textproduct: Honolulu

SYNOPSIS

A low pressure system lingers far north of the Hawaiian Islands producing light and variable winds with chances for showers into Thursday. A passing high pressure system will bring a short return to easterly trade winds with subtle drying trends from Thursday night into Saturday. A series of low pressure systems passing just north of the state will produce light southeasterly winds from Sunday into the middle of next week.

DISCUSSION

Looking into the big picture satellite imagery this morning, we see a low pressure system far north of the Hawaiian Islands, along with high and middle clouds drifting across the state associated with divergence under a Sub Tropical Jet stream in the upper levels of the atmosphere. These cloudy skies will linger into early next week with chances for light to moderate showers each day.

The low pressure system currently north of the islands will keep lighter large scale winds in the forecast into Thursday. This means local scale island day time heating will drive onshore sea breezes into all islands, building clouds and brief shower trends over island mountains and interior sections peaking during the afternoon hours.

A passing high pressure system north of the state from Thursday night into Saturday will briefly build in easterly trade winds across the region. Wind speeds will become strong enough to limit sea breezes to terrain sheltered leeward western slopes of each island. Subtle drying trends will develop during this time period due to a slight increase in subsidence, downward vertical motions creating warming and drying effects, making the atmosphere a bit more stable.

However, the return to easterly trade winds will be fleeting and vanish quickly by Sunday as a series of low pressure system develop and slowly track north of the state. These passing lows appear to track far enough north to limit any heavy rainfall or flooding issues for the islands. A weak ridge will settle in over the islands producing a stable southeasterly wind across the region. Any enhanced showers in this wind driven pattern will favor southeast slopes of Maui and the Big Island with modest additional rainfall amounts. Elsewhere rainfall will be limited as the passing cloud bands will move more parallel to island mountains and the Big Island will produce a leeside rain shadow across much of the islands in Maui County.

AVIATION

Trades should return today. Some isol SHRA and MVFR conds in those SHRA are possible, otherwise VFR prevails.

No AIRMETs in effect.

MARINE

Weak troughing west of the state will help to maintain gentle to locally moderate southeast flow through Thursday. The strongest breezes will occur through the typical windy channels surrounding Maui and the Big Island. Building high pressure then supports moderate to locally fresh trades across the waters Friday into the weekend.

A small, short-period, NW swell will continue to diminish into Thursday and remain subdued through the weekend. A small, medium- period, south swell will help boost surf along south shores through Friday, then lower over the weekend. Surf along east shores remains below the seasonal average as trades remain light. However, increasing trades by week's end should brings a slight bump to surf.

HFO WATCHES/WARNINGS/ADVISORIES

None.