Breezy to locally windy conditions will persist through Saturday. Widely scattered showers will advance in on the trade winds and primarily focus along windward exposures, upslope mauka and within higher terrain. Hurricane Fausto will travel west and weaken as he approaches the islands Tuesday. Tropical Storm Fausto or the remnants of Fausto is forecast to skirt north across the western half of the island chain mid next week.
Traditional trade-like weather is expected through the weekend. The pressure gradient back from a large 1037 mb surface high far north of the island chain will remain taunt enough to continue to support breezy to locally windy trades the next couple of days. Very dry air resides above 8k ft or above the stout 800 mb trade inversion. Early morning satellite imagery confirming what the near term guidance has been prognosticating; that of very dry mid layer air blanketing Hawaii and surrounding waters. Mid to upper level lower humidity (e.g., under 50 %RH at the 700 mb level) will persist through the weekend. The resident boundary layer will be deep enough (at near 8k ft) to efficiently support widely scattered, quick moving trade showers. Typical trade showers in the coming days with behavior similar to recent days. That of the thickest overcast hugging the higher terrain and the greater precipitation being recorded along windward exposures and higher elevation.
The main story going into early next week will be how TC Fausto survives the unfavorable environment (lower SSTs, higher shear) as he moves west of 140W. Recent IR satellite showing the impact of north northwest dry entrainment into the hurricane as Fausto struggles to maintain its strength west of 130W. Obviously, it is too far out to provide much of a forecast, but Fausto is projected to weaken along his westerly track toward the state. NHC's latest forecast calls for gradual to steady weakening that is in-line with recent model trends. The tropical cyclone is forecast to either weaken to a tropical storm or a remnant low by the time it reaches the area early next week.
A strong high pressure system north of the Hawaiian Islands will keep moderate to breezy trade winds in the forecast. Brief MVFR conditions are possible through the early morning hours, mainly along windward mountain slopes through the early morning hours.
AIRMET Tango remains in effect for moderate low level turbulence driven by the strengthening trade winds. These conditions may continue into the weekend.
Robust high pressure far north of the state continues to produce fresh to strong trade winds, and a Small Craft Advisory (SCA) remains in effect for all Hawaiian waters through the afternoon. For tonight through Saturday night, the SCA has been trimmed back to the typically windy waters around Big Island and Maui County due to an expected slight easing of the trades as the high drifts westward. Trades may decline slightly Sunday into Monday, but wind trends become less clear Tuesday due to uncertainty in the eventual track and strength of Hurricane Fausto. The current National Hurricane Center forecast calls for Fausto to be a tropical storm by Sunday with continued weakening as it passes near the islands Tuesday.
The current south southwest swell has peaked overnight and will maintain south shore surf above the High Surf Advisory threshold as it declines today. Offshore NOAA buoy 51002 has measured a decline in long period energy since last evening, but there are still several more hours of large surf expected at the nearshore Barbers Point PacIOOS buoy, which has shown the swell at more than 4 feet at 20 seconds during the past several hours. Surf along south facing shores will be at borderline advisory heights tonight, followed by another pulse of swell that will likely push surf above the advisory level Saturday and Sunday. The south southwest swell will slowly decline early next week, with a smaller south southwest swell possible during the middle of the week.
Rough east shore surf will remain a notch above seasonal average into Saturday, mainly from short period wind swell but also due to fading swell from dissipated TC Elida. The trade wind swell will drop slightly as long period swell from Hurricane Fausto begins to arrive late Saturday. The Fausto swell will likely produce advisory-level surf along east facing shores Sunday or Monday, with the largest surf expected Tuesday or Wednesday depending on the eventual track of the tropical cyclone.
Surf along north facing shores will remain at flat to tiny levels through the weekend. Some increase is expected as Fausto or its remnants pass over the area Tuesday and Wednesday.
High Surf Advisory until 6 PM HST this evening for Big Island South-Big Island Southeast-East Honolulu-Ewa Plain-Honolulu Metro-Kahoolawe-Kauai South-Kauai Southwest-Kona-Lanai Leeward- Lanai South-Maui Central Valley South-Maui Leeward West-Molokai Leeward South-Niihau-South Haleakala-South Maui/Upcountry- Waianae Coast.
Small Craft Advisory until 6 PM HST this evening for Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters- Kauai Northwest Waters-Kauai Windward Waters-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters.
Small Craft Advisory until 6 AM HST Sunday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
