Unusual Late Season Kona Low Drenches Portions of the Hawaiian Islands


...LATE SEASON KONA LOW BRINGS HEAVY RAINFALL TO PORTIONS OF THE 
STATE OF HAWAII...

An unusal late season kona low has produced heavy rainfall over
portions of the state during what is normally the start of the
Hawaiian Islands dry season. This appears to be the latest kona
low to directly affect the main Hawaiian Islands in at least the
last 20 years. The last impactful kona low in May was during 2002. 
Kona lows more typically affect the State of Hawaii from November 
through March.

The kona low developed several hundred miles north of Kauai on May 
15, then moved west and strengthened on May 16. The main rain band 
from the system moved over Oahu during the early morning hours of 
May 16, with cells of northward-moving heavy rain moving over the 
island over the next 24 to 36 hours.

Impacts mainly included minor flooding of streets in multiple
areas of Oahu. A rockslide also occurred near the Pali Highway
Tunnels on May 16. Gaged streams indicated elevated flow levels,
but none overflowed their banks.

The event is ongoing as of this statement. The main rain band has
moved west off of Oahu and is approaching Kauai. A potential for
flash flooding will persist for Kauai and Niihau through Saturday
night.

The following are notable automated rain gage totals for the 2-day 
period (48 hours) ending at 8 AM HST, May 17. All amounts are in 
inches. These totals are considered preliminary for information 
purposes only.

Location                            2-day total

Oahu

MAUH1 Maunawili                       10.84
STVH1 St. Stephens                     9.68
LULH1 Luluku                           9.11
WMLH1 Waimanalo                        8.31
WAWH1 Waiawa Corr. Fac.                7.98
WPPH1 Waihee Pump                      6.88
AHUH1 Ahuimanu Loop                    6.83
MITH1 Mililani                         6.47
KMHH1 Kamehame                         6.43
MKHH1 Makaha Stream (USGS)             6.37
PFSH1 Palolo Fire Station              6.35
KTAH1 Kahuku Training Area             5.50