(ABOVE) National Weather Service Base Reflectivity image from the Kohala radar, taken just before 8 p.m. HST

NEWS BRIEF

• UPDATE (11:00 p.m.) According to the National Weather Service:

At 10:25 pm hst… A line of heavy showers and thunderstorms was located from 54 miles north of Halawa Valley to 113 miles southwest of Barbers Point… Moving east at 50 mph. The line will be crossing entire Maui County during the next 2 and a half hours and northern Big Island within the next 2 to 3 hours. North Big Island includes Kailua-Kona town… Kamuela… Hawi… and Waipio Valley. Wind gusts to 55 mph are possible with these showers and storms.National Weather Service on Jan. 2 at 10:37 p.m. HST

• UPDATE (10:50 p.m.) The Hawaii Electric Light Company is reporting power outages across the island due to severe weather. At 9:50 p.m. HELCO reported 1,385 customers out of power in Kaohe Homestead Roadd, Leilani Estates, and the Lanipuna Gardens area.
• The National Weather service has issued a high wind advisory for Hawaii Island effective through 6 a.m. Saturday, January 3rd. Winds of 25-35 mph with gusts of over 50 mph are expected. There is a chance of strong thunderstorms and heavy rain overnight.
• At 6:54 pm HST, NWS reported a line of strong thunderstorms located from 69 miles north of Honolulu to 87 miles south of Lihue, moving east at 55 mph.

MEDIA

Audio message from Hawaii County Civil Defense:

PRIMARY SOURCES

The National Weather service has issued a high wind advisory for the Island of Hawaii effective through 6:00 AM tomorrow Saturday January 3rd. Winds of 25-35 mph with gusts of over 50mph are expected. The high winds are part of an advancing system that is forecasted to bring heavy rains and thunder showers in addition to the high winds. The onset of hazardous conditions for Hawaii Island is expected to begin late tonight and increase into the early morning hours tomorrow. The high winds are also expected to be magnified as it passes through the Saddle Road area and may present with hazardous driving conditions. Motorists are advised to be prepared for high winds, heavy rains, and ponding on roadways as well as possible unexpected road closures.

Everyone is advised to monitor local radio broadcasts for additional updates and to be prepared for possible storm conditions. Hawaii County Civil Defense on Jan. 2 at 7 p.m. HST

A strong cold front will sweep rapidly down the island chain tonight and early Saturday bringing bands of showers, locally strong Kona winds, and a chance of thunderstorms. Winds will shift to northwest and showers will diminish after the front pushes through. Cool and dry weather is expected behind the front on Sunday, with a relatively dry trade wind pattern resuming early next week.

Discussion
A complex area of low pressure along a front about 200 miles or so WNW of Kauai is expected to scoot eastward overnight and slowly deepen. The low will pull an active cold front through the island chain. The deepening low will be favorable for increasing Kona winds ahead of the front, and we are already seeing winds increase on Kauai. The highest Risk for strong winds will be in favored downslope areas to the NE of the mountains as well as with any convection that develops.

Still expecting to see an active squall line/qlcs develop along the front in light of strong forcing at the surface and aloft. Thanks to Lihue and Hilo for providing us with 18Z soundings today, which showed that some moisture return is well underway. The boundary layer is a little less moist than optimum for thunderstorms, with dewpoints in the low to mid 60s, which is limiting the instability. Thus have scaled back thunderstorm chances to slight chance for tonight. Although showers could be intense briefly along the front, the present thinking is that the fast motion of the front should greatly limit the potential for flash flooding, although we can’t completely rule it out. As the frontal band gets to the Big Island late tonight or early Sat, expecting to see blizzard conditions there above 11000 feet.

Most of the guidance clears the front past the Big Island Sat morning. Weather conditions will improve from W to E on Sat as a drier airmass builds into the state on NW winds behind the front. Dry and cool northerly flow will prevail on Sunday. Relatively dry trade wind conditions should resume on Monday and prevail through the middle of next week, as high pressure builds slowly eastward to the north of the state. A weak front approaching from the northwest may allow the trades to weaken and veer slightly by next Thursday or Friday, but no major weather changes are expected.

Aviation
Satellite loops show a front northwest of Kauai moving ESE around 25 kt. Strong SSW winds will continue over the area ahead of the front so airmet tango remains in effect for both strong surface winds and turbulence to the lee, NNE, of the mountains. Weather will remain generally VFR ahead of the front but localized MVFR is possible, mainly for southwest slopes, in prefrontal convergence lines.

A band of showery clouds along the front will bring mvfr/local IFR ceilings and vsby as it moves SE over the islands. The band will probably weaken as it moves from Kauai to the Big Island. The band is expected to be over Kauai between 03 and 12Z, over Oahu between 07 and 14Z, over Maui between 12Z and 18Z and over the Big Island between 16 and 21Z. Airmets for mtn obsc will likely be needed for all islands as the frontal band moves by.

The front is associated with a sharp trough aloft which will also be moving southeast over the main Hawaiian islands. This trough will drop the freezing level to around 11000 ft and icing will be possible in layered clouds along the front. The trough may also produce turbulence aloft.

Clouds and showers will diminish rapidly and winds will swing out of the northwest behind the front.

Marine
Most of the high resolution guidance is pointing toward localized gales near the front as it goes through, particulary in areas that are prone to acceleration in the various wind directions. Needless to say, the combination of strong, shifting winds and a series of low pressure areas passing nearby N of the islands will continue to create a combination of hazardous mixed swell and steep wind waves. Short to moderate period N and NW swells will continue to dominate the surf through the weekend. A short period NNW swell is forecast to build tonight and continue Sat through Sun. Resulting surf on N facing shores should remain below advisory levels.

Watches/Warnings/Advisories
Wind advisory until 6 am HST Saturday for Niihau, Kauai, Oahu, Big Island interior.

Wind advisory until 6 am HST Saturday for Molokai, Lanai, Kahoolawe, Maui, Kona, south Big Island, Big Island north and east, Kohala.

High wind warning until 6 pm HST Saturday for Big Island summits.

Blizzard warning until 6 pm HST Saturday for Big Island summits.

Gale warning until noon HST Saturday for Oahu leeward waters, Kaiwi Channel, Maui county windward waters, Maui county leeward waters, Maalaea Bay, Pailolo channel, Alenuihaha channel, Big Island windward waters, Big Island leeward waters, Big Island southeast waters.

Gale warning until 6 am HST Saturday for Kauai northwest waters, Kauai windward waters, Kauai leeward waters, Kauai channel, Oahu windward waters.National Weather Service discussion on Jan. 2 at 3:25 p.m. HST