Tropical Depression Kilo Struggles in Central Pacific; May Still Threaten Hawaii

August 21,2015

• Tropical Storm Kilo was downgraded to a tropical depression as of 11 p.m. EDT Friday (5 p.m. HST)
• This system was located about 580 miles south-southeast of Honolulu.
• While the intensity forecast is a bit uncertain, there is still a possibility that Kilo could eventually become a hurricane.
• Kilo is likely to be pulled northward toward the Hawaiian Islands early next week, but the timing of that northward turn is somewhat uncertain. Interests in Hawaii should monitor the progress of this system very closely.

(MORE: Expert Analysis | Hurricane Central)

Storm Information and Satellite

Tropical Storm Kilo formed early Friday morning in the central Pacific and remained a minimal tropical storm through most of the day. Some weakening was noted, as Kilo was downgraded to a tropical depression with the 11 p.m. EDT Friday advisory.
One of two scenarios is possible with Kilo. If Kilo continues to degenerate, it could become a remnant low this weekend. It is not uncommon for central Pacific tropical systems to suddenly weaken and dissipate. On the other hand, Kilo may still be able to better organize. The latest National Hurricane Center forecast continues to strengthen Kilo to a hurricane in the coming days.
Since the sea-surface temperatures are favorable for intensification and most of the computer guidance shows a strengthening trend, it seems plausible that Kilo could still eventually become a hurricane.
(MORE: Twin Typhoons in the Pacific)
Even with the unclear intensity forecast, Hawaii needs to watch this one. Kilo may get pulled northward later this weekend into early next week as a hurricane. However, uncertainty remains with exactly where this northward turn may occur and how organized the system may be at that time. These factors will dictate what impacts the populated parts of Hawaii may see.
The official forecast curves the storm northward soon enough to bring impacts of Kilo into parts of the Hawaiian Islands. However, the forecast has shifted a bit farther west, as have many of the track models used to guide forecasters. The center of Kilo may pass far enough west that among the inhabited Hawaiian islands, only Kauai and Niihau might be affected.
However, it's too early to take impacts off the table for Oahu, Hawaii's most populated island with nearly 1 million inhabitants.

Projected Path

The geography of Kilo's future path is not the only question. The timing and strength are also subject to some uncertainty.
A well-established upper-level low pressure system and vigorous southern branch jet stream remains in place near the islands. That subtropical jet will have to at least weaken or pull north to avoid ripping this system apart. Visible satellite imagery Friday showed Kilo was still very poorly organized, with just some scattered low clouds swirling near the center of circulation while the vigorous thunderstorm activity was detached well to the west of the center.
However, virtually all hurricanes near the Hawaiian Islands since 1950 have approached from the southeast, south, or southwest. Based on the CPHC forecast and much of the computer model guidance, Kilo could be a Category 2 or Category 3 hurricane upon its closest approach to the Hawaiian Islands.
In El Nino years, the trade winds that sometimes trap tropical cyclones well south of the islands relax, making these lingering storms south of the islands more susceptible to be drawn northward. Of course, an El Nino does not guarantee a hurricane will impact Hawaii.
(MORE: Hawaii's Hurricane History)
There is, of course, the question of when Kilo might impact Hawaii. The forecast has slowed a bit in that regard, bringing Kilo's center west of Kauai on Wednesday. However, it's still plausible that the storm could arrive as early as Tuesday of next week in that area.
Kilo is the fourth named storm to have formed in the central Pacific basin this season and the sixth to track through the basin this year, including eastern Pacific storms Guillermo and Hilda.
Four to five tropical cyclones typically form in the central Pacific each year, according to the Central Pacific Hurricane Center. CPHC says a record 11 named storms formed in 1992 and 1994.
(FORECASTS: Honolulu | Hilo | Kona Coast | Maui)
NOAA's 2015 Central Pacific hurricane season outlook cited El Nino's tendency for reduced wind shear and more storm tracks coming from the eastern Pacific as reasons to expect an active season in the central Pacific Basin.
Lowry says dating to 1950, there is a 13 percent increase in the chance of a named storm to track within 100 miles of the Hawaiian Islands during an El Nino year compared to a neutral year.
Stay tuned to The Weather Channel and check back with weather.com for updates on this system.

MORE: Hurricane Iniki, 1992