textproduct: Honolulu

SYNOPSIS

Easterly trade winds will continue to strengthen to breezy levels by tonight and hold through Tuesday. A remnant front moving in from the north will increase showers tonight into Tuesday with mainly light to moderate showers focusing along windward and mauka areas with periods of showers spilling over to leeward sides. A drier more typical locally breezy trade wind pattern is expected from Wednesday to Thursday. A cold front will become nearly stationary northwest of the state Friday into the weekend, veering winds out of the east southeast. This lighter pattern will allow for a hybrid trade wind and sea breeze regime to set up over the weekend. A wetter pattern shift may be possible early next week.

DISCUSSION

A storm force low far northwest of the state is sending some high clouds over the western half of the island chain this morning. A ridge of high pressure north of the state is generating locally breezy easterly winds across the state with limited low level clouds and showers along windward and mauka areas. Trade winds will strengthen to breezy levels speeds later this afternoon and early evening as the ridge continues to strengthen. A remnant band of clouds will push through the state tonight by these stronger easterly trade winds during this time. Expect increasing clouds and showers along windward and mauka areas with a few showers spilling over into leeward areas tonight into early Tuesday morning. Chances of showers will trend down through the day Tuesday after this band swiftly moves through the state.

The ridge of high pressure will weaken Christmas Eve through Christmas Day as the storm force low far northwest of the island lifts north. Trade wind speeds will gradually ease to locally breezy speeds during this time. Drier and more stable conditions will develop statewide as mid to upper level ridging develops over the state.

Friday the storm low will track east far north of the state with a trailing frontal boundary becoming nearly stationary northwest of Kauai by Friday. The proximity of this frontal boundary will place the weak surface ridge over the state veering winds out of the east southeast. Winds will become light to gentle over the western half of state while more locally breezy east southeast winds hang around the eastern half of the state. This setup will lead to a hybrid trade wind sea breeze pattern under a mostly dry and stable airmass as mid to upper level ridging holds over the state.

The extended range model guidance shows deep upper level troughing could lead to more instability developing over the western half of the state over the weekend into early next week. In addition, southerly flow at the surface will draw in more moisture, increasing chances of showers over the weekend into early next week. No significant weather is expected at this time but will continue to monitor for any changes.

AVIATION

The trade winds will gradually strengthen to breezy levels today across the state. AIRMET Tango will likely be issued later today for low level turbulence downwind of terrain as winds continue to strengthen. Increasing showers embedded within the trade winds will bring brief MVFR conditions to windward and mauka areas, especially this evening through early morning Tuesday. Otherwise, VFR will prevail.

There are no AIRMETs currently in effect.

MARINE

High pressure continues to build into the islands from the north, increasing easterly trade winds lasting into Wednesday morning. Trades then ease and wind directions will veer from a more southeasterly to southerly direction from Wednesday night onward as a low pressure system approaches from the northwest, driving the surface ridge axis over the islands. Briefly stronger winds are expected behind an old remnant frontal cloud band moving into Hawaiian waters from the north starting tonight through Tuesday. The Small Craft Advisory for the typical windier waters and channels near Maui and the Big Island remains in effect, this SCA will expand in coverage for most coastal waters starting tonight due to increasing trade wind speeds.

The current medium period north to north-northeast (360-020 degree) swell energy continues to slowly decline today and swell heights and periods are dropping at offshore and coastal buoys this morning. The forerunners associated with the next moderate north to north- northeast (360-020 degree) swell are forecast to arrive by late Wednesday, bringing moderate surf to favored northern exposures Wednesday night into Friday. Surf heights along west facing shores will be limited as the north-northeast swell direction and medium period swell energy is less favorable. A Marine Weather Statement may be needed for this next swell affecting north facing harbors possibly by Wednesday night, especially impacting the harbors of Kahului and Hilo.

Returning trades will build surf along E facing shores peaking with stronger trades on Tuesday. The north-northeast swell will likely boost choppy and rough surf heights a bit along east facing shores through Wednesday. Surf along south shores remains tiny with fleeting background south to southwest energy through the week.

HFO WATCHES/WARNINGS/ADVISORIES

Small Craft Advisory from 6 PM this evening to 6 PM HST Tuesday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters- Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters.

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