Photo Credit: James Grenz

Hilo

Today: Occasional showers. High near 76. Calm wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 100%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 63. East wind 5 to 8 mph becoming light and variable. Chance of precipitation is 100%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Occasional showers, mainly before 1pm. High near 77. Light and variable wind becoming east 5 to 9 mph in the morning. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after 1pm. Partly sunny, with a high near 79. Calm wind becoming west northwest 5 to 9 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly before 1am. Mostly cloudy, with a low around 61. West northwest wind around 5 mph becoming calm after midnight. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Isolated showers before 7am, then scattered showers after 1pm. Partly sunny, with a high near 79. Calm wind becoming west northwest 5 to 9 mph in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Occasional showers, mainly after noon. High near 74. North northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 52. Northeast wind around 14 mph, with gusts as high as 18 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Scattered showers. Partly sunny, with a high near 74. Breezy, with a northeast wind 13 to 17 mph, with gusts as high as 23 mph. Chance of precipitation is 50%. New precipitation amounts between a quarter and half of an inch possible.

Kohala

Today: Occasional showers. High near 70. Windy, with an east wind 24 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 100%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Occasional showers. Low around 45. Windy, with an east wind around 29 mph, with gusts as high as 41 mph. Chance of precipitation is 90%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Occasional showers. High near 70. Windy, with an east wind 23 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 79. Windy, with an east northeast wind 26 to 29 mph, with gusts as high as 37 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after midnight. Partly cloudy, with a low around 69. Windy, with an east northeast wind 26 to 29 mph, with gusts as high as 37 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Wednesday: Isolated showers. Mostly sunny, with a high near 79. Windy, with an east northeast wind around 29 mph, with gusts as high as 37 mph. Chance of precipitation is 20%.

Puna

Today: Occasional showers. High near 75. West wind 7 to 11 mph becoming east in the morning. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.

Tonight: Occasional showers. Low around 61. East wind 6 to 11 mph becoming north in the evening. Chance of precipitation is 90%. New precipitation amounts between a quarter and half of an inch possible.

Wednesday: Occasional showers, mainly before noon. High near 76. Northeast wind 6 to 13 mph becoming north northwest in the morning. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Scattered showers after noon. Mostly sunny, with a high near 80. East wind 6 to 9 mph becoming west northwest in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 61. West northwest wind 6 to 9 mph becoming east southeast in the evening. Chance of precipitation is 20%.

Wednesday: Isolated showers after noon. Mostly sunny, with a high near 80. East wind 7 to 9 mph becoming north in the afternoon. Chance of precipitation is 20%.

Detailed Forecast

Synopsis

High pressure north and northeast of the islands will keep breezy to windy trades in place through the weekend. An old frontal band will bring an increase in showers to the state today, targeting mainly windward areas. Drier trade wind weather is expected tonight through Wednesday night. Upper level troughing along with an influx of moisture from the east and southeast, will likely increase trade wind shower coverage and intensity Thursday through the weekend.

Discussion

Currently at the surface, a broad 1038 mb high is centered around 1500 miles northeast of Honolulu, while a cold front is located around 650 miles west-northwest of Kauai. The resulting gradient is producing moderate to breezy trade winds across the island chain early this morning, with winds lighter in the more sheltered leeward areas. Infrared satellite imagery shows clear to partly cloudy skies in most leeward areas, with mostly cloudy conditions in most windward locales. Radar imagery shows scattered showers moving into windward areas, with a few showers spilling over into leeward communities. Main short term concern revolves around trade wind trends during the next few days.
High pressure will hold in place northeast of the state today and tonight, as the cold front shifts eastward and weakens into a trough around 400 miles west-northwest of the islands by daybreak Wednesday. The trough will begin to retrograde westward early Wednesday as the high northeast of the islands begins to strengthen and shift closer to the state. The high will then merge with another high far north of the islands Wednesday night, and strengthen to a very impressive 1047-1048 mb Thursday into Friday. The high will then weaken as it shifts southward Friday night and Saturday, before merging with a new strong 1042-1044 mb high far to the north of the islands on Sunday.
Needless to say, robust high pressure north and northeast of the state will keep the gradient tight during the next 7 days. The one factor that will keep the trades from realizing their full potential will be the lack of a strong low level inversion during this time. Nevertheless, breezy to windy conditions can be expected statewide, with the trades peaking Wednesday through Friday. Wind Advisories will likely be required for portions of the state as the trades peak.
As for the remaining weather details, we will likely see shower activity continue to increase across windward Maui and the Big Island early this morning as a band of low clouds and showers associated with an old front moves in. This band of moisture should continue to march westward through the morning hours, bringing an increase in showers to the remaining smaller islands. Showery weather will likely continue across Kauai as well as windward Maui and Big Island this afternoon, with some improvement expected over Oahu and Molokai. Drier and more typical trade wind conditions should then develop statewide tonight through Wednesday night as precipitable water values drop to an inch or less in most areas. Showers will favor windward and mauka areas during this time, particularly at night and during the early morning hours, with a stray shower reaching leeward communities at times due to the strength of the trades.
Thursday through the weekend, model solutions are in decent agreement showing troughing aloft developing over the island chain, with moisture moving in from the east and southeast. This should bring an increase in trade wind shower coverage and intensity during this time, which could linger into early next week.

Aviation

Occasional MVFR has been noted over Windward Big Island this morning as better moisture and more organized showers approach from the east. Conditions are still expected to deteriorate to more widespread MVFR with greater shower coverage during the remainder of the morning. Windward Maui will likely follow suit within the next few hours. The approaching band of showers will traverse the remaining islands during midday resulting in an eventual increase in clouds and showers over the windward slopes and coasts.
AIRMET Sierra is in effect for tempo mountain obscuration for Windward Big Island and may be expanded to include portions of Maui later this morning.
AIRMET TANGO is in effect for lee turbulence below 9kft for the entire state.

Marine

A strong high far northeast of the state will continue to drive fresh to strong easterly trades across most Hawaiian Island coastal and offshore waters. The mid week strengthening of this high will further tighten the pressure gradient back across the central Pacific. This will ultimately increase local trade wind speeds from Wednesday into the weekend. A Small Craft Advisory is in effect for the majority of the coastal waters, with the exception of those waters southwest of Kauai, to account for the strengthened trades and responding rough seas. The potential of winds within the Alenuihaha Channel to frequently gust to gale force has prompted a Gale Watch that will be in effect from this evening through Wednesday afternoon.
Recent ASCAT satellite passes confirm a large region of strong trades upstream of the state generating a long fetch that will be the impetus to the arrival of higher easterly swells. Strong trade winds will also build large wind-driven easterly seas. The combination of both heightened trade wind waves and east swells will translate to rough sea conditions and higher east-facing shoreline surf. Surf heights along eastern-facing shores will exceed surf advisory levels this week. A High Surf Advisory (HSA) will remain in effect for most island’s eastern exposures for the remainder of the week.
A couple of small, overlapping relatively longer period west to northwest swells will travel around the islands the next few days. The first of these swells has arrived and will level out through the day. The second set of similar low west to northwest swells will move through during mid to late week. Surf along north and west-facing shores will remain well below HSA levels through Friday. Surf along south-facing shores will remain small into the weekend. A small bump in southern swell arriving later in the week will provide a slight increase to south-facing shoreline surf by Friday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Saturday for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, South Big Island, Big Island North and East.
Small Craft Advisory until 6 PM HST Wednesday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.
Gale Watch from this evening through Wednesday afternoon for Alenuihaha Channel.
Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel.

Data Courtesy of NOAA.gov