Light and variable flow will persist across the islands this morning with easterly winds filling in for Oahu southward later today. Residual moisture stretching southeast from Tropical Storm Lowell down to Big Island and portions of Maui County may bring a renewed threat of heavy showers, while sea breezes trigger spotty afternoon showers across the rest of the state. Trade winds will slowly build over the state late tonight into Thursday, though moisture remains elevated across much of the state. Drier trade wind weather is expected to develop Thursday night into early next week.
Morning satellite water vapor imagery shows drier air beginning to spread southward across Kauai and Oahu, and a band of remnant moisture from Tropical Storm Lowell extending southeast and then westward into Maui and the Big Island. This band of moisture with precipitable water (PW) near 2" is forecast to remain in place across portions of Maui and the Big Island into this afternoon. The above normal PW and diurnal heating will aid in more robust shower activity over the Big Island interior this afternoon. Instability remains marginal, but enough to maintain a slight chance of thunderstorms. Similar conditions are expected over Haleakala on Maui, but confidence is a bit lower. Still, a few heavier afternoon showers are possible, especially over the southwest slopes of Haleakala near Kula. The Flood Watch remains in effect through this afternoon for the Big Island. Diurnally driven sea breezes could bring lighter showers to interior regions of the remaining smaller islands.
By Thursday, light to moderate trades will return to the entire state. The deeper moisture, now caught up in the trades, may bring an enhancement to mainly windward showers on all islands. Some of these showers may occasionally push over the terrain and onto the leeward sides. Once again, diurnally driven heavier showers are forecast to develop over Big Island's interior and upper slopes of Mauna Kea and Mauna Loa during the afternoon. With PW will not be quite as high on Thursday, so rainfall rates and amounts are likely to be lower.
Friday through the weekend, troughing far northeast of the state will help to ease trades back into the light to moderate range with a more typical trade showers concentrated along windward locations in the night to early morning hours.
Weak southerly flow remains over the islands with now Tropical Storm Lowell north of the main Hawaiian Islands. Lowell will continue to weaken and move further away from the islands. The southerly flow will remain in place for much of today, but expect trades to slowly filter back in tonight and tomorrow from east to west.
Moisture being pulled north from Tropical Storm Lowell, particularly over Kauai, Maui, and the Big Island is causing clouds, lingering showers, and some mountain obscuration. These islands are experienced periods of MVFR conditions, and as such, AIRMET Sierra for mountain obscuration remains in effect. With light winds and expected sea breeze, should see additional clouds and showers develop this afternoon and evening, leading to more mountain obscuration. Satellite derived precipitable water suggests that these clouds and showers will likely linger over Maui and the Big Island.
With light southerly winds expected, not anticipating any AIRMETs for turbulence today.
Tropical Storm Lowell is about 460 miles NNW of Lihue and is now well away from the offshore waters. Lingering moisture from Lowell will continue to produce some scattered downpours over the eastern half of the coastal and offshore waters. Light and variable winds will gradually transition to light to moderate easterly trade winds starting this evening over the eastern half of the state and slowly spreading westward through Thursday. By Thursday evening, we should see moderate to locally fresh trade winds across the state through the weekend.
A moderate long-period south swell peaked last night, but continues to produce elevate surf along south facing shore this morning. This long-period south swell combined with short-period southwest to west swells from Lowell will produce advisory level surf through today. The long-period south swell will gradually fade through the weekend, by which point south shore surf is expected to become small.
Surf along east facing shores remains elevated from a medium-period east swell generated by former tropical cyclone Marie. With light trade winds, surf will hover near seasonal averages through Friday. The east swell will fade gradually, allowing surf to fall below seasonal averages by this weekend. Surf along north facing shores continues to receive a small bump due to Lowell. This short-period northwest swell will quickly fade, allowing surf to become tiny along north facing shores on Thursday as Lowell weakens and tracks away from the islands.
High Surf Advisory until 6 PM HST this evening for Big Island South-Big Island Southeast-East Honolulu-Ewa Plain-Honolulu Metro-Kahoolawe-Kauai South-Kauai Southwest-Kohala-Kona-Lanai Leeward-Lanai South-Maui Central Valley South-Maui Leeward West- Molokai Leeward South-Molokai Southeast-Molokai West-Niihau- South Haleakala-South Maui/Upcountry-Waianae Coast.
Flood Watch until 6 PM HST this evening for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Kohala-Kona.
