West Side

Today: Breezy. Mostly sunny with isolated showers. Highs 80 to 87. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 72 to 78. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 81 to 87. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

South Side

Today: Sunny and breezy. Highs around 88. Northeast winds 15 to 25 mph.

Tonight: Partly cloudy. Breezy. Lows 72 to 81. Northeast winds 10 to 20 mph.

Wednesday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 88. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

North Shore

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to 67 to 72 near 5000 feet. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows around 74 near the shore to around 59 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 82 near the shore to around 70 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 88. Northeast winds 20 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 74. East winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 82 to 89. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 71 at the visitor center to around 73 at the summit. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 56 at the visitor center to around 49 at the summit. East winds 10 to 25 mph. Chance of rain 50 percent.

Wednesday: Windy. Partly sunny with scattered showers. Highs 65 to 82. East winds 15 to 20 mph increasing to 15 to 30 mph in the afternoon. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to 67 to 72 near 5000 feet. East winds 15 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Numerous showers in the evening, then occasional showers after midnight. Lows around 74 near the shore to around 59 near 5000 feet. East winds 10 to 25 mph. Chance of rain near 100 percent.

Wednesday: Mostly cloudy. Breezy. Occasional showers in the morning, then numerous showers in the afternoon. Highs around 82 near the shore to around 70 near 5000 feet. East winds 10 to 25 mph. Chance of rain 90 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 78 to 84. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows 69 to 74. Northeast winds 15 to 25 mph.

Wednesday: Mostly sunny. Breezy. Scattered showers in the afternoon. Highs 78 to 85. East winds 10 to 25 mph. Chance of rain 30 percent.

Kaunakakai

Today: Windy. Mostly sunny with isolated showers. Highs 77 to 90. Northeast winds 15 to 30 mph. Chance of rain 20 percent.

Tonight: Windy. Partly cloudy with isolated showers. Lows 64 to 78. Northeast winds 15 to 30 mph. Chance of rain 20 percent.

Wednesday: Windy. Mostly sunny with isolated showers. Highs 77 to 90. East winds 15 to 30 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

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.

Discussion

No significant changes to the forecast this morning. Although the PoP grid was adjusted, little change through Thursday night. For Friday there is a marked decrease in shower activity over the islands as Lowell will have moved further from the islands.
Clouds and showers continue to be carried in on the trade wind flow, and as a result are focused over the windward and mauka areas. A surface trough about 350 miles east of the islands will continue to move towards the islands today and weaken. Moisture from that trough will reach the islands tonight, helping to boost shower activity tonight.
Tropical Storm Lowell is about 550 miles southeast of the Big Island early this morning, and the latest forecast from the National Hurricane Center (NHC) has Lowell strengthening to a hurricane within the next 12 hours. The latest track and cone for Lowell has the system passing south of the islands Wednesday night through Friday. Outer rainbands and moisture from Lowell could begin to spread across the islands today, increasing chances of passing trade wind showers, however the bulk of moisture will likely pass south of the state. Additionally dewpoint temperatures are expected to exceed 70 degrees, which will make the atmosphere muggier than normal. Trade winds will stay breezy due to a strong surface high remaining far north of the area.
Overall expect an uptick in passing showers over the next few days, due to the moisture from the trough mentioned above tonight, and moisture loosely associated with Lowell passing through the state.
The latest forecast from the NHC has Lowell passing a little over 300 miles south of the Big Island Wednesday night into Thursday as a category 3 Major Hurricane. While probabilities for tropical storm force winds remain low over the state, the tightening of the pressure gradient over the islands will likely produce very windy and gusty trade winds as early as Wednesday afternoon through Friday. Winds could reach advisory thresholds with wind gusts over 50 mph possible during this time.
As we head into the weekend, as Lowell exits, our focus will shift more to Hurricane Karina which is currently about 1500 miles east of the Big Island. The latest forecast from NHC for Karina brings it about 600 miles east of the Big Island on Saturday. We will continue to monitor Karina over the coming days to discern its potential impacts on the state.
The forecast spread drastically increases over the Labor Day weekend into early next week as an upper level trough/low develops north of the state. Several models show Lowell taking a sharp northward turn over the weekend. While confidence has increased on Lowell passing south of the state during the week, the forecast still remains very uncertain over Labor day weekend due to the northward turn in the various models. Also during this time, we could see Karina within the vicinity of the islands late this weekend. Please keep an eye out on the hurricanes.gov page for the official NHC forecast for Lowell and Karina.

Aviation

Moderate to breezy trade winds will persist through this period. Occasional MVFR decks and brief organized showers riding within the trades will generally favor windward exposures 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.

Marine

A strong surface high will remain nearly stationary far north of the Hawaiian Islands this week, keeping moderate to locally strong trade winds in place. A Small Craft Advisory remains in effect for the typically windy waters as a result of the locally strong trades. Tropical Storm Lowell, now in the Central Pacific, is forecast to intensify into a hurricane today and will track very close to the southern offshore waters, bringing tropical storm conditions (with the core of hurricane force winds remaining outside the offshore waters) from Wednesday into Thursday. There is still some uncertainty with the forecast track of Lowell, especially closer to this weekend as the cyclone begins to gain latitude, which will have significant impacts on the wind, wave, and surf forecast for the region. Regardless of Lowell's final path, trade winds will increase by Wednesday afternoon through Friday as a result of the gradient between high pressure to the north and Lowell to the south. By this weekend, Hurricane Karina, approaching the region from the east, will increasingly be a factor in the forecast of seas and surf as well.
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. Also by Wednesday, medium-period energy from Lowell could start filling in across south and southeast shores. South shore surf is likely to be elevated, but stay below 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 elevated surf heights along all east-facing shores through the coming week. Tonight, a 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.

Fire weather

Breezy trades today are expected to strengthen further as early as Wednesday afternoon through Friday as Tropical Storm Lowell passes south of the islands as a hurricane. Strong gusty winds over 50 mph will be possible across select areas during this time. While fuel conditions are not at critical levels due to abundant rainfall we have received over the past several weeks, moderate fire danger will be possible for areas mainly due to very windy conditions. Dewpoints are expected to increase in the upper 60s and low 70s by Tuesday afternoon and hold through the week, keeping minimum humidities in the 50s for the most part. A few leeward areas could still see humidities down into the mid 40s especially on Thursday as a pocket of dry air moves in. The exact track of Lowell remains uncertain and thus potential for meaningful rainfall remains uncertain at this time. The inversion will hover between 5500 ft and 6500 ft over the next couple of days.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Wednesday for Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters, Maalaea Bay, Pailolo Channel.

Data Courtesy of NOAA.gov