Moderate trades turn breezy mid-week delivering showers windward and mauka through the period.
Deeper moisture (relative to last night) lurks immediately upstream and will be ushered through the forecast area tonight through Tuesday by persistent moderate trades in the lowest levels. For the most part, a typical distribution of showers focused windward and mauka is expected. However, veering winds within the deepening boundary layer (up to approximately 10kft) yields potential for some leeward convergence downwind of Maui County potentially bringing enhanced shower coverage to Leeward Oahu mainly after midnight tonight continuing into Tuesday morning. As this moisture advances west of the islands mid-week, trades rebound under a broad low amplitude subtropical ridge. Breezy trades, high stability, and limited showers focused windward and mauka then prevail through the weekend.
Moderate to locally breezy trade winds will persist through Tuesday and increase slightly Wednesday. This morning, an area of enhanced moisture moved onto windward Maui County, where widespread MVFR conditions have necessitated AIRMET Sierra for mountain obscuration, and as the moisture spreads westward, the AIRMET will likely be expanded to additional islands overnight. VFR conditions will prevail over most leeward areas. Drier conditions are expected to build in from the east late Wednesday.
The trade winds will hold at mostly moderate speeds today through Tuesday as very broad troughing has produced a weakness in the subtropical ridge to the northwest of the Hawaiian Islands. Trade winds strengthen to fresh and locally strong speeds Wednesday through Friday as high pressure strengthens north of the island chain.
Surf observations continue to show advisory level surf affecting south facing shores today. A High Surf Advisory remains in effect through Tuesday afternoon, during which time the swell is expected to hold and keep surf at lower-end advisory levels. This swell will then slowly fade during the middle of the week. A new long-period south swell arrives Tuesday night, builds on Wednesday, and peaks on Thursday, keeping surf elevated above the summertime average through the weekend.
Surf along east-facing shores will remain slightly below seasonal levels today through Wednesday as the trades ease upstream of the islands. East shore surf should then build back close to seasonal levels late this week and through the weekend as stronger trades return over and upstream on the islands. Additionally, swell generated by former tropical cyclone Elida may give a slight boost to east shore surf during the middle of the week. This weekend, larger surf for east shores generated by Tropical Storm Fausto is possible.
Surf along north-facing shores will remain at flat to tiny levels through the weekend.
High Surf Advisory until 6 PM HST Tuesday for all south-facing shores.
