Surface high pressure will continue to build northeast of the state through Wednesday and bring locally breezy easterly trade winds. Brief passing showers will favor windward and mountain areas, mainly during the overnight and early morning hours. Late Wednesday through this weekend, trade winds will ease slightly and veer to a more east-southeast direction, shifting shower activity over east and southeast facing slopes of most islands. However, overall rainfall amounts are expected to remain limited. An approaching front may bring unsettled wet weather by early to mid next week.
Visible satellite imagery shows a much drier scene this afternoon compared to this morning, with abundant sunshine across the state and only limited low clouds and isolated light showers moving into windward and mauka areas. Although the trade flow remains primarily out of the east, the low-level steering flow is beginning to take on a slight southerly component, as evidenced by clouds and showers moving more parallel to the island chain in an east-southeast direction.
High pressure to the northeast of the state will continue to build through midweek, bringing increased stability and strengthening trades through Wednesday. Limited clouds and light showers will generally favor windward and mauka areas through this period, especially during the overnight to early morning hours, along with the Kona slopes of the Big Island during the afternoon hours.
By Thursday, winds will veer out of a more east-southeast direction as a cold front approaches from the northwest. In this pattern, showers will favor southeast and east facing slopes of the Big Island and Maui, along with interior portions of the other islands due to the development of sea breezes in the lighter, somewhat blocked flow. Model guidance remains in good agreement through this period, showing this front stalling just to the west of the state as its parent low shoots off to the far northwest.
The evolution of weather features in the Pacific becomes less clear over the weekend as model spread increases. The GFS and the ECMWF both show a deep mid- to upper-level trough developing northwest of the state, spawning a surface low to the west- northwest. Strengthening southerly flow between that low and high pressure to our northeast could draw deep tropical moisture (with precipitable water values near 2 inches) toward or over the western end of the state early to mid next week. The exact placement of this moisture band and the strength of the southerly winds remain uncertain and will be monitored closely in the coming days.
Stable trade winds will strengthen to fresh to strong levels and become more easterly tonight into Wednesday, delivering clouds and showers mainly windward and mauka. Pockets of MVFR are likely, but VFR is forecast to prevail during this time. AIRMET Tango for lee turb is in effect and will should remain in place through Wednesday.
Fresh to strong trade winds will build and become increasingly easterly on Wednesday as surface high pressure strengthens far northeast of the islands. Wednesday night into Thursday, winds will veer out of the east-southeast around Oahu and Kauai as the high drifts eastward and broad low pressure develops northwest of the state. A Small Craft Advisory (SCA) is in effect for the typically windy waters around the Big Island and Maui County today, then expands to windward waters of Big Island and Maui County tonight and Wednesday as veering winds lead to accelerations north of those islands. Minor adjustments will need to be made, but the SCA will likely continue for some areas through the weekend. As low pressure slowly advances toward the islands early next week, local winds could veer increasingly southerly.
The current moderate northwest swell will continue a gradual decline through Thursday. A small west-northwest swell will arrive on Friday and hold through the weekend, followed by a small north-northwest swell early next week. Choppy east shore surf will build to near seasonal average by Wednesday as trade winds strengthen over and east of the islands. Little change is expected along east facing shores through the weekend, followed by a possible decline early next week if winds veer southerly. Surf along south facing shores will remain small to tiny through the weekend, and some islands may an increase in choppy surf if southerly winds develop early next week.
A Coastal Flood Statement remains in effect through early Wednesday morning due to the combination of peak monthly high tides and water levels that are running higher than predicted. This may lead to minor flooding along the shoreline and in low- lying coastal areas during the high tide between midnight and daybreak.
Small Craft Advisory until 6 AM HST Thursday for Maui County Windward Waters-Big Island Windward Waters.
Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
