The National Weather Service has continued the High Surf Advisory for our east facing shores now effective through 6pm Saturday evening due to overhead windswell. It is likely that Saturday will see a slight increase, so this advisory will likely get extended through Sunday as well. A new northwest swell is due to arrive overnight tonight into Saturday, but it will most likely peak just a couple of feet overhead. There is a slight chance that the best exposed breaks could see a bit more size, but let’s not count on it. Another northwest swell should arrive Sunday night into Monday at higher levels, potentially near or at advisory levels. A reinforcing northwest swell is also expected to arrive Tuesday which should be able to push us to advisory levels if we’re not already there. The long-range models go on to show similar episodes arriivng Thursday and Saturday. So it looks like we’ll have plenty surf through at least next weekend, but nothing significant is on the charts. The windswell should also hold on at overhead levels through the forecast period as well. Looking far into the model forecasts, a potentially significant swell may be in our near future. More details to come as we get a little closer.
Windswell along the east and northeast facing shores will continue around 5-8 foot again today and we should see a slight increase through Sunday. North and northwest facing shores won’t have much surf to mention aside from wrapping windswell around 3-5 foot, but a small new northwest swell is expected to arrive later today, probably overnight into Saturday. Upper West shores may also see a bit of wrapping windswell around 1-4 foot or so. South facing shores have no swell to mention and will stay flat at 0-2 foot but select breaks could pull in wrapping windswell if you know where to look.
Wind and Tide Information
High tide at Kahului was 2.94 foot at 2:44 AM late last night, dropping to a low of 0.59 foot at 9:14 AM this morning, then rising to a high of 1.47 foot at 1:52 PM early this afternoon, before once again dropping to a low of -0.63 foot at 8:07 PM early this evening. The sunrise was at 07:03 am this morning and will set at 06:04 pm this evening. The Moon has reached New Moon phase and will now begin to wax crescent until reaching First Quarter phase next Friday.
Weather Outlook for Friday
The trade winds will continue to gradually diminish today and tonight. Showers carried by the weakening trades will mainly affect windward facing slopes today, with a slight chance of thunderstorms possible this afternoon over parts of the Big Island and leeward Maui. Relatively light winds will prevail over most islands this weekend, which will allow local afternoon sea breezes and nighttime land breezes to develop. Therefore, expect clouds and showers to favor mauka and interior areas of the islands each afternoon this weekend.
A strong 1041 mb surface high is nearly stationary near 37°N 141°W, or less than 1550 miles northeast of Hilo. A surface ridge extends southwest from this high to a point about 170 miles northwest of Lihue. The pressure gradient south of this higher pressure to the north of the aloha state is maintaining trade winds across the islands early this morning. Elsewhere, a nearly north to south oriented surface trough is evident about 230 miles east southeast of Hilo. This trough and its area of enhanced low-level moisture and thunderstorms is traveling toward the west northwest at 10 to 15 mph.
Aloft, an upper tropospheric low is evident about 600 miles north northeast of Hilo. A trough extends south of this low to a point about 245 miles east northeast of the Big Island. Water vapor imagery also shows a sharp trough aloft moving rapidly toward the east northeast about 275 miles north of Lihue. As a result, a surface front about 480 miles northwest of Lihue, which was a reflection of this upper level trough, is weakening as it stalls. With the close proximity of the upper level low and trough to the east of the state, the early morning soundings indicated slightly unstable conditions continue across the state. However, low-level moisture decreased somewhat, but the satellite derived precipitable water values show increasing moisture just east of Maui and the Big Island.
The trades are transporting clouds and mainly isolated showers to windward areas of Maui and the Big Island. The cold pool of air aloft associated with the upper level low and increasing moisture will bring a chance of winter weather to the Big Island summits from later today through Saturday. Temperatures will remain near or below freezing, but the precipitation type will depend on the moisture depth and if deep convection develops over the interior of the Big Island. The primary winter weather threats appear to be freezing rain/fog, but deep convection could bring periods of snow showers. When confidence in the timing and intensity of possible convection increases, a winter weather advisory may be issued.
The upper level low / trough will remain in the vicinity of the windward Big Island today. This will maintain a relatively unstable air mass, especially over the eastern end of the state, through Saturday. At the same time, the strong surface high far northeast of the islands will shift northeastward. The surface trough southeast of the Big Island will also move closer to the islands before dissipating near Kauai by Sunday. This will result in weaker synoptic flow across most the islands, even though there will be stronger winds over the outer edges of the windward coastal waters.
Nights and mornings will be mostly dry and clear, with clouds and showers developing over interior and mauka areas each afternoon as sea breezes converge over the islands. The sea breezes expected over the weekend combined with deeper moisture associated with the approaching surface trough and the atmospheric instability may produce some locally significant rainfall from the afternoon cloud buildups, especially over Maui and the Big Island. Therefore, a slight chance of thunderstorms remains in the forecast for select areas this afternoon and Saturday afternoon.
By early next week, the low aloft moves off to the east, and ridging aloft will develop in the vicinity of the islands. Another surface front will approach Kauai from the northwest. This front is expected to weaken as it moves down across the aloha state. The latest forecast guidance not only weakens this front, but keeps the trade winds weaker following the frontal passage on Tuesday. The forecast indicates light winds will continue through Monday, with light to moderate trade winds after the front passes. The front will focus its limited moisture over north and east facing slopes and coasts. However.it will likely provide little relief to drought stricken areas of leeward Maui and the Big Island. The post-frontal trade wind flow is still expected to be drier than normal due to the ridging aloft over the islands.
Central Valley (Kahului, Spreckelsville):
Mostly clear. Isolated showers early in the evening. Lows around 61. Southeast winds 10 to 15 mph. Chance of rain 20 percent.
Leeward West (Lahaina, Ka`anapali):
Mostly clear with isolated showers. Lows 60 to 69. East winds 10 to 15 mph. Chance of rain 20 percent.
Windward West (Wailuku, Waiehu):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST SATURDAY. Partly sunny in the morning then clearing. Scattered showers. Highs 69 to 79. Northeast winds 10 to 15 mph. Chance of rain 50 percent.
Windard Haleakala (Hana, Haiku, Makawao):
HIGH SURF ADVISORY IN EFFECT UNTIL 6 PM HST SATURDAY. Partly sunny. Showers likely in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 79 at the shore to around 65 at 5000 feet. East winds 10 to 15 mph with higher gusts. Chance of rain 70 percent.
Leeward Haleakala (Kihei, Wailea, Makena):
Mostly clear. Slight chance of thunderstorms and isolated showers early in the evening. Lows around 62 at the shore to around 48 at 5000 feet. East winds around 10 mph. Chance of rain 20 percent.
Partly cloudy. Slight chance of thunderstorms and isolated rain showers early in the evening, then isolated rain showers in the late evening and overnight. Lows around 43 at 7000 feet to around 36 at the summit. Southeast winds 10 to 15 mph. Chance of rain 20 percent.