Photo Credit: James Grenz

Hilo

Today: Partly sunny early in the morning then becoming mostly sunny. Scattered rain showers early in the morning, then isolated rain showers in the late morning and afternoon. Highs 81 to 87 near the shore to 66 to 75 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 74 near the shore to around 60 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 84 near the shore to 63 to 72 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Sunny. Isolated rain showers in the late morning and afternoon. Highs 83 to 89 near the shore to around 71 near 5000 feet. North winds up to 10 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 71 to 77 near the shore to 49 to 56 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Wednesday: Mostly sunny. Scattered showers in the late morning and afternoon. Highs 80 to 88 near the shore to around 70 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Mostly sunny with isolated rain showers. Highs 68 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 66 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny with isolated rain showers. Highs 68 to 89. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 73 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 66 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny and breezy. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 20 mph.

Tonight: Mostly clear. Breezy. Lows 71 to 77 near the shore to around 52 near 5000 feet. Northeast winds 10 to 20 mph.

Wednesday: Sunny. Isolated showers in the late morning and afternoon. Highs 81 to 87 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny early in the morning then becoming mostly sunny. Scattered rain showers early in the morning, then isolated rain showers in the late morning and afternoon. Highs 81 to 87 near the shore to 66 to 75 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Lows 67 to 74 near the shore to around 60 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Wednesday: Partly sunny with scattered showers. Highs 78 to 84 near the shore to 63 to 72 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Sunny. Highs 83 to 90 near the shore to 67 to 75 above 4000 feet. Northeast winds up to 10 mph shifting to the north around 10 mph in the afternoon.

Tonight: Mostly clear. Lows 72 to 77 near the shore to 50 to 57 above 4000 feet. Northeast winds around 10 mph.

Wednesday: Sunny. Highs 80 to 90 near the shore to 67 to 74 above 4000 feet. North winds up to 10 mph.

Detailed Forecast

Synopsis

A weak boundary northeast of the state may increase showers near Kauai and Oahu by mid week. Additionally, light to moderate easterly trades will focus low clouds and showers across windward areas through the end of the week. Trades may be light enough at times to allow localized afternoon sea breezes to generate clouds and a few showers across leeward areas.

Discussion

Radar this morning shows scattered showers drifting across the islands, with a majority of showers lingering west of the state in an area of deeper moisture. Satellite data shows limited cloud cover as drier air streams in from the east. Overall expect limited clouds and showers to influence the islands through tonight, as dry and stable air moves westward.
A surface boundary about 350 miles north-northeast of the islands will further weaken as it slowly drops southward toward the state into Wednesday, while the surface ridge north of the state gradually reestablishes itself. This pattern will maintain a weak pressure gradient and light to moderate easterly trade wind flow across the islands this week. These winds will direct showers to mainly windward areas in a typical trade wind weather pattern. However, localized sea breeze clouds and showers remain possible for some leeward areas this week.
The airmass will differ greatly across the state this week as a sharp moisture gradient sets up. The front sagging southward will enhance a layer of deeper moisture over the western islands while much drier and more stable air filters in across the central and eastern islands through much of the week. Forecast moisture depths will remain around 7k feet across the eastern half of the state with PW values generally around 1.25 inches or less. Deeper moisture depths between 8k-11k feet and PW values of 1.60 inches or greater, are forecast to increase over the western end of the state, mainly Wednesday and Thursday. The drier PW values forecast across the eastern end of the state, are well supported by the latest satellite based layer blended total precipitable water values around 1.18 inches near the Big Island. This pattern will limit the areal coverage of showers for Maui and the Big Island into Friday. Moisture pooling along the front north of the area, will increase the areal coverage of showers some across Kauai tonight before expanding southward toward Oahu Wednesday into Thursday.
The latest trends support a weaker pressure gradient redeveloping once again by the weekend, as another surface boundary drops southward. The weakened surface pressure gradient could allow for a return of localized afternoon and early evening sea breeze showers for some leeward areas and island interiors into the beginning of next week. The latest trends support the best chances for showers and potential for enhanced rainfall, remains across the western end of the state as deeper moisture pools along the boundary dropping southward.

Aviation

A ridge of high pressure passes north of Hawaii and will produce moderate trade winds today. Scattered clouds and showers are carrying from the east focusing over windward slopes and bringing brief MVFR conditions. However, VFR conditions will prevail today and no AIRMETs are anticipated. The showers are expected to linger through the early morning before decreasing.

Marine

A front will remain in place between a high to our north and the main Hawaiian islands. This will keep trade winds in the light to moderate range over the next several days for most waters. However, terrain-induced acceleration may briefly boost winds to Small Craft Advisory threshold today and tonight across typically windy waters around Maui and the Big Island.
South swell will continue to lower through Wednesday. Another small longer period south swell will fill in Wednesday night and Thursday with a slight reinforcement expected Friday and Saturday. A slightly larger long period south swell may arrive around Sunday. No significant north or northwest swells are expected through Thursday night, with a small short period northwest swell expected Friday and Saturday. Another small but longer period northwest swell may arrive on Sunday. Short period choppy surf will remain rather small over the next few days across east-facing shores, with a slight increase possible later in the week and on into the weekend.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov