textproduct: Honolulu

SYNOPSIS

High pressure to the north will drive breezy trade winds this week. Shower activity will remain limited with a brief increasing trend on Tuesday, and again from Thursday through Friday as a weak easterly wave moves from east to west across the state. Any showers will that develop in this trade wind pattern will favor windward mountain slopes of each island during the overnight to early morning hours.

DISCUSSION

The satellite imagery this morning shows a weak easterly wave near 150W longitude riding the easterly trade winds towards the Big Island. This weak trough will bring a brief period of increasing shower trends to the state on Tuesday. Another stronger trough currently near 130W longitude, loosely associated with the remnants of former tropical cyclone Douglas, will ride the trade winds into Hawaii from Thursday to Friday producing another round of showers spreading east to west across the state. Rainfall amounts with this first system will be limited due to the stable ridge aloft, the second trough will bring significant increases to humidity levels and the potential for higher rainfall amounts favoring island mountain slopes.

Otherwise, easterly trade winds will continue through the end of this week as the subtropical ridge remains locked in place north of Hawaii. Subtle day to day changes to the trade wind speeds should be expected. Mostly stable weather conditions are forecast for the next seven days with slight increases in shower activity on Tuesday, and stronger rainfall trends from Thursday through Friday as two easterly waves drift through the island chain. Rainfall amounts over the next seven days will remain limited due to large scale stability, with the highest amounts forecast during the Thursday to Friday time period.

AVIATION

Moderate to locally breezy trades will continue through Monday. Low clouds and scattered showers will continue to impact windward and mountain areas, with some spillover into leeward sites. VFR conditions are broadly expected, with localized MVFR mainly for windward/mauka sites.

AIRMET Tango remains in effect for moderate low level turbulence over and downwind of terrain for all islands. This AIRMET will likely continue through the next several days.

MARINE

High pressure maintains fresh to locally strong trades through the week. A Small Craft Advisory is in effect for all local waters.

A moderate, long period, SSW swell is filling in today and boosting surf along S shores to just shy of the Advisory threshold. Energy associated with this swell is spread across the spectrum and not necessarily focused in the long period bins. This increases confidence that an Advisory will not be needed.

Surf along E facing shores will remain choppy through the week as fresh to locally strong trades hold. Surf along N shores remains flat to tiny.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Monday for all Hawaiian waters-