Daily Weather

Oct 22, 2014 3:30 PM HST

Synopsis
Light to moderate easterly southeasterly flow will continue tonight with showers focusing over windward and mauka areas. Clouds and showers from earlier sea breeze convection will linger around leeward and interior areas of the smaller islands through early this evening. A high building far north of the islands will bring moderate trade winds Thursday and Friday with showers focusing over windward and mauka areas. Winds will again weaken and shift to the east southeast over the weekend as a front approaches from the northwest.

Discussion
An e-w oriented sfc ridge remains located far NE of the aloha state, while tropical storm Ana gradually approaches the French Frigate Shoals from the S. This synoptic scenario is keeping a rather light to moderate e/se wind pattern across the island chain through tonight.

A relatively stable but moist airmass along with the SE flow are bringing scattered to numerous passing showers over most of the smaller islands, with pwats hovering between 1.5 and 1.7 inches. Moisture advection from an old boundary just E of the islands will keep feeding windward and mountain showers, while sea breeze circulations bring cloud cover and showers over leeward and interior areas through early this evening.

On Oahu, showers and the heaviest rain focused over the Koolau range, the area of Manoa valley, the Honolulu metro area and Pearl City during the afternoon hours. On Maui county, the heaviest showers were affecting W Molokai, windward Maui and E Lanai. Rainfall accumulations remain generally light to moderate, but isolated higher amounts are possible with the heaviest showers.

The Big Island will keep providing some blocking of the prevailing SE flow tonight with stronger flow over the NE and SE Big Island areas, and lighter winds around the smaller islands.

For the rest of the work week, models remain in good agreement in depicting a gradual strengthening of the aforementioned sfc ridge far NE of the aloha state, bringing a stronger trade wind regime Thu and Fri. This will shift shower activity back to mainly windward and mauka areas, and drier conditions over leeward areas. But this solution will be short-lived as a frontal boundary approaches the area from the NW, weakening the ridge and pushing it further to the S. This will bring back the lighter SE flow across the islands with another round of stronger sea breezes and afternoon showers favoring leeward and interior areas during the upcoming weekend.

Aviation
An area of enhanced moisture moving across the state this afternoon and tonight will continue to produce widespread cloudiness and above normal shower activity. Periods of MVFR conditions and mountain obscuration will be likely across many areas of the smaller islands as well as on the windward Big Island, and airmet sierra is in effect. Trade winds along with a drier airmass will return to the state on Thursday, with VFR conditions prevailing.

Marine
The north swell will continue to decrease through tonight. Then two other small north northwest swells are expected to arrive on Thursday and Saturday respectively. Surf from these swells should remain below the advisory levels at north and west facing shores. Only small surf is expected at south and east facing shores.

Winds and seas will remain below small craft advisory levels through the forecast period.

Watches/Warnings/Advisories
None.

All surf height observations and forecasts are for the full face surf height, from the trough to the crest of the wave.

Advisory and Warning Criteria
Location Advisory Warning
North-Facing Shores 15 Feet (8') 25 Feet
West-Facing Shores - Big Island 8 Feet (4'+) 12 Feet
West-Facing Shores - Remaining Islands 12 Feet (7') 20 Feet
South-Facing Shores 8 Feet (4'+) 15 Feet
East-Facing Shores 8 Feet (4'+) 15 Feet

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