textproduct: Honolulu

SYNOPSIS

Moderate to locally breezy trades will persist through much of the week as high pressure remains anchored north of the state. A dry and stable air mass will keep windward showers sparse and leeward areas mostly dry. Trades may ease briefly late this week before strengthening again next weekend as high pressure rebuilds to the north. Tropical systems far east of the state will be monitored, but pose no immediate impacts to the islands.

DISCUSSION

Broad surface high anchored well north of the Hawaiian Islands remains the dominate synoptic feature through much if the forecast period. This pattern will support moderate the locally breezy trades through the next several days. Trades are expected to ease slightly late this week as the surface high weakens and shifts northeastward, though this lull should be brief. Guidance continues to indicate the high will rebuild and strengthen during the latter half of the forecast period, allowing trades to increase once again.

Despite the persistent trade wind regime, typical embedded trade showers will remain limited as a notably dry air mass persists across the state. Water vapor imagery continues to depict widespread low- to mid-level dry air, and forecast precipitable water values remain around 1 to 2 standard deviations below climatological normals through much of the upcoming week. However, some model guidance is hinting at a modest uptick of moisture Tuesday into Wednesday of next week, but total accumulation is expected to still be sparse. Overall, rainfall will generally favor isolated, light windward and mauka showers, with leeward areas remaining predominately dry.

Forecast confidence beyond the middle of the next week becomes increasingly dependent on the evolution of the tropical disturbances currently located well east of the Central Pacific near the Mexican coast. While deterministic and ensemble guidance suggests some westward progression, it remains far too early to determine whether any of these systems or their associated moisture will influence the Hawaiian Islands. At this time, no changes to the sensible weather forecast are warranted, though these tropical features will continue to be monitored closely over the coming days as forecast confidence increases.

AVIATION

Moderate trades will continue through the forecast period. Clouds and isolated to scattered showers will remain over windward and mauka locations. Conditions will be VFR apart from isolated MVFR over windward and mauka areas in clouds and showers.

No AIRMETs are in effect.

MARINE

Fresh to locally strong trades will continue today, and a Small Craft Advisory (SCA) remains in effect for the typically windy waters around Maui and the Big Island through 6 pm. The trades will ease tonight and Monday as high pressure north of the islands weakens, with the trades then holding at moderate speeds through Tuesday. The trades will restrengthen back to fresh and locally strong speeds Wednesday and Thursday as high pressure strengthens north of the island chain.

Surf along south facing shores will remain a bit below the summertime average today. A larger, south swell is expected to build late today and tonight, then peak around the advisory level Monday into early Wednesday. A High Surf Advisory will likely be required for south facing shores of all islands later today or tonight. As this swell slowly fades during the middle of the week, a new long period south swell will arrive on Thursday, keeping surf elevated through next weekend.

Surf along north-facing shores will remain at flat to tiny levels through next weekend.

Surf along east facing shores will remain close to seasonal levels today, then lower slightly Monday through Wednesday as the trades ease upstream of the islands. East shore surf should then build back close to seasonal levels late in the week through next weekend. Additionally, swell from Tropical Storm Elida may give a slight boost to east shore surf during the middle of the week.

HFO WATCHES/WARNINGS/ADVISORIES

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