Moderate to breezy trades will persist through tonight, slightly decrease on Sunday, then remain at mostly moderate speeds through late next 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. Some enhancement to the showers may occur at times Monday through Wednesday as deeper pockets of low level moisture move through.
Moderate to breezy trade winds continued across the islands today, driven by a rather strong 1034 mb surface high centered well north northeast of the state. Patches of low clouds, caught in this trade flow, can be seen pushing towards the windward coasts from well upstream of the islands. Radar has picked up on a few light showers embedded in these low clouds, but nothing particularly of note. Clouds and showers have been limited today to mainly along windward areas and mountain slopes with rainfall totals generally topping out at a few hundredths of an inch. Meanwhile, fountaining from episode 50 of Kilauea's eruption on the Big Island officially began at 1010 AM HST this morning. VOG will likely affect southern portions of the Big Island, especially over the next several hours. Fortunately, deep east northeast trade wind flow should keep most of the VOG away from the smaller islands.
Tonight though Sunday, the aforementioned surface high meanders a tad northward, allowing local pressure gradients to ease slightly and trades to gradually trend weaker. Typical of this pattern, shower activity will be most prevalent during the night and early morning hours with less coverage during midday. From the south Kona slopes to Pahala on the Big Island, however, expect greater cloud cover and shower activity during the afternoon as local sea breezes push upslope.
Seasonal summertime moderate trades will dominate all next week as a surface high pressure remains anchored well north of the state. Monday through Wednesday, both the GFS and ECMWF show a deepening boundary layer, at times, as a few deeper pockets of low level moisture advect in on the trades. Model cross sections indicate the boundary layer briefly rising to between 8,000 and 10,000 feet which would allow for more trade showers to pass over onto the leeward sides. For Thursday and beyond, a more seasonal shallower moisture layer returns. Meanwhile, a weak upper level low forming to the northwest of Hawaii may bring periods of increased mid to upper level clouds from the southwest.
Moderate to breezy trades through at least Sunday. Low clouds and scattered showers will occur at times, mainly over windward and mauka areas, making for intermittent MVFR conditions. Otherwise VFR conditions are expected.
AIRMET Tango is in effect for moderate turbulence downwind of terrain due to the 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 next week. The Small Craft Advisory (SCA) continues through tonight for Oahu Leeward Waters, all coastal waters and channels around Maui, and windier waters near the Big Island. Winds may slightly decrease from Sunday into Monday, but will likely remain at SCA levels for our typical windier waters near Maui and the Big Island through this period.
The current small, long period south swell will peak on Sunday, before gradually declining through the first half of next week.
Surf along east facing shores will remain rough and choppy with a slight decline possible early next week due to minor fluctuations of our trades. Surf heights along north facing shores will remain small to tiny through the first half of next week.
Small Craft Advisory until 6 AM HST Sunday for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel- Big Island Leeward Waters-Big Island Southeast Waters.
