Hilo

Today: Breezy. Showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Cloudy. Numerous showers in the evening, then showers after midnight. Lows around 65 near the shore to around 51 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Kona

Today: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. East winds up to 15 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 65 to 70 near the shore to around 52 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. East winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Waimea

Today: Mostly cloudy. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 71 to 78 near 3000 feet. East winds 15 to 35 mph with gusts to 70 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds 15 to 30 mph with gusts to 65 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 71 to 78 near 3000 feet. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Kohala

Today: Mostly cloudy. Windy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 71 to 78 near 3000 feet. East winds 15 to 35 mph with gusts to 70 mph. Chance of rain 70 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds 15 to 30 mph with gusts to 65 mph. Chance of rain 50 percent.

Saturday: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 71 to 78 near 3000 feet. East winds 15 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny in the morning then becoming partly sunny. Windy. Isolated showers. Highs around 83 near the shore to around 72 near 5000 feet. East winds 15 to 30 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Windy. Isolated showers in the evening. Lows around 67 near the shore to around 51 near 5000 feet. East winds 15 to 30 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Windy. Isolated showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. East winds 20 to 30 mph. Chance of rain 20 percent.

Puna

Today: Breezy. Showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Cloudy. Numerous showers in the evening, then showers after midnight. Lows around 65 near the shore to around 51 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Northeast winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Highs around 82 near the shore to 66 to 73 above 4000 feet. East winds 10 to 25 mph decreasing to up to 20 mph in the afternoon. Gusts up to 65 mph.

Tonight: Mostly clear. Lows around 69 near the shore to 47 to 55 above 4000 feet. East winds up to 15 mph with gusts to 60 mph.

Saturday: Mostly sunny. Highs around 82 near the shore to 66 to 73 above 4000 feet. East winds up to 15 mph with gusts to 45 mph.

Detailed Forecast

Synopsis

A strong high pressure system north to northeast of the state will continue to produce blasting trade winds across the Hawaiian Islands into the weekend. Expect a slight decrease in trade wind speeds from Saturday to Sunday as the high center slowly drifts eastward away from the island chain. However, breezy trade winds will continue to blow across the region into the first half of next week. Several upper level lows along an upper trough will remain over the islands keeping periods of beneficial showers in the forecast through much of next week, especially during the overnight and early morning hours.

Discussion

Blasting trade winds with strong potentially damaging wind gusts remain in the forecast into the weekend as a strong high pressure system lingers north to northeast of the state. Wind speeds will slowly decrease into the breezy range from Saturday to Sunday as the high center drifts slowly eastward away from the region. High Wind Warning and Wind Advisory products were extended in time statewide through Saturday morning for the warning and Saturday afternoon for the advisory. High Wind Warning products will likely be dropped to advisory levels by tonight for Oahu and Saturday morning for the Big Island as wind speeds begin to ease.
Regional GOES satellite shows an upper level low on water vapor imagery just south of the island chain. This low is embedded in an upper trough extending from west to east over the islands. High level cirrus clouds outline this unstable upper level trough. Upper level divergent forcing from this system will keep periods of trade wind showers in the forecast through much of next week. This upper trough will likely produce seven days of beneficial rainfall over all islands with the highest shower amounts focused over the windward and mountain slopes as Pacific moisture is lifted over island mountains. Shower coverage will tend to favor the overnight to early morning hours due to typical higher nocturnal rainfall trends in the tropics.
Trade wind speeds decrease slightly from windy trades to more breezy wind speeds from late Saturday into early next week. However, another strong high pressure system builds northwest of the region, crossing the Dateline far north of the state from Tuesday to Wednesday. A couple of challenges are developing with the medium range wind forecast for next week. Initially on Tuesday we may see more moderate to locally breezy trade winds, due to a combination a cold front passing far north of the state weakening the surface ridge and divergence from the upper trough potentially forming a weak surface trough over the islands. This surface trough may weaken pressure gradients over the state and shift the belt of strongest winds slightly north of the island chain.
Global forecast model guidance is coming into better agreement on the strength of this surface trough and the strength of the trade winds by the middle of next week. Our confidence is increasing on keeping locally windy trade winds out of the forecast from Tuesday through Wednesday. Either way longer range model solutions continue to agree that another round of blasting trade winds will return by next Thursday and Friday. Overall this breezy to windy trade wind pattern may remain locked in over the Hawaii region through for much of next week with subtle changes day to day changes in wind speeds, stay tuned.

Aviation

A strong surface high pressure system located far north-northeast of the state continues to produce very strong and gusty trade winds across the islands. Sustained surface winds in excess of 30 kt with higher gusts will continue to be possible for some locations today. Based on the fact that PHOG on Maui had winds of about 40 kt at 2000 ft AGL Thursday afternoon, there will likely be low-level wind shear there again this afternoon. Scattered to broken low clouds with embedded scattered showers continue to stream into the windward sides of most islands, especially the Big Island. Therefore, expect brief periods of MVFR conditions over the windward sections of most of the islands. VFR conditions will likely prevail over most leeward areas.
AIRMET Tango remains in effect for sustained surface winds of 30 kt or greater. AIRMET Tango also remains in effect for moderate to isolated severe low-level turbulence over and downwind of the higher terrain on all islands. Both of these AIRMETs will likely be needed through this afternoon. In addition, AIRMET Sierra remains in effect for mountain obscuration over the windward Big Island.

Marine

Strong easterly trade winds are here to stay through next week, with periods of gales possible in the typically windier areas and channels. Gales are mostly likely in these areas through Saturday, then may near these levels again late next week with a similar pattern potentially setting up. Morning buoy observations reflect the strong winds and continue to climb, with wave heights now in the 10 to 15 ft range (around 6 ft of that in the 2-4 second band).
Surf along east facing shores will remain rough through next week in response to the aforementioned pattern we are locked in. Warning-level surf is likely to persist through Saturday, then back to the advisory level Sunday through early next week. Impacts associated with this long-duration event associated with a combo of strong onshore winds and large surf will translate to significant beach erosion, powerful rip/alongshore currents, and occasional overwash onto vulnerable sections of the coast (best overwash chances at and around the peak daily high tide cycle just before/around daybreak).
Surf along north and west facing shores peaked overnight from a north-northwest swell moving through, but will ease quickly today as it moves out (mostly missed us to the north). A small long-period northwest swell is expected to fill in over the weekend, then peak through the first half of next week.

HFO Watches/Warnings/Advisories

High Wind Warning until 6 AM HST Saturday for Kohala, Big Island North.
High Wind Warning until 6 PM HST this evening for Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Honolulu Metro, Ewa Plain, Koolau Leeward.
Wind Advisory from 6 PM this evening to 6 AM HST Saturday for Waianae Coast, Oahu North Shore, Central Oahu, Waianae Mountains, Honolulu Metro, Ewa Plain, Koolau Leeward.
Wind Advisory until 6 AM HST Saturday for most of the Hawaiian Islands.
High Surf Warning until 6 PM HST Saturday for all exposed east facing shores.
Gale Warning until 6 PM HST Saturday for Kaiwi Channel, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Saturday for most Hawaiian coastal waters.

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Data Courtesy of NOAA.gov