Hilo

Today: Showers likely, mainly before 1pm. Partly sunny, with a high near 82. East southeast wind 8 to 14 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 64. South wind 3 to 5 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 82. East wind 5 to 8 mph becoming calm in the afternoon. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after 1pm. Increasing clouds, with a high near 82. East wind around 11 mph becoming west in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before midnight. Mostly cloudy, with a low around 63. Calm wind becoming east southeast around 5 mph after midnight. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers, mainly after noon. Partly sunny, with a high near 82. East southeast wind 5 to 10 mph becoming west in the morning. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Waimea

Today: Scattered showers, mainly after 2pm. Mostly sunny, with a high near 75. North northwest wind around 7 mph becoming west in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 1am. Mostly cloudy, with a low around 50. West wind 5 to 7 mph becoming northeast in the evening. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers. Partly sunny, with a high near 75. Southwest wind around 5 mph becoming north northeast in the morning. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Scattered showers. Partly sunny, with a high near 68. Northeast wind around 7 mph becoming southeast in the afternoon. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 41. East wind around 7 mph becoming west in the evening. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 68. Breezy, with a west wind 7 to 15 mph becoming east in the morning. Winds could gust as high as 21 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers before 1pm. Partly sunny, with a high near 83. Windy, with an east wind 18 to 23 mph, with gusts as high as 29 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers after 8pm. Partly cloudy, with a low around 71. Breezy, with an east northeast wind 16 to 18 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Tuesday: Isolated showers before noon. Mostly sunny, with a high near 82. Breezy, with an east wind 16 to 18 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Puna

Today: Showers likely, mainly before 1pm. Partly sunny, with a high near 80. East southeast wind 10 to 13 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Showers likely, mainly after midnight. Mostly cloudy, with a low around 62. East northeast wind around 5 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Tuesday: Showers likely, mainly before noon. Mostly cloudy, with a high near 80. East wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Scattered showers after 1pm. Increasing clouds, with a high near 81. West northwest wind 8 to 13 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before 8pm. Partly cloudy, with a low around 61. North wind around 5 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tuesday: Scattered showers after noon. Partly sunny, with a high near 81. West wind 5 to 7 mph becoming light and variable in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

Gradually easing trade winds will deliver a few windward showers this morning, but a trough developing over the area may lead to an increase in rainfall coverage tonight and Tuesday, especially over Kauai and Oahu. Trade winds will restrengthen as the trough moves west on Wednesday, remaining locally breezy through the second half of the week, bringing brief showers to windward areas. Shower coverage may increase over all islands toward the end of the week as an upper trough moves over the area. High clouds are expected to blanket island skies Tuesday through Thursday.

Discussion

Although model guidance generally agrees on the large scale pattern over the next several days, there remain significant differences as to some of the details. This is somewhat understandable, given that a sharp upper trough will dig sharply southward along 170W today, then give birth to a closed low aloft that will become cutoff to the W of the islands on Tuesday.
After lurking W of the islands near 20N 170W for a day or two, a weakened version of the low may eventually move over the islands around Thursday and Friday. The initial development of the low may bring a period of instability to the W portion of the chain tonight and Tuesday, which may give rise to greater shower coverage as mid- level temperatures cool to near -11C. Later Tuesday into Thursday, most of the instability associated with the low should remain sufficiently W of the islands to keep island weather somewhat settled, with brief showers favoring windward areas. On Thursday and Friday, there could be greater shower coverage as instability increases, but guidance is divergent as to the extent. The nearby low will deliver periods of high clouds this week, potentially quite thick Tuesday through Thursday.
Locally breezy trade winds, supported by surface high pressure to the NE, will weaken later today and tonight as a surface trough develops near and N of the islands, and the high weakens. Winds will then strengthen Tuesday night and Wednesday as the trough moves W of the area and surface high pressure builds to the N. The resultant locally strong trade winds will likely be veered to the ESE, as the surface trough lingers W of the area.
With E to ESE trade winds in the forecast most of the week, most showers will fall over windward portions of the islands, with some exceptions. The diminished trades may allow sea breezes to the drive the formation of a few leeward showers this afternoon (and again tomorrow) on the smaller islands, as indicated by most of the short- term high-resolution guidance. Additionally, as has been the case the past couple of days, the Kona slopes can expect afternoon and evening showers through the week. On that note, worth mentioning that over an inch of rain was recorded in both Honaunau and Kealakekua overnight.
Long range deterministic and ensemble guidance indicates a mid-level cold pool, associated with the lingering trough, will persist near the islands through next weekend before warming thereafter. This leads to the general expectation of a wet trade wind pattern, with the GFS continuing to indicate higher PWAT fueling greater shower coverage than ECMWF guidance.

Aviation

Moderate trades will focus clouds, showers, and occasional MVFR over windward and mauka areas until they weaken late this morning into this afternoon. The emergence of a modified sea breeze pattern during peak heating as an upper low approaches from the northwest will provide favorable conditions for showers to develop over the smaller islands by this evening.
AIRMET Tango for lee turbulence remains in effect in the near term but will likely be cancelled during the morning as trades gradually weaken.

Marine

A deepening trough northwest of the islands will cause winds to weaken and shift out of the east to potentially southeast today through Tuesday. Therefore, the Small Craft Advisory has been dropped this morning. As the surface trough moves westward Tuesday night and Wednesday, high pressure will build to north of the islands, leading to an increase in trades for the second half of the week.
Surf will remain well below advisory levels on all shores this week. The current northwest swell will slowly decline through Tuesday. Trade wind swell energy will diminish through Tuesday as well, then rebuild Wednesday and Thursday as trade winds strengthen. A near average south swell will decline today. A near-seasonal south- southwest swell is possible next weekend.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov