textproduct: Honolulu

SYNOPSIS

Strengthening trade winds will bring scattered showers across windward and mauka areas today. Tropical Storm Lala will move over or just south of the islands this weekend but wind, rain and surf impacts will be felt statewide. A Hurricane Warning is in effect for Big Island, a Tropical Storm Warning is in effect for Maui County, and a Tropical Storm Watch is in effect for Oahu, Kauai, and Niihau.

DISCUSSION

Breezy and dry trade winds today with limited showers across windward areas.

The main forecast concern for the next few days will be potential impacts from what is now Tropical Storm Lala. As of 11 AM HST, Tropical Storm Lala was located near 17.2N 150.9W and moving west northwest 14 mph. Based on the latest forecast from the National Hurricane Center (NHC), Lala is expected to move near the southern end of the Big Island Saturday, then continue moving to the west- northwest, with the center of circulation remaining south of the smaller islands. Impacts from Lala are expected to begin for the eastern end of the state tonight, and continue through the weekend. Remember impacts can occur well outside the center of the storm. Please stay up to date on the latest forecasts, and prepare for the potential impacts described below.

STRONG AND GUSTY WINDS...Damaging tropical storm force winds (39 mph to 73 mph) may begin as early as tonight across parts of the Big Island. Tropical storm force winds will reach Maui County by Saturday morning, with the potential for tropical storm force winds to impact the rest of the state later Saturday into Sunday. A Hurricane Warning is in effect for the Big Island and its surrounding waters (due to a non-negligable chance of hurricane force winds), a Tropical Storm Warning has been issued for Maui County and its surrounding waters, and a Tropical Storm Watch has been issued for Oahu, Kauai, and Niihau and surrounding waters. Localized areas of highly enhanced and damaging winds are possible over mountainous terrain, even well away from the tropical cyclone center.

HEAVY RAINFALL...Periods of heavy rainfall are expected starting with the Big Island tonight, reaching Maui County on Saturday, and Oahu and Kauai later Saturday and Sunday. Orographic enhancement will result in locally higher rainfall totals where moist tropical flow interacts with island terrain. If heavier rainfall persists over the same locations, flash flooding and rapidly rising streams are possible. The location of heaviest rain currently favors the Big Island and parts of Maui. The current forecast has 10 to 15 inches of rain, with locally higher amounts across windward Big Island. Rainfall totals of 8 to 12 inches are possible on windward Maui and up 8 inches of rainfall could occur across the remainder of the island chain. While the highest rainfall amounts will be focused over windward areas, leeward areas will also have a significant flood risk. Heavy rain could persist into Monday for some areas. A Flood Watch has been issued for the Big Island and Maui County from tonight evening through late Saturday night and for Oahu, Kauai, and Niihau from Saturday evening to early Monday morning.

LARGE AND ROUGH SURF...Lala is expected to generate a large easterly swell as it moves northwestward. Surf may build along exposed east and southeast facing shores from east to west as the system approaches today. Very large and extremely rough seas are expected to rapidly increase Saturday and Sunday on exposed southeast and east shores and may produce damaging surf, significant beach erosion, and overwash across vulnerable coastal infrastructure, mainly on the Big Island of Hawaii.

In anticipation of critical new updates with each of the advisory packages issued by the National Hurricane Center (NHC), the NWS Honolulu will continue delaying the issuance of our typical forecast package products (AFD, SFT, PFM, ZFP, SPF, CWF, etc.) until after the release of NHC's suite of products, to incorporate the latest and most up-to-date information on Tropical Storm Lala.

AVIATION

Breezy trade winds will strengthen today and become locally strong. Scattered showers will focus mainly over windward and mountain areas, decreasing this afternoon. Tropical Storm Lala will continue to approach the Big Island from the east-southeast today and bring deteriorating weather conditions (MVFR to IFR) including low visibility, low ceilings, heavy rain, isolated thunderstorms, as well as very strong winds late this evening through the weekend for all islands as it moves northwestward up the island chain.

AIRMET SIERRA is currently in effect for north through east sections of all islands above 2500 feet due to low clouds and showers.

AIRMET TANGO for moderate turbulence remains in effect immediately south and west of mountains due to strengthening low- level winds and will likely continue for the next couple of days. As wind speeds strengthen by the end of today, an AIRMET for strong winds greater than 30 kt will likely be added Saturday as Tropical Storm Lala approaches the island chain from the east southeast.

MARINE

NE winds will strengthen areawide this afternoon through Saturday as Tropical Storm Lala passes over or immediately south of the Big Island. The strongest winds are anticipated Saturday evening into Saturday night for the waters surrounding the Big Island and Maui. Winds peak for the waters surrounding Kauai and Oahu during Sunday. Hurricane Warnings, Tropical Storm Warnings, and Tropical Storm Watches are in effect. Expect dangerous conditions including torrential rainfall, a few thunderstorms, and high surf. Lala will track WNW through the weekend, clearing the western islands by Monday. Tuesday into the rest of the week, a return to easterly trades is expected.

Surf initially trends slowly upward for E shores in response to strengthening trades, but will quickly build tonight as Lala approaches. The High Surf Warning remains in effect for E facing shores of the Big Island and Maui as well as the SE facing coasts of the Puna and Ka'u Districts where surf will likely be maximized. Surf is likely to reach the Advisory threshold for Oahu and Kauai as early as Saturday night and has potential to eclipse the Warning threshold for Oahu.

For north shores, anticipate choppy conditions with swell energy wrapping from the east through the weekend. For S shores, surf will remain below the advisory threshold and will slowly diminish until another long period south swell arrives late Sunday into Monday providing a small boost to existing surf.

FIRE WEATHER

Moderate to breezy trade winds and relatively dry air will raise fire weather concerns today. Criteria for a Fire Weather Watch are not forecast, but it's close. Temperature inversion heights will range between 5,000 to 7,000 feet today. Increasing humidity and rainfall with Lala will remove fire weather concerns from Saturday into at least early next week.

HFO WATCHES/WARNINGS/ADVISORIES

Tropical Storm Watch for Central Oahu-East Honolulu-Ewa Plain- Honolulu Metro-Kauai East-Kauai Mountains-Kauai North-Kauai South-Kauai Southwest-Koolau Leeward-Koolau Windward-Niihau-Oahu North Shore-Olomana-Waianae Coast-Waianae Mountains.

Flood Watch from Saturday evening through late Sunday night for Central Oahu-East Honolulu-Ewa Plain-Honolulu Metro-Kauai East- Kauai Mountains-Kauai North-Kauai South-Kauai Southwest-Koolau Leeward-Koolau Windward-Niihau-Oahu North Shore-Olomana-Waianae Coast-Waianae Mountains.

Tropical Storm Warning for Haleakala Summit-Kahoolawe-Kipahulu- Lanai Leeward-Lanai Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui Central Valley South-Maui Leeward West- Maui Windward West-Molokai Leeward South-Molokai North-Molokai Southeast-Molokai West-Molokai Windward-South Haleakala-South Maui/Upcountry-Windward Haleakala.

Flood Watch from 6 PM HST this evening through late Saturday night for Big Island East-Big Island Interior-Big Island North- Big Island South-Big Island Southeast-Big Island Summits- Haleakala Summit-Kipahulu-Kohala-Kona-Maui Central Valley North- Maui Central Valley South-Maui Leeward West-Maui Windward West- South Haleakala-South Maui/Upcountry-Windward Haleakala.

High Surf Warning from 6 PM this evening to 6 AM HST Sunday for Big Island East-Big Island North-Big Island Southeast-Kipahulu- Maui Windward West-South Haleakala-Windward Haleakala.

Hurricane Warning for Big Island East-Big Island Interior-Big Island North-Big Island South-Big Island Southeast-Big Island Summits-Kohala-Kona.

Tropical Storm Watch for Kauai Channel-Kauai Leeward Waters- Kauai Northwest Waters-Kauai Windward Waters-Oahu Leeward Waters- Oahu Windward Waters.

Tropical Storm Warning for Kaiwi Channel-Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Pailolo Channel.

Hurricane Warning for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters-Big Island Windward Waters.

Small Craft Advisory until 6 PM HST Saturday for Kauai Channel- Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward Waters-Oahu Leeward Waters-Oahu Windward Waters.

Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel- Maalaea Bay-Maui County Leeward Waters-Maui County Windward Waters-Pailolo Channel.

Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters- Big Island Windward Waters.