Strong trade winds will gradually ease and veer toward the east- southeast through early next week. Plumes of moisture will produce passing showers across windward and mountain areas through Saturday. A drier weather pattern is expected Sunday into early next week with light to moderate east to east-southeast winds. Winds should be light enough for sea breezes to develop during the day and land breezes at night, especially early next week.
A 1033 mb high far north-northeast of the state is currently producing breezy easterly trades across the state this afternoon. Latest satellite and radar imagery is showing scattered showers mainly across windward and mountain areas this afternoon and the Kona slopes of the Big Island. For tonight, shower activity will generally increase, with showers focused over windward and mountain areas and scattered showers over leeward areas. Latest HREF model shows moderate showers over select windward areas tonight, especially east Maui, which is a favorable area for rain under the east-southeast flow.
Over the weekend, we should expect passing showers across the state through Saturday morning. As the day goes on, we should see showers generally decrease through the day Saturday with the exception of leeward areas. With the trades veering toward the east-southeast and weakening slightly on Saturday, this should allow sea breezes to develop over leeward areas, which could lead to afternoon clouds and some showers. A drier air mass should move in by Sunday, so overall we should less showers on Sunday as well as lighter winds with sea breezes developing over many leeward areas Sunday afternoon.
For early next week, high pressure will be centered far northeast of the state, while a low pressure system lingers north of the state. We will be in a hybrid wind pattern early next week with light to moderate east-southeast winds over windward areas and generally light winds over leeward areas. Due to limited moisture, we are not expecting much rainfall early next week, but some light passing showers should be expected over windward areas, as well as some light showers over leeward areas during the afternoon with the sea breezes developing.
For the second half of next week, latest guidance is showing quite a bit of uncertainty, but overall the GFS and ECMWF models are showing some type of upper level trough over the area. The ECMWF shows a much deeper upper level trough with a surface trough developing near the state. Meanwhile, the GFS is showing a much weaker upper level trough, with the surface high north of the state maintaining trade winds during the second half of the week. Stay tuned to the extended forecast, as the forecast will change over the next several days. The current forecast aligns more with the GFS due to it being closer to climatology for this time of year.
Locally strong ENE trade winds persist, but subtle veering and weakening of the low-level flow is anticipated through tonight. VFR is forecast to prevail, particularly leeward, aided by a strong inversion anchored between 6-8kft. Isolated MVFR possible within passing showers, mainly windward and mauka.
AIRMET Tango for lee turb remains in effect through today.
A 1033 mb surface high, centered around 1000 nm northeast of the state, will remain nearly stationary through tonight and allow moderate to locally breezy easterly trade winds to persist. From this weekend through early next week, this feature is expected to drift slowly eastward. Low pressure deepening well northwest of Hawaii will help to gradually veer these winds east southeasterly and weaken them.
A Small Craft Advisory (SCA) remains in effect for all waters surrounding the Big Island and Maui county with the exception of Maalaea Bay and the southeast Big Island waters. These areas are typically less windy during easterly or east southeasterly flow. As the flow weakens further tonight, most remaining zones will likely be dropped from the advisory, leaving only the Alenuihaha Channel by mid-Saturday morning.
Surf heights will remain below advisory thresholds for all shores through the forecast period. A small northwest, medium period swell will peak tonight, then slowly subside through the weekend. Thus, expect small surf to continue along north and northwest facing shores. Breezy trades will produce choppy, rough surf along east facing shores through Saturday, which is expected to lower later this weekend as easterly or east southeasterly flow weakens. This afternoon, both Kaumalapau and Barbers Point buoys showed energy from a 2 foot 10 to 12 second south southeasterly swell, which matches guidance well. Expect small surf along south facing shores through the forecast period with pulses of 1 to 2 foot medium to long period swell.
Small Craft Advisory until 6 AM HST Saturday for Maui County Windward Waters-Maui County Leeward Waters-Pailolo Channel-Big Island Windward Waters-Big Island Leeward Waters.
Small Craft Advisory until 6 PM HST Saturday for Alenuihaha Channel.
