textproduct: Honolulu

SYNOPSIS

A kona low northwest of Kauai will shift southward through Tuesday. Light to breezy southeastly flow will gradually strengthen from east to west across the state through tonight as the low moves just west of Kauai. This will keep showers and thunderstorms over the state for the next couple of days, leading to a continued threat of flash flooding. Winds will strengthen Monday into Tuesday. In addition, significant snow and ice accumulations are expected on the Big Island Summits over the next couple days. The low will weaken southwest of the state Tuesday through mid-week, allowing chances of thunderstorms and heavy rain to taper off. However, lingering moisture and weak upper level troughing could still keep chances of rain over the state through the week.

DISCUSSION

Radar and satellite clearly show the impact of the kona low across the area. Rainfall amounts over the last 6 hours have been significant, and a series of flood advisories have been issued, with some still in effect. As of 3 PM HST, showers and thunderstorms were widespread, with the strongest thunderstorms off the coast south and west of Kauai County. An area of showers and thunderstorms was moving north toward the state and is expected to move slowly across the area through the remainder of the afternoon and into tonight.

This kona low will continue to bring significant weather to the state over the next few days. As of 3 PM HST, the low was about 300 miles northwest of Kauai. It is forecast to move southwest and then back southeast, staying within a few hundred miles of the western end of the island through Tuesday. This low will bring more rain and thunderstorms, and a continued threat of flooding. The statewide Flood Watch remains in effect through Monday afternoon, and this may need to be extended into Tuesday. Winds will also increase statewide, becoming close to wind advisory levels in some coastal areas. At this time, confidence in winds meeting criteria over a large enough area is not high enough for a wind advisory.

Strong winds and snow/ice are expected on the summits of the Big Island over the next couple of days. Snow accumulations of greater than a half of a foot and heavy ice accumulations are possible. Summit roads have been closed. The High Wind Watch for the summits has been upgraded to a High Wind Warning, and a Winter Storm Warning was previously issued. Both of these are in effect from 6 AM HST Monday to 6 AM HST Tuesday.

Moisture has been drawn northward and PW values are going to continue to rise. Values presently around 1.7 inches are expected to rise to 2 inches Wednesday. Even though moisture rises, the best chance for flooding is through Monday (possibly into Tuesday) due to the proximity of the kona low and its associated cold air and lift aloft, along with enhanced low level convergence. The threat decreases as the low moves away from the state late Tuesday and then weakens considerably Wednesday/Thursday. Showers will remain in the forecast through the week. Low level winds will be easterly to southeasterly through Thursday before becoming light Friday into Saturday. This should allow for two days of sea- and land-breeze-dominated showers.

Next weekend, a band of strong westerlies aloft will move toward the state. A low far north of the area may push a cold front through late next weekend, and the deterministic models seem to be converging on this solution. But it is seven days out, so confidence is not that high.

AVIATION

A kona low to the west of the islands continues to bring clouds, showers and thunderstorms to the region. Expect such weather to continue into Monday night. This will produce MVFR conditions, with localized IFR conditions. Icing is possible in the layered clouds moving over the islands.

AIRMET Sierra for mountain obscurations remains in effect for most areas, and will continue through much of Monday. AIRMET Tango is in effect for turbulence in the mid to upper levels. The may be expanded to lower elevations Monday as surface winds increase. AIRMET Zulu is in effect for the possibility of icing.

MARINE

A kona low, now churning just outside the far northwest offshore waters, will continue a slow western movement the next few days. This low will and has introduced frequent periods of locally heavy rain, thunderstorms, and strengthening winds across both the offshore and nearshore Hawaiian waters. As the low tracks further west into Tuesday, east to southeast winds will strengthen to strong to local gale force, then slowly weaken Wednesday. In addition, seas will be building from 10 to near 15 feet across most nearshore waters by early Monday morning. Expect rough, elevated seas the next several days. A Gale Warning is in effect from Monday morning through early Tuesday morning for the Alenuihaha Channel. A Small Craft Advisory is in effect for the remaining waters through at least Tuesday evening.

A moderate, medium period north to northeast (020 degree) swell continues to subside through Monday. A small size, medium period northwest (310 degree) swell will arrive later Tuesday and hang on through Friday.

An easterly wind fetch generated by lowering pressures south and west of the islands will significantly increase easterly wind wave swell. This building east swell will impact most eastern facing shores of all islands through early Wednesday. This smaller period chop will reach advisory heights early Monday. A High Surf Advisory is in effect for all east-facing shores from Monday morning through early Wednesday morning.

The higher new year spring tide will hang on another day or so. Therefore, the Coastal Flood Statement has been extended through early Tuesday morning. Expect minor low lying coastal area flooding during Monday and Tuesday's early morning high tides.

HFO WATCHES/WARNINGS/ADVISORIES

Flood Watch through Monday afternoon for Niihau-Kauai Leeward- Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West- Maui Leeward West-Haleakala Summit-Kona-Kohala-Big Island Interior-Kauai North-Kauai East-Kauai South-East Honolulu- Honolulu Metro-Ewa Plain-Koolau Windward-Koolau Leeward-Molokai- Lanai Windward-Lanai Leeward-Lanai South-Maui Central Valley North-Maui Central Valley South-Windward Haleakala-Kipahulu- South Maui/Upcountry-South Haleakala-Big Island South-Big Island Southeast-Big Island East-Big Island North.

High Surf Advisory from 6 AM Monday to 6 AM HST Wednesday for Olomana-Kauai East-Kauai South-East Honolulu-Koolau Windward- Molokai Windward-Molokai Southeast-Windward Haleakala-Kipahulu- South Haleakala-Big Island Southeast-Big Island East-Big Island North.

Winter Storm Warning until 6 AM HST Tuesday for Big Island Summits.

High Wind Warning from 6 AM Monday to 6 AM HST Tuesday for Big Island Summits.

Small Craft Advisory until 6 PM HST Tuesday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay- Pailolo Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters.

Small Craft Advisory until 6 AM HST Monday for Alenuihaha Channel.

Gale Warning from 6 AM Monday to 6 AM HST Tuesday for Alenuihaha Channel.