Breezy east northeasterly trade winds will prevail through the week and could ease slightly by Friday and become more easterly. Showers will favor windward and mountain areas, as well as the night time and early morning hours. Early Friday into the weekend, an upper- level low could bring an uptick in shower coverage and higher humidity, with heavy showers possible.
At the surface, a dominate high pressure system resides far to the north of the Hawaiian islands, and will keep east to east northeast trade winds blowing through the weekend and into next week. Showers will be pushed over the typical windward and mountain areas, favoring the night time and early morning hours.
By Friday through the weekend, models continue to show a mid to upper- level cutoff low moving over the region, bringing cooler temperatures aloft and increasing instability. Precipitable water values at that time are expected to climb to 1.5 to almost 2 inches over the eastern end of the state as moisture is drawn up from the south. The latest GFS model run and some recent high resolution model runs show an increased probability of pockets of heavy rain forming. Exactly where and when remains to be seen, but localized heavy showers especially over the mountain ranges look like a possibility at this time. This upper low is also expected to usher in muggier conditions as dew points climb into the lower 70s and the extra moisture could linger into early next week.
High pressure far north of the islands will maintain a breezy trade wind pattern through Thursday. Passing showers will continue to be carried in on the trade wind flow. At times these showers could bring some mountain obscuration to various islands, mostly at night and during the morning hours. Otherwise, VFR conditions are expected to prevail.
AIRMET Tango remains in effect for mechanical turbulence to the lee of the mountains due to the breezy trade winds. Expect this to remain in place through at least tonight.
AIRMET Sierra remains in effect for mountain obscurations over N thru E sections of Kauai and windward areas of the Big Island due to the scattered showers.
Slow eastern-moving surface high pressure centered far northeast of the islands will maintain generally moderate to locally strong Small Craft Advisory criteria trades through tomorrow (Thursday) afternoon. An upper level low dropping south in the wake of this east-exiting high will increase north and west local water shower chances from Friday into the weekend.
A small to medium size, long period northwest (330 degree) swell will arrive later today, fill in overnight and peak Thursday. This swell will lift north-facing surf to around or slightly over head high heights. Very small, medium period background south swell will occur through the remainder of week. A small, long period south southwest (200 degree) swell arrives this weekend. This bump will add another foot on to south-facing surf. Enhanced trades will maintain above seasonable eastern shore wind wave chop the next several days.
Monthly tidal heights reach their maximum of around 2.5 ft MLLW (0.75 feet MHHW) this weekend. Several days of moderate trades, along with a slight boost in southern swell, will push overall water levels to around 3.0 feet MLLW (1.0 foot MHHW) by Saturday. This may bring some overwash into low lying coastal areas during times of high tide from this weekend into early next week.
Small Craft Advisory until 6 PM HST Thursday for Kaiwi Channel- Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters- Big Island Southeast Waters.
