SynopsisA ridge to the north will produce breezy trade winds through the rest of this week and this weekend. Remnants of a front will maintain wet weather over Oahu and Kauai overnight and Friday. Drier weather will develop during the weekend as the frontal remnants dissipate, with a more typical pattern of trade wind showers focused mainly over windward and mauka areas. The trade winds will subside early next week as the ridge weakens.
DiscussionWet weather continues across Oahu and parts of Kauai this evening, due to the remnants of an old frontal boundary lying over those islands. Rainfall has been widespread particularly over Oahu, but generally light to moderate with no heavy downpours observed recently. Drier weather prevails over Maui county and the Big Island, with just scattered light showers over windward areas. Breezy trade winds prevail over the state, to the south of an east-west high pressure ridge axis located about 750 miles north of Honolulu. Aloft, a mid level ridge is centered SE of the Big Island, with a broad trough west of the state. Mimic-tpw satellite imagery shows a narrow swath of enhanced moisture, associated with the frontal remnants, over the western half of the state, with a somewhat drier airmass over the Big Island. The 00Z soundings show weak inversions around 7-8 kft, and pwats ranging from 1.24 inches at Hilo to 1.47 inches at Lihue.
The frontal remnants will drift slowly westward overnight, with the axis of wettest weather shifting from Oahu to Kauai by late tonight. Showers will also remain likely across the windward Big Island. The existing forecast appears to be on track, and no updates are planned for this evening.
High pressure north of the state will maintain a breezy trade wind pattern over the islands through the weekend. A weak front will pass far to our north and northeast Friday into Saturday, and a new high will build behind the front to our north during the weekend. This high will flush the moisture associated with the frontal remnants to the south of the state Friday night into Saturday morning. This will allow for a return to more typical trade wind conditions during the weekend and into next week, with clouds and showers focused mainly over windward and mauka areas. Trade winds should decrease somewhat over the islands early next week as another weak front passes by to our north, then strengthen again by midweek as yet another high builds in behind that front.
AviationThe remnants of an old front will remain centered over Oahu this evening, producing extensive MVFR cond. Airmet sierra for mtn obsc remains posted for Oahu this evening, and may be needed through the remainder of the night. The frontal remnants may bring mtn obsc amd MVFR conditions to Kauai late tonight into Friday morning.
Breezy trade winds will continue to produce turbulence in the lee of the mountains. Airmet tango continues for moderate turb S thru W of the mountains over all islands.
MarineThe Thursday morning ascat pass found large areas of 25 kt winds in the channels and south of the Big Island, with some 30 kt winds in the Alenuihaha channel. High pressure north of the area will produce locally strong trade winds over the coastal waters through the weekend. A small craft advisory /sca/ is posted for most coastal waters, and the SCA may need to be extended through the weekend for some areas. These strong trades will continue to produce elevated and rough surf along east facing shores.
A moderate northwest swell will persist overnight into Friday. A larger northwest swell is expected to arrive Friday night, peak Saturday afternoon and Saturday night, then slowly subside early next week. This swell will produce surf above the advisory criteria on north and west facing shores during the weekend. Surf will remain small along south facing shores through the weekend and into next week.
HFO Watches/Warnings/AdvisoriesSmall craft advisory until 6 pm HST Friday for Kauai northwest waters, Kauai windward waters, Kauai leeward waters, Kauai channel, Oahu windward waters, Oahu leeward waters, Kaiwi Channel, Maui county windward waters, Maalaea Bay, Pailolo channel, Alenuihaha channel, Big Island leeward waters, Big Island southeast waters.