The National Weather Service has issued a High Surf Advisory for our south facing shores effective through 6am Saturday morning due to a large south swell. This advisory will almost certainly be extended through the weekend as another potentially larger south swell arrives Saturday. Another south swell in this series is expected to arrive Sunday, followed by still another Tuesday to keep the summer surf going into the second half of the week. We may be able to pull in a much smaller south swell next Friday thanks to another fetch setting up well southeast of New Zealand today and into the weekend, but this fetch is not aimed well in our direction which will produce more of a background swell for Hawai`i. A gale developing east of Japan and south of Kamchatka over the weekend keeps looking better and better and may be able to produce a long-period near moderate west-northwest to northwest swell that would reach our islands around Wednesday. More details to come. Tropical Storm Alvin has spun up far east-southeast of the islands but it is a weak system and is expected to slowly fall apart over the next several days with no danger to Hawai`i whatsoever. Have fun today.
South facing shores will continue to see surf in the 5-8+ foot range along the better exposed shores, with smaller surf likely at the lesser breaks. East and northeast facing shores have a minor short-period east-northeasterly windswell around 2-4 foot but it won’t amount to much. North and northwest facing shores have no swell to mention and will stay near flat at 0-3 foot while Upper West shores come in even closer to flat at 0-2 foot.
Wind and Tide InformationLow tide at Kahului was 0.69 foot at 3:34 AM early this morning, rising to a high of 0.82 foot at 7:36 AM this morning, then dropping to a low of 0.61 foot at 12:23 PM early this afternoon, before once again rising to a high of 1.76 foot at 8:25 PM this evening. The sunrise was at 05:45 am this morning and will set at 06:58 pm this evening. The Moon will reach First Quarter phase today and will then begin to wax gibbous until reaching Full Moon next Friday.
The east to northeasterly tradewinds should continue at moderate to breezy levels around 15-20 mph through the day but a weakening trend is expected to begin tomorrow that will likely keep the winds light and variable through at least mid-week due to an approaching trough.
Sunset: 6:57 PM
Weather Outlook for Friday
Moderate to locally breezy trades will continue through Saturday. Showers will favor windward and mountain areas, with some of the larger showers reaching leeward locations at times. A trough will approach the islands on Saturday, bringing a weakening of the trades. This will allow for increasing moisture and shower activity across the area as sea and land breezes develop each day from Sunday and through much of next week.
Surface high pressure northeast of the state still dominates the area, keeping a trade wind weather regime in place through the next couple of days. The trades over the islands will remain moderate to locally breezy at times. Showers will continue to favor windward and mauka areas, with some of the larger showers reaching leeward locations at times, especially at night. There is still some shower activity enhancement due to an upper level low right above the islands. This feature lingers through Friday, then pushes east as a long wave upper trough moves across the north central Pacific and digs further south towards the islands on Saturday.
Global models remain in fair agreement regarding the evolution of the aforementioned upper trough during the weekend and into early next week. The trough is expected to amplify and reach south toward the main Hawaiian islands, destabilizing the airmass by bringing cooler temps aloft and increasing deep moisture. Latest model solutions suggest a low level reflexion with a surface trough developing across the islands. This will bring a blocking pattern of the trades and possibly establishing a hybrid wind regime with light southeast flow over windward areas of the Big Island and Maui, and a weak northeast flow over the west half of the island chain.
If the surface trough materializes, it will weaken the winds, especially over O`ahu and Maui county. This will allow for sea and land breeze circulations to develop each day from Sunday through at last the middle of next week. This synoptic scenario will support widespread shower activity across the islands, with higher chances of rain over interior and mountain areas.
The expected southeast flow around the Big Island next week may combine with the light winds elsewhere in order to bring widespread vog across the smaller islands, which should also remain in place through at least the middle of next week.
Central Valley (Kahului, Spreckelsville):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 AM HST SATURDAY. Partly cloudy with isolated showers. Lows 65 to 71. Northeast winds 10 to 20 mph. Chance of rain 20 percent.
Leeward West (Lahaina, Ka`anapali):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 AM HST SATURDAY. Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 65 to 71. East winds 15 to 20 mph. Chance of rain 30 percent.
Windward West (Wailuku, Waiehu):
Partly sunny with scattered showers. Highs 65 to 84. East winds 15 to 20 mph. Chance of rain 40 percent.
Windard Haleakala (Hana, Haiku, Makawao):
Partly sunny with scattered showers. Highs around 81 at the shore to around 68 at 5000 feet. East winds 10 to 20 mph. Chance of rain 40 percent.
Leeward Haleakala (Kihei, Wailea, Makena):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 AM HST SATURDAY. Partly cloudy. Isolated showers after midnight. Lows around 67 at the shore to around 53 at 5000 feet. Northeast winds 10 to 15 mph and gusty. Chance of rain 20 percent.
Mostly sunny with isolated showers. Highs around 63 at 7000 feet to around 58 at the summit. Southeast winds 10 to 20 mph. Chance of rain 20 percent.
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