textproduct: Honolulu

SYNOPSIS

Windy and gusty northeast trade winds will prevail through at least Tuesday and then decrease a notch by mid week into the second half of this week. Cool and dry air should keep showers light and over windward and mountain areas for the next few days, except windward areas of the Big Island where lingering moisture could keep scattered showers through Monday. A cold upper trough this week could slightly enhance trade wind showers during the night time and early morning hours each day this week. By Friday into next weekend, winds could become light and variable.

DISCUSSION

A 1036 mb high pressure to the far northwest and a 1006 mb low to the far northeast is currently driving the windy and gusty northeast trade winds. Current observations across the state show northeast trade winds gusting to between 30 and 40 mph. Windy trade winds are expected to remain in place for the next few days as the high to the northwest remains nearly stationary. Showers can be observed mostly over windward Big Island and windward Kauai this morning with dry conditions elsewhere. This is due to a cool and dry airmass filling in behind a trough that came through earlier this weekend.

Showers should remain light and primarily over windward and mountain areas today. By Monday night, a cold upper trough moving through and a small increase in surface moisture could boost night time and early morning showers each day of the week. No heavy rain is expected at this time due to the state being on the drier side of the upper trough, although a few brief downpours for windward areas cant be ruled out.

By the middle of this week, the high pressure to the northwest which has been driving the trade winds is forecast to weaken and move east, which in turn will weaken the trade winds. Friday into the weekend could see light and variable winds, with another upper trough swinging through, potentially boosting showers.

AVIATION

A weak trough is gradually moving northeastward away from the Hawaiian Islands, while a broad area of high pressure builds in its wake. Lingering showers from the trough continue over portions of the Big Island, but are expected to have minimal impact on the terminals. VFR conditions are anticipated to prevail under moderate trades throughout the forecast period.

No AIRMETs currently in effect.

MARINE

A low pressure system far northeast and a moderate high pressure system to the far north-northwest of the coastal waters will maintain fresh to strong northeasterly trade winds through Monday. As the low weakens and drifts northeast, high pressure will build north of the islands, allowing winds to gradually weaken and veer to the east. A Small Craft Advisory has been extended for all Hawaiian coastal waters due to a combination of locally strong trade winds and elevated seas from the building north northeast swell through tonight.

The current small medium period northwest swell will continue to decline today. A new, moderate to large short period north northeast swell will build through the day potentially reaching High Surf Advisory (HSA) levels along north and exposed east shorelines when it peaks tonight before slowly declining through the week. A Marine Weather Statement (MWS) has also been issued starting at 6pm today through Monday night for harbor surges, particularly in Hilo and Kahului harbor coinciding as the north- northeast swell fills in over the eastern end of the state and holds through Monday.

Along south-facing shores, a small medium period swell will continue to provide small surf for the next few days. Surf along west facing shores will be small through the week. Surf along east facing shores will remain rough and choppy also due to the moderate to locally strong trade winds through the first half of the week.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 AM HST Monday for Kauai Northwest Waters-Kauai Leeward Waters-Kauai Channel-Oahu Leeward Waters- Kaiwi Channel-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.

Small Craft Advisory until 6 AM HST Monday for Kauai Windward Waters-Oahu Windward Waters-Maui County Windward Waters.