textproduct: Honolulu

SYNOPSIS

A front that has stalled out in the vicinity of Oahu will hold its position through the afternoon before moving slowly back to the north and west tonight and Monday. This will bring continued chances for moderate to heavy rain to the western end of the state through tomorrow. The chance of rain decreases Monday night into Tuesday, but returns Tuesday night into Wednesday as the remains of the current front fuse with a new one and they move back into the western part of the state. Confidence in location is not as high with this next system, as guidance has trended away from bringing it as far east as Oahu.

DISCUSSION

Radar and satellite have shown repeated episodes of moderate to heavy rain moving over Oahu this afternoon, with lesser amounts over western Molokai and eastern Kauai. Rainfall amounts of 2 to just over 3 inches were recorded in the past 24 hours on Kauai, with over an inch in just the past 3 hours in several locations on Oahu. Moderate to heavy rainfall is likely over much of Oahu for the remainder of the afternoon and into tonight. A flood watch for flash flooding remains in effect for Niihau/Kauai/Oahu through late Monday night.

This first weakening front will recede westward tonight and Monday as a new front rapidly approaches from the northwest. The new front will combine with the remains of this current system and approach Kauai/Niihau Tuesday night. Latest model consensus is that this next front will not make it as far east (to/past Oahu) as the current one. It is too early to be sure, however. Folks from Oahu westward should remain alert to the possibility of another moderate/heavy rain event with potential flooding Wednesday through Thursday night.

Moisture is forecast to linger of the state with light winds later in the week and into next weekend. This could allow for yet additional showers and warm humid conditions.

AVIATION

A cold front is currently over Oahu with a slug of moisture riding up along it from the southwest. IFR/MVFR cigs and vsbys are widespread over Oahu due to the at times heavy showers. A few isol tstms are still possible. MVFR/VFR conds exist at the other sites with exception of Lanai which is also IFR. Moderate southerly winds are ongoing ahead of the front, with light and variable winds in its wake. Moderate southerly winds will build back across the entire state tonight as the front dissipates.

AIRMET Sierra in effect for mtn obsc for Kauai and Molokai.

AIRMET Sierra in effect for IFR conds for Oahu and Lanai.

MARINE

Winds have weakened behind a front that is presently positioned in the vicinity of Oahu. Winds become locally fresh out of the south late tonight through mid-week as another front approaches from the west. Gentle to locally moderate S to SSW winds are then forecast for the remainder of the forecast period. The Small Craft Advisory for elevated seas remains in effect for western waters.

Incoming large, medium period WNW (290-300) swell registered higher than anticipated at offshore NDBC Buoys 51101 and 51001 this afternoon prompting an upward revision to surf values for N and W facing shores of Kauai and Oahu and N facing shores of Maui as swell rapidly builds this evening. It is not out of the question that surf briefly touches the High Surf Warning threshold as it peaks overnight but uncertainty and borderline nature precludes an upgrade to a warning at this time. The surf forecast was likewise revised upward for W facing shores of Leeward Big Island where the 290-300 degree trajectory is favorable for building surf there by Monday morning. A High Surf Warning has been issued for these zones. A combination of moderate northwest and north swells will keep surf elevated through the week.

E facing shores remain tiny to small given the lack of trade winds but shorelines exposed to N swell energy may remain slightly elevated through Wednesday. Surf along S shores increases due to short period wind wave chop, mainly over the western islands associated with the passing front.

FIRE WEATHER

Weather conditions will remain below critical fire weather thresholds through the forecast period. Unsettled light to moderate southerly winds are forecast for the western half of the state, while more stable and drier easterly winds will continue over Maui and the Big Island. Temperature inversion heights near Maui and the Big Island will range from 7,000 to 8,000 feet today.

HFO WATCHES/WARNINGS/ADVISORIES

Flood Watch through late Monday night for Niihau-Kauai Leeward- Kauai Mountains-Waianae Coast-Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Kauai North-Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain-Koolau Windward-Koolau Leeward.

High Surf Advisory until 6 PM HST Monday for Niihau-Kauai Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kauai North-Molokai Windward-Molokai North-Molokai West-Maui Central Valley North-Windward Haleakala.

High Surf Warning from 6 AM Monday to 6 AM HST Tuesday for Kona- Kohala.

Small Craft Advisory until 6 PM HST Monday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel- Oahu Windward Waters.