Image source: Brendan Stephen
West Kauai
today: breezy. Mostly sunny with scattered showers. Highs are about 79 near shore to about 67 above 3,000 feet. Winds are northeasterly 15 to 20 knots. Chance of rain is 20 percent.
Tonight: Mostly clear. breezy. Scattered rain showers after midnight. Lows are around 66 near shore to around 55 above 3,000 feet. Winds are northeasterly 15 to 20 knots. Chance of rain is 20 percent.
Friday: Sunny and breezy. Highs are about 80 near shore to about 67 above 3,000 feet. Winds are northeasterly 15 to 20 knots.
South Kauai
today: Mostly cloudy. breezy. Rain is likely in the morning, then scattered rain in the afternoon. High around 78. Northeast wind 20 to 25 mph. The chance of rain is 70 percent.
Tonight: breezy. Partly cloudy with scattered showers. Lows from 63 to 69. Northeast winds, 20 to 25 miles per hour. Chance of rain is 50 percent.
Friday: breezy. Partly sunny with scattered showers in the morning, then mostly sunny with scattered showers in the afternoon. High 76 to 81. Northeast wind 20 to 25 mph. 40 percent chance of rain.
Kauai Mountains
today: Mostly cloudy. windy. Scattered showers in the morning, then possible showers in the afternoon. Highs 66 to 74 in valleys to about 60 above 4,000 feet. Winds are northeasterly 15 to 30 knots. Chance of rain is 90 percent.
Tonight: windy. Partly cloudy with a chance of rain. Lows range from 55 to 60 in the valleys to about 49 above 4,000 feet. Winds northeasterly 20 to 30 knots. The chance of rain is 70 percent.
Friday: Partly sunny in the morning then becoming mostly sunny. windy. Scattered rain showers. Highs 66 to 74 in valleys to about 61 above 4,000 feet. Winds northeasterly 20 to 30 knots. Chance of rain is 50 percent.
North Kauai
today: Mostly cloudy. breezy. Scattered showers in the morning, then possible showers in the afternoon. High 71 to 78. Northeast wind 15 to 20 mph. The chance of rain is 80 percent.
Tonight: breezy. Partly cloudy with a chance of rain. Lows from 58 to 67. Northeast winds from 15 to 25 miles per hour. The chance of rain is 70 percent.
Friday: Mostly sunny. breezy. Scattered showers in the morning, then scattered showers in the afternoon. High 71 to 79. Northeast wind 15 to 25 mph. Chance of rain is 50 percent.
East Kauai
today: Mostly cloudy. breezy. Scattered showers in the morning, then possible showers in the afternoon. High 71 to 78. Northeast wind 15 to 20 mph. Chance of rain is 80 percent.
Tonight: Mostly cloudy. breezy. Scattered rain in the evening, then rain is likely after midnight. Lows from 56 to 69. Northeast winds 20 to 25 miles per hour. The chance of rain is 70 percent.
Friday: breezy. Partly sunny with scattered showers in the morning, then mostly sunny with scattered showers in the afternoon. High 71 to 79. Northeast wind 15 to 25 mph. Chance of rain is 50 percent.
summary
Trade winds will remain locally strong and gusty through the weekend. Less rain is expected on Kauai and Oahu over the next couple of days, while the Big Island and Maui will continue to see a fair amount of windy rain. Another period of enhanced rainfall is possible statewide starting late Monday.
discussion
An active night of weather as areas of increasing humidity and strong trade wind flow interact with the island's topography and instability associated with the high low to bring widespread heavy rain and isolated thunderstorms with gusty winds. Water vapor imagery and model analyzes indicate a closed low high directly above the island chain, with associated 500 mb temperatures approaching -16°C. This supports sharp low and mid-level lapse rates which in turn promote the development of strong updrafts, leading to charge separation/lightning in the strongest cells. However, overall shower coverage and intensity have trended lower over the past two hours.
A pair of surface high-pressure cells are located to the extreme northeast and northwest of the islands, with an associated low pressure gradient that supports strong and gusty trade winds. Deep moisture and cold temperatures above led to periods of snow and freezing rain overnight on the Big Island's peaks, where winter weather warnings remain in effect today.
Today there is a trend toward less (and less intense) rainfall in some areas as the upper low weakens/moves away to the southwest, allowing average temperatures to warm over the area. The NS gradient in PWAT is also expected to develop, falling to less than 1″ over Kauai and Oahu, while remaining near 1.4″ over the Big Island. This will likely bring wet conditions over the leeward Big Island and possibly Maui, with less rain elsewhere. A trough stuck above will ensure that the bearish reversal reversal is either weakened or higher over the next couple of days. In addition, high clouds will thicken over southern parts of the state during the next two days.
Guidance increasingly indicates that a destabilizing depression will return over the islands from the southwest early next week, bringing an increase in precipitation statewide Monday night into Wednesday. Average temperatures are not expected to be as cold as they are currently, making thunderstorms less likely, but heavy rain appears possible again.
The passage of the front well northward from the area will result in a slight weakening of the surface ridge today, which may allow the trade wind speed to be very subtly mitigated. As the high to the northwest slowly builds eastward, easterly winds are expected to strengthen again tonight, with the slow-moving high supporting local wind conditions through the weekend. The high will then move quickly away from the region early next week as a strong low/front fills the central North Pacific, with trade winds weakening Tuesday into Wednesday. The front is currently expected to move down the island chain next Wednesday/Thursday, with a fair amount of agreement typical of the timing. Strong N winds will create a cold air mass over the islands after the front passes, if current guidance holds.
airline
A strong high pressure system building north of the islands will continue to produce breezy to locally gusty trade winds across the Hawaiian Islands through Saturday. An upper level drop will also bring periods of unstable rain with gusty winds affecting all islands through today. Scattered thunderstorms are possible on Maui and the Big Island this morning.
AIRMET Sierra Mountain Blocking remains in effect to the north across the eastern section of Kauai, Oahu, Molokai, Maui and the Big Island. This AIRMET will continue until the morning hours.
AIRMET Tango of locally moderate to severe disturbances over and southwest of the island mountains remains in effect. Severe turbulence was reported at PIREP this evening near Lanai Island. This AIRMET is likely to continue through the rest of the week.
Navy
High pressure upstate will slowly drift eastward over the next few days with strong to near gale-force trade winds maintained across all coastal water areas through the weekend. Another high pressure is expected to form north of the islands at the end of the week, with a slight change in wind speed. A Small Vehicle Advisory (SCA) has been issued for all nearshore coastal areas through Saturday. As the surface pressure gradient intensifies from Friday through the end of this week, stormy conditions may develop in the typical wind channels surrounding the Big Island and Maui.
A stagnant low will remain over the islands today and will bring enhanced showers and isolated thunderstorms to the area, although the waters of the Big Island and Maui are mainly concentrated. These showers and storms may produce short periods of locally strong winds and reduced visibility. A more typical trade wind pattern will return by Friday as the bottom weakens.
Continued fresh to strong circulation will continue to generate rough and choppy surf along east-facing beaches through the week. Despite these extremely rough conditions, easterly waves are expected to remain below the high surf advisory heights. A small to moderate northwest swell (310 degrees) will persist today before subsiding on Friday. A moderate swell is set to build to the northwest (320 degrees) Friday night, peaking Saturday near high surf advisory levels.
HFO Watches/Warnings/Advice
Winter Weather Advisory until 6pm GMT this evening for the Big Island Peaks.
Small Boat Advisory until 6 a.m. GMT Saturday for all Hawaiian waters.
Data provided by NOAA.gov
