Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 86 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then showers after midnight. Lows 65 to 71 near the shore to 54 to 59 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 80 percent.

Sunday: Partly sunny in the morning then becoming cloudy. Scattered showers. Highs 77 to 87 near the shore to around 69 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Mostly sunny. Scattered showers in the afternoon. Highs 82 to 88 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to 50 to 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 83 to 89 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 81 near the shore to 68 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to around 59 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 74 to 81 near the shore to 68 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs 74 to 81 near the shore to 68 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to around 59 near 3000 feet. East winds up to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs 74 to 81 near the shore to 68 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 85 near the shore to around 67 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 73 near the shore to around 52 near 5000 feet. Northeast winds up to 20 mph becoming 10 to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 76 to 86 near the shore to around 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers in the evening, then showers after midnight. Lows 65 to 71 near the shore to 54 to 59 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 80 percent.

Sunday: Partly sunny in the morning then becoming cloudy. Scattered showers. Highs 77 to 87 near the shore to around 69 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny and breezy. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 66 to 74 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Isolated showers in the evening. Lows around 74 near the shore to around 55 above 4000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Sunday: Sunny in the morning then becoming partly sunny. Breezy. Highs 84 to 89 near the shore to 67 to 74 above 4000 feet. Northeast winds up to 20 mph.

Detailed Forecast

Synopsis

A high pressure system north of the Hawaiian Islands will continue to gradually weaken and drift slowly west over the next several days. Trade wind speed trends will remain in the moderate to breezy range through Sunday, and then lower to moderate levels from Monday onward. Strong and stable subsidence aloft will limit shower potential for most days into next week. However, a slight increase in cloud and shower trends will continue through the day today as a weak easterly wave moves from east to west down the island chain.

Discussion

Looking into the satellite picture this morning we see an upper level cold core low and an area of thunderstorms roughly 700 to 800 miles northwest of Kauai. High level cirrus clouds are streaming up from the south over the western islands, riding in along an upper level subtropical jet stream. We also see a slight counter clockwise (cyclonic) rotation in the low level cumulus cloud field associated with a weak trough in the trade winds. This weak easterly wave will continue to slowly move through the islands today, pushing up on the trade wind temperature inversion, and increasing cloud and shower trends into the evening hours. Most of the enhanced showers will form during the typical diurnal rainfall maximum in the overnight to early morning hours.
In the larger scale, a strong high pressure system north of the Hawaiian Islands will continue to produce moderate to breezy trade winds across the region today. The high center will continue to weaken and drift slowly westward, with decreasing wind speed trends into the moderate to breezy range from Saturday to Sunday, and then further weakening to more moderate levels from Monday on through much of next week.
Through much of next week expect fairly stable conditions under an upper level ridge will continue to limit vertical cloud heights and shower development into much of next week. One wrinkle in this forecast was mentioned above with the low level trough adding some short range instability to the mix through tonight. Otherwise stable and mostly dry weather with trade wind thermal inversion heights in the 4,000 to 6,000 foot height range will prevail across the state.

Aviation

Breezy trade winds will hold in place today and tonight, strongest and most gusty from mid morning through late afternoon. Low clouds and showers will favor windward and mauka areas through the period, bringing MVFR cigs/vsbys at times.
AIRMET Sierra remains in effect for mountain obscuration over windward sections of most islands. Conditions should improve by mid morning.
AIRMET Tango remains in effect for moderate low-level turbulence over and downwind of the terrain of all islands. This AIRMET will likely continue through the day.

Marine

Strong surface high pressure far northeast of the state will maintain fresh to locally strong trades through the weekend. A Small Craft Advisory has been extended for the typical windier areas around Maui County and the Big Island through Sunday. By early next week, the aforementioned high is forecast to drift west and allow trades to ease into the gentle to fresh range.
Overlapping small, medium to long period south swells will continue to provide small surf along south facing shores today. Surf along east facing shores will remain choppy with short period wind waves. Local wind swell may wrap into select north and south facing shores. Surf along north facing shores will remain nearly flat, typical of this time of year.

Fire weather

Breezy trade winds and low relative humidity will keep elevated fire weather concerns over leeward areas through Sunday. Locations such as West Maui and leeward Kohala on the Big Island are of particular concern. Trade winds will remain in the moderate to breezy range through Sunday, and then down to moderate levels from Monday onward as the pressure gradient over the state relaxes.
Most leeward areas will remain dry. Brief periods of showers will move into windward areas mainly in the overnight hours. Humidity levels will see good to excellent overnight recoveries. Exceptions to this humidity rule will be for elevations in the 4,000 to 8,000 foot range, which may see periods of warmer temperatures with much drier conditions, within and above the subsidence temperature inversion level.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov