textproduct: Honolulu

SYNOPSIS

Breezy trade winds continue through the weekend with clouds and showers focused windward and mauka. Hurricane Lowell is forecast to move close to Kauai County Monday night as a category 2 to 3 hurricane. Weather impacts such as high surf and heavy rain are forecast to extend hundreds of miles from the center of Hurricane Lowell, potentially impacting any of the islands.

DISCUSSION

Radar and infrared satellite show partly cloudy skies and isolated trade showers this evening. Breezy trade winds continue through the weekend. Clouds and showers will gradually increase through the weekend as trade winds push in a bit more upstream moisture. Focus of the showers will be windward and mauka and occur mostly during the overnight and early morning hours through Sunday.

Our attention will then turn to Hurricane Lowell, now a category 5 on the Saffir-Simpson scale (140 mph maximum sustained winds), and impacts to Hawaii. Lowell is about 600 miles south southwest of Kauai this evening still tracking to the west. A gradual decrease in the forward speed of Lowell remains in the forecast for the next 12-18 hours, followed by a turn to the northwest Saturday and north-northeast Sunday. Lowell is expected to make its closest approach to the main Hawaiian Islands Monday night as a category 2 to 3 hurricane, and any deviation eastward from its forecast track could bring more severe wind impacts especially to Kauai County. It is currently too early for tropical watches and warnings tonight, but will be discussed and determined soon.

As far as expected impacts, there remains a risk for high surf, strong winds, and heavy rainfall for all islands. A south swell has already elevated surf across south facing shores and will become extra large out of the southwest Sunday night/Monday as Lowell approaches. High surf will have the greatest coverage across the state as the swell moves from the storm, so confidence is highest with the surf and surge impacts.

Winds will shift southward and deep tropical moisture will advect across all islands late Sunday through Tuesday, producing warm and humid weather conditions. Heavy rainfall is likely to impact most islands at some point during Lowell's passage. NBM guidance initially brings heavy rain across south slopes of Maui and Big Island as early as Sunday evening followed by the rest of Maui County and Oahu Monday morning, and Kauai Monday afternoon. Initial storm total rainfall estimates range from 2 to 8 inches statewide. With a significant period of south to southeast winds forecast, we expect locally higher amounts (around 10 inches) along south and southeast slopes. Please continue to closely monitor the weather forecast for early next week as the track and associated impacts with Hurricane Lowell may change over time.

High pressure builds back over the islands from Tuesday afternoon onward as a wet trade wind pattern with periods of passing showers sets up across the state into the end of next week. A moist area left from the remains of Karina is now modeled to move through the area Wednesday afternoon through Wednesday night, possibly providing an especially wet period.

AVIATION

Breezy trade winds will gradually decrease in strength through Sunday as the ridge north of the islands weakens. Hurricane Lowell roughly 600 miles south of Kauai continues to journey westward. Bands of unsettled clouds are developing in the trade winds just northeast of the Hawaiian Islands. Expect increasing cloud and shower trends bringing MVFR conditions over windward mountain areas lasting into the early morning hours with the potential for an AIRMET Sierra issuance for mountain obscurations later this evening.

AIRMET Tango remains in effect for low level mod turb over and south through west of all island mountains.

MARINE

A surface high persists north of the Hawaiian Islands and will slowly drift east through the weekend. Currently, Hurricane Lowell is passing near 520 nm south to southwest of the islands as it continues to track west. The interaction between the two has kept trade winds fresh to locally strong across the all coastal waters zones. A Small Craft Advisory (SCA) is in effect for all coastal waters through tonight and has been trimmed back on Saturday for only the windier waters and channels around Maui County and the Big Island through Saturday afternoon. As Lowell begins its expected turn northward this weekend, by early next week winds are likely to veer to the southeast to south with the strongest winds over the western end of the state.

Confidence has grown with the latest updates from the National Hurricane Center for the potential for hurricane conditions in the offshore waters west of 160W on Sunday through potentially Tuesday. How close it gets to the state, is yet to be determined. As for Hurricane Karina, it is expected to weaken and pass to the north and northeast of the state.

Southerly swells from Hurricane Lowell will keep surf elevated above High Surf Advisory (HSA) conditions through Saturday. A large, medium- period east swell is filling in from Hurricane Karina producing HSA level surf along east facing shores. The HSA is in effect for all south and east facing shores of all islands as well as the west facing shores of the Big Island through Saturday afternoon and will likely be extended.

The swell from Lowell will gradually veer from south to southwest early next week. While the forecast for swells and seas for next week will highly depend on the eventual track and intensity of Lowell, confidence is beginning to increase for the potential of extra- large surf (exceeding warning levels) along south and western exposures early next week. Coinciding also with monthly high tides, this will create the potential for impacts to harbor entrances, channels, as well as coastal properties and infrastructure including roadways.

FIRE WEATHER

Periods of passing showers will mainly impact windward and mountain slopes through early Sunday. Considerably more showers are likely over most areas from Sunday afternoon into early next week. The temperatures inversion heights near Maui and the Big Island will range from 6,000 to 7,000 feet elevation tonight and Saturday.

HFO WATCHES/WARNINGS/ADVISORIES

High Surf Advisory until 6 PM HST Saturday for Niihau-Kauai Leeward-Waianae Coast-Olomana-Kahoolawe-Maui Leeward West-Kona- Kauai East-Kauai South-East Honolulu-Honolulu Metro-Ewa Plain- Koolau Windward-Molokai Windward-Molokai Southeast-Molokai West- Molokai Leeward South-Lanai Leeward-Lanai South-Maui Central Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry- South Haleakala-Big Island South-Big Island Southeast-Big Island East-Big Island North.

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

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