The National Weather Service has issued a High Surf Advisory for Maui’s north shores effective through 6pm Friday evening due to a large northwest swell producing surf approaching 15 foot on the face. Another larger northwest swell is expected to arrive Sunday and it will likely reach warning levels with a slow fade through the middle of the week. A fun sized south to south-southwest swell over the weekend should provide some fun sets at select breaks through the weekend and into the upcoming week. The current swell was produced as a deep low aimed a fetch of strong gales toward the islands, with a small area of hurricane-force winds embedded within. The system raced across the central North Pacific so we should expect the swell to fade rather quickly over the weekend. Further west, a large low pressure system bombed last Tuesday setting up a fetch of strong gales reaching near hurricane speeds aimed nicely toward the islands. The resulting swell is expected to arrive while we sleep Saturday into Sunday morning, beginning out of the west-northwest and then slowly shifting out of the northwest later Sunday and Monday. This will be a very large swell, very likely reaching above warning levels. Looking further out, most of the activity will be focused near Kamchatka which will result in smaller swells. Still, we shouldn’t go flat any time soon.
Today’s Surf Summary
North and northwest facing shores will start off on the smaller end but should steadily rise into the 8-12+ foot range. Upper West shores should also rise into the 5-8+ foot range with much larger sets possible at the best locations. Windswell along the east and northeast facing shores should be around 3-5 foot. Surf along the south shores is expected to slowly rise to fun levels around 2-4 foot today, potentially rising to head-high levels later in the weekend.
Wind and Tide Information
High tide at Kahului was 2.4 foot at 1:25 AM late last night, dropping to a low of 1.0 foot at 7:41 AM this morning, then rising to a high of 1.5 foot at 11:58 AM shortly before noon, before once again dropping to a low of -0.4 foot at 6:35 PM early this evening
The sunrise was at 06:56 am this morning and will set at 05:50 pm this evening. The Moon is currently 27 days old, and is in a New Moon phase. The next Waxing Crescent will occur at 10:07 AM on Saturday, November 29th.
Northeasterly tradewinds will be in the 10-20 mph range across much of the island today with gusts reaching near 40 mph expected in some areas. The winds should decrease over the weekend as a front approaches the islands, returning to strong levels once again by mid-week.
Sunset: 5:50 PM
Weather Outlook for Friday
Moderate trade winds will keep mostly light showers focused over windward slopes into the weekend. From Sunday night into Monday, a front will spread rain, cold air, and strong northerly winds across the state from the northwest. Unsettled weather will continue through about Tuesday, before returning gradually to trade-wind conditions by the end of next week.
Surface observations around the main Hawaiian islands reported mostly moderate trade winds. Guidance strongly supported a decrease in wind speeds through the day, but a few outlying observations suggested that this process may take longer than currently expected. For now, we will follow prior thinking.
The inversion height and strength, cloud cover, and shower activity still approximated climatology. Radar detected slightly fewer showers over the coastal waters, but orographic lifting continued to squeeze out widespread, if generally light, accumulation over rain gauges, despite persistently low precipitable water. Aloft, strong and broad ridging kept cirrus layers from the ITCZ south of the Big Island, but only just.
Guidance still agreed fairly well that a long-wave mid-level trough will dig toward the state from the northwest through the weekend, effectively displacing the ridge by Sunday evening, and then sharpening toward the southwest into Tuesday. This development aloft will support the approach of a cold front at the surface. Through about Sunday, the subtropical ridge will recede toward the east ahead of the front, causing surface winds around the islands to diminish and become more southeasterly. From Sunday night into next week, the front will work its way southeast across the state. With significant support from the digging trough aloft, the front will have the opportunity to produce widespread rain. The push of cold air at low levels behind the front also will bring strong northerly winds.
Perhaps most importantly, a very cold pool of air aloft will accompany the mid-level trough. This cold pool will destabilize the atmosphere significantly, introducing a non-trivial Risk of thunderstorms around Monday, mainly from Molokai northwest. A slight chance of thunderstorms has been introduced into the forecast following the local tool run off of model consensus. Strong vertical wind shear will improve the ventilation of any thunderstorms that do develop, potentially allowing some to become severe. It remained much too early to consider a severe thunderstorm watch, but possible high impacts required continued vigilance with respect to this matter.
The cold pool also will introduce the possibility of winter weather over higher elevations of Maui and the Big Island. This far out, much remained uncertain, but generally speaking the available moisture appeared limited largely to below the summits through most of the forecast period. Where both cold temperatures and available moisture coincided, a slight chance of light snow has been included in the forecast as a place holder. Deeper moisture, or thunderstorms developing further south than expected, could increase the Risk of winter weather over the summits dramatically.
From Wednesday into Friday of next week, the trough aloft will lift out toward the northeast, and conditions will return toward climatology. Recent solutions tended to draw out this process, so the relatively quick return of trade-wind weather in the forecast may be too optimistic, and should be reevaluated as more runs become available. On the whole though, trade-wind weather should return by next weekend.
Central Valley (Kahului, Spreckelsville):
Mostly clear. Lows 62 to 67. Northeast winds 10 to 15 mph with gusts to 30 mph.
Leeward West (Lahaina, Ka`anapali):
Mostly clear. Lows 63 to 71. East winds 10 to 15 mph.
Windward West (Wailuku, Waiehu):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST THIS EVENING. Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs 64 to 81. Northeast winds 10 to 20 mph. Gusts up to 40 mph decreasing to 30 mph in the late morning and afternoon. Chance of rain 50 percent.
Windard Haleakala (Hana, Haiku, Makawao):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST THIS EVENING. Breezy. Partly sunny with scattered showers. Highs around 79 at the shore to around 65 at 5000 feet. East winds 10 to 20 mph with gusts to 40 mph. Chance of rain 50 percent.
Leeward Haleakala (Kihei, Wailea, Makena):
Mostly clear. Lows around 66 at the shore to around 54 at 5000 feet. East winds 10 to 15 mph.
Breezy. Mostly clear with isolated showers. Lows around 54 at 7000 feet to around 49 at the summit. Southeast winds 15 to 25 mph with gusts to 45 mph. Chance of rain 20 percent.
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