Photo Credit: Laila Reiss

West Side

Today: Sunny and breezy. Highs 82 to 89. East winds up to 20 mph.

Tonight: Mostly clear. Breezy. Lows 69 to 76. East winds 10 to 20 mph.

Friday: Sunny and breezy. Highs 82 to 89. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

South Side

Today: Sunny and breezy. Highs 86 to 91. North winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Clear and breezy. Lows around 70. North winds up to 20 mph.

Friday: Sunny and breezy. Highs 86 to 91. North winds up to 20 mph shifting to the northeast 10 to 20 mph in the afternoon.

North Shore

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 87 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 73 near the shore to around 55 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 81 to 87 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Central Maui

Today: Sunny and breezy. Highs around 89. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Lows 68 to 74. Northeast winds 10 to 15 mph.

Friday: Sunny and breezy. Highs around 89. Northeast winds 10 to 20 mph.

Upcountry

Today: Sunny. Highs around 60 at the visitor center to around 57 at the summit. Northeast winds up to 10 mph.

Tonight: Mostly clear. Lows around 47 at the visitor center to around 44 at the summit. East winds up to 10 mph.

Friday: Sunny. Highs around 64 at the visitor center to around 61 at the summit. Northeast winds up to 10 mph.

East Maui

Today: Breezy. Mostly sunny with isolated showers. Highs 81 to 87 near the shore to around 65 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 66 to 73 near the shore to around 55 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs 81 to 87 near the shore to around 68 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Lanai City

Today: Sunny and breezy. Highs 76 to 85. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows around 69. Northeast winds 10 to 20 mph.

Friday: Sunny and breezy. Highs 76 to 85. Northeast winds 10 to 20 mph.

Kaunakakai

Today: Sunny and breezy. Highs 80 to 90. Northeast winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows 63 to 74. Northeast winds 10 to 20 mph.

Friday: Sunny and breezy. Highs 80 to 90. Northeast winds 10 to 20 mph.

Detailed Forecast

Synopsis

Shower activity will trend lower for all islands as more stable and drier air moves into the region through Friday. Wind speeds will decrease to moderate levels from Friday through the weekend as the ridge far north of the state weakens. Deeper tropical moisture, associated with remnants of former tropical cyclone Fernanda, will rise from east to west starting on Sunday. Humidity levels and rainfall activity will increase for all islands through Tuesday night, favoring Maui and the Big Island. A transition back to more typical trade wind weather starts next week Wednesday.

Discussion

Starting with the water vapor satellite imagery this morning we see a similar pattern from last night, showing a narrow upper level trough, the TUTT, with two embedded upper lows just northwest of the islands. This upper trough will drift eastward today and help to weaken Tropical Storm Greg as it continues to track westward, remaining far south of the Hawaiian Islands. Subsidence to the north of Greg will produce stable and fairly dry conditions over the region through Friday. Upper air balloon soundings from Lihue and Hilo at 2 AM HST this morning show the trade wind temperature inversion height already dropping to the 5,000 foot level.
The high pressure ridge far north of Hawaii will keep moderate to locally breezy trade winds in the forecast through tonight. The ridge will weaken north of the state on Friday, slightly decreasing trade wind speeds through the weekend. Trade winds will restrengthen into the moderate to breezy range by Tuesday as the remnants of Fernanda pass to the south of the state.
A small scale ridge forming just north of Greg will produce a slight drying trend over the islands through Friday as trade wind temperature inversion heights remain around 5,000 feet elevation. Low cloud cover and shower activity will decrease across the region due to the low temperature inversion heights capping vertical cloud development. These stable dry trends will begin to ease up on Saturday with a return to brief passing showers over windward areas in the overnight to early morning hours.
Deeper tropical moisture, associated with the remnants of former tropical cyclone Fernanda will move into the eastern islands starting on Sunday, and spread westward across the state on Monday and Tuesday. Global model guidance showing the deepest moisture with this remnant trough will remain south of the island chain. However, we continue to see enhanced rainfall activity increasing across most islands as the trough moves westward through the region. Locally heavy rain is possible with this pattern along with isolated thunderstorms. The highest rainfall amounts are forecast to fall from Monday afternoon through Tuesday morning along windward and mountain slopes, favoring Maui and the Big Island. A transition back to more typical trade wind weather starts next week Wednesday.

Aviation

Surface high pressure northeast of the state will allow for moderate to locally breezy conditions to persist through the remainder of the forecast period. Isolated to scattered showers will affect mainly windward areas this morning. Drier air is forecast to filter in from the east later today and lead to a decrease in overall shower coverage.
No AIRMETs are currently in effect.

Marine

The presence of Tropical Storm Greg south of the Hawaiian Islands is maintaining moderate to strong trades through tonight. As a result, Small Craft Advisory remains in effect for the typical windy waters around Maui and the Big Island through tonight. Winds then weaken to moderate levels Friday through Sunday as Greg weakens and continues its trek westward. Trades become locally strong once again early next week as the remnants of Tropical Storm Fernanda approach the islands from the east.
A series of small reinforcing northwest swells will keep north shore surf up above typical summertime flat levels through the remainder of the work week. North and west shore surf will return to flat levels Saturday through early next week. South shore surf will remain small and below the summertime average through the weekend, with mainly background southerly swells. A small south swell may boost south shore surf up close to the summertime average early next week.
East shore surf will remain below normal levels through the weekend due to lack of strong trades upstream of the island chain. Long period east swell generated from Tropical Storm Hillary off Baja California could impact east facing shores during the middle of next week but still dependent on the size and intensity of the storm.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 4 AM HST Friday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov