Trades are expected to gradually weaken and remain light throughout the forecast period, instilling a land-sea breeze regime in response. Shower activity will be minimal, with only a few isolated showers supported. By the end of the week, a weak front will advance toward the state, but stall and dissipate over the western islands. Another potentially stronger front propagates toward the Hawaiian Islands and may bring enhanced shower activity to much of the state early next week.
A broad area of high pressure currently positioned northeast of the islands will continue to migrate eastward toward CONUS. As a result, trades will weaken gradually today and remain light through the remainder of the forecast period. With decreasing winds, a land- sea breeze regime will instill, supporting a few isolated showers across leeward and interior areas of most islands. Overall rainfall will remain minimal. In addition, latest observations from mid-level water vapor imagery indicates an area of drier air will move into the vicinity of the islands from the east, increasing the overall stability across the state and further limit shower activity along windward areas.
Latest model guidance continues to showcase a shallow, weak frontal boundary advancing from northwest to southeast during the day on Friday before stalling across the western half of the island chains. This feature may bring a modest increase in shower activity to Kauai on Friday, possibly extending into Oahu early during the weekend due to lingering moisture from the latest event from earlier this week. Elsewhere across the state will remain generally dry aside from any isolated showers associated with the ongoing land-sea breeze regime. By the middle of the weekend, the aforementioned front is expected to dissipate, along with any remaining associated moisture.
Model guidance hints at another, potentially stronger frontal system early next week in response to an amplified mid-level trough just north of the islands. Both GFS and ECMWF guidance depict precipitable water values on the order of two to three standard deviations above climatological average associated with this feature. However, confidence remains low at this time regarding the timing, strength, and overall evolution of this system due to considerable model uncertainty at this time. Forecast details will be refined with additional analysis as the event approaches.
Breezy east to southeast wind speeds will gradually ease as a ridge north of the state erodes from the west. Showers have trended down early this morning as drier air from the east filters in, thus have cancelled AIRMET Sierra for mountain obscurations for Kauai and the Big Island. Expect mostly VFR conditions today, with brief MVFR conditions over windward and southeast slopes as few isolated to scattered clouds and showers pass through. MVFR conditions could develop along sheltered leeward slopes and interior areas this afternoon as winds weaken, allowing for sea breezes to develop. AIRMET Tango remains in effect for moderate turb over and west of terrain due to the gusty winds. This AIRMET will likely be taken down as winds ease later this morning and afternoon.
Moderate to locally fresh east-southeast winds will prevail across the coastal waters today as a ridge builds north of the region. A Small Craft Advisory (SCA) remains in effect for the typically windy waters of Maui County and the Big Island, though winds are expected to fall below SCA criteria across all waters by this afternoon. A front approaching the state from the northwest will further weaken the winds to light to moderate speeds on Thursday as they shift more southerly. This frontal boundary will weaken as it enters the coastal waters Friday, then dissipate near the central islands by Saturday, with light to gentle winds expected. Another front will approach the state from the northwest on Sunday, then move down the island chain early next week.
A small, long period, northwest (310 degree) swell will build this morning, peak later today and tonight, then slowly decline through Friday. Forerunners for the next significant large, long period north-northwest swell (330 degree) are expected to arrive Friday night and peak Saturday. This swell will likely produce warning level surf along exposed north and west facing shores. Another, large to extra large, north-northwest swell may fill in early next week with surf heights peaking well into warning levels.
Surf along east facing shores has fallen below advisory levels early this morning and will continue to sharply decline over the next couple of days as a north-northeast swell fades and easterly wind swell decreases.
Small Craft Advisory until 6 PM HST this evening for Maui County Windward Waters-Pailolo Channel-Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.
