Trade winds will ease slightly today, then remain at mostly moderate speeds through the rest of the week. Bands of low clouds and showers will periodically push across the islands, focusing primarily over windward and mountain areas during the overnight and early morning hours. A couple bands of enhanced moisture will move through the islands tonight through Thursday morning, bringing an increase in shower coverage and intensity, with some locally heavy rainfall possible. In addition, humidity levels will rise, making the first half of the work week feel rather muggy across the island chain.
Currently at the surface, a 1035 mb high is centered around 1700 miles north-northeast of Honolulu, driving moderate trade winds across the island chain early this morning. Infrared satellite imagery shows mostly cloudy conditions in windward and mauka areas, with partly cloudy skies prevailing in most leeward locales. Radar imagery shows scattered showers moving into windward slopes and coasts, with a few showers spilling over to leeward communities at times. Main short term focus revolves around trade wind trends and rain chances.
High pressure will meander north and northeast of state during the next 7 days, keeping trade winds solidly in place through the period. Moderate to locally breezy trades tonight, will ease slightly on Sunday, then remain at mostly moderate speeds Monday through late next week.
As for the remaining weather details, fairly typical summertime trade wind weather is expected through the period, with showers favoring windward and mauka areas, particularly during the night and early morning hours. A couple bands of enhanced moisture will affect the state during the first half of the week however. The first batch of enhanced moisture is evident in satellite imagery near 150W or about 250 miles east of the Big Island. This band of moisture is expected to ramp up shower coverage and intensity as it moves from east to west across the islands tonight through Monday evening. The next area of enhanced moisture currently close to 140W or about 950 miles east-northeast of the state, is forecast to move through the islands Tuesday night through early Thursday, increasing shower coverage and intensity once again.
Both these bands will raise precipitable water values into the 1.5 to 2.0 inch range and elevate inversion heights to between 10 and 12 kft. Some locally heavy rainfall can't be ruled out as these bands of moisture move through, particularly the second batch of moisture affecting the islands during the middle of the week. That said, with the trades in place, a widespread flash flood threat is not expected, but some minor flooding could very well necessitate flood advisories during this time. Additionally, dewpoints are forecast to increase to around 70 or the lower 70s beginning Monday and continuing through the middle of the week, making it feel more muggy across the island chain.
Moderate to locally breezy trades are expected through the forecast period. Low clouds and scattered showers may occur at times over primarily windward sites, making for intermittent MVFR conditions. Otherwise VFR conditions are expected.
AIRMET Tango is in effect for moderate turbulence downwind of terrain due to breezy trade winds and will continue through the forecast period.
A high pressure ridge far north of the Hawaiian Islands will remain anchored in place, keeping trade winds blowing across the region through much of this week. The Small Craft Advisory (SCA) remains in effect through this afternoon for the typical windier waters near Maui and the Big Island.
The current small, long period south swell will peak today, before gradually declining over the next few days. Another larger south swell energy pulse will arrive next weekend.
Surf along east facing shores will remain rough and choppy with a slight decline possible early in the week as trade winds weaken slightly. Surf heights along north facing shores will remain nearly flat.
Small Craft Advisory until 6 PM HST this evening for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
