textproduct: Honolulu

SYNOPSIS

A strong pressure gradient has developed over the state as a strong high sits north of the state and Major Hurricane Lowell passes several hundred miles south southwest of the Big Island. This gradient is generating windy and gusty trades over Maui County, the Big Island, and over Oahu. Expect isolated to scattered showers during the nights and early mornings along windward locations. By this weekend, the National Hurricane Center projects Hurricane Lowell to take a rather sharp turn northward. Lowell could be at or near major hurricane strength when it moves near the westernmost main Hawaiian Islands late Monday and Monday night. While it is still too soon to determine the exact track of the hurricane, Lowell could bring storm surge, wind, and rainfall impacts to portions of Hawaii early next week. This is a good time for all residents to ensure they have their hurricane plan and supply kit in place.

DISCUSSION

Latest satellite imagery loop shows the distinct eye of major Hurricane Lowell well south southwest of the Big Island, along with all accompanying deep convection. Only patches of cirrus clouds on the northern fringes of the TC have managed to spread over Big Island, Maui County, and Oahu. According to the latest 5 AM HST NHC advisory package, Lowell is 450 miles south southwest of Hilo and moving west at 10 mph.

Across the state, isolated trade showers continue to affect windward locations with rain rates generally less than 0.10" an hour. Breezy conditions will allow a few of the showers to pass over the elevated terrain and onto leeward sides. Gusty winds have been noted across much of the island chain over the past several hours. Local surface pressure gradients have tightened across the state as Hawaii remains sandwiched between a 1030 mb surface high far north of Hawaii and low pressure from Lowell's passing to the south. Winds continue to gust between 35 and 50 mph over the most wind prone passes, ridgelines, and to the lee of terrain. A Wind Advisory remains in effect for select portions of Oahu, Maui County, and Big Island through early Friday morning. However, this product may need to be extended through the day on Friday if current guidance holds. Similar local weather conditions are expected Saturday through midday Sunday with typical summertime breezy trade winds and night/early morning windward showers.

Attention will shift late this weekend into early next week to the forecast track of Hurricane Lowell. Confidence has been increasing of a northward jog of the major hurricane in response to a digging upper level low, north of Hawaii. While it is still too soon to determine the exact track of the hurricane, Lowell could bring storm surge, wind, and rainfall impacts to portions of Hawaii early next week. Interests in Hawaii should continue to closely monitor the progress of Lowell through the upcoming Labor Day weekend, listen to the advice of officials, and ensure they have their hurricane plan and supply kit in place.

Please visit the hurricanes.gov page for the official NHC forecast for Lowell.

AVIATION

VCSH along windward sides of the islands through this morning with cigs locally going down to MVFR. Elevated winds will remain through the TAF period; moderate confidence in wind gusts over 30 kts at some TAF sites by this afternoon, including PHNL, PHMK, and PHOG. VCSH returns to the same areas this evening and overnight with locally MVFR cigs returning.

Hurricane Lowell will continue to pass south of the island chain the next couple of days. On this westerly track, regional trade winds will remain strong per a tight pressure gradient between the hurricane and high pressure to the far north.

AIRMET Tango remains in effect for moderate low level turbulence south through west downstream of high terrain. AIRMET Tango will likely be in effect for the foreseeable future.

MARINE

A strong surface high persists far north of the Hawaiian Islands. Hurricane Lowell is passing to the south. The interaction between the two will strengthen the trade winds across the coastal waters to fresh to locally near gale force. A Small Craft Advisory (SCA) remains in effect for all Hawaiian Waters through 6AM Friday with an extension possible.

While there is still plenty of uncertainty regarding the exact track of Lowell, confidence is fairly high that the southwest and western offshore waters will see Hurricane conditions. How close it gets to the state, is yet to be determined. As for Hurricane Karina, confidence is increasing that Karina will pass to the north and northeast of the state.

Swells from Hurricane Lowell will steadily fill in across rest of the island chain today and will likely produce advisory level surf for south and southeast exposures throughout the state. Swells from Lowell will likely linger through next week and will gradually veer from southeast to south today and eventually towards the 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. Additionally, the current moderate long period south swell will decline through the rest of the week.

A large, medium-period east swell from Hurricane Karina will steadily fill in Friday into the weekend and will likely produce high end advisory level surf or warning level surf along east facing shores by this weekend.

FIRE WEATHER

Trade winds will remain strong and gusty into Friday. Gusts to, or over 50 mph, will be possible in the typical windy areas. Relative humidity values are forecast to remain too high for critical fire criteria to be reached, and fuels are currently rated as not critical. Therefore, the strong winds will not trigger fire weather watches or warnings. The trade inversion is forecast to be 6000 ft to 7000 ft today.

HFO WATCHES/WARNINGS/ADVISORIES

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

Wind Advisory until 6 AM HST Friday for Waianae Coast-Central Oahu-Waianae Mountains-Lanai Mauka-Kahoolawe-Maui Windward West- Maui Leeward West-Kohala-East Honolulu-Honolulu Metro-Ewa Plain- Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Lanai South- Maui Central Valley North-Maui Central Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry-South Haleakala-Big Island South-Big Island Southeast-Big Island North.

Small Craft Advisory until 6 AM HST Friday for all Hawaiian waters-