West Side

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 88. Light winds. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 72 to 79. Light winds becoming east up to 15 mph after midnight. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers. Highs 79 to 87. East winds up to 15 mph. Chance of rain 20 percent.

South Side

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 89. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 73 to 81. Light winds becoming northwest up to 15 mph after midnight. Chance of rain 20 percent.

Thursday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 87. North winds up to 20 mph. Chance of rain 20 percent.

North Shore

Today: Partly sunny with scattered showers. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 75 near the shore to around 60 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs around 81 near the shore to 67 to 72 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 83 to 89. North winds up to 10 mph shifting to the southeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 72 to 77. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Breezy. Mostly sunny with isolated showers. Highs 81 to 87. Northeast winds up to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Partly sunny. Scattered showers in the morning, then numerous showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 73 at the visitor center to around 71 at the summit. Light winds becoming east up to 10 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows around 57 at the visitor center to around 48 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Thursday: Partly sunny with isolated showers. Highs 64 to 82. East winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

East Maui

Today: Partly sunny with scattered showers. Highs around 83 near the shore to around 72 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 75 near the shore to around 60 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Thursday: Partly sunny with scattered showers. Highs around 81 near the shore to 67 to 72 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 79 to 85. Light winds. Chance of rain 40 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 69 to 74. Light winds becoming east up to 10 mph after midnight. Chance of rain 40 percent.

Thursday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 84. Northeast winds up to 15 mph. Chance of rain 30 percent.

Kaunakakai

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 78 to 91. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 64 to 79. East winds up to 15 mph. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers. Highs 77 to 90. East winds 10 to 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light and variable flow will persist across the islands this morning with east or southeasterly winds filling in across Big Island and Maui County later today. A weak band of 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, but conditions will remain somewhat wet. Drier trade wind weather is expected to develop Thursday night through the weekend.

Discussion

Latest IR satellite imagery loop shows a weakened and highly sheared Tropical Storm Lowell drifting northward, beyond our offshore waters, several hundred miles north northwest of Kauai. A band, or ribbon, of enhanced moisture can also be seen extending southeast from Lowell down through Maui and the Big Island. The 12Z Hilo sounding indicated a lower level moisture depth of 13,000 feet and a PWAT (precipitable water) value of 2.1″, significantly higher than the early September average of 1.4″. This healthy moisture profile, along with light to locally moderate east or east southeast flow, will help maintain scattered showers this morning along windward and southeast Big island as well as the eastern slopes of Haleakala on Maui. Elsewhere, a drier atmosphere continues to dominate with limited shower coverage. Both the GFS and ECMWF show the ribbon of moisture draped over the eastern third of the state during the afternoon. This, combined with diurnal heating, will aid in more robust shower activity over the Big Island interior. Models indicate rather marginal instability, but still enough for a slight chance of thunderstorms. Similar conditions are expected over Haleakala on Maui, but confidence is a bit lower. Maui County appears to sit on the leading edge of this moisture as it slowly drifts east to west across the state. Still, a few heavier afternoon showers are possible, especially over the southwest slopes of Haleakala near Kula. The Flood Watch will remain in effect through this afternoon Big Island. However, diurnally driven sea breezes could bring 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.
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.

Aviation

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, particularly over Maui and the Big Island is producing mountain obscuration to those areas. Lingering clouds and showers over Kauai is having the same impact there. All these islands are experienced periods of MVFR conditions, and as such, AIRMET Sierra for mountain obscuration remains in effect. Some improvement is anticipated today for Kauai as a drier airmass to the south and southeast moves over the Garden Isle. Satellite derived precipitable water suggests that the clouds and showers will likely linger over Maui and the Big Island.
With light southerly winds expected, not anticipating any AIRMETs for turbulence today.

Marine

Tropical Storm Lowell is tracking away from the Hawaiian Islands this morning. The far northwestern offshore waters now lie at the fringes of Lowell's tropical storm-force wind field, which should allow the Tropical Storm Warning to be dropped later this morning. Elsewhere, light and variable winds will gradually transition to light to moderate easterly trade winds through the remainder of the week.
Surf along south facing shores remains choppy, but below advisory criteria, from a mix of lingering southwest and west swells from Tropical Storm Lowell that will continue fade today. A moderate, medium-period south swell originating southeast of New Zealand will linger for the next few days, keeping south shore surf heights elevated. This swell fades gradually 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.

Fire weather

Fire weather risk will remain low the next several days due rather light winds and lingering moisture. Expect a slight chance of thunderstorms over the Big Island this afternoon and possibly Thursday afternoon. Temperature inversion heights are expected to remain elevated or weak.

HFO Watches/Warnings/Advisories

Flood Watch through this afternoon for Big Island,

Data Courtesy of NOAA.gov