Daily Weather

Oct 20, 2014 3:45 AM HST

Synopsis
All tropical storm warnings for the aloha state and coastal waters have been discontinued. Showers and slight chances of thunderstorms continue through the morning hours as Ana slowly pulls away from the aloha state. A moderate easterly and southeasterly flow will begin establishing during the next couple of days. Then light to moderate trades should prevail for the second half of the week with showers favoring windward and mountain areas. The trades should be light enough at times to allow for afternoon sea breezes to develop and bring clouds and a few showers over leeward and interior areas.

Discussion
All tropical storm warnings for the aloha state have been discontinued. A flash flood watch remains in effect for Oahu and Kauai county until 6 pm HST this evening, and it will be adjusted as necessary.

Radar data still show a rather large field of moisture associated with departing Ana, keeping plenty of showers and slight chances of thunderstorms around Oahu and Kauai county through the morning hours. And although conditions are slowly improving, it is possible to experience localized heavy showers today, especially over Kauai and Niihau. The 06Z soundings show a drier airmass starting to filter into the area from the E with pwats on the Hilo sounding at 1.4 inches, while Lihue still has more than 2 inches. But despite this trend, lingering moisture from Ana will still be able to fuel clouds and showers especially over the W half of the aloha state through Tue.

For the first half of the week, Ana will continue to move W and NW away from the islands and allow for a generally e/se moderate flow to begin establishing across the area starting today. Models are now backing down from keeping a more S flow over the W edge of the island chain. Thus, the forecast wind field across the area will be mainly from the e/se. An increasingly stable airmass will gradually move into the area in the wake of Ana.

For the second half of the week, model solutions show winds relaxing a little and allowing for sea breezes to become more prominent each afternoon, with clouds and showers affecting leeward and interior areas of the smaller islands and the Kona side of the Big Island.

Aviation
Overall conditions continue to improve for the islands as Ana moves away. Tropical storm Ana at 1200Z was located at 20.6°N 162.6°W, 200 nm WSW of PHLI. Kauai, including PHLI, is likely to experience extended periods of lower cigs/vis with deep layered clouds at least through the morning period. Slight chance for thunderstorms also remains over Oahu and Kauai through the morning. Airmet sierra for mountain obscuration and airmet zulu for icing remain posted over Kauai. They have been cancelled for all other areas.

Vfr conditions will prevail for terminals Oahu through Big Island. Showers will mainly focus on windward and mauka area as moderate E winds return to the state. Possible periods of MVFR conditions can be expected. High clouds will linger over Maui county and Oahu through the morning. Airmet tango is posted for low level turb.

See tc sigmet quebec series for tropical storm Ana.

Marine
A small craft advisory /sca/ remains in effect through this morning due to elevated rough seas across the waters surrounding Kauai and over parts of the Oahu leeward waters due to tropical storm Ana swells. As Ana continues to move west away from the area, these tropical cyclone swells will slowly diminish. Otherwise, winds and seas are expected to remain below the SCA criteria over the coastal waters through Friday.

The swells produced by Ana will also maintain elevated surf along west and south facing shores of Kauai and Niihau this morning. An above average north northwest swell will also keep the surf elevated along north facing shores of the islands from Kauai and Niihau to the Big Island. As a result, a high surf advisory remains in effect for these shorelines through this morning. The north northwest swell will eventually shift to a more northerly direction, and gradually lower through Wednesday. A new small northwest swell is expected to arrive Thursday and continue through Friday.

Watches/Warnings/Advisories
Flash flood watch until 6 pm HST this evening for Niihau, Kauai, Oahu.

High surf advisory until noon HST today for Niihau, Kauai windward, Kauai leeward, Oahu south shore, Waianae coast, Oahu north shore, Oahu Koolau, Molokai, Maui windward west, windward Haleakala, Big Island north and east.

Small craft advisory until noon HST today for Kauai northwest waters, Kauai windward waters, Kauai leeward waters, Kauai channel, Oahu leeward waters.
Otherwise only small to moderate swells are expected to affect west and north facing shores. A larger northwest swell is then expected over the weekend.
More generic marine definitions click this link http://www.prh.noaa.gov/hnl/pages/marinedef.php

All surf height observations and forecasts are for the full face surf height, from the trough to the crest of the wave.

Advisory and Warning Criteria
Location Advisory Warning
North-Facing Shores 15 Feet (8') 25 Feet
West-Facing Shores - Big Island 8 Feet (4'+) 12 Feet
West-Facing Shores - Remaining Islands 12 Feet (7') 20 Feet
South-Facing Shores 8 Feet (4'+) 15 Feet
East-Facing Shores 8 Feet (4'+) 15 Feet

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