textproduct: Honolulu

SYNOPSIS

Breezy trades expected through the forecast period. Moisture will continue to fill in across the state from east to west into Friday increasing chances of showers mainly for windward and mauka areas. Chances of heavy rain, isolated thunderstorms and flood potential will increase Thursday into Friday as an upper level disturbance moves overhead. Drier air will move back in this weekend as trades continue. Moisture from the remnants of Tropical Depression 15-E may bring another round of enhanced trade showers early next week.

DISCUSSION

Radar and satellite imagery shows some scattered showers over windward and mauka locations across the state. Moderate trades were observed across the state. Moderate trades will increase today into the breezy levels.

An upper level trough will sink down over the state today and tonight just as the deepest surge of moisture from remnants of Norbert begin to move across the state. This will result in a sharp increase in moderate to heavy showers late tonight through early Friday. Instability will be sufficient for an isolated thunderstorm as well.

Moisture will decrease late Friday through the weekend. Latest guidance shows another area of increasing moisture (from the remnants of tropical depression 15-E) moving into the area Monday or Tuesday next week. The GFS shows better upper level support that could enhance the trade showers while ECMWF shows mid level ridging that could help limit heavy shower potential. Will continue to monitor all available guidance to determine exact impacts with future updates.

AVIATION

Moderate to locally breezy trade winds will strengthen to breezy levels this afternoon and a trough will approach the area from the east. Showers and low clouds associated with that trough will increase with the trade wind flow from east to west starting early tonight for the eastern half of the state, then spread west late tonight into tomorrow morning. More widespread MVFR conditions will be possible as the moisture associated with the trough moves in, especially for windward and mountain areas.

No AIRMETs are currently in effect. There is the possibility for AIRMET Tango during the afternoon once trade winds strengthen.

MARINE

A building ridge to the north of the Hawaiian Islands and broad low pressure south of the islands leads trades to increase to fresh to locally strong today. A Small Craft Advisory has been issued for the typically windy waters around the Big Island and Maui County through tonight. Locally strong winds may briefly diminish tonight into Thursday, but look to return later this week and last into the weekend. The remnants of Tropical Storm Norbert in combination with another weak low pressure to the south will bring isolated thunderstorms to area waters this afternoon through Saturday.

A series of long-period south to southwest swells will fill in through the rest of the week, leading to a gradual increase in surf for south-facing shores through the weekend. Surf is initially small today, but will trend upward toward the High Surf Advisory threshold by this weekend. Surf along east-facing shores increases today into Thursday as trade winds strengthen and a small, medium-period east swell from the remnants of Tropical Storm Norbert arrives. Flat to tiny surf along north facing shores is expected through the forecast period.

FIRE WEATHER

Fire weather risk should remain low through the remainder of the week due to moderate to breezy winds and increased relative humidity and moisture from the remnants of Norbert. Showers will dramatically increase late tonight through early Friday. Inversion heights will be around 7,500 to 8,500 ft.

HFO WATCHES/WARNINGS/ADVISORIES

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