Breezy trade winds today will become strong and gusty as early as tomorrow afternoon. Showers will generally favor windward and mauka areas, particularly during the overnight through early morning hours each day. Tropical Storm Lowell is about 500 miles southeast of the Big Island early this morning, and is forecast to pass south of the Big Island late Wednesday into Thursday. Winds are expected to remain strong and gusty through Friday as Lowell passes south of the islands. The forecast remains uncertain for Labor Day weekend, with the potential for Lowell and Karina in the the vicinity of the state.
18z TAFS - Active showers this morning impacting Maui and Big Island bringing MVFR conditions and locally IFR in heaviest showers. Otherwise, moderate trade winds will persist through this period. Diurnal trends of MVFR conditions and brief showers through the trades will generally favor windward exposures, mauka and higher terrain. Otherwise, VFR conditions will prevail. Tropical Cyclone Lowell is forecast to pass far south of the island chain the next few days. On this track, late week trade winds will strengthen as the pressure gradient tightens between Tropical Cyclone Lowell and high pressure to the far north.
AIRMET Sierra is in effect for mountain obscuration for the north through east districts of Big Island due to persistent low clouds and shower coverage. AIRMET Sierra will remain in effect for Big Island through this morning.
AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.
A strong surface high will remain nearly stationary far north of the Hawaiian Islands this week, keeping fresh to locally strong trade winds in place. A Small Craft Advisory (SCA) remains in effect for the typically windy waters as a result of the locally strong trades. The SCA will likely need to be expanded as trade winds gradually strengthen across the state to strong to possible locally gale force late Wednesday through Thursday as Lowell passes far south. The offshore waters will likely see tropical storm conditions over the south waters as the core of hurricane force winds remains just outside the area Wednesday into Thursday. There is still some uncertainty with the forecast track of Lowell, especially this weekend and early next week as the cyclone begins to gain latitude, which will have significant impacts on the wind, wave, and surf forecast for the region. Adding to the extended forecast uncertainty will be the approach of Hurricane Karina from the east.
A moderate, long-period south swell arrives today. This swell will build through the day and overnight before peaking on Wednesday, bringing surf heights to just below advisory thresholds. This swell will then gradually decline through the rest of the week. A small, medium-period south southeast swell energy from Lowell could start filling in across south and southeast shores. South shore surf will likely remain elevated near to just advisory levels through at least Friday. Beyond that point, the surf forecast is highly dependent on the eventual track and intensity of Lowell, which has the potential to be a significant source of south to southwesterly swell through this weekend and into next week depending on how sharply and quickly the cyclone turns to the north.
Trade wind swell energy will keep rough, choppy surf along all east-facing shores through the coming week. Tonight, a small, medium- period east swell arrives from Hurricane Karina that will build through the week and could push east shore surf to advisory thresholds by this weekend and into next week.
Small Craft Advisory until 6 PM HST Wednesday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
