Issued: Dec 12, 2013 4:28 PM HST
Variable winds and warm conditions will continue into the weekend for most areas, while some exposed windward coastlines will feel stronger southeast flow. Light windward showers will continue into the weekend with some afternoon cloud buildups over interior areas of the islands. A front approaching from the northwest will bring wetter weather to Kauai and Oahu Sunday and the rest of the state early next week.
Afternoon convection and southeast flow around the islands has produced some windward clouds and sparse showers this afternoon. Expect the majority of clouds and light showers to remain over windward waters tonight while land breezes clear skies over leeward and most windward locations. Temperatures will drop below normal in some places, like Kahului, over the next few nights as drainage flow brings cooler air down the mountain slopes. Afternoon soundings from Lihue and Hilo depict a dry, stable airmass with a strong temperature inversion near 6 thousand feet. Breezy trade southeast winds continue over Big Island and Maui county waters with some of the stronger winds affecting exposed coastal areas. Moisture levels will slowly increase over the next few days as the winds turn southerly and advect moisture over the islands from the tropics.
A cold front is expected to stall 300 miles NW of Kauai tonight. Light southeast flow will prevail over Kauai and Oahu through Saturday while the moderate SE winds will continue around Maui county and the Big Island. Expect sea breezes along leeward coasts each afternoon with warm, humid conditions. Light windward showers will continue through Saturday with some afternoon cloud buildups over interior island areas. Volcanic haze may creep up over the smaller islands over the weekend as the southeast winds advect the particulates from the Big Island toward the northwest.
Another cold front sweeping down out of the north Pacific will kick start the original front Saturday night and send it in motion again toward the aloha state. The chance of rain will increase over Kauai Saturday night as the front approaches, and continue into Monday. Oahu and Maui county's rainfall chances rise Sunday and Monday as the front moves along. The atmosphere will also begin to destabilize as cold air aloft infiltrates the mid and upper atmosphere bringing a slight chance of thunderstorms Sunday, and remaining into Monday. Tuesday, the cold air aloft moves near the Big Island and the chance of afternoon convection and tstms increases over the orchid isle.
Overall, the surface forcing is not impressive with this front as it passes through the islands Sunday and Monday. The temps aloft will be colder than normal and there should be enough moisture to set off isolated thunderstorms and some locally heavy rainfall. However, without the strong surface forcing have kept rainfall coverage on the low side, except over Kauai where the forcing will be greatest. Otherwise, expect humid and cloudy conditions moving from west to east Sunday and Monday with trade winds attempting to return Tuesday and Wednesday.
Stable E to ESE low level flow will produce isol MVFR cigs over E facing terrain through the night. Lingering VFR cigs over leeward terrain will clear during the evening with VFR prevailing at the terminals.
A large NW swell will build rapidly Friday morning and afternoon, bringing advisory level surf for north and west facing shores through Saturday night. This swell may be large enough to bring small craft seas conditions to the exposed coastal waters Friday night and into the weekend.
High surf advisory from 4 pm Friday to 6 am HST Sunday for Waianae coast, Oahu north shore, Oahu Koolau, Molokai, Maui windward west, Maui central valley, windward Haleakala.
High surf advisory from 10 am Friday to 6 am HST Sunday for Niihau, Kauai windward, Kauai leeward.