The National Weather Service has extended the High Surf Advisory through 6pm Sunday evening due to another round of large south swell hitting the islands today. This series of south swells will continue throughout the entire forecast period, with smaller reinforcing swells expected Monday, late Tuesday, and again Friday. A minor bump may appear along the north and northwest facing shores later today, but it won’t be worth getting excited over. Another small to low-end moderate out-of-season west-northwest to northwest swell is expected to arrive late Tuesday into Wednesday as well. The surf along the summer shores will be more consistent due to the overlapping swells so there could be long sets with high wave counts and even some double-ups as sets combine. The only bad news is that the weather may not cooperate well, but at least the winds will be light.
Currently, a gale continues to build far east of Japan, but it is expected to peak overnight into Sunday and then fade out before reaching the international dateline Monday. This should be able to produce a fun sized west-northwest to northwest swell that would arrive late Tuesday and slowly fill in Wednesday. No other swell sources are expected through the forecast period aside from very tiny background swell. The activity in the South Pacific has all exited our swell window as a more zonal west to east pattern emerges, and the models aren’t showing anything that could produce any swells above background levels throughout the forecast period. In other words, get what you can while it’s here. A flat period is looming after this run of great south swells.
South facing shores should see surf in the 5-8 foot range at the better breaks while lesser breaks come in at half that size. The best locations could see larger sets if you know where to look. East and northeast facing shores have a minor windswell around 2-4 foot but it is on the way down. North and northwest facing shores could see a slight bump around 2-4 foot while Upper West shores see less action around 1-3 foot. Be safe on those south shores and have fun!
Wind and Tide InformationLow tide at Kahului was 0.53 foot at 4:11 AM early this morning, rising to a high of 1.01 foot at 10:06 AM shortly before noon, then dropping to a low of 0.81 foot at 2:21 PM early this afternoon, before once again rising to a high of 1.71 foot at 9:19 PM late this evening. The sunrise was at 05:45 am this morning and will set at 06:59 pm this evening. The Moon is in a waxing gibbous phase and will reach Full Moon phase next Friday.
Light east to northeasterly winds around 5-15 mph are expected today due to a nearby trough, becoming more northerly Sunday and Monday while slowly swinging back to a more easterly direction over the second half of the week.
Sunset: 6:58 PM
Weather Outlook for Saturday
Trade winds will weaken today, and turn toward the north on Kauai and Oahu, as a trough develops near the islands. The trough will move slowly east this weekend, and light to moderate northerly winds will spread to Maui county, while light south winds will prevail near the Big Island. With light winds, clouds and showers will favor afternoon hours, and will primarily affect leeward areas. The presence of the trough will help to intensify any showers that form over the islands the next several days.
A somewhat unseasonable weather pattern, and low confidence forecast, are in the works for the next couple of days. Currently, water vapor imagery shows a weakening low aloft moving slowly ESE just N of Maui county, with the low becoming increasingly ill-defined over the past few hours. At the surface, a weakening trade wind flow is being supported by a surface high about 1550 miles NE of the islands, but the latest surface analysis places a sharpening surface trough near Maui county that will become a primary player in island weather over the next several days. Despite weakening, the presence of the low aloft is maintaining a moderately unstable airmass over the islands, as seen in early morning soundings, and highlighted by the strong radar returns emanating from showers. Meanwhile, water vapor imagery shows a rapidly sharpening trough aloft N of the islands near 30°N 160°W, which will be an important player in island weather over the next several days.
Have introduced a slight chance of thunderstorms over interior and leeward Big Island for this afternoon, due to the instability and recent radar observations. In other areas, localized downpours are possible.
The forecast calls for the weakening upper low near the islands to move ESE before dissipating E of the Big Island later today, while the new trough aloft digs aggressively SE over waters N and NE of the islands. This strongly digging trough will develop into a closed low aloft by Sunday, with this low then meandering in an area about 550 miles NE of the islands into the middle of next week. The proximity of the closed low will maintain a moderately unstable island airmass, and enhance any showers that develop. The low will linger N of the islands until the middle of next week before finally dissipating.
A weak surface low is forecast to develop NE of the islands in response to the developing low aloft, with a sharp surface trough extending southward over the islands. The trough will interrupt the trade flow, and turn winds to the N and NE over Kauai and Oahu by tonight, while winds near the Big Island veer to the S. As the trough slides E tonight and Sunday, the light to moderate N winds will spread to Maui county, with this general wind flow persisting through Monday. On Tuesday the surface trough over the islands will weaken, but light E to ESE winds are expected to prevail statewide for much of next week, as the trough lingers N of the islands.
Biggest short term forecast challenge hinges on the strength and axis of the developing low level trough in relation to the island chain. This will have profound effects on island weather, and confidence in the details of the forecast over the next couple of days are lower than normal. The ongoing forecast is calling for a land and sea breeze regime over the islands, but will need to be fine tuned as events unfold, as the n/ne winds W of the trough axis may be strong enough to override island-scale land/sea breeze winds.
Central Valley (Kahului, Spreckelsville):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST SUNDAY. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 82 to 88. East winds up to 10 mph shifting to the north in the late morning and afternoon. Chance of rain 30 percent.
Leeward West (Lahaina, Ka`anapali):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST SUNDAY. Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 78 to 86. Northeast winds around 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.
Windward West (Wailuku, Waiehu):
Partly cloudy. Lows 55 to 67. Light winds.
Windard Haleakala (Hana, Haiku, Makawao):
Mostly cloudy with scattered showers. Haze through the night. Lows around 67 at the shore to around 52 at 5000 feet. Southeast winds up to 10 mph early in the evening becoming light. Chance of rain 50 percent.
Leeward Haleakala (Kihei, Wailea, Makena):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST SUNDAY. Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 87 at the shore to around 69 at 5000 feet. Light winds becoming northeast around 10 mph late in the morning, then shifting to the west in the afternoon. Chance of rain 50 percent.
Partly cloudy with isolated showers. Lows around 48 at 7000 feet to around 43 at the summit. Light winds. Chance of rain 20 percent.
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