Increased trade winds, combined with relatively dry conditions, will elevate the fire weather threat through Friday. 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 west-northwest towards the main Hawaiian Islands. A Hurricane Warning is in effect for Big Island and a Tropical Storm Watch is in effect for Maui County.
Late this afternoon, satellite and radar imagery show a few areas of low clouds and showers embedded within the trade winds moving into windward and mauka areas. However, rainfall has been light, with only brief light showers passing through. Mostly dry conditions are expected to continue through tonight and much of Friday as well, with windward and mauka areas experiencing scattered showers at times. Trade winds will gradually trend up, becoming breezy 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 5 PM HST, Tropical Storm Lala was located near 16.2N 147.5W and moving WNW around 10 knots (11 mph). Based on the latest forecast from the National Hurricane Center (NHC), Lala is expected to move near the southern end of the Big Island Saturday morning, then continue moving to the WNW, with the center of circulation remaining south of the smaller islands. Impacts from Lala are expected to begin for the eastern end of the state Friday night, and continue through the weekend. Please stay up to date on the latest forecasts, 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 approach critical fire weather criteria, but the forecast currently stays just below. However, strong winds can lead to extreme fire behavior even if RH values are not quite low enough to officially make criteria.
STRONG AND GUSTY WINDS, Winds will 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 Lala have nudged a bit farther south. However, even if the center of the system remains south of the coast, winds can still produce damage. For now, confidence is highest in wind impacts for the Big Island and surrounding waters. Therefore, a Hurricane Warning has been issued for the Big Island and its surrounding waters, and a Tropical Storm Watch has been issued for Maui County.
HEAVY RAINFALL, This system will bring periods of heavy rainfall. Orographic enhancement will 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 experience heavy rain bands as well). The current forecast has 10-15 inches forecast for eastern Big Island, and 5-10 inches over the remainder of Big Island and eastern Maui, with locally higher amounts possible. All islands will see an elevated risk of heavy rain and flash flooding. As far as timing, heavy rainfall is currently forecast to impact the Big Island as early as late Friday night, spread to Maui Saturday, and Lanai, Molokai, Oahu, and Kauai 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 continue delaying the issuance of our typical forecast package products (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 continue to strengthen and become locally strong by 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.
AIRMET Sierra remains in effect for windward locations of the Big Island due to mountain obscurations from passing low level clouds and showers. This AIRMET may need to be expanded overnight as shower coverage increases for all windward and mauka locations.
AIRMET Tango has been issued for moderate turbulence immediately south and west of mountains due to strengthening low- level winds and will likely continue for the next couple of days. As wind speeds strengthen overnight and Friday an AIRMET for strong winds greater than 30 kt may also needed to be added as Tropical Storm Lala approaches the island chain from the southeast.
Breezy trades continue strengthen as governing high pressure sags southward toward the islands and Tropical Storm Lala approaches from the east. The Small Craft Advisory remains in effect and is still scheduled to expand in coverage tonight as winds undergo a modest increase in strength.
NE wind associated with Tropical Storm Lala, presently about 500nm SE of Hilo, will undergo considerable strengthening Friday through Saturday with strong winds potentially expanding to the remainder of the state late Saturday into Sunday. A Hurricane Warning is now in effect for the Big Island surrounding waters and a Tropical Storm Warning has been issued for Maui County and surrounding waters. Dangerous conditions including torrential rainfall, a few thunderstorms, and high surf should be expected. Lala will track WNW through the weekend, clearing the western islands by Monday.
The High Surf Advisory remains in effect for S and W shores as long period S swell peaks today and remains elevated through tonight. Surf associated with this swell then begins to diminish as the period shortens. Another long period S swell arrives late Sunday into Monday bringing another boost to surf.
For E shores, surf initially trends slowly upward in association with gradually strengthening trades. Additional swells generated by TC Lala will arrive on Friday followed by the main energy arriving with the system itself this weekend. Surf along E facing shores is expected to exceed the High Surf Warning threshold during this time. Based on the latest forecast track and intensity from the National Hurricane Center, dangerous surf will develop 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.
Tropical Storm Watch for Haleakala Summit-Kahoolawe-Kipahulu- 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.
Flood Watch from Friday evening through late Saturday night for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Haleakala Summit- Kipahulu-Kohala-Kona-Maui Central Valley North-Maui Central Valley South-Maui Leeward West-Maui Windward West-South Haleakala-South Maui/Upcountry-Windward Haleakala.
Hurricane Warning for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Kohala-Kona.
Tropical Storm Watch for Kaiwi Channel-Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Pailolo Channel.
Hurricane Warning for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters-Big Island Windward Waters.
Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel- Maui County Windward Waters-Oahu Leeward Waters.
Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay- Pailolo Channel.
Small Craft Advisory until 6 PM HST Friday for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST Friday for Big Island Windward Waters.
