Increased trade winds through Friday, combined with dry conditions, will elevate the fire weather threat for the end of the work week. Meanwhile, occasional showers will favor windward and mauka areas through Friday. For the weekend, we are continuing to monitor Tropical Storm Lala as it moves northwestward towards the main Hawaiian Islands. Residents and visitors should prepare now for potential rain, wind, and surf impacts this weekend. Please monitor www.hurricanes.gov for the latest information.
Early this morning, satellite and radar imagery shows a few areas of low clouds and showers embedded within the trade winds moving into windward and mauka areas. However, rainfall overnight has been light, with only brief light showers passing through. Mostly dry conditions are expected to continue through today and much of the day on Friday as well, with windward and mauka areas experiencing scattered showers at times through Friday. Meanwhile, episode 53 of lava fountaining in Halema'uma'u at the summit of Kilauea officially ended at 123am HST this morning. No further impacts from tephra emissions are expected over the next few days. Trade winds will gradually trend up for the next 48 hours, becoming breezy by tonight and locally strong on Friday.
The main forecast concern for the next few days will be potential impacts from what is now Tropical Storm Lala. As of 5am HST, Tropical Storm Lala was located near 15.2N 145.5W and moving west around 9 knots (10 mph). Based on the latest forecast from the National Hurricane Center (NHC), Layla is expected to move near the Big Island late Friday or early Saturday, then continue moving off to the northwest through the rest of the weekend, with the center of circulation remaining south of the smaller islands. Impacts from Layla are expected to begin for the eastern end of the state as early as Friday night and will continue through the weekend as it tracks northwestward. Interests within the main Hawaiian Islands should closely monitor for forecast updates and prepare for the potential impacts described below.
FIRE WEATHER, Fire weather concerns will increase on Friday ahead of any potential tropical cyclone's arrival. Winds will begin to strengthen while a dry and stable air mass with low relative humidity moves overhead. This combination of lower relative humidity and increasing wind speeds will likely lead to high wildfire risk, though confidence is not high enough at this time to issue any fire weather headlines for Friday.
STRONG AND GUSTY WINDS, Winds could strengthen further on Saturday, though the timing, direction, and magnitude of the strongest winds remain highly dependent on the track and intensity of the system. With the past few cycles, the track forecast for Layla have nudged a bit farther south. However, even if the center of the system remains away from the islands, the north semicircle of the storm will still produce damaging winds. For now, confidence is highest in wind impacts for the Big Island and surrounding waters. Therefore, a Hurricane Watch has been issued for the Big Island and its surrounding waters. Although the official intensity forecast at this time from NHC keeps Lala as a high end Tropical Storm as it passes near the Big Island, there is enough uncertainty in the forecast to warrant the Hurricane Watch at this time.
HEAVY RAINFALL, This system could bring periods of heavy rainfall, particularly across east and southeast-facing slopes. Orographic enhancement could result in locally higher rainfall totals where moist tropical flow interacts with island terrain. If heavier rainfall persists over the same locations, flash flooding and rapidly rising streams are possible. Again, the location of heaviest rain and any bands that would move through the islands will be highly dependent on the system's track, which currently favors the highest rainfall totals for the Big Island and Maui County (though the remaining islands could also experience heavy rain bands as well). The current forecast has 5-10 inches of rain with locally higher amounts Friday through the weekend. As far as timing, heavy rainfall is currently forecast to impact the Big Island as early as Friday, spreading to Maui on Saturday, and Lanai, Molokai, Oahu, and Kauai on Saturday night into Sunday. A Flood Watch may be needed for at least portions of the state.
LARGE AND ROUGH SURF, Lala is expected to generate a large easterly swell as it moves northwestward. Surf may build along east-facing shores from east to west as the system approaches, with warning level surf of 15 feet or larger possible into the weekend.
In anticipation of critical new updates with each of the next few advisory packages issued by the National Hurricane Center (NHC), the NWS Honolulu will begin delaying the issuance of our typical forecast package products starting Thursday morning (AFD, SFT, PFM, ZFP, SPF, CWF, etc.) until after the release of NHC's suite of products to incorporate the latest and most up-to- date information on Tropical Storm Lala.
Breezy trade winds will gradually strengthen through Friday. Scattered showers will focus over mostly windward and mountain areas, especially during the evening/overnight hours. Some showers will spill over to leeward areas. Expect mostly VFR during the day with periods of MVFR especially during the overnight and in showers.
There are currently no AIRMETs in effect. However, AIRMET Tango may be needed later today for moderate turbulence immediately south and west of mountains due to strengthening low-level winds. Aviation interests should also monitor for updates on Tropical Storm Lala and its potential impacts to the islands.
High pressure to the far northeast will slowly drift into a position just north of the Hawaiian Islands into the weekend, producing moderate to locally strong trade winds across the region. The Small Craft Advisory (SCA) has been extended through afternoon for the windier waters and channels around Maui and the Big Island. As the high builds north of the state, the trade winds will strengthen tonight into Friday, which causes SCA conditions to expand to include the Kaiwi Channel and adjacent waters (Leeward Oahu and Windward Maui).
The weather pattern will change significantly by Friday night as Tropical Storm Lala, currently around 650 nautical miles east- southeast of the Big Island, approaches the region. The tropical storm moves into the offshore waters southeast of the Big Island on Friday, with winds beginning to ramp up for the coastal waters by Friday night. While the National Hurricane Center forecast depicts Lala as a high-end tropical storm passing near the Big Island, model guidance suggests some potential for the cyclone to reach category 1 hurricane strength. As such, a Hurricane Watch has been posted for the coastal waters surrounding the Big Island from Friday night through Saturday night to highlight the potential for winds to reach hurricane strength. After passing near the Big Island on Saturday, Lala is forecast to track west- northwest, with high confidence that the system remains south of the rest of the island chain. Therefore, marine interests throughout Hawaii should be prepared for possible tropical cyclone impacts, including strong winds and large swells, for both offshore and coastal marine zones lasting through the weekend.
A High Surf Advisory (HSA) is in effect for south and west facing shores as a long- period south swell peaks today and remains elevated tonight. This south swell energy may linger at advisory thresholds into Friday and then will slowly fade into Saturday. Another small reinforcement is expected late Sunday into Monday out of the south.
Surf along east facing shores will trend upward gradually through Friday with continued moderate to locally breezy trade winds which are forecast to increase out ahead of Potential Tropical Cyclone One-C. Additional swells generated by One-C are likely to arrive on Friday, but the main energy from the Potential Tropical Cyclone is expected this weekend and should produce surf heights exceeding warning levels along east facing shores. Based on the current forecast from the National Hurricane Center, dangerous surf conditions are expected around Maui and the Big Island on Saturday and around Oahu and Kauai Saturday night into Sunday.
High Surf Advisory until 6 AM HST Friday 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-Molokai West-Niihau-South Haleakala-South Maui/Upcountry-Waianae Coast.
Hurricane Watch for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Kohala-Kona.
Hurricane Watch for Alenuihaha Channel-Big Island Leeward Waters- Big Island Southeast Waters-Big Island Windward Waters.
Small Craft Advisory from 6 PM this evening to 6 PM HST Friday for Big Island Windward Waters-Kaiwi Channel-Maui County Windward Waters-Oahu Leeward Waters.
Small Craft Advisory until 6 PM HST Friday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Maalaea Bay-Pailolo Channel.
