Cold Front Brings Heavy Rain to Parts of the State January 17-19, 2021

A cold front supported by a low pressure system aloft produced heavy rainfall and flooding over portions of the main Hawaiian Islands. The cold front reached Kauai on Sunday, bringing with it intense, but fast moving showers. The front rapidly moved eastward through Sunday night before stalling over the northern portion of the Big Island on Monday. Moisture associated with the front then drifted westward over the islands from Maui to Kauai Monday and Tuesday.

The highest rainfall totals occurred along the windward slopes of Maui County and on Kauai with several peak totals exceeding 10 inches in 48-hours. Flash flood impacts included the closure of Kamehameha V Highway on south Molokai near Kamalo and Pukoo. On Maui, a road closure due to flooding occurred in Makawao, and rockslides were reported on the Honoapiilani Highway near Honokohau, and on several spots along the Hana Highway. Heavy rain on Kauai (some of it not captured in the listed rainfall totals) caused the closure of Kuhio Highway near Hanalei Tuesday afternoon.

The following are selected preliminary rainfall totals covering the 48-hour period ending at 8 AM HST Tuesday, January 19, 2021. All totals are in inches.

Location                                     Rainfall
...Kauai...
Kilohana (USGS)                              14.91
Waiakoali (USGS)                              6.37
Mount Waialeale (USGS)                        3.29

...Oahu...
Makaha Stream (USGS)                          8.34
Poamoho Rain Gage No. 1 (USGS)                7.07
Nuuanu Upper                                  6.80
Makua Ridge (BLM)                             5.36
Poamoho                                       5.28
Tunnel Rain Gage (USGS)                       5.18
Manoa Lyon Arboretum                          5.03
Niu Valley                                    4.14

...Molokai...
Puu Alii (NPS)                               16.11
Molokai 1 (DLNR)                              7.78
Makapulapai (NPS)                             1.88

...Maui...
Puu Kukui (USGS)                             10.85
West Wailuaiki (USGS)                         9.16
Pukalani                                      6.16
Wailuku                                       5.81
Hana Airport                                  5.77
Waikapu Country Club                          3.90
Kahakuloa                                     3.86
Lahainaluna                                   2.64
Kahului Airport                               2.54

...Big Island...
Mountain View                                 4.54
Honokaa                                       3.70
Kawainui Stream (USGS)                        2.29
Hilo Airport                                  2.05
Kamuela Upper                                 1.81