Daily Weather
Jan 22, 2015 3:30 AM HSTSynopsis
Winds over the islands will turn to the south and southwest while becoming stronger from today and through Friday, especially over Kauai and Oahu, as a front approaches the area from the northwest. This front will bring increasing showers, starting over Kauai county on Friday and spread down the island chain through the weekend. High pressure will bring a dry trade wind regime in the wake of the front on Sunday and into early next week. Large surf from a northwest swell will also continue through the weekend.
Discussion
The persistent sfc ridge that provided light winds, stable conditions and a dry airmass during the last few days will continue to migrate to the E of the island chain in response to an approaching cold front boundary from the NW. This will allow for winds across the islands to turn out of the S and SW while becoming stronger today and through Fri. The front is expected to reach the island chain Fri when wind speeds and gusts will be strongest, especially over windward slopes and the windward coastlines of the smaller islands. So far, models do not suggest that the wind speeds will reach advisory levels, but the situation will continue to be closely monitored and the forecast will be adjusted accordingly.
Showers will increase across the islands with the fropa, starting Fri over Kauai county, Oahu by Fri night, and Maui county by Sat. Best chances of rain will reside over SE facing slopes. The front should move from NW to SE, all the way down to the Big Island by Sat night. The front itself will likely be almost dissipated by then, so impacts over the Big Island will likely be minimum. Expect increasing clouds and mainly moderate showers along the front. Upper level support seems to remain well to the N of the island chain, therefore deep convection is not anticipated attm.
Winds will turn N and then NE in the wake of the fropa with very dry and stable air establishing across the area on Sun. However, some lingering moisture could affect the windward Big Island and the Hana coast of Maui, bringing lingering clouds and showers Sun and Mon. Otherwise, returning trades should bring a benign weather pattern for early next week.
Aviation
Could see some temporary MVFR cigs at PHNY through the remainder of the overnight, with more predominant MVFR cigs expected later today. Elsewhere, VFR conditions are anticipated through the taf forecast period. No airmets are in effect and none are expected today.
Marine
A very large west-northwest swell will continue to affect the coastal waters through the weekend. Surf will begin to gradually decrease over the next couple of days, but remain at warning levels until Friday. The westerly component of this swell will allow some of the swell to reach select areas along the south shores, for which advisories remain in effect. The Kona coast of the Big Island should also experience warning level surf from later tonight and into Thursday. The swell will remain large and keep surf elevated through the weekend. The highest tides will occur in the early morning hours allowing for increased wave run-up.
Winds will remain below the small craft advisory threshold of 25 kt for the next few days, but the large northwest swell will produce seas above the 10-foot advisory threshold. Strengthening trade winds may reach advisory criteria early next week.
Watches/Warnings/Advisories
High surf advisory until 6 pm HST Friday for Oahu south shore, Lanai makai, Kahoolawe, Maui leeward west, leeward Haleakala.
High surf warning until 6 pm HST Friday for Niihau, Kauai windward, Kauai leeward, Waianae coast, Oahu north shore, Oahu Koolau, Molokai, Maui windward west, windward Haleakala, Kona, Kohala.
Small craft advisory until 6 pm HST Friday for all Hawaiian waters except Maalaea Bay,.
Small craft advisory through 600 pm Thursday for all Hawaiian waters except Maalaea Bay.
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
