Marine Weather and Tide Forecast for Haiku-Pauwela, HI

DISCUSSION
Visible satellite and radar show a band of showery low clouds moving east to west across Hawaii with the breezy trade winds.
Showers have been anchoring over windward slopes of Kauai and Oahu, and Maui County to lesser extent. Expect another 12-24 hours of the passing showers across windward sides of the smaller islands before Hawaii sees the end of this band.

A 1028 mb high is centered far north northeast of Hawaii drifting slowly northeastward. Soundings show an inversion over the state around 7000 feet with precipitable water around 1.2 inches. The stable conditions will limit rainfall amounts with most occurring windward due to terrain effects, and occurring during the nighttime and early morning hours.

An approaching cold front will begin to influence the wind flow over the islands as early as Wednesday. Winds will weaken to moderate on Wednesday, then gentle by late Thursday into the weekend as the front moves closer and the subtropical high drifts away to the northeast. This in turn will allow for a hybrid pattern of weak trade winds combined with sea and land breezes Thursday and Friday, with all land/sea breezes Saturday. Daytime sea breezes will result in interior clouds and showers, while nighttime land breezes clear out the cloud cover across the islands. Models show the front stalling and dissipating well northwest of Hawaii Sunday, with trades expected to strengthen again early next week.



AVIATION
Moderate to breezy trade winds will continue before gradually weakening heading into midweek. Showers embedded within the tradewind flow will continue to primarily impact windward and mountain areas, with some spillover into leeward areas. MVFR conditions are expected within showers, while VFR prevails elsewhere.

AIRMET Sierra remains in effect for mountain obscurations for N through SE sections of Kauai and Oahu, as these two islands are receiving most of the showers. These conditions are intermittent, and the AIRMET could be expanded to include other islands overnight.

AIRMET Tango is in effect for mechanical turbulence downwind of the mountains due to breezy trade winds, and this is expected to continue until midweek.



MARINE
Trade winds will gradually ease through Friday. Currently, fresh to locally strong trade winds are being driven by a 1027 mb high centered far northeast of Hawaii with an associated ridge stretching west about 600 nm north of Kauai. The high will be pushed eastward over the next several days, and its associated ridge will be displaced southward, resulting in the slow decrease in local trades. Based on the latest guidance, the Small Craft Advisory (SCA) for the typically windy waters around Big Island and Maui has been extended into Tuesday afternoon. By late Tuesday, trades should be down into the moderate to locally fresh range, and the SCA will likely be dropped. Trades will fall to gentle to moderate strength by Friday and may hold into the weekend.

A series of southern hemisphere swells will continue through the week with the largest due to arrive this weekend. Currently, a building long-period south swell is overlapping a fading medium- period swell. The bulk of the new swell energy was aimed east of Hawaii, which still leaves some uncertainty in resulting surf heights through Tuesday. Nearshore PacIOOS buoys are measuring a combined swell above 2 feet across a broad spectrum of periods, and long-period energy has been slowly rising this afternoon, which is consistent with trends observed at offshore NOAA buoy 51002. Expect south shore surf to build to around seasonal average tonight and Tuesday, and then decline Wednesday, followed by a smaller pulse of south-southwest swell Thursday and Friday.

A much larger south-southwest swell will arrive Saturday night and Sunday. A storm just southeast of New Zealand is producing a fetch of seas in excess of 40 feet aimed at Hawaii, and there is growing confidence that south shore surf will well exceed High Surf Advisory levels during the peak Sunday into early next week, with High Surf Warning conditions possible. This swell will coincide with the peak monthly tides and will likely lead to significant wave runup and impacts to coastal infrastructure.

Small west-northwest is possible over the next few days, while rough east shore surf slowly declines below seasonal average. Surf along east facing shores will decline further later this week.



HFO WATCHES/WARNINGS/ADVISORIES
Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.