Photo Credit: James Grenz

Hilo

Today: Scattered showers. Mostly sunny, with a high near 77. Light and variable wind becoming northeast 5 to 8 mph in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 63. North wind 5 to 9 mph becoming light and variable after midnight. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers. Partly sunny, with a high near 77. Light and variable wind becoming east 5 to 7 mph in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Increasing clouds, with a high near 79. East wind 5 to 7 mph becoming west southwest in the afternoon.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 61. Calm wind becoming north northwest around 5 mph after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Isolated showers after noon. Sunny, with a high near 79. West northwest wind 3 to 7 mph. Chance of precipitation is 20%.

Waimea

Today: Isolated showers before noon. Mostly sunny, with a high near 74. Breezy, with a northeast wind 9 to 16 mph, with gusts as high as 23 mph. Chance of precipitation is 20%.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 52. Northeast wind around 6 mph becoming calm in the evening. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Isolated showers. Mostly sunny, with a high near 74. Calm wind becoming northwest around 5 mph. Chance of precipitation is 20%.

Kohala

Today: Scattered showers. Mostly sunny, with a high near 70. Breezy, with an east northeast wind 13 to 18 mph becoming light east in the afternoon. Winds could gust as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 45. Northeast wind 5 to 7 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers, mainly after noon. Partly sunny, with a high near 70. Northeast wind around 5 mph becoming calm in the morning. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers after noon. Sunny, with a high near 75. Breezy, with an east wind 16 to 20 mph, with gusts as high as 25 mph. Chance of precipitation is 10%.

Tonight: Isolated showers after midnight. Partly cloudy, with a low around 70. East northeast wind 7 to 10 mph. Chance of precipitation is 20%.

Friday: Sunny, with a high near 75. East northeast wind 5 to 10 mph becoming light in the morning.

Puna

Today: Scattered showers. Mostly sunny, with a high near 76. Northwest wind around 8 mph becoming north northeast in the morning. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 61. North northwest wind 5 to 10 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Friday: Scattered showers. Partly sunny, with a high near 76. East wind around 6 mph becoming light and variable in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Isolated showers after noon. Sunny, with a high near 80. Breezy, with an east southeast wind 7 to 16 mph becoming west northwest in the morning. Winds could gust as high as 23 mph. Chance of precipitation is 20%.

Tonight: Clear, with a low around 61. Northeast wind 3 to 6 mph.

Friday: Sunny, with a high near 80. Light and variable wind becoming northwest around 6 mph.

Detailed Forecast

Synopsis

A surface low and trough located east and northeast of the Big Island will maintain moderate to locally strong northeast winds across the area through today. The trades weaken to light to moderate tonight, and continue into the weekend. A dissipating front will bring a boost to windward and mauka showers over the weekend. A more typical east- northeast trade wind flow returns Saturday night at which point temperatures will be not be as cool. Humidity will be on the rise early next week as southeast winds take over.

Discussion

A northeast trade wind flow will maintain cool temperatures, especially at night, through Saturday. This wind flow is brought on by a slow moving surface low and trough located some 1000 miles northeast of Oahu, and a broad surface high centered far northwest of Kauai. The northeast flow weakens from moderate to locally strong today, to light to moderate tonight and Friday.
As this low/trough ejects out to the northeast tonight, a new surface low forms 500 miles further west along 150W on Friday, resulting in our light to moderate northeast winds becoming more northerly. This new low gets kicked out to the northeast on Saturday, and a weak surface high follows in Saturday night resulting in the return of a more typical east- northeast trades. Between Sunday night and Monday, the trade wind gives way to light southeast winds. Under this wind regime, the weather pattern changes from trades to convective of daytime sea breeze and afternoon showers, and nighttime land breeze.
A front is expected to reach Kauai Friday morning, then on to Oahu in the afternoon. The front stalls and dissipate over Maui County Saturday. As the trade winds return to its usual east- northeast component Saturday night, trade showers will return to all islands.
The windward and mountain sections of most islands are experiencing passing mainly light showers. The lee areas of the smaller islands are feeling a few drops from time to time as well. We anticipate the frequency of these showers to ease off toward late morning, becoming isolated by this afternoon. Scattered showers will pick up once again after the sun sets.

Aviation

Moderate trade winds will persist through this morning and allow for scattered showers to affect mainly the windward coasts and slopes. Brief periods of MVFR ceilings and visibility may be associated with this activity. Otherwise, expect partly cloudy skies and VFR conditions for the leeward locations.
No AIRMETS are currently in effect and none are expected today,

Marine

A trough of low pressure east of the Big Island and broad surface high pressure northwest of the state will maintain moderate and fresh northeast trade winds through today. Last night’s ASCAT satellite pass verified locally strong winds through the Alenuihaha Channel and waters south of the Big Island. Thus, have extended the Small Craft Advisory for those windier waters of Maui County and south of the Big Island through 6 PM HST tonight. Trades will begin to ease tonight and into Friday in response to the northeast trough moving further away from the islands and a developing new low north-northeast of the islands. A weakening front will reach the northern offshore waters this afternoon. The front will dissipate upon reaching Maui County Saturday. A new surface high follows in behind this front Saturday night, ushering in a light to moderate east-northeast trade wind flow. This wind flow changes to a more east to southeast direction Sunday night and Monday. Early to mid week winds will become light and variable as surface high pressure ridging orients itself west- to- east just north of the islands.
Surf will remain small along north and west facing shores through Thursday. A series of moderate, short period north swells will fill in beginning Friday and last through the weekend. This will increase surf along north facing shores through the weekend with an expected slow decline early next week. Surf from these north swells will remain well below high surf advisory levels. East facing shore surf will also remain small through Thursday. North swell may wrap around into some eastern exposures and provide a small bump in east facing shoreline weekend surf. As any remaining south southwest swell fades through Thursday, south facing shore surf will stay small into early Friday. Distant long period swell energy from the southern hemisphere arriving in a couple of days will provide a small boost to southern shoreline surf from Friday into the weekend.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov