Photo Credit: James Grenz

Hilo

Today: Scattered showers, with thunderstorms also possible after noon. Partly sunny, with a high near 77. Calm wind becoming northeast 5 to 7 mph in the afternoon. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Occasional showers. Low around 64. East northeast wind 5 to 8 mph becoming calm in the evening. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely, mainly before noon. Partly sunny, with a high near 77. Light and variable wind becoming northeast 5 to 9 mph in the afternoon. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers and thunderstorms after noon. Partly sunny, with a high near 80. Light and variable wind becoming west 5 to 8 mph in the afternoon. Chance of precipitation is 30%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers, mainly before midnight. Partly cloudy, with a low around 62. North northwest wind 5 to 7 mph becoming calm after midnight. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Scattered showers after noon. Mostly sunny, with a high near 79. Southwest wind 6 to 11 mph becoming light and variable in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Scattered showers, with thunderstorms also possible after noon. Partly sunny, with a high near 75. Breezy, with a northeast wind 5 to 10 mph increasing to 12 to 17 mph in the afternoon. Winds could gust as high as 24 mph. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Scattered showers. Mostly cloudy, with a low around 53. Breezy, with a northeast wind 16 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Scattered showers. Partly sunny, with a high near 74. Breezy, with a northeast wind 13 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Scattered showers, with thunderstorms also possible after noon. Partly sunny, with a high near 71. Windy, with an east southeast wind 5 to 10 mph becoming east northeast 18 to 23 mph in the morning. Winds could gust as high as 32 mph. Chance of precipitation is 50%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

Tonight: Occasional showers. Low around 46. Windy, with an east northeast wind 22 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely. Partly sunny, with a high near 70. Breezy, with an east northeast wind 15 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers, with thunderstorms also possible after noon. Mostly sunny, with a high near 80. Windy, with an east wind 20 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 70. Windy, with an east northeast wind 21 to 25 mph, with gusts as high as 32 mph. Chance of precipitation is 20%.

Thursday: Isolated showers. Mostly sunny, with a high near 79. Windy, with an east wind 21 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers, with thunderstorms also possible after noon. Partly sunny, with a high near 76. West wind 5 to 10 mph becoming northeast in the afternoon. Chance of precipitation is 50%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Tonight: Occasional showers. Low around 62. North northeast wind 6 to 10 mph. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Showers likely, mainly before noon. Partly sunny, with a high near 76. North northeast wind 8 to 13 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: A 20 percent chance of showers and thunderstorms after noon. Mostly sunny, with a high near 81. Breezy, with an east southeast wind 7 to 16 mph becoming north in the morning. Winds could gust as high as 22 mph.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 62. Breezy, with a northeast wind around 16 mph, with gusts as high as 22 mph. Chance of precipitation is 20%.

Thursday: Isolated showers after noon. Mostly sunny, with a high near 80. Breezy, with a northeast wind 13 to 18 mph decreasing to 7 to 12 mph in the afternoon. Winds could gust as high as 25 mph. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

A typical trade wind pattern will hold in place across the island chain during the next 7 days. Moderate trade winds are expected through Friday, with the trades strengthening to breezy levels over the weekend, and becoming windy early next week. Passing showers will favor windward and mauka areas through the period, particularly at night and during the early morning hours, with a stray shower spreading leeward from time to time. The trade showers could become more active Sunday through Monday as some old frontal remnants move through the island chain.

Discussion

Currently at the surface, a 1046 mb high is centered around 2000 miles north-northwest of Honolulu, while another 1030 mb high is centered around 2200 miles northeast of the state. In between these two highs is a trough of low pressure, which is effectively limiting the trade wind response to the strong highs. As a result, moderate trade winds prevail across the island chain early this morning. Infrared satellite imagery shows a mix of high and low clouds resulting in partly cloudy conditions in most areas, with a few pockets of more substantial cloud cover in windward locales. Radar imagery shows scattered showers moving into windward areas, with a decaying shower or a few sprinkles reaching leeward areas from time to time. Main short term concern revolves around the potential for thunder on the Big Island this afternoon.
Model solutions show a shortwave trough passing over the Big Island this afternoon, and when combined with an increase in mid- level moisture and some lingering instability, a thunderstorm or two can’t be ruled out. As a result, will include a slight chance of thunderstorms over the Big Island this afternoon. Otherwise, fairly typical trade wind weather will prevail statewide through the forecast period. Passing showers will favor windward and mauka areas, particularly at night and during the early morning hours, with a stray shower spreading leeward from time to time. The trade showers could become more active Sunday through Monday as some old frontal remnants move through the island chain.
The trades are expected to hold at moderate levels through Friday, with only minor fluctuations in strength. A new strong high north of the state will gradually become more dominant over the weekend as it builds southward and closer to the island chain. This is expected to ramp the trades up to breezy levels over the weekend, with even windier conditions possible early next week.

Aviation

Moderate to locally strong trade winds will develop today as high pressure builds far north of the area. AIRMET TANGO for tempo moderate low level turbulence over and immediately downwind of the terrain of all islands will go into effect at 20Z.
Trade winds will carry in passing showers along exposed east facing slopes and coasts, resulting in brief periods of MVFR visibility and ceilings. Highest chances will be across the Big Island and Maui as upstream moisture makes its way towards this area. A slight chance for thunderstorms is forecast for the Big Island this afternoon. No AIRMETs are in effect for mountain obscurations at this time given the low coverage areas this morning, but could be issued later today if and when cloud cover fills in a bit more.
Few to scattered high clouds along the subtropical jet will move over the islands today.

Marine

Fresh to strong northeast to east trade winds will continue through the weekend as high pressure builds to the north. The Small Craft Advisory has been extended for the typically windier waters around Maui County and the Big Island and may need be expanded to other areas over the weekend.
Surf along south facing shores will hold just under the advisory level today, then slowly ease tonight through Friday as the south swell moves through. Over the weekend, a mix of background southerly swells along with short-period southeast energy should be enough to keep the surf from going flat along southern exposures.
Surf along north and west facing shores will trend up today as a small, northwest swell arrives and builds down the island chain. This source should hold into Friday, then lower into the weekend. Guidance depicts a decent gradient setting up over a large area north of the islands between 1035 mb high and low pressure forming over the northeast Pacific over the weekend. Strong- to near gale-force northeast winds focused at the islands within the 020-040 directional bands will be enough to generate a decent north-northeast swell for north facing exposures by or come early next week.
Trade winds will continue to keep surf steady along east facing shores through Friday. Surf along east facing shores will trend up over the weekend through early next week due to a combination of strong easterly trades locally and the aforementioned north- northeast swell arriving. Heights could reach advisory levels early next week if this scenario materializes.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Thursday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov