textproduct: Honolulu

SYNOPSIS

Moderate trades weaken giving way to land and sea breezes through early this week. Increasing moisture will move up the island chain from the southeast through the early portion of the week resulting in increased shower coverage over island interiors. Trades return late Wednesday and continue through the forecast period.

UPDATE

Minor adjustments were made to PoP to account for current trends, otherwise previous forecast remains on track.

PREV DISCUSSION

Latest satellite imagery shows the sheared shortwave approaching from the north. This wave is nestled along the poleward side of the subtropical jet and will gradually sag south through tomorrow. At the surface, weak convergence and confluent easterlies centered around 850mb are focusing a plume of moisture around 10kft in depth toward portions of Windward Big Island and the adjacent waters to the south. The favorable nocturnal period should allow at least Puna and South Hilo Districts to see an increase in shower coverage tonight. Northward extent of shower coverage is in question as satellite suggests the moisture band is a touch further south than model guidance indicates.

As the aforementioned shortwave advances through the area, increasing showers will be most pronounced over the eastern end of the state through Monday then expand up the island chain by Tuesday. Trades back to northeasterly and strengthen to moderate during the early portion of the week, focusing showers windward and mauka. Breezy trades then establish during the second half of the week as the subtropical ridge strengthens north of the area.

AVIATION

AIRMET Sierra is in effect for tempo mtn obsc above 2500 feet for windward Maui and windward/southeast Big Island this afternoon as clouds and showers linger at the eastern end of the state. These areas will likely remain under the AIRMET tonight as upstream moisture slowly moves in. Additional windward areas of Oahu and Molokai could be added to the AIRMET overnight. VFR conditions will prevail elsewhere with no other AIRMETs anticipated.

MARINE

The trade winds have weakened into the light to moderate range today as a large North Pacific low has weakened the ridge north of the islands. The ridge will gradually restrengthen north of the state Monday and Tuesday, allowing the trades to slowly return to moderate and fresh levels. High pressure north of the islands will strengthen further by the middle to latter part of next week, bringing fresh to strong trades back to the waters. Small Craft Advisories are likely to be required for the typically windy waters around Maui and the Big Island by as early as Tuesday.

The current long-period south swell is beginning to fade this afternoon, with surf falling below advisory criteria. Surf will remain below advisory criteria tonight and Monday as forerunners from a new long-period south swell arrive, the first hints of which have just been detected on offshore buoys this afternoon. This next south swell looks to be larger than the previous, with surf expected to return to advisory levels Tuesday through Thursday. There is some potential that surf will peak close to warning levels on Wednesday.

Surf along north-facing shores will remain small through Monday, then trend slightly higher Tuesday through Friday as a pair of overlapping small north-northwest swells move through. North shore surf will drop back to nearly flat levels next weekend.

East shore surf will remain below normal through Tuesday due to lack of trade winds over and upstream of the state. Surf will trend upward Wednesday and Thursday and hold close to seasonal levels Friday through next weekend.

HFO WATCHES/WARNINGS/ADVISORIES

None.