Photo Credit: Brendan Stephen

West Kaua’i

Today: Mostly sunny. Isolated showers in the morning. Highs around 82 near the shore to around 69 above 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 66 near the shore to around 56 above 3000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Friday: Mostly sunny with isolated showers. Highs around 82 near the shore to around 68 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

South Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 83. East winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 78 to 83. East winds 10 to 15 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny. Numerous showers in the morning, then scattered showers in the afternoon. Highs 73 to 79 in the valleys to around 62 above 4000 feet. East winds around 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 58 to 64 in the valleys to around 54 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers. Highs 73 to 78 in the valleys to around 62 above 4000 feet. East winds around 10 mph. Chance of rain 50 percent.

North Kaua’i

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 71 to 81. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 59 to 67. East winds up to 10 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 71 to 81. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

East Kaua’i

Today: Mostly cloudy in the morning then becoming mostly sunny. Scattered showers. Highs 71 to 81. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 59 to 70. East winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 72 to 81. East winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A ridge to the north of the islands will maintain gentle to locally breezy trade winds into the weekend. Limited showers riding in on the trades will be focused over windward and mauka areas. A front approaching from the northwest will weaken winds early next week.

Discussion

Some changes were made to the forecast this morning. In the short term, the winds were nudged toward a blend of the models. It held some wind speeds steady, and weakening others. Similarly the PoPs were adjusted, mostly to nudge them lower given the overall dry and stable airmass over the islands. In the longer term, changes to the winds, PoPs and associated fields, were made due to the trend in the latest global models for the front that is expected during the second half of the week. Northerly winds behind the front, and an uptick in shower activity with the front. Additionally, the summit winds were increased during the Sunday to Thursday time period. Winds would peak at summit advisory levels on the Big Island Sunday night and Monday, and again Wednesday night.
High pressure remains far to the northeast of the islands, with a surface ridge to the north of the islands. Trade winds continue, but with more of a east to southeast trend in the direction. A front to the northwest of the ridge is expected to weaken as it moves to the east into the weekend, which will push the ridge towards the islands. This in turn will weaken the winds over the region, with light winds expected to begin the new week.
Overnight soundings from Lihue and Hilo showed precipitable water (PW) of 0.82 and 0.94 inches respectively. Both are on the dry side of normal. Satellite derived PW shows little change upstream of the islands. The global models are in good agreement with little change in PW into the middle of the new week. As such, we can expect some showers, but not expecting a lot in the way of rainfall totals.
As winds weaken early next week, expect some localized land and sea breezes to set up, which could bring a few more clouds and showers during the afternoon and evening hours. A new front will approach the islands from the northwest during the first half of the week, but at this time it appears the southern portion of the front will fizzle out before reaching the islands. This will maintain some light winds through Monday night. Global models are suggesting a stronger front approaching the islands during the middle to second half of the week, that could reach the islands and bring another round of showers to the island chain. Northerly winds would filter in behind the front.

Aviation

Moderate to breezy easterly trades will gradually ease into the light to moderate range and shift out of the east-southeast by the end of the 24-Hr TAF period as the ridge weakens north of the area. Although VFR conditions will prevail, brief periods with MVFR CIGs/VSBYs in light showers moving through are possible through the early morning hours for windward areas. Some afternoon cloud development is possible over leeward areas where localized sea breezes form.
AIRMET Tango for moderate lee turbulence below 8,000 ft remains in effect for areas over and downwind of all island terrain this morning. This will likely be cancelled by noon as the winds begin to ease.

Marine

A high pressure system far northeast of the state will continue to drift slowly eastward away from the islands through Friday. A low pressure system and trough approaching the islands from the northwest will weaken the ridge north of the islands through the first half of next week. Trade wind speeds will weaken into the weekend, with light to moderate winds forecast over the western islands starting on Friday. These lighter winds will spread to all islands by Sunday. The Small Craft Advisory (SCA) has decreased in coverage today, back to the typical windier eastern waters and channels as winds and seas continue to ease. Winds and seas will weaken below SCA thresholds for all Hawaiian waters from Friday into the middle of next week.
The northeast swell continues to diminish today and the eastern facing buoys are reporting seas below High Surf Advisory (HSA) levels this morning. Therefore the HSA was cancelled for all east facing shores with this mornings forecast package.
Surf heights along north and west facing shores will continue to slowly decline today as the current northwest (310 deg) swell continues to diminish. Models show that another moderate size northwest (310-320 deg) swell will move swiftly into the region from Friday morning into the weekend. Surf heights will approach advisory levels early Friday morning, then reach low end High Surf Advisory levels by Friday afternoon for exposed north and west facing shores of the western islands. This new northwest swell will likely fall below HSA thresholds by Saturday night, and then continue to decline through the first half of next week. The next extra large long period northwest (320 deg) swell arrives by next week Thursday with the potential for extra large surf well above warning levels along exposed north and west facing shores. Stay tuned.
Expect small background south swell pulses to continue through the middle of next week. A small (200-220 deg) swell with Tasman Sea origins may produce a slight bump in south shore surf from Friday through Sunday.

HFO Watches/Warnings/Advisories

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

Data Courtesy of NOAA.gov