The trade winds are slowly edging upwards and are expected to build to strong and gusty levels over the windier spots across Maui County and the Big Island today. Winds will be on the uptick across Kauai and Oahu as well, but not quite as strong as the southern islands. The uptick in winds is in response to Hurricane Lowell, currently about 440 miles south of Hilo, tracks west, and a high pressure system far to the north. Moisture being carried in on the trade winds will focus clouds and showers mostly to the windward and mauka areas, particularly during the overnight through early morning hours each day. The forecast remains uncertain for the upcoming Labor Day weekend due to both Lowell and Karina remaining in the central Pacific over the coming days.
Wet start to the day with numerous showers passing through the islands leading to MVFR and pockets of IFR under heaviest showers. Satellite shows up stream clearing so showers will taper off 19-20Z with more VFR conditions. Still could see some VCSH/MVFR this afternoon/evening on windward locations and upper slopes. Moderate to locally strong trade winds will prevail today, especially later this afternoon. Will need to keep an eye on LLWS with highest chances for HOG and HKO. Hurricane Lowell is forecast to pass far south of the island chain the next couple of days. On this westerly track, regional trade winds will remain strong per a tight pressure gradient between the hurricane and high pressure to the far north.
AIRMET Sierra has been issued for IFR and SHRA for KAUAI OAHU MOLOKAI MAUI through 20Z.
AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.
As a strong surface high persists far north of the Hawaiian Islands and interacts with Hurricane Lowell passing to the south, trade winds will strengthen across the coastal waters to become fresh to locally near gale force. The Small Craft Advisory (SCA) has been expanded to include all waters and extended through Thursday night. The offshore waters will likely see tropical storm conditions over the far south waters while the core of hurricane force winds remains just outside the area today through Thursday. A Tropical Storm Warning is in effect for the far southern offshore waters.
While there is still plenty of uncertainty regarding the exact track of Lowell, confidence is fairly high that the southwest and western offshore waters will see Hurricane conditions. How close it gets to the state, is yet to be determined. Adding to the extended forecast uncertainty will be the approach of Hurricane Karina from the east.
A moderate, long-period south swell will peak later today just below advisory levels and hold into Thursday. This swell will then gradually decline through the rest of the week. A moderate, short to medium- period south-southeast swell from Lowell will fill in through the day and become more southerly Thursday through Friday. A High Surf Advisory for southeast Big Island has been issued for the rising surf associated with Lowell through tonight and could spread to the smaller islands on Thursday. These combined swells will keep south and southeast shores surf elevated over the next few days. Beyond that point, the surf forecast is highly dependent on the eventual track and intensity of Lowell, which has the potential to be a significant source of south to southwesterly swell through this weekend and into next week. Confidence is increasing for warning level surf along south and western exposures next week due to the rapid strengthening of Lowell during the past 24 hours.
Trade wind swell energy will keep rough, choppy surf along all east- facing shores through at least the weekend. A small, medium- period east swell from Hurricane Karina began filling in overnight and is expected to gradually build through the week, possibly pushing east shore surf to advisory, or even warning thresholds by this weekend and into next week.
Wind Advisory until 6 AM HST Friday for Big Island North-Big Island South-Big Island Southeast-Kahoolawe-Kipahulu-Kohala- Lanai Leeward-Lanai Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui Central Valley South-Maui Leeward West- Maui Windward West-Molokai Leeward South-Molokai North-Molokai Southeast-Molokai West-Molokai Windward-South Haleakala-South Maui/Upcountry-Windward Haleakala.
High Surf Advisory until 6 AM HST Thursday for Big Island Southeast.
Small Craft Advisory until 6 AM HST Friday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters- Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters-Pailolo Channel.
