textproduct: Honolulu

SYNOPSIS

Moderate trades will build back into the region today. A weak trough near the Big Island this morning is producing showers and clouds over the eastern end of the island chain. As this trough weakens and moves westward, expect showers to trend down by tonight. Elsewhere, drier conditions will prevail. Trade winds are anticipated to become breezy by the end of the week as high pressure strengthens north of the state. Slightly wetter trades will be possible this weekend.

DISCUSSION

Early this morning, a surface trough is located over the eastern side of the Big Island. Showers and widespread cloud cover associated with this trough have been moving over Big Island windward locations throughout the night, and will continue throughout the morning. Several locations across the Big Island have picked up over an inch of rain since 8pm HST, with a couple of spots receiving over an inch in a half in the past 24 hours. With that said, radar estimated rainfall rates have been steadily in the light to moderate range, precluding any flooding concerns at this time. To a lesser extent, some of the moisture associated with this weak trough has spread to portions of Maui as well. Elsewhere across the state, drier air remains in place with fewer clouds and showers occurring.

Today the trough will weaken as it moves westward, while a low aloft moves off to the east. Prevailing clouds and showers associated with the trough will diminish later this morning, but lingering moisture nearby may enhance afternoon clouds and shower activity over the Big Island interior. Moderate trade winds will be building back into the region, and may become locally breezy within typically windy areas by this afternoon. A few passing showers will be possible for the smaller islands today, mainly favoring windward and mauka locations.

By Wednesday, conditions are forecast to become drier as the aforementioned features will have moved well away from the islands. Trade winds then are expected to increase Thursday into the weekend as high pressure to the north becomes established and strengthens. As trade winds increase, passing showers will favor windward and mountain areas, and could increase slightly this weekend.

AVIATION

Light to occasionally moderate trades will persist through the day. Lighter winds may allow for the development of localized daytime sea breezes within more trade wind-protected leeward areas. Afternoon warmth will create thickening upslope clouds and isolated showers that may introduce brief periods of MVFR ceilings and visibilities. Otherwise, VFR conditions will prevail.

AIRMET SIERRA is in effect for mountain obscuration along Big Island's east and southeast-facing slopes until further notice.

MARINE

Gentle to moderate trade winds will persist through Wednesday as as a surface ridge remains anchored far northeast of the state and a weak trough dissipates near the Big Island. Trades will strengthen to moderate to locally fresh Thursday as surface high pressure builds far north of the state. Trades will further strengthen to fresh to locally strong late Friday through the weekend and a Small Craft Advisory (SCA) will likely be needed for the typically windy waters around Big Island and Maui.

A fresh, long period northwest swell will build today, pushing surf along north and west facing shores to near seasonal averages through Wednesday. This swell will decline Thursday and Friday. By late Friday, a medium period north- northwest swell will build and once again help bring surf to near seasonal averages through the weekend.

South shore surf will remain elevated through Wednesday as a long period south- southwest swell slowly declines. Another long period south swell will help produce surf near seasonal average Thursday into early this weekend.

Surf along east facing shores will remain small through Thursday as small wind waves and tiny east swell persist. Choppy surf will increase slightly as trade winds strengthen across the region Friday into the weekend.

FIRE WEATHER

Moderate trade winds will continue through the first half of the week. Dry air will keep RH levels near-critical values each afternoon for parts of the state for the next several days, but winds will be a limiting factor. Inversion heights will range from near 5,000 feet over the western end of the state to around 12,000 feet over the eastern end. Winds will increase during the second half of the week, but moisture levels are also expected to increase a bit.

HFO WATCHES/WARNINGS/ADVISORIES

None.