textproduct: Honolulu

SYNOPSIS

Moderate to locally breezy trade winds will continue through Monday before gradually decreasing by midweek, and then reintensifying late in the week. The remnants of TD 15-E have a 70 percent chance of reforming into a tropical system later this week. The track may bring it south of, and close to, the state.

DISCUSSION

The radar remains nearly "empty" this afternoon, with only isolated light showers seen over Kauai County as of 2:30 PM HST. Showers may also develop over the Kona region on the Big Island, but most folks will remain dry. Trade winds were averaging 10 to 20 mph, with gusts 25 to 35 mph in the usual breezy places. Skies were mostly sunny except for the typical windward/mauka areas.

An upper level low that has been lingering to the north and west of the state will slowly weaken and pull away to the northeast through late Tuesday. As it does, a new weak trough will move in from the west. Upper level flow to our south remains weak, which matters because it may allow the remnants of TD 15E to redevelop this week. NHC has now raised the percentage chance of reformation to 70%, and the deterministic GFS and EC now develop the storm late this week. Both models move it to the south of us. It is too soon to know what will come of this, but it is well worth keeping an eye on as it may bring (at least) another round of heavy rain to the area.

Other than that, we expect trades to continue through the week, growing a little weaker midweek before strengthening again late in the week. Should a tropical storm develop to our south, it would enhance the pressure gradient, and hence the trade winds. Again, it is too soon to say this will happen, but we feel it is important to continue to discuss the possibility. With increased moisture drawn northward by a potential system as depicted in the models, we have kept isolated thunderstorms in the forecast, mainly over the eastern half of the state, from Tuesday night through midday Saturday. There is more uncertainty than usual with the forecast this week due to the potential tropical system. Interests should continue to monitor the status of tropical cyclone development via hurricanes.gov and local weather forecasts at weather.gov/hfo.

AVIATION

Breezy trades will continue into Monday. Isolated showers and brief MVFR conditions are possible mainly over windward and mountain areas. Shower activity may increase by Monday night, especially over windward areas of Big Island.

AIRMET Tango remains in effect for moderate low-level turbulence downwind of island terrain due to the breezy trades.

MARINE

The gradient between weak high pressure north of the islands and pressure falls south of the islands will maintain fresh to locally strong trade winds across the region through at least Monday night. Therefore, the Small Craft Advisory has been extended through Monday night for the typical windy channels and waters of Maui County and the Big Island. After a slight reduction in trade wind speeds heading into mid week, they will restrengthen during the latter half of the week as a trough or potential weak tropical disturbance moves south of the islands. Shower coverage will also increase, along with the potential for isolated thunderstorms, particularly across the eastern waters.

Surf along south facing shores will remain above average over the next couple of days as a long period SSW swell holds relatively steady. This swell will then gradually fade heading into mid week. A slightly smaller, long-period south-southwesterly swell will fill in late this week into next weekend generated by a series of lows near New Zealand. West facing shores will experience a bit of the southerly wrap through most of the week.

Breezy trade winds will maintain moderate surf along east facing shores for the next several days. Surf along north facing shores will remain flat to tiny through Monday, but will see a slight bump Tuesday into Wednesday as a small, medium-period northwest swell fills in from an Aleutian low. Then a small, long-period west-northwest swell expected to be generated by Tropical Storm Dujuan as it curves northeast near Japan and potentially strengthens into a hurricane will build locally Friday into next weekend, increasing surf along north and west facing shores.

FIRE WEATHER

Fire weather risk remains low. Locally breezy trade winds are expected through at least Monday. However, dewpoints in the low 70s will keep relative humidity in check. Inversion heights are around 6000 feet statewide.

HFO WATCHES/WARNINGS/ADVISORIES

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