(BIVN) – A Hurricane Warning has been issued for Hawaiʻi island, replacing the Hurricane Watch that was previously issued due to the approaching Tropical Storm Lala.
Tropical Storm Lala was 555 miles east southeast of Hilo as of 5 p.m. on Thursday evening. Lala was moving west northwest at 12 mph.
Lala is expected to strengthen into a hurricane as it nears Hawaiʻi on Saturday. Heavy rainfall will begin to impact the Big Island on Friday.
The National Weather Service listed these potential impacts:
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.
Forecasters noted the situation could be somewhat favorable for tornadoes, as well.
From the Central Pacific Hurricane Center discussion at 5 p.m. HST:
Lala continues to steadily intensify. While the associated central convection has changed little over the past several hours, aircraft data show that the peak 700 mb flight-level winds have increased to 61 kt, and the pressure has dropped to 997 mb, although with a surface dropsonde wind of 49 kt. Based on these data, the initial intensity is raised to 50 kt for this advisory.
The initial motion estimate is west-northwestward, or 295/10 kt. The overall track forecast philosophy remains largely unchanged. A strong mid-level ridge north of the Hawaiian Islands should continue to steer the cyclone west-northwestward during the next several days. The cyclone’s forward motion is forecast to slow somewhat as it approaches and begins to interact with the terrain of the Big Island on Saturday. Some short-term deviations in the track are also possible during this time due to these terrain interactions. Lala should then resume a faster west-northwestward motion as it passes south of the smaller islands through the remainder of the weekend, and south of the Northwestern Hawaiian Islands Sunday night into early next week. The latest NHC track forecast is very similar to the previous advisory, except for a slight northward adjustment in the lee of the Big Island, and lies close to the multi-model consensus (HCCA) and Google DeepMind ensemble mean.
Environmental conditions are expected to remain generally favorable for strengthening during the next couple of days, with the primary limiting factor being the dry mid-level air that continues to be entrained into the cyclone’s large circulation. Steady strengthening is forecast, and Lala is expected to become a hurricane as it approaches the Big Island on Saturday. Interaction with the terrain of the Big Island could result in short-term changes in the cyclone’s structure and intensity during its closest approach. Thereafter, an upper-level low is forecast to produce increasing vertical wind shear with increasing dry air continuing to entrain into the circulation as Lala passes south of the smaller islands, which should result in some weakening through the remainder of the weekend. Re-strengthening is forecast early next week as the cyclone moves away from the Hawaiian Islands and into a more favorable environment. The latest NHC intensity forecast is similar to the previous advisory and remains near the middle to upper end of the guidance envelope.
