Moderate to locally breezy trades will prevail for the next several days. Showers are expected across windward and mauka areas with limited spillover into leeward locations. A nearly stationary upper- level low northeast of the islands will enhance clouds showers through Friday. By the weekend, the disturbance aloft is forecast to finally meander farther northeast away from the state. However, periods of windward and mauka showers will continue.
Moderate to locally breezy trade winds continue to prevail across the island chain, steered by two areas of high pressure centered north and northeast of the islands that are separated by a front that extends from southern Alaska to near 30N. An upper-level low northeast of the state is causing some local instability resulting in deeper clouds and some enhanced shower activity this morning particularly across windward and mauka locations with some showers reaching into leeward areas.
The aforementioned upper-level low will remain nearly stationary through Friday, which will continue the wet trade wind pattern. Showers will favor windward slopes of all islands, with some showers drifting into leeward areas. By this weekend, the upper- level low will finally exit the region. Periods of showers will continue to favor windward and mauka areas with only slight variations in day- to-day trade winds expected over this time frame.
By early next week, model guidance shows a shallow cold front and another upper-level trough approaching the islands from the northwest. At this time, it is uncertain how much moisture can be expected from this system.
Moderate to locally breezy trades prevail through the period as an upper-level low positioned just northeast of the Hawaiian Islands enhances shower activity mainly over the windward mountain areas. In addition, some leeward areas, especially along western islands slopes, could see showers develop each day as sea breezes converge with trade winds.
Currently, no AIRMETs in effect, however, once shower activity increases, AIRMET Sierra for windward tempo mountain obscuration and AIRMET Tango for leeward tempo moderate turbulence could come into play.
A area of high pressure, centered to our north, will slowly move east through Friday and generate widespread fresh to locally strong trade winds across the local waters. A Small Craft Advisory is currently in effect for the typical windy channels around Maui County and the Big Island. By this weekend, a front passing far north of the state will nudge the aforementioned high further east and allow trade winds to decrease to moderate to locally fresh.
The current small, northwest to north-northwest (320-330 degree), swell will slowly decline into Friday and produce small surf along north facing beaches. A North Pacific gale- force low will send a moderate, longer- period northwest swell toward the islands late Friday into Saturday and generate above average surf along north and west facing shores. Average H1/10 heights for north facing shores is 6 feet for the month of May (Goddard- Caldwell Database). However, surf heights should remain below advisory levels.
Surf along south-facing shores will remain small through the rest of this work week, with mainly background south to southwest swell expected. A small, long period, south-southwest pulse should arrive late Friday and give a bump up to south facing shores through this weekend.
Surf along east-facing shores will remain slightly elevated through Friday as trades remain fresh to locally strong. Trades will slowly weaken this weekend and allow surf along east-facing shores to lower.
Small Craft Advisory until 6 PM HST Friday for Kahoolawe.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
