textproduct: Honolulu

SYNOPSIS

As the kona low exits to the north of the Hawaiian Islands, remnant bands of moderate showers continue over Leeward Big Island and Maui while conditions improve elsewhere. Toward the latter end of the week, another threat of heavy rain is anticipated as low pressure develops west of the islands.

DISCUSSION

Remnant bands of moderate showers continue to affect leeward Big Island and and portions of Maui County, and are expected to persist through at least tonight and possibly through Tuesday. However, recent observations indicate hourly rainfall rates remain below a tenth of an inch across both islands. In response to the reduced rainfall intensity and improved flooding thread, the Flash Flood Watch for Maui County and the Big Island has been cancelled with the issuance of this morning's forecast package.

Observations from the Maunakea Weather Center, along with model guidance indicating strong winds near the 600 mb level, suggest that high winds across the Big Island summits and Haleakala will persist beyond the previously scheduled 6 AM HST expiration time. As a result, the High Wind Warning has been extended through 6 PM HST this evening. Conditions will continue to be monitored and reevaluated with the next forecast cycle.

Confidence in the extended forecast beyond Monday remains somewhat limited as model guidance continues to evolve. Current solutions maintain an upper-level trough across the region, supporting a pattern of light and variable winds with periods of showers and the potential for isolated thunderstorms through much of the week. Toward the latter part of the week, model guidance diverges somewhat, with the GFS depicting a flatter and more progressive surface low while the ECMWF suggests a deeper and slower-moving system. The latest GFS run has trended closer to the ECMWF solution, increasing confidence that organized low pressure could develop over or near the island by late week. Given the uncertainty at this range, the forecast will continue to be refined in subsequent updates.

AVIATION

The system that has plagued the area continues to move northeast. Low cigs and SHRA continue across the area and will slowly decrease from west to east through today. MVFR conds are possible. The lone exception is Lanai which is LIFR with fog thats expected to last well into the morning. Winds have weakened over the state and will continue that trends today. There still could still be some gusty winds especially over Maui and the Big Island.

AIRMET Sierra is in effect for mtn obsc for Maui Lanai and the Big Island. Conds in general will improve west to east and this AIRMET will be adjusted as necessary. AIRMET Tango remains in effect for mod mid-upper level turb between 130 and FL330. It is is also in effect for turb downwind N thru E of terrain statewide. As winds diminish and this system moves further away from the islands this will also be adjusted as necessary.

MARINE

Conditions over the marine area will continue to improve during the next couple of days, as the recent kona storm moves northeast and away from the area. Winds and seas have dropped below advisory levels early this morning, therefore the Small Craft Advisory (SCA) has been cancelled. The gradient in the wake of the storm will remain rather weak Tuesday and Wednesday, with light and variable winds prevailing over the waters. The pattern becomes more uncertain late in the week. A brief period of light to moderate trades will be possible Thursday as a weak ridge builds north of the state, followed by light to moderate southerly winds on Friday as a new storm system approaches from the west.

Surf along south facing shores will trend down lower today as south to southwesterly winds ease. A new long period south swell will then arrive late tonight and Tuesday, giving a nice and extended boost to south shore surf through late this week.

A moderate sized short-period west swell associated with the recent kona storm will affect north and west facing shores today, but surf will remain below advisory levels. As a result, the High Surf Advisory for west facing shores of the Big Island has been cancelled. The short-period west swell will lower tonight and Tuesday, while a new medium-period north-northwest swell fills in. This north-northwest swell could bring surf up close to advisory levels Tuesday night and Wednesday, with the swell then shifting more northerly and lowering below advisory levels Thursday into next weekend.

Surf along east facing shores will remain well below normal levels through late in the week as trade winds over and upstream of the islands appear to remain mostly disrupted.

HFO WATCHES/WARNINGS/ADVISORIES

High Wind Warning until 6 PM HST this evening for Haleakala Summit-Big Island Summits.