textproduct: Honolulu

SYNOPSIS

Increased trade winds combined with dry conditions will elevate the fire weather threat for today. Occasional showers will favor windward and mauka areas today. For the weekend, we are continuing to monitor Tropical Storm Lala as it moves west-northwest towards the Hawaiian Islands. 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 5 AM HST, Tropical Storm Lala was located near 16.7N 149.5W and moving west northwest around 14 knots (12 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 night, 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 may begin as early as tonight across parts of the Big Island. Tropical storm force winds will reach Maui County by Saturday, 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, 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 should focus mainly over windward and mountain areas, especially this morning. 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 Oahu and the Big Island above 2500 feet due to low clouds and showers, but will likely need be extended to all other islands today as well.

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 may also needed to be added as Tropical Storm Lala approaches the island chain from the east southeast.

MARINE

Breezy trades continue to strengthen ahead of Tropical Storm Lala today. As such, the Small Craft Advisory has been expanded to cover all coastal waters. Lala is forecast to strengthen to a hurricane on approach to the islands, with hurricane conditions possible as early as this afternoon once the cyclone reaches the offshore waters. Coastal waters near the Big Island will see deteriorating conditions as early as tonight, for which a Hurricane Warning is in effect and a Tropical Storm Warning remains in effect for Maui County beginning Saturday. Tropical storm conditions are possible for the coastal waters around Oahu and Kauai by Saturday night, for which a Tropical Storm Watch is now in effect. Dangerous conditions including torrential rainfall, a few thunderstorms, and high surf should be expected. 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.

For east facing shores, surf initially trends slowly upward with strengthening trade winds today, but will begin to quickly build tonight as an east swell generated by Tropical Storm Lala reaches the islands. A High Surf Warning has been issued through Saturday night for very large surf along east facing shores of the Big Island and Maui as Lala tracks very close to the Big Island. Surf will be highest for the Big Island, likely exceeding warning level by several feet. High surf will take a bit longer to build for Maui, but warning levels should be reached by late Saturday. Advisory level surf is possible for east facing shores of Oahu and Kauai by Saturday night. As Lala begins to gain distance from the islands on Sunday, surf will rapidly trend down. For north shores, conditions may be choppy with some wrapping swell energy from the east through the weekend.

The High Surf Advisory for south facing shores has been canceled as the moderate, long period south swell that peaked yesterday gradually fades through the weekend. Surf just below advisory criteria along south and west facing shores today will slowly diminish until another long period south swell arrives late Sunday into Monday. This may provide a small boost to surf, but it will remain below advisory criteria for southern shores.

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

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

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

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

Hurricane Warning for Big Island-

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

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

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

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

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

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