Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to 66 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to around 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to 66 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then cloudy with scattered showers in the afternoon. Highs around 85 near the shore to around 69 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 73 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Sunny in the morning, then cloudy with scattered showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 40 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs 68 to 86. East winds up to 25 mph increasing to 15 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 70 near the shore to 56 to 64 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Sunday: Windy. Mostly cloudy with scattered showers. Highs 69 to 87. East winds 10 to 30 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs 68 to 86. East winds up to 25 mph increasing to 15 to 25 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 64 to 70 near the shore to 56 to 64 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Sunday: Windy. Mostly cloudy with scattered showers. Highs 69 to 87. East winds 10 to 30 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 85 near the shore to around 69 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 55 near 5000 feet. Northeast winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 20 percent.

Sunday: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs around 86 near the shore to around 70 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 82 near the shore to 66 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with numerous showers. Lows 65 to 72 near the shore to around 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Sunday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to 66 to 73 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Breezy. Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 82 to 88 near the shore to 67 to 76 above 4000 feet. Northeast 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 52 to 58 above 4000 feet. Southeast winds up to 25 mph with gusts to 45 mph. Chance of rain 20 percent.

Sunday: Sunny in the morning then becoming partly sunny. Windy. Highs 84 to 90 near the shore to 68 to 76 above 4000 feet. Northeast winds up to 30 mph.

Detailed Forecast

Synopsis

A high pressure system far north of Kauai will slowly drift east over the next two days, keeping moderate to breezy trade winds in the forecast through much of next week. A weak low level disturbance passing through the islands today will enhance cloud and shower activity for all islands. Drier and more stable conditions with breezy to locally windy trade winds are forecast for Sunday. Passing trade wind showers will continue through Tuesday night. Deep and unstable tropical moisture from the remnants of Bonnie will drift into the region from east to west on Wednesday and Thursday, boosting rainfall coverage across the state.

Discussion

The satellite imagery this morning shows broad low level troughing and extensive cumulus clouds moving westward into the windward Big Island and East Maui. This disturbance will enhance cloud and shower coverage a bit today as it continues on its westward journey across the island chain. A subtropical jet stream in the upper levels just northwest of Kauai continues to produce high level cirrus clouds over most of the islands, likely enhancing Hawaiian sunrise and sunset colors into early next week. Local radar imagery this morning shows scattered to numerous showers developing across the state with most of these showers affecting windward and mountain areas. Some of the stronger showers are drifting into the typically drier leeward sections of the smaller islands.
The short term forecast shows a high pressure center far north of Kauai, this system will slowly drift eastward this weekend keeping moderate to breezy trade winds blowing across the region for most of the week. In the low levels, we see a broad low level trough moving into the islands from the east. Less stable low clouds will produce scattered to numerous showers over windward and mountain sections of each island, with brief showers possible over leeward areas lasting through this evening. On Sunday 500 MB streamlines show an stable upper level ridge building over the region, increasing stability with stronger subsidence, and decreasing shower trends. Stronger subsidence will also lower the trade wind inversion height and the near surface boundary layer to around 5,000 to 6,000 feet. This shallow boundary layer will help boost trade wind speeds into the locally windy range in some terrain wind favored areas around the state. Trade wind speeds on Sunday may reach low end Wind Advisory thresholds for these windier areas, especially over mountains and through valleys of Maui and the Big Island. Moderate to locally breezy trade winds with passing showers over windward and mountain areas will return on Monday and Tuesday.
In the longer range forecast wetter trends remain. A deep and unstable tropical moisture pool, associated with the remnants of Tropical Cyclone Bonnie, will drift over the islands late Wednesday into Thursday. Weather conditions will become more humid than normal and rainfall activity will increase across the region. The boundary layer will rise as this tropical moisture drifts through the islands and trade wind inversion heights will increase to the 10,000 to 12,000 foot elevation range. This means that clouds will be much deeper than normal, resulting in enhanced rainfall as this deep moisture is lifted by the breezy trade winds over all island mountains and falling out as rain. Another tropical moisture pool may move into the region by next weekend (July 16th) adding to these wet weather trends. The rainfall amounts from this first system will depend heavily upon the track of these moisture remnants, with less rainfall if the center of the moisture tracks north or south of the state. Stay tuned for more information as the time period grows shorter and the island by island weather impacts evolve over time.

Aviation

High pressure far north of the state will help to maintain breezy east northeasterly trades across the islands through the forecast period. Thus, most showers will be limited to windward portions of the islands. However, a few showers may push over the mountainous terrain and affect leeward areas. Any heavier shower activity would capable of bringing brief periods of MVFR ceilings and visibility.
AIRMET Tango remains in effect for low level turbulence to the lee of higher elevations statewide.
AIRMET Sierra remains in effect above 2500 feet for north thru east portions of Oahu and Kauai due to mountain obscuration from low clouds and showers.

Marine

No significant changes to the forecast this morning. Winds are expected to trend upwards a bit tonight and Sunday, which may prompt an expansion of the Small Craft Advisory (SCA). At this time will monitor the trends this morning before making any such change. The existing SCA remains posted for the typical windier waters around Maui County and the Big Island through Monday.
No significant swells are expected through the weekend. A series of southerly swells are expected to start arriving Sunday, boosting surf along south facing shores at or above the summer average by the middle of next week. A much larger south swell is possible the following weekend (around the 17th) as a deep low occludes southeast of New Zealand this weekend. As the trades strengthen this weekend, some east facing shores may see a slight increase, but nothing significant is expected. A small, medium period, east swell generated by tropical cyclone Bonnie, currently in the East Pacific, may arrive early next week.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov