11 AM: Excessive Rainfall Possible Into Weekend

A Hurricane Warning remains in effect for O‘ahu, Maui County including the islands of Lana‘i, Moloka‘i and Kaho‘olawe.

A Tropical Storm Warning is in effect for Hawai‘i County.

A Tropical Storm Watch is in effect for Kaua‘i County including the island of Ni‘ihau.

“Hurricane Lane continues to pose a serious risk of life-threatening wind and water hazards to all of the Hawaiian Islands, as it moves very slowly, and dangerously close to the island chain,” said Dr. Rick Knabb, hurricane expert at The Weather Channel. “Even if landfall of the center does not occur, wind and water hazards will extend far outside of the track forecast cone of uncertainty. Heavy rainfall—with storm totals that could be measured in feet and not just inches—could cause devastating flash floods on any of the islands during the next few days, even on Sunday and beyond after the storm is forecast to be moving away. Winds of at least tropical storm force during the next couple of days could cause long-lasting power outages and some damage.”

Hazards affecting land:

WIND: Tropical storm conditions are already occurring on the Big Island, Maui County and O‘ahu. Hurricane conditions are expected over portions of of Maui County and O‘ahu starting tonight. Tropical storm conditions are possible on Kaua‘i starting Saturday.

RAINFALL: Rain bands from Lane will continue to affect the main Hawaiian Islands with excessive rainfall possible into the weekend. These rains could lead to additional major flash flooding and landslides. Lane is expected to produce total rain accumulations of 10 to 20 inches in some areas. Localized storm total amounts up to 40 inches are possible, mainly on the windward side of the Big Island where over 30 inches of rain has already fallen in some areas.

SURF: Very large swells generated by the slow moving hurricane will severely impact the Hawaiian Islands into this weekend. These swells will produce life-threatening and damaging surf along exposed shorelines, particularly today through Saturday. In addition, a prolonged period of extreme surf will also likely lead to significant coastal erosion.

STORM SURGE: The combination of a dangerous storm surge and large breaking waves will raise water levels by as much as 2 to 4 feet above normal tide levels along south and west facing shores near the center of Lane. The surge will be accompanied by large and destructive waves.

Lane continues to struggle against 30 to 40 kt of southwesterly shear as analyzed by the UW-CIMSS shear analysis. The CDO continues to be very asymmetric and elliptical. Radar, lightning data, and 1645z Windsat pass indicated that the active convection has been shunted to the northwest through north of the low level circulation center, indicating that the core of the tropical cyclone is getting torn apart by the shear. Subjective current intensity estimates were unanimous at 5.0, and CIMSS-ADT had 5.1. The initial intensity was lowered to 90 kt for this advisory.

The initial motion estimate a rather uncertain 360/4. The changes to Lane’s structure make the near term track forecast very difficult, as the steering layer will be rapidly evolving in the short term. The proximity to island terrain makes the steering flow even more complex, at least until the vortex completely seperates from the persistent convection as a shallow low level circulation. Until then, the motion is likely to be somewhat slow and erratic.

The reliable track guidance suggests a slow north or north-northeastward drift for the next 12 hours, followed by an abrupt shift toward the west at some point afterward. The consensus models show a general westward motion from 24 through 96 hours, then turning more toward the northwest. The only significant change to the track forecast during this time was to slow Lane’s forward motion. If anything is left of Lane between 96 and 120 hours, the low level circulation may gain latitude and try to merge with a large upper low over the Northwestern Hawaiian Islands.

As long as Lane can maintain central deep convection, the weakening trend will remain more gradual. More rapid weakening will commence within 12 to 24 hours, once the convection is no longer able to remain anchored to the low level circulation center. All of the guidance indicates rather rapid weakening in the near term, and our forecast agrees though is at the high end of the guidance in deference to Lane’s persistent core. Although the current forecast retains Lane as a tropical cyclone through 5 days, it’s very possible that Lane will not last that long as the low levelcirculation crosses underneath a band of very strong wind shear.