Flooding downpours hammer Hawaii as Kilo nears

By AccuWeather

While Kilo will not make its closest approach to Hawaii until midweek, potentially flooding downpours are already a concern across the state.

Honolulu received nearly 3 inches of rain in less than 12 hours on Sunday local time.

Residents and visitors will need to monitor the strength and track of Tropical Depression Kilo, currently spinning southwest of the Hawaiian Islands.

As of 8 a.m. HST Sunday (2 p.m. EDT Tuesday), Kilo was a tropical depression and located about 730 miles southwest of Honolulu, Hawaii.

The combination of shallow warm water and low wind shear could allow Kilo to re-strengthen into a tropical storm and perhaps a minimal hurricane this week.

While the west to northwest track makes it seems like the tropical depression is tracking away from Hawaii, Kilo is expected to curve back toward the islands on Tuesday.

Whether or not Kilo aims at Hawaii later in the week or makes another turn back to the northwest will determine if significant impacts of damaging winds and coastal flooding reach Ni'ihau, Kaua'i and Oahu.

Current indications point toward Kilo turning back away from the islands following a midweek approach, but that solution is not etched in stone.

"We cannot rule out any scenario at this time," AccuWeather Meteorologist Dave Samuhel said. "Until it strengthens, computer models may struggle to handle the future track of Kilo."

Even with Kilo spinning several hundred miles away, downpours indirectly linked to Kilo will persist through at least the first half of this week.

According to AccuWeather Senior Meteorologist Alex Sosnowski, at this point Kilo is sort of an afterthought.

"High pressure over the northern Pacific has pushed a front to just north of Hawaii and has enhanced the plume of tropical moisture to the south," Sosnowski said. "This moisture will likely hold around Hawaii much of this week, regardless of the track of Kilo."

Humidity levels will remain uncomfortable, and showers and thunderstorms will occur daily, including over the drier leeward areas.

Enough moisture is present for some downpours to be unleashed, potentially leading to flash flooding and mudslides. The flood risk will only increase as the wet weather persists and the ground becomes saturated.

Even if flash flooding does not ensue, the downpours threaten to make travel difficult by reducing visibility and heightening the risk of vehicles hydroplaning at highway speeds. Residents and vacationers may have to alter their outdoor plans.

The downpours are not entirely bad news for Hawaii.

"Except for the east-facing slopes of the islands, much of the island chain could stand a thorough soaking, shy of flooding rainfall," Sosnowski said. "Portions of all of the islands are either abnormally dry or in moderate drought, according to the United States Drought Monitor."

In addition to the downpours, surf along the south-facing shoreline of the islands will gradually build through the week as Kilo strengthens and approaches.

AccuWeather.com will continue to provide updates on Kilo and other tropical systems through the week.

Should Kilo drift northward and wander very close to the islands, it could greatly enhance the already existing rainfall.

A northward track is uncommon for systems to take in the central Pacific.

According to AccuWeather Meteorologist Brian Lada, typically, tropical systems approach Hawaii from the east.

"Storms that move in from the east tend to weaken considerably before reaching the Big Island," Lada said.

El Niño years are a reason for concern for possible tropical storm and hurricane strikes on Hawaii.

During El Niño, it is not uncommon for there to be a higher-than-normal number of tropical systems in the central Pacific due to the warmer waters of the Pacific Ocean.

This means that Hawaii could face a few more tropical threats heading into the fall before the tropical cyclone season in the central Pacific comes to an end.

A few systems have hit Hawaii from the south. These tend to have much more impact. Hurricane Iniki was the strongest tropical system to ever hit Hawaii.

Kilo is not the only tropical system roaming the central Pacific. Tropical Storm Loke is spinning well to the west of Hawaii and will not impact the state.

"At this point, we do not expect this system to impact any landmasses, except for the remote Atolls near Midway," stated AccuWeather Meteorologist Evan Duffey.

"Counting Kilo and Loke, there have been five tropical systems that have developed over the waters of the central Pacific, meaning that it will only take one more system to make 2015 an above-normal year for tropical cyclone activity," added Sosnowski.

The pattern over the next couple of weeks is loaded with the potential for additional tropical system to form in or move into the Central Pacific basin.

"While the track of the additional systems is uncertain this far out, it will keep the possibility of rainfall rather high through the middle of September," Sosnowski said.