textproduct: Honolulu

SYNOPSIS

Moderate to breezy trades are expected to prevail through Saturday, slightly decrease on Sunday, then remain at mostly speeds through late next week. Bands of low clouds and showers will periodically push through the islands, focusing primarily over windward and mauka areas during the overnight and early morning hours.

DISCUSSION

Currently at the surface, a 1031 mb high is centered around 1300 miles north of Honolulu, driving breezy trade winds across the island chain this evening. Infrared satellite imagery shows mostly cloudy conditions in most windward areas as well as leeward Big Island, with partly cloudy conditions elsewhere. 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 breezy trades tonight and Saturday, 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 appear to target the state late Sunday night and Monday, and again Tuesday night through Wednesday night. These bands will raise precipitable water values to above 1.5 inches in most areas and elevated inversion heights to between 10 and 12 kft, increasing coverage and intensity of showers along with the amount of leeward spillover. In addition, dewpoints are forecast to increase to around 70 or the lower 70s beginning Monday and continuing through the middle of next week, making it feel more muggy across the island chain.

AVIATION

Moderate to breezy trades will continue through Saturday. Low clouds and scattered showers may occur at times across windward and mauka areas as moisture moves toward the islands, making for intermittent MVFR conditions. Otherwise VFR conditions are expected.

AIRMET Sierra is in effect for mountain obscuration for windward sections of Kauai, Oahu, Molokai, Maui, and the Big Island. Conditions may continue overnight due to ongoing showers.

AIRMET Tango is in effect for moderate turbulence downwind of terrain due to the breezy trade winds and will continue through the forecast period.

MARINE

High pressure to the north will dominate through at least the first half of next week, keeping moderate to locally strong trade winds in place across Hawaiian waters. The Small Craft Advisory (SCA) was extended this evening covering Oahu Leeward Waters, all coastal waters and channels around Maui, and windier waters near the Big Island. This SCA will continue through Saturday afternoon. Winds may slightly decrease from Sunday into Monday, but will likely remain at SCA levels for our typical windier waters.

A small, medium-period south swell will gradually ease tonight into Saturday. Another small, long-period south swell will arrive and fill in on Saturday, then peak on Sunday before gradually declining early next week. This swell should boost surf heights back up to near normal for this time of year.

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. A tiny bump in surf is possible for north-facing shores on Saturday with the arrival of a very small, medium period west-northwest swell.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Saturday 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.