textproduct: Honolulu

SYNOPSIS

Moderate to locally breezy trades will taper off Wednesday and Thursday becoming light and variable by this weekend. Shower activity will be kept to a minimum with just a few windward and mauka clouds and showers through the end of the week.

DISCUSSION

A stationary upper low persists northeast of the state. At the surface, a 1028 mb surface high is centered far north of Hawaii driving fresh to locally strong trade winds across the area. Moisture levels are below average, with precipitable waters running around 0.9 inches, so while some instability from the upper low and orographic lifting will bring a few windward showers tonight, rainfall amounts will be limited by the moisture levels. Expect another cool night lows in the low to mid 60s and dew points in the upper 50s.

Looking ahead, trades will begin to ease Wednesday into Thursday as the surface high weakens and shifts eastward with a surface trough developing east of Hawaii. This feature will weaken the trade wind flow to moderate over the islands through the rest of the week. Rainfall will be limited to occasional small batches of moisture moving in from the east by the trades.

A front will approach from the west during the first half of next week. Winds will weaken, shift southeasterly, then south, while a pre-frontal convergence band drags tropical moisture up over the islands. Still significant model differences in the long-range GFS and ECMWF for the synoptic setup, but something to watch out for mid to late next week.

AVIATION

Moderate to locally breezy trade winds will continue into tonight. Winds will taper off tomorrow morning. Isolated showers are possible tonight along windward and mauka areas which may lower ceilings and visibilities to MVFR at times. Otherwise, VFR conditions will prevail.

AIRMET Tango is in effect for mod turb blw 080 downwind of terrain.

MARINE

A 1030 mb high pressure north of Hawaii will elongate and shift eastward through the week, causing trade winds to gradually diminish. The Small Craft Advisory for fresh to locally strong trade winds remains in effect across all Hawaiian waters through Wednesday morning. By that point, a weakening pressure gradient means that strong trade winds are expected to be limited to favored channels only. Winds become moderate to fresh northeasterly for the majority of the waters by this weekend.

Moderate north and east-facing shore surf continues to be generated by a short period north-northeast (020 degree) swell which will gradually diminish tonight and Wednesday as it veers northeast. Shores better exposed to this NNE swell will experience decent wind wave chop generated by solid moderate trades.

Surf along west-facing shores will remain dominated by wrap around from the north-northeasterly swell and will gradually diminish in kind through the week. The next small, medium-period northwest and west-northwest swells arrive this weekend to bring a small bump in surf for west-facing shores. Along south-facing shores, expect continued impulses to sustain small surf through the week.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 AM HST Wednesday for all Hawaiian waters-