textproduct: Honolulu

SYNOPSIS

Moderate to breezy trade winds will strengthen through the week and deliver periodic showers to windward and mountain areas. Tropical Cyclone Fausto (or its remnants) may impact the state towards the middle of next week, but details are not yet available due to the time frame.

DISCUSSION

Radar and satellite show isolated to scattered showers moving over the state early this morning, with showers mainly over windward and mauka areas. As of 3:00 AM HST, the largest area of showers was north of Molokai, moving west toward Oahu. These showers should decrease through the morning as more stable air moves into the region.

High pressure centered north of the state near 45N will gradually move westward over the next few days. Moderate to breezy trades will continue into the weekend before weakening slowly next week. Relatively dry and stable air will move in with the trade winds, bringing isolated mainly windward and mauka showers, most numerous during the overnight to early morning hours. Very little rainfall is expected to make it over to leeward areas through this weekend.

Next week, the weather across the state will depend on the eventual track and intensity of Tropical Cyclone Fausto. The National Hurricane Center is forecasting a gradual weakening of this system as it tracks westward and enters the Central Pacific this weekend, with further weakening expected early next week as it moves into a more hostile environment with cooler waters and increased shear. At this time, its too early to predict any direct impacts from Fausto on Hawaii, though confidence is increasing in east-facing shores receiving a decent swell late this weekend into early next week. See the marine discussion below for more details.

AVIATION

A strengthening high pressure system north of the Hawaiian Islands will increase trade winds with wind speeds peaking this afternoon. A band of unsettled clouds are riding into the islands on the trade winds tonight. Expect brief MVFR conditions mainly along windward mountain slopes through the early morning hours. Weather conditions will show improving trends after 9 AM HST.

AIRMET Sierra for mountain obscuration was expanded in coverage this morning to include Kauai, Oahu, Molokai, Maui and the Big Island. These conditions will likely diminish shortly after sunrise.

AIRMET Tango remains in effect for moderate low level turbulence driven by the strengthening trade winds. These conditions may continue through Friday morning.

MARINE

High pressure far north of the state will maintain fresh to locally strong trades through the weekend. A Small Craft Advisory (SCA) remains in effect for the typical windier channels and waters around Maui and the Big Island, then will expand to include all the Hawaiian Waters today through tonight. Widespread fresh to strong winds are expected during this time with near gales possible for the windier waters around Maui County and the Big Island. The strong high to the north is expected to eventually shift westward and weaken some, which should allow the trade winds to weaken a notch around Sunday evening. Trends in the strength and direction of winds early next week become less clear as a result of the uncertain track of a weakening Hurricane Fausto (forecast to become a tropical storm by Monday) in the central Pacific.

Offshore and nearshore buoys this morning are showing an increase in long period energy as the incoming south swell builds through the day. A High Surf Advisory (HSA) is in effect today as surf is expected to reach advisory levels by daybreak with the potential to approach warning levels tonight into Friday as the swell peaks. Over the weekend, reinforcing long-period energy may allow advisory level surf to persist and may require an extension of the HSA. The swell will then slowly decline into the beginning of next week.

Surf along east-facing shores will remain rough and choppy, with a small, medium- period east swell which was likely generated by former TC Elida. This weekend, larger surf generated by Hurricane Fausto is possible and could bring advisory level surf along east facing shores by late Sunday into early next week.

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

HFO WATCHES/WARNINGS/ADVISORIES

High Surf Advisory until 6 AM HST Friday for Big Island South- Big Island Southeast-East Honolulu-Ewa Plain-Honolulu Metro- Kahoolawe-Kauai South-Kauai Southwest-Kona-Lanai Leeward-Lanai South-Maui Central Valley South-Maui Leeward West-Molokai Leeward South-Niihau-South Haleakala-South Maui/Upcountry- Waianae Coast.

Small Craft Advisory until 6 AM HST Friday for Big Island Windward Waters-Kaiwi Channel-Kauai Channel-Kauai Leeward Waters- Kauai Northwest Waters-Kauai Windward Waters-Maui County Leeward Waters-Maui County Windward Waters-Oahu Leeward Waters-Oahu Windward Waters.

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