SynopsisBreezy to locally windy trade winds will persist into Sunday followed by a gradual decline early in the work week. A stable trade wind weather pattern will focus rainfall along windward terrain this weekend, though showers will be periodically carried over leeward sections on the gusty trades. Moderate trade winds and a typical pattern of windward and mauka showers will prevail during the work week, with pockets of moisture leading to brief increases in shower activity.
DiscussionBreezy to locally windy trade winds will continue today. A relatively strong 1027 mb high is parked about 800 miles north- northwest of Kauai. Overnight soundings revealed a slightly elevated inversion around 9000 ft, and Radar VAD wind profiles have been showing trade winds at a steady 25 to 30 kt below the inversion. As mid level ridging builds over and north of the islands today, the inversion should come down a couple thousand feet, which could cause advisory level wind gusts to be more widespread though still confined over and downwind of island terrain. A wind advisory remains in place through the evening.
Rainfall will be focused over windward terrain today, though a few showers will be blown across leeward portions of the smaller islands, mainly in the late afternoon. Overnight soundings and satellite data show precipitable water (PW) values near seasonal normal over the state. PW values decrease upwind of the islands, but scattered shower-bearing cumulus observed over these waters suggests that windward slopes will continue to receive some rainfall.
Trade winds will gradually decline starting Sunday. The surface high driving the trades will be nudged westward and weakened by a deepening trough occupying much of the northeast Pacific. Locally, winds will still be breezy and gusty on Sunday, followed by a more pronounced drop to moderate strength on Monday and Tuesday. Trades will rebuild on Thursday or Friday as the northeast Pacific trough shifts eastward, allowing stronger high pressure to move north of the state.
Stable trade wind weather will dominate through much of the week, though pockets of moisture will periodically lead to increases in shower activity. One such area of moisture, the remnants of a front, are expected to pass over the island chain Sunday night.
AviationStrong and gusty trade winds are expected to continue through the weekend, and as such, AIRMET TANGO for low level turbulence to the lee of the islands will remain posted. Expect surface winds of 20 to 30 kts throughout the islands.
Clouds and showers being carried in on the trade winds brought MVFR conditions to the mountains overnight, but have since thinned. AIRMET SIERRA for mountain obscuration over the east sides of Maui and the Big Island was recently canceled. VFR conditions are expected to prevail, but expect some brief MVFR conditions in clouds and showers.
MarineA Gale Warning is in place for the typically windy waters around the Big Island and Maui, while a Small Craft Advisory (SCA) remains posted for remaining Hawaiian waters. The Gale Warning will likely be downgraded to an SCA sometime tonight, and the SCA should be extended through Sunday. By Monday, SCA conditions will likely be confined to the typically windy waters around the Big Island and Maui. Another round of widespread stronger trades is possible by Thursday or Friday.
A high surf advisory is in effect for east facing shores through Sunday afternoon. PacIOOS buoys have been measuring seas of 9 to 10 ft at 8 to 9 seconds across waters exposed to the rough seas generated by the trade winds. Expect little change in these seas through at least tonight, followed by a slow decline starting Sunday. The only significant long period swell due this week is a moderate northwest swell on Tuesday and Wednesday. Otherwise, small surf will prevail on north, south and west shores.
HFO Watches/Warnings/AdvisoriesWind Advisory until 9 PM HST this evening for Niihau, Kauai, Oahu, Molokai, Lanai, Kahoolawe, Maui Windward West, Maui Leeward West, Maui Central Valley, Windward Haleakala, Leeward Haleakala, South Big Island, Big Island North and East, Kohala, Big Island Interior.
High Surf Advisory until 6 PM HST Sunday for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, South Big Island, Big Island North and East.
Gale Warning until 6 AM HST Sunday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Big Island Windward Waters.
Public and Marine...Wroe