Hilo

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 64 to 71 near the shore to around 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Kona

Tonight: Partly cloudy. Lows around 74 near the shore to 49 to 54 near 5000 feet. Light winds.

Tuesday: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 84 to 90 near the shore to around 69 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows around 74 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 66 to 86. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 64 to 72 near the shore to 57 to 63 near 3000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs 66 to 86. East winds up to 15 mph. Chance of rain 20 percent.

Tuesday Night: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 73 near the shore to 57 to 64 near 3000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

South Big Island

Tonight: Mostly clear. Lows around 74 near the shore to around 53 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph after midnight.

Tuesday: Sunny in the morning then becoming mostly cloudy. Highs around 86 near the shore to around 71 near 5000 feet. East winds up to 15 mph.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Lows around 75 near the shore to around 54 near 5000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 54 to 59 at 4000 feet. West winds up to 10 mph in the evening becoming light. Chance of rain 50 percent.

Tuesday: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 80 to 86 near the shore to 66 to 72 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Tuesday Night: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 64 to 71 near the shore to around 57 at 4000 feet. East winds up to 10 mph. Chance of rain 90 percent.

Waikoloa

Tonight: Partly cloudy. Lows around 75 near the shore to 52 to 57 above 4000 feet. Southeast winds up to 10 mph in the evening becoming light.

Tuesday: Sunny in the morning then becoming mostly cloudy. Highs 85 to 90 near the shore to 67 to 74 above 4000 feet. North winds up to 10 mph.

Tuesday Night: Partly cloudy with isolated showers. Lows around 75 near the shore to around 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate E to ESE winds will continue with passing windward and mauka showers through mid-week. A slight increase in showers will be possible from late Tuesday into Wednesday, especially over the eastern islands. Trades will decrease Thursday through the weekend, supporting daytime sea breezes and nighttime land breezes. Moderate trades will return early next week.

Discussion

This afternoon, an area of high pressure centered about 1700 miles northeast of Honolulu is producing moderate trade winds over the islands, though late morning advanced scatterometer (ASCAT) passes from both ASCAT-B and ASCAT-C showed that the trades have veered slightly east-southeasterly. As a result, low- level convergence zones have developed “plumes” of clouds and showers emanating from Molokai towards Oahu, and from Oahu towards Kauai. These “plumes” significantly increased daytime cloud cover and moisture over portions of Oahu and Kauai today, which necessitated some updates to the near-term forecast. Measured rainfall totals have generally remained fairly light, however, with nearly all locations across these islands reporting less than a quarter of an inch of rain since 8am HST (and most much less than that).
Moderate E to ESE winds will continue through at least the first half of the work week. Therefore, expect continued passing showers mainly over windward and mountain areas of each island, favoring the typical overnight to early morning hours. It is possible that island “plumes” could develop again on Tuesday if winds continue from a slightly east-southeast direction, but confidence is low at this time. Additionally, a disturbance moving into the islands from the east late Tuesday into Wednesday could further increase shower coverage, especially over the eastern half of the state.
A low pressure system and a pair of fronts moving across the North Pacific during the second half of the week will weaken trade wind speeds slightly from Thursday into the weekend. This should allow local scale sea breezes (and increased cloudiness with a few showers) over the islands during the day and land breezes (with clearing skies) at night. High pressure will return far northeast of the islands early next week, allowing moderate trades to return.

Aviation

Surface high pressure northeast of the state will continue to generate moderate trades tonight. Low clouds and showers along windward areas with brief MVFR cigs/vis within showers through the evening. Otherwise, VFR conditions expected and currently no AIRMETs in effect.

Marine

The combination of surface high pressure to the NE and developing low pressure to the NW will support moderate to fresh E to ESE winds on the large scale for the next couple of days. Near shore winds may become locally strong as they interact with island terrain, especially during peak vertical mixing in the afternoons. A trend toward lighter NE winds is anticipated later in the week as the high and low weaken, and a new high builds far NW of the islands. The expectation is that wind speeds will remain below Small Craft Advisory criteria.
A fading shorter period N swell will continue to diminish overnight. A new medium-period NW swell will build tonight and Tuesday, with peak swell heights near 4 feet late Tuesday. This swell's period and height will diminish as it becomes N Wednesday and Thursday. Small, short-period N swell will likely prevail next weekend, with the potential for a larger long-period NW swell by Monday.
A small long-period SW swell is expected to receive a gradual boost from the SSW beginning tonight and persisting into Wednesday, with peak swell heights near 3 feet. Thus far, NDBC buoys to the S show only marginal increases in long-period energy. An even larger long-period S swell appears likely to arrive Sunday, and peak near High Surf Advisory levels early next week.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov