(BIVN) – Tropical Storm Lowell was 1,470 miles east-southeast of Hilo on Friday evening, moving slowly to the west near 7 mph.
Forecasters expect Lowell to strengthen into a hurricane as it gradually moves closer to Hawaiʻi.
Farther to the east is Tropical Storm Karina, which is also expected to become a hurricane over the Pacific. Karina does not appear to be tracking towards the Hawaiian islands at this time, the National Hurricane Center website shows. However, Karina could have a major influence on the future development of Lowell, and whether or not Lowell becomes a threat to Hawaiʻi.
“The tropics remain remain active with the primary focus at the moment being Tropical Storm Lowell,” the National Weather Service in Honolulu stated at 3 p.m. Friday. “This system is forecast by NHC to become a hurricane this weekend. Even though it is already around 135W, or about 1500 miles SE of Hilo, weak steering winds delay any potential arrival to/around the Hawaiian islands to beyond the 7 day forecast period.”
The National Hurricane Center provided this detailed analysis at 5 p.m. HST:
Lowell remains a sheared tropical cyclone this afternoon. Moderate easterly vertical wind shear continues to displace the bulk of the convection over and west of the low-level circulation center. There has been little evidence of strengthening during the past several hours, and a blend of the latest objective intensity estimates and subjective Dvorak intensity estimate from TAFB support holding the initial intensity at 40 kt for this advisory.
The cyclone continues to move slowly westward, with an initial motion of about 275/5 kt. A low- to mid-level ridge is forecast to strengthen north of the cyclone during the next couple of days, which should cause the cyclone to continue westward with a gradual increase in forward speed. This general westward motion is expected to continue through the weekend and into early next week. Track forecast uncertainty increases considerably thereafter due in part to the potential influence on the steering flow from TS Karina to its northeast. There remains considerable spread in the guidance, particularly in forward speed, with the multi-model consensus (HCCA) and Google DeepMind ensemble mean generally faster than the GFS and ECMWF solutions. In addition to the along-track spread, the cross-track spread also increases considerably by day 5. Given these differences, the latest NHC track forecast reflects a blend of the previous forecast, Google DeepMind ensemble mean, and HCCA.
The easterly vertical wind shear currently affecting Lowell is forecast to hold into the weekend, then steadily decrease by the latter half of the weekend, which should allow the cyclone to become better organized and gradually strengthen. However, the current sheared structure and nearby mid- to upper-level dry air should temper the rate of intensification in the short term. Environmental conditions are forecast to become more favorable thereafter, and a faster rate of strengthening is possible beginning by early next week. The intensity forecast becomes more uncertain later in the period due to Lowell’s potential interaction with Karina. A faster westward track would likely keep the cyclones sufficiently separated and allow Lowell to continue strengthening, while a slower solution could expose Lowell to stronger shear associated with outflow from Karina. The latest NHC intensity forecast is similar to the previous advisory and continues to show Lowell becoming a hurricane in about 60 h.
