textproduct: Honolulu

SYNOPSIS

Stable and dry conditions with light southeasterly background winds will continue into Wednesday. Expect daytime sea breezes and nighttime land breezes during this time. A weakening front will approach from the northwest, increasing chances of showers for the western islands Wednesday. Trade winds will build back into the region Thursday onward, returning a more typical trade wind pattern off passing showers along windward and mountain areas especially during the overnight to early morning hours.

DISCUSSION

Satellite imagery shows a band of clouds associated with a weakening frontal boundary roughly 500 miles northwest of Kauai early this morning. High clouds ahead of the front continue to break apart and thin out over the state. Meanwhile, a high pressure ridge remains in place over the island chain, which will result in yet another day of stable conditions and light southeasterly background winds. This morning soundings show inversion heights between 5 to 6 kft from Kauai to Hilo, respectively. Mainly scattered light showers can be seen passing over windward and mauka areas of the the Big Island and Maui early this morning. Given the light background flow, can expect daytime sea breezes to increased interior clouds over the islands this afternoon and clear tonight as land breeze circulations resume.

Global models continue to show the front mentioned above to gradually weaken as it approaches over the state through today and possibly moving over Kauai Wednesday before stalling. As this occurs, shower activity will likely increase over Niihau and Kauai for 12 to 24 hours, until the front breaks apart and slowly retrogrades westward away from the islands. Differences between the various global models remain, with the ECMWF notably showing wetter trends for the islands in Kauai County. The GFS, however, continues to favor a drier solution where the weakening boundary stalls and then moves back westward away from the state before reaching the Garden Isle. Mid and upper level ridging will remain over the state limiting cloud height, thus not expecting any significant heavy rainfall with this event.

A surface high pressure system northeast of the state will gradually build as the remnant weakens west of the state Thursday. This will strengthen wind speeds from east to west across the state and back winds to more of an easterly direction by Thursday night into next weekend. Expect more of a typical trade wind shower pattern to return during this time with brief passing showers forecast along windward and mountain areas, favoring the overnight to early morning hours each day.

AVIATION

A light south to southeasterly wind regime will continue into Wednesday as a front approaches the state from the northwest. Expect daytime sea breezes and overnight land breezes to occur. Mostly VFR conditions are expected under a relatively dry and stable air mass through today. Brief MVFR conditions are possible mainly along exposed windward areas this morning due a band of clouds and embedded showers moving through. Localized MVFR conditions may also occur along leeward and interior areas this afternoon as seabreezes develop. A thinning veil of high clouds will break apart as it moves west to east across the state today.

No AIRMETs are in effect and none are expected.

MARINE

A weak surface ridge will remain over the area today and maintain light to moderate southeast background flow. This pattern will allow for daytime sea breezes and nighttime land breezes along waters adjacent to the coasts. A cold front, currently around 400 NM northwest of the state, is forecast to approach Kauai on Wednesday, then stall and weaken into a trough by Thursday. The trough is projected to retrograde back westward, away from the state. Late Thursday through this weekend, a ridge of high pressure building north of the region will bring a return of moderate to locally strong easterly trades. A Small Craft Advisory may be need for the typical windier zones surrounding Maui and the Big Island.

The current moderate, medium period, northwest swell (310-330) will continue to slowly lose energy today. Thus, the High Surf Advisory was cancelled earlier this morning for all islands. A series of northwest to north- northwest (310-340 degree) swells are expected during the second half of the week, with each pulse becoming slightly bigger and veering with each passing day. The first pulse, a medium period northwest swell, will begin to fill in on Wednesday, and generate surf just shy of advisory levels. A slightly larger and longer period pulse is expected on Thursday out of the northwest followed by a slightly larger north- northwest on Friday. Surf heights should exceed advisory thresholds Thursday through through Saturday, with the peak approaching warning levels late Thursday into Friday. A Small Craft Advisory for combined seas (10+ ft) affecting exposed waters may be needed during the peak of the event.

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

FIRE WEATHER

Critical fire weather conditions are not expected this week. Although stable and dry conditions will persist through Wednesday, winds will remain below critical fire weather thresholds. Locally breezy trades will return during the second half of the week, but increased relative humidity is expected.

HFO WATCHES/WARNINGS/ADVISORIES

None.