Locally breezy trade winds will ease to moderate levels Tuesday and Wednesday, then strengthen Thursday into the weekend. Showers will continue to favor windward and mauka areas, with a slight uptick in moisture expected Tuesday and Wednesday.
Trade winds have eased slightly compared to the past several days but will remain locally breezy today. The surface high driving the trades remains quite strong at 1034 mb far north of Hawaii, but a weak mid-level trough just northeast of the islands is beginning to erode the local pressure gradient. As the trough drifts westward through tonight, trades will continue a gradual decline. Even with the mid-level trough nearby, stable conditions will persist, keeping showers focused across typical windward and mauka areas. The greatest amount of rainfall today will be on windward Big Island, where a narrow line of moisture is producing enhanced showers.
A noticeable decrease in trade winds will occur Tuesday and Wednesday. The positions of the surface high will change little, but the mid-level trough will drift westward over the islands, leading to a weakening of the local pressure gradient and resulting trades. Guidance suggests that shallow moisture riding along the moderate trade wind flow will keep windward shower activity somewhat enhanced. If trades weaken enough, localized sea breezes could produce clouds and a few showers across leeward terrain each afternoon.
Trade winds should rebuild Thursday and Friday as the mid-level trough moves away. Another factor in the the restrengthening trade winds could be development of a tropical cyclone far south of Hawaii. At this time, it does not appear that any of this tropical activity would directly impact the islands.
Breezy trade winds will gradually easy through Tuesday, carrying intermittent showers into windward areas of the islands through the forecast period, most active in the overnight and early morning hours. MVFR conditions are possible under showers, though VFR is generally expected to prevail. Trade winds are expected to gradually weaken over the next few days.
AIRMET Tango remains in effect for low-level turbulence over and downwind of terrain, and is expected to continue for the next day or so as we remain under a breezy trade wind pattern.
Trade winds will gradually ease through Tuesday as the high pressure north of the islands lifts northeast and weakens. A Small Craft Advisory (SCA) is now in effect for most waters through this evening and will get trimmed through tonight to mainly the windier waters and channels around Maui County and the Big Island. The SCA will likely not be needed for any waters Tuesday as winds should have decreased to below criteria. These lighter trades should continue through Wednesday night, then may increase a bit Thursday and Friday as high pressure northeast of the islands drops a bit further south and tightens up the local pressure gradient.
The current small, long-period southwest swell will peak today, then gradually decline through the middle of the week. A series of overlapping small south and southwest swells will then give a small boost to the surf along south facing shores Thursday through next weekend, with perhaps a more sizable south swell moving in early next week.
Surf along east-facing shores will steadily decline through the middle of the week. Surf will then hold steady at slightly below normal levels along east facing shores late in the week through the weekend.
A series of small, long to medium period west to west-northwest swells generated by former Super Typhoon Bavi will be possible throughout the week. Otherwise, no significant north or northwest swells are expected, so surf along north-facing shores is expected to remain flat to tiny.
Peak monthly high tides combined with water levels that are running slightly higher than predicted will lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible around the daily peak tide, which will be during the afternoon hours. A Coastal Flood Statement remains in effect through Tuesday afternoon.
Small Craft Advisory until 6 AM HST Tuesday for Kauai Northwest Waters-Kauai Leeward Waters-Maalaea Bay-Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters.
