Rest Of Today: Showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Highs around 77 near the shore to 62 to 67 at 4000 feet. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain near 100 percent.
Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 64 near the shore to around 50 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.
Friday: Mostly cloudy with scattered showers. Highs around 78 near the shore to 63 to 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.
Kona
Rest Of Today: Cloudy with scattered showers and isolated thunderstorms. Highs around 83 near the shore to around 69 near 5000 feet. Light winds. Chance of rain 40 percent.
Tonight: Partly cloudy with isolated showers. Lows around 70 near the shore to around 54 near 5000 feet. Light winds. Chance of rain 20 percent.
ARTICLE CONTINUES BELOW AD
ARTICLE CONTINUES BELOW AD
Friday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. West winds up to 10 mph. Chance of rain 50 percent.
Waimea
Rest Of Today: Breezy. Cloudy with numerous showers and isolated thunderstorms. Highs around 76 near the shore to 66 to 75 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.
Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 63 near the shore to 48 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.
Friday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 77 near the shore to 67 to 75 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.
Kohala
Rest Of Today: Breezy. Cloudy with numerous showers and isolated thunderstorms. Highs around 76 near the shore to 66 to 75 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.
ARTICLE CONTINUES BELOW AD
Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows around 63 near the shore to 48 to 61 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.
Friday: Breezy. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Highs around 77 near the shore to 67 to 75 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
Rest Of Today: Cloudy and breezy. Isolated showers and thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs around 81 near the shore to around 70 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.
Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 69 near the shore to around 54 near 5000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.
Friday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 81 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.
Puna
ARTICLE CONTINUES BELOW AD
Rest Of Today: Showers and isolated thunderstorms in the morning, then numerous showers and isolated thunderstorms in the afternoon. Highs around 77 near the shore to 62 to 67 at 4000 feet. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain near 100 percent.
Tonight: Mostly cloudy. Scattered showers in the evening, then numerous showers after midnight. Lows around 64 near the shore to around 50 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.
Friday: Mostly cloudy with scattered showers. Highs around 78 near the shore to 63 to 68 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.
Waikoloa
Rest Of Today: Cloudy. Isolated showers and thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Highs 78 to 84 near the shore to 65 to 73 above 4000 feet. North winds up to 15 mph. Chance of rain 50 percent.
Tonight: Partly cloudy with isolated showers. Lows around 71 near the shore to 48 to 58 above 4000 feet. Southeast winds up to 15 mph. Chance of rain 20 percent.
Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 78 to 83 near the shore to 64 to 72 above 4000 feet. Northeast winds up to 20 mph. Chance of rain 20 percent.
Detailed Forecast
Synopsis
The strong high pressure system far north of the state will continue to slowly weaken with breezy trade winds decreasing into the moderate to locally breezy range through Saturday. Embedded weak upper lows north of the state will enhance some shower activity over eastern islands near Maui and the Big Island today with isolated thunderstorms. The ridge will weaken further on Sunday and Monday producing drier southeasterly winds over most areas. A low pressure system and cold front approaching the islands from the northwest on Tuesday will produce southerly winds with increasing shower activity over the western islands by Wednesday.
Discussion
The satellite water vapor imagery this morning shows the high level cirrus clouds with the subtropical jet stream are slowly drifting eastward. Scattered to numerous showers are showing up on the local radar imagery. However, most of these shower bands are moving towards the west-northwest direction, and passing just north of the smaller islands west of Maui. Upper air balloon soundings from 2 AM HST this morning show the trade wind inversion height around 8,000 feet, which supports this mornings shower coverage.
The subtropical jet stream over the islands will continue to weaken today with decreasing upper level cloud cover over the western half of the state. This jet stream remains just south of a narrow upper level trough with embedded weak upper lows. Weather guidance suggests one of the upper lows will become strong enough to cause a low level trough to form near Maui and the Big Island today increasing shower trends for both islands. Some of these showers will be locally heavy at times with the potential for isolated thunderstorms. The rest of the islands west of Maui will see less rainfall activity as the ridge north of the state continues to weaken into the weekend.
By Sunday and Monday, the weather pattern changes as the ridge north of the state weakens in response to a cold frontal system moving into the region from the northwest. Easterly trade winds will veer from a more southeasterly direction, causing a rain shadow effect for all islands west of the Big Island, and keeping passing showers moving more parallel to Maui, Lanai, Molokai, Oahu, Niihau and Kauai. Drier conditions are expected for all areas except over the Big Island where southeasterly winds will enhance showers over the southeastern slopes near the Ka'u and Puna Districts.
Big changes are coming to the long range Hawaii weather forecast from Tuesday through next Thursday. Recent forecast guidance continues to show a low pressure system and cold front approaching the western half of the state on Tuesday. Weather model solutions are unfortunately still highly variable on the timing and location of showers associated with this next unstable weather system. A trailing cold front extending south from the approaching low moves into western islands from late Tuesday to Wednesday. This system may bring large scale southerly winds to the western islands. Unstable deep tropical moisture, converging surface winds and upper level forcing are all favorable ingredients for widespread moderate to locally heavy showers and possible thunderstorms.
The European (ECMWF) 13/00Z model is now trending towards the American (GFS) 13/06Z model with a large band of showers ahead of the cold front stalling out near Kauai and Oahu. Our confidence remains only moderate that some islands, especially Kauai, Niihau, Oahu and Molokai, will see a round of widespread rainfall by the middle of next week. The confidence in the potential onset timing and duration of heavy rain and thunderstorm impacts for each island remain low at this time.
Please stay tuned to next weeks weather forecast as locally heavy rain and thunderstorms are possible over the western half of the state. Expect changes to the current weather forecast with evolving weather impacts as the time period grows shorter.
Aviation
High pressure well north of the state will maintain moderate to locally breezy trade winds today. This trade wind pattern will focus a majority of showers and lower cloud cover across windward areas through the TAF period. Mainly VFR conditions are expected, with MVFR conditions at times in heavier showers. AIRMET Sierra is in effect for Windward Big Island. Conditions are expected to improve after noon.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of higher terrain across all islands. Conditions are expected to improve this evening when trade winds are forecast to weaken.
Marine
The 1039 mb high pressure cell centered approximately 1,300 miles northeast of Oahu will begin to move east as a new high expanding down from the Aleutian Islands replaces it far northwest of the state Friday. This will relax the pressure gradient upstream of the islands as the high slowly meanders east southeast the next day or so. This morning's ASCAT satellite pass did show continued Small Craft Advisory (SCA) winds through more eastern island bays and channels, as well as south of Big Island. The local buoys are observing a slow decline in short period north northeast wind waves this morning with many buoys currently reporting 8 to 10 foot combined seas. A Small Craft Advisory (SCA) is in effect through early Friday morning for the typically windy waters surrounding Maui County and Big Island along with the Maui and Big Island windward waters. The SCA may need to be extended into Friday afternoon for the more notoriously winder marine zones surrounding Maui County and Big Island. After a weekend of relatively light trade flow, fresh to locally strong trades will return early next week as the new high establishes itself east northeast of the state and re-tightens the upstream pressure gradient.
An ongoing small, short period north northeast (10-40 degree) swell will maintain near waist high surf along many north to northeast-facing shores through tonight. A small, medium period northwest (320 degree) swell is scheduled to arrive late Friday and fill in Saturday morning. This swell will maintain waist to near head high surf along many north-facing shores…near knee to waist high surf along west-facing shores Saturday. East-facing shores will experience continued choppy conditions through Friday in response to several days of this upstream fresh trade fetch. Surf along east-facing shores will slowly subside going into this weekend as trades fall off a notch. Small, background south swell energy will maintain knee to chest high surf along many southern shores. A very small, medium period south southwest bump in swell arriving tonight into early Friday will result in a small boost in weekend surf.
HFO Watches/Warnings/Advisories
Small Craft Advisory until 6 AM HST Friday for Kaiwi Channel, Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
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