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Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans: Select a text product: Hawaiian Islands Synoptic Discussion and Guidance Hawaiian Islands Short Term Forecast Hawaiian Islands 7-day Zone Forecast Hydrologic Outlook Flash Flood Warning Flash Flood Watch Flash Flood Statement Tornado Warning Severe Weather Statement Severe Thunderstorm Warning Special Weather Statement Winter Storm Warnings/Watches/Advisories Urgent Weather Message Marine Weather Statement/High Surf Advisory/Warning Special Marine Warning Radar Message Special Messages Unknown Terminal Aerodome Foreasts (TAFS) Area Forecast for Hawaii and Adjacent Coastal Waters Upper-level Winds and Temperature Forecast for the 4 Major Hawaii AP AIRMETs for IFR Conditions, Turbulence, and Icing Thunderstorm SIGMETs Hawaiian Islands Satellite Interpetation Message Central/North Pacific Tropical Weather Outlook Central/North Pacific Tropical Weather Summary Central Pacific Tropical Cyclone Summary South Pacific Tropical Cyclone Summary Tropical Cyclone SIGMETs Buoy Winds and Wave Forecast Oahu Surf Observation and Forecast/Coastal Forecast for Hawaiian Waters Offshore Forecast for Hawaiian Waters North Pacific High Seas Forecast South Pacific High Seas Forecast Hawaiian Islands Automated Surface Observation System Hourly Weather Roundup Hawaiian Islands Wind Data Hawaiian Islands Rainfall Summary Hawaii Temperature and Precipitation Summary Daily Hawaii Cooperative Observations Honolulu AP Climate Summary Lihue AP Climate Summary Kahului AP Climate Summary Hilo AP Climate Summary Atlantic Tropical Cyclone Discussion Atlantic Tropical Weather Outlook East Pacific Tropical Cyclone Discussion East Pacific Tropical Weather Outlook Central Pacific Tropical Cyclone Discussion Central Pacific Tropical Weather Outlook West Pacific Tropical Cyclone Discussion West Pacific Tropical Weather Outlook

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Hawaiian Islands Synoptic Discussion and Guidance 874 FXHW60 PHFO 190636 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 836 PM HST Tue Jun 18 2019 .SYNOPSIS... Moderate to locally breezy trade winds will deliver just a few brief windward showers through Thursday, but then winds will weaken and shift to the southeast from Friday through the weekend. The lighter winds will lead to daytime sea breezes, spotty showers and muggy conditions. && .DISCUSSION... As a surface trough to the NW distanced itself from the islands today, the trade wind supporting high centered to the NE was able to build over the area, thus strengthening the trade winds while backing them to a more typical E direction. These locally breezy trade winds will continue through Thursday, delivering just a few brief windward showers that will favor nights and mornings as the island atmosphere will be stable, and no organized moisture sources are anticipated. Leeward areas will be mostly dry. Some relatively thin high cloudiness is possible the next couple of days, but the high clouds may briefly thicken on Thursday due to the passage of a weak trough aloft. While little significant change is expected with the high to the NE into next week, the trough to the NW will become reinvigorated by a developing closed low aloft beginning Thursday. This cutoff low and associated trough aloft is expected to linger NW of the islands well into next week, supporting the development of several weak surface lows along the persistent surface trough, while also causing the trough to drift closer to the islands. The ridge extending SW from the high will move over the islands in response to the sharpening trough, causing winds to weaken and veer to the S and SE along the W end of the island chain, with light to moderate E to SE winds near the Big Island. Initially, this flow looks to support only limited showers, although increasing surface dew points will combine with the light winds to bring increasing afternoon mugginess. As the deep-layer trough axis nears Kauai Friday night and Saturday, models indicate increasing moisture advecting northward over waters W of Kauai, which could lead to a period of showery weather over Kauai county as well. Meanwhile, a mostly dry weather pattern is expected over the remainder of the state through Saturday. Later in the weekend into early next week, there is increased uncertainty as to where clouds and showers will occur (and when), due to the veered wind flow and gradually increasing low-level moisture. While mostly dry weather (outside of brief windward showers), will continue over the Big Island, the other islands could see spotty showers from Sunday into Wednesday. Some showers could form in the afternoons over interior areas due to daytime heating and sea breeze convergence, with others forming within eddies and cloud plumes peeling off other islands, potentially bringing much needed showers to leeward areas. Additionally, conditions will be warm and muggy. Long range outlook presented by latest GFS/ECMWF guidance has delayed the return of trade winds until the end of next week, as low pressure lurking NW of the islands continues to veer and weaken the normally-expected trade winds. Low-level convergence associated with the low could bring spotty showers, some briefly heavy, primarily to the W end of the island chain. && .AVIATION... Relatively strong high pressure far to the northeast of Hawaii will remain stationary through the period. This will keep light to moderate trade winds from the east/northeast through at least Wednesday night. There will be fairly stable conditions with drier air over most parts the islands. Most of the shower activity will be confined to the windward slopes, especially on Maui and the Big Island. Winds will be moderate again Wednesday afternoon in the same areas as Tuesday but they should not be strong enough to produce strong low level turbulence. There are currently no AIRMETs in effect. && .MARINE... A surface high far northeast of the area will maintain locally locally strong trade winds over the coastal waters through mid- week. A Small Craft Advisory is in effect for the Pailolo and Alenuihaha Channels and waters south of the Big Island through Wednesday afternoon. Winds will weaken and shift out of the southeast during the second half of the week as a trough deepens west of the offshore waters. The southeast flow will be partly blocked by the Big Island, resulting in light and variable winds around the smaller islands Friday into the weekend. Existing small surf will fade even more through Wednesday. Surf will remain well below the advisory threshold along all shores through the coming weekend, aside from a small boost in east shore surf as a short-period, northeast swell builds over the weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Birchard AVIATION...Chevalier MARINE...TS Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office

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This page was last modified on: Wed, Dec 17 2014 - 1841 UTC
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