textproduct: Honolulu

SYNOPSIS

Breezy trades will continue through Tuesday, bringing limited showers mainly windward and mauka. An upper level low will help weaken winds and turn them out of the southeast Wednesday, and showers will increase as moisture increases. Heavy rainfall may occur late Wednesday into next weekend.

DISCUSSION

High pressure north of Hawaii and a weak disturbance passing south of the area will result in breezy trade winds and stable weather through Monday. Scattered low clouds and isolated showers will move through the trade wind flow and primarily impact windward slopes, but rainfall accumulations will remain light.

Winds will weaken and veer southeasterly by late Tuesday, and south by Wednesday, as a sharp trough approaches from the northwest. A surface low will form along the trough and the southerly winds will draw deep tropical moisture over the islands from Wednesday night or Thursday through next weekend. PW values will increase to around 2 inches and dewpoints will rise to around 70 Thursday and into the lower 70s Friday. As this deeper moisture moves in, heavy rain will become likely. The exact trajectory of this moisture is not known with high confidence yet, but at this time it appears all the islands will be impacted. It will take a few more days for the models to converge on the location and evolution of the surface low, and that will help dictate where the moisture advection is maximized.

AVIATION

Moderate trades will continue through Monday with isolated showers across windward and mountain areas where short-lived MVFR conditions are possible.

Otherwise, VFR conditions will prevail across the state through at least Monday.

AIRMET Sierra for mountain obscuration will be cancelled as conditions have improved on the Big Island.

MARINE

High pressure north of the Hawaiian Islands will produce fresh to locally strong trade winds through Monday. The Small Craft Advisory for the windier waters and channels around Maui County and the Big Island has been extended through Monday afternoon. After this point, high pressure to the north weakens and trades will start to diminish. By Wednesday, troughing developing northwest of the islands is increasingly likely to cause winds to veer out of the southeast and bring increased shower activity for the latter half of the week.

Surf along south-facing shores will remain below average today. A new small, long-period south swell will slowly fill in tonight and Monday, with a peak slightly above average Tuesday into Wednesday. Near or slightly below average surf will hold through the rest of the week be maintained by a mix of new, small south swells.

A small, medium-period northwest swell will arrive tonight and peak Monday, producing a small bump in surf through Tuesday. Surf will continue to trend up for north shores as a slightly larger long-period northwest swell peaks Wednesday. Surf may approach moderate levels late in the week as a medium-period northwest swell further increases. Surf along east facing shores will be elevated and choppy through Monday due to the locally strong trades.

A small, long-period west swell originating from Typhoon Choi-wan is forecast to reach the islands Thursday into the weekend, which may produce moderate surf for west-facing shores of the Big Island.

FIRE WEATHER

Breezy trades will continue through Monday. RH values are forecast to hover just above the critical threshold for fire weather each afternoon through Tuesday. Fire weather risk then diminishes through the remainder of the week as moisture increases, winds decrease, and showers increase in coverage. The inversion should range from 6 kft to 8 kft through Monday.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory until 6 PM HST Monday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters.