advisory until 6 PM HST this evening for Kaiwi Channel-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Walsh MARINE...JT FIRE WEATHER...Bohlin