Synopsis16 Jun 2019 20:12:00 GMT: Fresh trades will continue today with mostly dry and stable weather. Winds will shift slightly southeast for Monday and Tuesday, and back easterly for Wednesday and Thursday. Clouds and showers will focus across windward and mauka areas and remain mostly light.
Discussion16 Jun 2019 20:12:00 GMT: A 1026 mb surface high is centered far northeast of Hawaii driving fresh trade winds across most of the state this morning. 12Z soundings show strong atmospheric stability with an inversion near 6000 feet at Lihue to 8000 feet at Hilo. Visible satellite shows mostly sunny skies over most of the state with some low cloud build ups on windward Kauai and Oahu, and the lower slopes of the Big Island to a lesser extent. Radar shows very little, if any, precipitation falling. Expect a warm and pleasant condition for the rest of today. Late tonight, a few more clouds and showers will move in the trade wind flow and may impact windward sections of Maui and the Big Island.
A longwave trough is positioned across the North Central Pacific and to the northwest of Hawaii. A surface reflection of the trough is located west of our area and will begin to strengthen and develop tonight and Monday. While this activity will not directly impact our area, we are expected to see a subtle shift in wind direction to slightly south of due east for Monday and Tuesday. Wind speeds should remain moderate to fresh, but blocking downstream may weaken winds for leeward areas particularly across Kauai and Oahu. Scattered clouds and showers will remain focused windward and may increase Monday into Tuesday. Rainfall amounts will be on the light side.
Wednesday and Thursday, the surface high northeast of the state will push back winds easterly, bringing in more typical trade wind weather. A repeat of the the developing trough to our west will repeat Friday with a more dramatic shift to southeast winds into next weekend.
Aviation16 Jun 2019 20:12:00 GMT: Surface high pressure will remain to the northeast of Hawaii, providing moderate to locally strong trade winds to the area through tonight. Passing low clouds and isolated showers will affect windward and mountain areas of the islands at times. Mainly VFR conditions will prevail, though windward and mountain areas may see brief MVFR ceilings/visibility.
No AIRMETS are expected today, though will continue to monitor the potential for AIRMET Tango for low-level turbulence continues due to the rather robust trade winds.
Marine16 Jun 2019 20:12:00 GMT: High pressure far northeast of the state will maintain fresh to locally strong trades through the middle of the week. Winds may veer east-southeasterly Monday into Tuesday as a weak trough develops far west of the state. A Small Craft Advisory (SCA) is in effect for the typically windy waters around the Big Island and Maui through early Monday morning. This will likely need to be extended at least into Tuesday.
Surf has dropped some along south facing shores today, but is still holding at levels slightly above the summer average. We should continue to see a gradually drop of the south-southwest swell into Monday. A new small long-period south-southwest swell is expected to fill in on Tuesday and peak on Wednesday with heights around the summer average. Surf heights are expected to stay below advisory levels for the foreseeable future along south facing shores.
A reinforcing northwest swell will continue to produce surf in the small to moderate range along north facing shores through today. Additional pulses of tiny northwest swell are expected through the week. Also, surf along east facing shores will begin to rise early this week as trade winds become more established.
HFO Watches/Warnings/Advisories16 Jun 2019 20:12:00 GMT: Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
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