Slightly weaker trade wind flow is expected on Tuesday with a few light windward showers. Wednesday into Thursday, light easterly flow will lead to the development of daytime sea breezes and nighttime land breezes. Thus, most cloud cover and shower activity will be limited to interior and mountain areas during the afternoons. In addition, deeper moisture moving in from the southeast Wednesday through Friday should bring increased shower chances to the Big Island and Maui.
This afternoon, mostly dry and stable conditions are prevailing across the main Hawaiian Islands. Rain gauges across the state reveal that even the few showers that are present are light, with the vast majority of the state picking up no measurable rainfall today. High pressure centered far northeast of the island chain is steering locally breezy trade winds over the region.
Tonight, an upper level trough and its associated surface front will move eastward, north of the state. As this occurs, the high pressure to the northeast will become displaced farther away, weakening local trade wind flow. Moderate trades will continue Tuesday, with little overall change in the weather pattern and a few light windward showers.
By Wednesday, the local pressure gradient is expected to weaken even further, with background winds becoming light and variable. Daytime heating, combined with weak surface flow, will lead to daytime sea breezes and nighttime land breezes. Clouds and showers should mainly be limited to over the island interiors and mountainous terrain, particularly during the day. By late Wednesday or Wednesday night, however, global forecast models remain consistent in a pocket of deeper moisture associated with a weak surface trough moving northward from the southeast towards the Big Island. This feature could act to increase shower coverage, especially along eastern portions of the Big Island. Long range models continue to push this band of moisture up through Maui County and, to a lesser extent, Oahu on Thursday into Friday before lifting it northward. Light southeast flow, combined with this batch of moisture, could lead to an increase in shower activity over the islands interiors during the afternoons. More typical trade wind weather should return by this weekend.
Moderate trades will continue through the period. Generally VFR conditions expected, save for the occasional isolated shower over windward sites.
AIRMET Tango remains in effect for moderate turbulence over the Big Island between FL300 to FL400.
Moderate to fresh trade winds will become light to moderate by the middle of the week as a couple of surface troughs develop northwest of the state, weakening the surface ridge north of the area. The ridge will strengthen late in the week and over the weekend as the troughs weaken and lift far north, allowing fresh to moderate trades to return.
A large, long period south southwest swell will maintain warning level surf through tonight. A High Surf Warning remains in effect until 6 AM HST Tuesday for all south-facing shores. Buoy 51002 readings this afternoon have dropped a foot since this morning and are now hovering around 4 to 5 feet at 15 to 16 seconds. Continue to expect a slow decline in surf as this large swell fades over the next couple of days. Surf along south-facing shores will drop to High Surf Advisory (HSA) levels by Tuesday morning and then could further drop below HSA levels Wednesday. Another south southwest swell is expected to fill in Wednesday night into Thursday that could push surf back up to advisory levels.
Very little swell energy is arriving along north-facing shores, keeping surf tiny to flat. A small bump in surf is possible for north-facing shores Tuesday into Wednesday with the arrival of a small northwest swell and a smaller north swell. Surf along east-facing shores will remain below average as winds ease through midweek.
A Coastal Flood Statement remains in effect for minor coastal flooding of vulnerable low-lying coastal roadways, docks, boat ramps and other coastal infrastructure due to King Tides. King Tides combined with water levels that are running higher than predicted will lead to minor flooding potential around the daily peak tide, which will be during the late afternoon and early evening hours, through Tuesday and possibly Wednesday. While minor coastal flooding is expected along all shorelines, the combination of the large south southwest swell and peak daily high tides will make low-lying coastal areas along south and west shores susceptible to more widespread coastal flooding for another day or so.
A Marine Weather Statement also remains in effect due to the large, long-period south southwest swell producing harbor surges and breaking waves near harbor entrances along south and west-facing harbors.
High Surf Warning until 6 AM HST Tuesday for Niihau-Kauai Leeward-Waianae Coast-Kahoolawe-Maui Leeward West-Kona-Kohala- Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Molokai Southeast-Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central Valley South-Kipahulu-South Maui/Upcountry-South Haleakala-Big Island South-Big Island Southeast.
