Weather Forecast

Hawaii County Weather Forecast for April 28, 2021

April 28, 2021, 7:16 AM HST
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Hilo

Today: Scattered showers, mainly after 10am. Partly sunny, with a high near 84. East wind 5 to 9 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.

Tonight: Showers likely, mainly after 8pm. Mostly cloudy, with a low around 63. Light and variable wind. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 83. East wind 3 to 7 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers, mainly after 10am. Partly sunny, with a high near 84. Light and variable wind becoming west 5 to 8 mph in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before 8pm. Partly cloudy, with a low around 63. East northeast wind around 5 mph becoming calm in the evening. Chance of precipitation is 30%.

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Thursday: Scattered showers after noon. Partly sunny, with a high near 83. Calm wind becoming northwest 5 to 7 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

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Today: Scattered showers, mainly after 11am. Partly sunny, with a high near 76. Light and variable wind becoming northwest around 6 mph in the afternoon. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 52. Northeast wind 5 to 9 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 75. Northeast wind around 8 mph. Chance of precipitation is 30%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

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Today: Showers likely, mainly after 2pm. Mostly cloudy, with a high near 68. North northwest wind 5 to 9 mph becoming calm. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Tonight: Showers likely. Mostly cloudy, with a low around 44. Calm wind becoming east northeast 5 to 7 mph after midnight. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 67. East northeast wind 7 to 9 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Isolated showers before 10am. Mostly sunny, with a high near 84. North wind 5 to 7 mph becoming south in the morning. Chance of precipitation is 20%.

Tonight: Partly cloudy, with a low around 69. East wind 5 to 11 mph.

Thursday: Isolated showers after noon. Mostly sunny, with a high near 83. East wind 11 to 13 mph. Chance of precipitation is 20%.

Puna

Today: Scattered showers, mainly after 10am. Partly sunny, with a high near 82. West wind 5 to 9 mph becoming east in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 8pm. Mostly cloudy, with a low around 61. Northeast wind around 5 mph becoming light and variable. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Thursday: Showers likely, mainly before noon. Mostly cloudy, with a high near 81. East northeast wind 5 to 8 mph. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Scattered showers after 10am. Partly sunny, with a high near 82. East southeast wind 5 to 9 mph becoming west northwest in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before 8pm. Partly cloudy, with a low around 62. East wind 5 to 9 mph becoming calm after midnight. Chance of precipitation is 30%.

Thursday: Mostly sunny, with a high near 81. Calm wind becoming northwest around 5 mph in the afternoon.

Detailed Forecast

Synopsis

A weak cold front approaching from the northwest will maintain daytime sea breezes today. The front will weaken tonight near the western end of the state, and high pressure will build in behind the front. This will bring a return of trade winds, with leftover frontal moisture riding in on the trades into the weekend.

Discussion

General forecast philosophy remains the same with the morning package, with relatively minor tweaks in the short term. Longer range the forecast has been modified to trend more towards the ECMWF solution.
Satellite shows the thin high clouds over the islands last night have largely cleared the region as expected. The lower clouds near the islands appear to be moving in from the northwest in the background flow. Meanwhile wind observations across the state show light winds over most locales. Clouds have largely cleared out over the smaller islands in the light flow, while low clouds have lingered over the Big Island.
The cold front to the northwest of the islands has edged closer, and the leading edge of the low cloud band associated with the front is entering the coastal waters about 40 miles northwest of Kauai at 3 am. The leading edge of the cloud band is starting to show signs of breaking up. Still expecting what remains of the front to stall out near Kauai tonight, and dissipate. Some aspects of this feature could make their way into portions of Maui County.
High pressure building to the northwest behind the front will help to quickly usher in trade winds behind the front. Trades will return first to Kauai, and then spread to the remaining islands from north to south. The main part of the front will remain to the northeast of the islands, and moisture from the front is expected to ride in on the trades during the second half of the week.
The next big weather question comes early next week. The ECMWF and GFS show a front with an upper level trough to the northwest of the islands on Monday. The GFS has a deeper trough developing, but the ECMWF is quicker to form an upper level low along the trough. The latest runs of each of these models keeps the upper level low to the west of the islands. With both models somewhat in agreement, have trending the forecast for Monday onwards towards the ECMWF solution which is a little more tame than the GFS. Will need to watch the trend in both models to determine what further refinements may be needed. At this time, it looks like trades will hold on during the period, but shower activity could increase.

Aviation

Clouds and showers associated with an old front are moving into Kauai from the NW and showers ahead of the front are moving SE mainly over the coastal waters. A batch of these showers are in the vicinity of PHKO and will bring isol MVFR conditions to the leeward Big Island into the morning hours. Increasing chances of MVFR due to low clouds and shra around Kauai and Oahu are expected today as trade winds return.
No AIRMETs in effect, but may be needed for mtn obscuration over the north facing slopes of Kauai later this morning.

Marine

A weak cold front making its way into the northwest waters today is producing moderate north to northeast winds in its wake. Winds ahead of this boundary will remain light and variable. The front will continue to become more diffuse and eventually dissipate across the central island waters by tonight. Weak high pressure filling in behind the front will allow for the return of trade winds from west to east across the entire region by Thursday evening. Winds and seas are expected to remain below Small Craft Advisory (SCA) levels through Thursday. Trades will become more easterly Friday and strengthen while producing rough seas this weekend. As strengthening high pressure moves further northeast of the state, SCA conditions may develop from late Friday into the weekend across those typically windier waters surrounding Maui County and south of the Big Island.
A small to moderate, mid period west-northwest swell will continue to fill in today and become more northwesterly through Thursday. Due to the west component of this swell, there may be some Kauai blocking for Oahu and Maui this morning. These islands will experience rising surf as this swell veers more northwest and comes out of Kauai’s shadow through the afternoon. Surf will peak in the 6 to 8 foot range (face value) for many north and northwestern facing coastlines Thursday. Forerunners of a longer period west-northwest swell are scheduled to arrive late Thursday into early Friday with the main northwest swell originating from a NW Pacific storm arriving late Friday. This swell may peak surf along north and west facing shores to near or slightly above High Surf Advisory criteria Friday night and Saturday with a slow fall through early next week. Small background southerly swells can be expected throughout the remainder of the week. A small bump in energy from southern hemisphere swells, along with wrap from the west-northwest swell, may slightly boost surf along southwest to south facing shores Thursday and Friday. Due to the recent absence of trades, east facing shore surf will remain small the next couple of days. Trades will return and strengthen later this week which will provide an uptick in eastern coastline surf from higher wind wave swell.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov

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