textproduct: Honolulu

SYNOPSIS

Light winds prevail across much of the state, maintaining a dry. mostly stable land and sea breeze regime. A slow-moving frontal passage will stall just west of Kauai today, resulting in enhanced shower activity and increased cloud coverage across much of the Garden Isle through this evening before the front weakens to a trough and retrogrades back westward and dissipates. High pressure builds northeast of the state, allowing moderate trades to return Thursday as well as showers across windward and mauka areas.

DISCUSSION

Light winds prevail maintaining stable and mostly dry conditions, allowing a land and sea breeze pattern to dominant across the Hawaiian Islands. The highlighted feature remains to be a slow- moving frontal passage northwest of the islands that continues to propagate toward Kauai. Latest model guidance of the GFS and ECMWF are now seemingly in fairly decent agreement that the front will ultimately stall just west of Kauai. That said, pre-frontal shower activity, especially over northern slopes and interior areas of the Garden Isle could experience over an inch of precipitation prior to the front weakening to a trough and retrograding back westward in the absolute wettest scenario. The latest Total Precipitable Water (PWATs) Normalized Anomaly from the GFS and ECWMF both depict roughly 1 to 2 standard deviations above normal over Kauai as the front approaches. This isn't implying a widespread heavy shower event, but it is suggesting that, even though the front is anticipated to stall west of Kauai, it may very well still bring in a significant amount of moisture.

With models lining up a bit better than previous runs, confidence has increased that this will be the most likely scenario as the front crawls towards Kauai. Meanwhile, the remainder of the state will remain unimpacted under the same dry, mostly stable land and sea breeze regime through the next couple of days.

The aforementioned front has also has an impact on retaining the subtropical ridge near Kauai, leading to predominately southeasterly background flow, as depicted by the latest observations. As a result, this has escorted some volcanic emissions (vog) from the most recent Kilauea activity across portions of the state. While many of the air quality sensor, particularly across leeward Big Island show slightly higher concentrations, the overall consensus showcases the highest concentrations remain in the offshore west of the state and are not significantly impacting the islands themselves. Moreover, visibility does not seem to be restricted much either, though some haze may still persist in low-lying areas.

By Thursday, the broad surface-level high pressure system well northeast of the islands will gradually build as the weakened frontal passage begins to dissipate. Trades will respond accordingly to the tightened pressure gradient, strengthening to a more moderate pattern, further pushing away any of the remaining deeper moisture away from Kauai. Conversely, expect a more typical trade shower pattern mainly over windward and mauka areas across the state, prevailing through early next week.

AVIATION

Light winds persist resulting in daytime sea breezes and overnight land breezes to occur. A slowly advancing front is expected to stall just west of Kauai, resulting in enhanced shower activity and increased cloud coverage which may bring periods of MVFR conditions predominately to northern slopes and interior areas of Kauai. Moderate trades return toward the end of the forecast period, focusing showers across windward and mauka areas. Otherwise, VFR conditions prevail.

No AIRMETs are in effect and none are expected.

MARINE

A cold front approaching from the northwest is expected stall west of Kauai today, before weakening to a trough Thursday and retrograding back to the west. Thursday through this weekend, a ridge of high pressure is expected to strengthen northeast of the region, which will allow moderate to locally strong easterly trades. As trades increase, a Small Craft Advisory (SCA) will likely be needed for the typical windier zones surrounding Maui and the Big Island. A moderate to large NW swell could also bring seas to SCA criteria (10 feet) Thursday night into Friday. So at this time, a SCA for winds to 25 kt and seas 10 feet or higher look likely by Thursday afternoon.

The current moderate, medium period northwest swell (310-330) has been holding overnight at the nearshore buoys. Meanwhile the next swell (310-330) reached Buoy 51101 to the northwest of the islands around 8pm. This swell is expected to reach Kauai around sunrise, and Oahu a little later in the morning. This is the first in a series of northwest to north-northwest (310-340) swells that are expected over the coming days. This swell will be reinforced by another on Thursday that should bring surf to advisory levels Thursday into Friday. Another slightly larger northwest swell is expected to arrive on Friday, which will maintain the elevated surf.

East shore surf will remain small today due to weak winds, then become choppier by Thursday as trade winds increase from Thursday through the weekend. Expect minimal background energy for south facing shores through much of the week.

There is the potential for minor coastal flooding from December 4th to December 6th. Peak monthly tides combined with water levels that are running higher than predicted could lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible around the daily peak tide, which will be during the early morning hours. This could also magnify effects of the expected high surf on coastal areas around the same time frame.

FIRE WEATHER

Critical fire weather conditions are not expected this week. Light winds persist through the day, with increased rainfall probability on Kauai associated to an advancing frontal passage. Elsewhere across the state will remain dry and mostly stable. Moderate trades will return under critical fire weather thresholds thereafter and prevail through early next week. The temperature inversion heights over Maui and the Big Island will range from 6500 to 7500 feet today.

HFO WATCHES/WARNINGS/ADVISORIES

None.