Weaker Tropical Storm Darby Makes Landfall on Big Island of Hawaii

A weakened Tropical Storm Darby made landfall on the southern end of the Big Island of Hawaii on Saturday.  At 11:00 p.m. EDT on Saturday the center of Tropical Storm Darby was located at latitude 19.3°N and longitude 155.8°W which put it about 195 miles (310 km) southeast of Honolulu, Hawaii.  Darby was moving toward the west at 10 m.p.h. (16 km/h).  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were wind gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1006 mb.

Tropical Storm Warnings are in effect for Oahu, Hawaii County, Maui County including Maui, Molokai, Lanai and Kahoolawe, and Kauai County including Kauai and Niihau.

Air Force Reserve Hurricane Hunters investigated Tropical Storm Darby on Saturday and documented its weaker, less well organized structure.  Darby does not have a well formed inner core and the center of low pressure is broad and diffuse.  Most of the rain and thunderstorms are occurring south of the center of circulation.  The remnant of the primary spiral band consists of a short arc of thunderstorms southeast of the center of circulation.  There are few showers in the northern part of the circulation.

Tropical Storm Darby is moving toward water where the Sea Surface Temperature is near 28°C.  However, the center is moving over the Big Island of Hawaii, which will further disrupt the circulation.  Drier, more stable air is north of Darby and that will limit the potential for further convection.  If Darby retains sufficient organization after it moves back over water, it could continue as a tropical storm for another day or so.  However, if passage over land completely destroys the inner core, then Darby could dissipate during the next several days.

Tropical Storm Darby is nearing the western end of a subtropical ridge that has been steering toward the west.  When Darby reaches the end of the ridge, it is expected to turn more toward the northwest, which is why tropical storm warnings are in effect for a number of the Hawaiian Islands.   Locally heavy rain and the potential for flash flooding are the primary threats from Tropical Storm Darby.