Marine Weather and Tide Forecast for Lahaina, HI

DISCUSSION
This morning's satellite and radar imagery shows a plume of moisture moving in across the state this morning. Most of the shower activity has been over windward areas this morning, but we should see some showers over leeward areas as well especially this afternoon. A surface high far north of the state will maintain moderate trade winds through Monday. Meanwhile in the upper levels, we do have a weak trough aloft that should produce some unsettled weather today. With the added moisture and some instability aloft, I would not be surprised to see an isolated thunderstorm especially over the Big Island slopes this afternoon. Elsewhere across the state, some brief downpours will be possible especially during the afternoon and evening hours.

On Monday, we should see a typical moderate trade wind day as the upper level trough shifts away from the state and a drier air mass moves in the lower levels of the atmosphere.

Starting Tuesday, we should see an upper level low northwest of the state drop further southward, which will cause the trade winds to weaken and veer toward the south. Light to moderate southeast to south winds over the state will bring increasing showers across the state with a large gradient in rainfall expected between the western end of the state and the eastern end. The Island of Kauai will be the closest to the low pressure system and should see the greatest rainfall from this event. This is in line with the latest QPF guidance from the ensemble models. Flash flooding will be the main concern and a Flood Watch will likely be needed for Kauai and possibly Oahu during the Tuesday through Wednesday time frame and possibly lingering into Thursday. Heavy downpours with isolated thunderstorms should be expected over the western half of the state during this time. For rest of the state, scattered showers with some moderate rainfall totals will be possible. By Friday, the upper level low should lift further north and away from the state which should bring the return of stable conditions, although trade winds may not return till later in the weekend.



AVIATION
Moderate trades will persist through today and weaken slightly heading into Monday, ushering clouds and showers into windward and mauka areas. However, winds will be light enough to support isolated sea/land breeze development that will bring additional clouds and showers to some leeward and interior areas during the afternoon hours and clearing of these areas overnight. MVFR conditions will be possible in any showers, otherwise VFR conditions should prevail.

No AIRMETs are currently in effect.



MARINE
Moderate to locally fresh easterly trade winds will ease on Monday and veer southerly for Tuesday through Friday. Trades will decline slightly on Monday as a 1040 mb high, currently centered far northeast of Hawaii, weakens and surface trough develops about 650 nm northwest of Kauai. On Tuesday, the trough will deepen into a low about 500 nm northwest of Kauai, causing moderate winds to veer out of the south across most waters, with moderate to fresh southeast winds developing around the Big Island. A band of deep moisture associated with the low will bring a chance of heavy showers and thunderstorms, mainly over the western half of the island chain.

Small surf will prevail along north shores through much of the week. Nearshore PacIOOS buoys are showing a north-northwest swell of around 3 feet at 12 seconds this morning. As this swell fades Monday night, another tiny northwest swell will fill in and maintain small surf into Wednesday. Minimal surf is expected later Wednesday through Friday, followed by another small pulse of northwest swell next weekend.

South shore surf will be near April average through tomorrow, followed by a larger south-southwest swell on Tuesday. The PacIOOS Kaumalapau buoy is showing the current swell at around 2 ft 15 seconds this morning. The swell hold tomorrow then decline on Tuesday as a larger swell builds. Surf along south facing shores is expected to rise above summer average heights through Wednesday, then decline through Friday.

Small surf along east facing shores will hold at current heights through Monday, then drop further by mid week as southerly winds develop.

HFO WATCHES/WARNINGS/ADVISORIES
None.