Current Conditions | ||
Temp | ![]() | 1.1 C |
RH | ![]() | 17 % |
Wind | ![]() | NNE 21 mph |
Road | ![]() | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 261 FXHW60 PHFO 140206 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 406 PM HST Fri Dec 13 2019 .SYNOPSIS... Surface high pressure passing north of the islands tonight will keep breezy to locally windy trades blowing tonight. The trades will ease some over the weekend as the high moves away. The trades will bring rainfall to mostly windward and mauka locales, with a few showers briefly reaching leeward spots. The high level jet stream will bring increasing high clouds later today into tonight. A dry, stable airmass will take control of our weather this weekend and the first half of next week, with few showers and considerable sunshine. The next high passing far to the north will return locally windy trades Monday and Tuesday. && .DISCUSSION... A surface trough is moving away to the west of the islands. Meanwhile, high pressure passing about 800 mi to the N of Honolulu is bringing locally windy conditions to the islands this afternoon. This high will continue to the east over the next couple of days, so trade winds will trend down just a bit over the weekend. An mid-to-upper level trough to the west of the islands has been making the local airmass more unstable over the last few days and enhancing trade wind showers. This trough will continue to weaken as we head into the weekend, leading to fewer and less intense trade showers. High level moisture riding in on the subtropical jet will continue to bring high clouds at times, and these will increase tonight into Saturday before pushing away later Saturday as the jet shifts to the SE of the islands. Trade wind showers will decrease further early next week, as decreasing moisture and warm mid-level temperatures overspread the islands. Locally, precipitable water may drop below 1 inch with 700 mb temperatures near double-digits. A strong mid-level anticyclone centered just to our N will make for generally nice pre-holiday weather with lots of sunshine and relatively few showers. Rainfall amounts will be light, and should favor windward and mauka sections during the nights and mornings. Showers will likely increase again starting about Thursday as mid- level heights fall near the islands and cooler temperatures aloft start to make the airmass a little more unstable again. The surface high to the N will continue eastward into the weekend, so trade wind speeds on Saturday will be a notch below today's levels. Winds will even be a notch lower on Sunday as a col between two highs passes N of the islands. The next surface high will pass well N of the islands on Monday, returning breezy to locally windy trade wind speeds for Mon and Tue. The winds should ease Wed, but may increase again on Thu as the next in the series of highs passing to the N approaches our longitude. && .AVIATION... An area of enhanced moisture will continue to reside over the islands late this afternoon in association with a dissipated front. Showers will remain over mainly interior/windward areas of Oahu and Kauai as well as windward areas of Molokai, Maui and the Big Island. Brief MVFR conditions and mountain obscuration may occur due to the passing showers. Surface high pressure to the northeast of the state will allow for moderate to occasionally breezy easterly trades to persist through the period. AIRMET TANGO will remain in effect for areas below 9000 feet south thru west of the mountains on all islands due to tempo moderate turbulence. && .MARINE... The current northwest swell will continue to subside and the High Surf Advisory has been cancelled for all islands. Surf tonight will hold just below the advisory level along north and west facing shores, then lower to moderate levels Saturday. A short period north- northeast swell will keep surf elevated along exposed east facing shores, mainly on Kauai and Oahu, tonight but should stay just below the advisory levels. A reinforcing large northwest swell is forecast to build late Sunday into Monday and peak Monday night, possibly near warning levels. This swell should slowly decline Tuesday into Wednesday, but will likely be reinforced by another large northwest swell Wednesday night into Thursday. High pressure north of the state will keep moderate to locally strong trade winds over the area through Saturday. The combination of the current northwest swell and the strong trade winds is resulting in a Small Craft Advisory for all coastal waters, except the Maui leeward waters. Winds will begin to trend down slightly, likely only keeping small craft winds through the typically windier areas around Maui County and the Big Island Saturday. Seas will also lower as the northwest swell subsides. A slight decline in trade winds and period without Small Craft conditions is possible Sunday as the current high moves east and a new high builds north. Trade winds should return to moderate to locally strong speeds by early next week and seas will build again with the reinforcing northwest swell. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for all Hawaiian Coastal Waters except Maui Leeward Waters. && $$ DISCUSSION...R Ballard AVIATION...Thomas MARINE...EATON Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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