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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 622 FXHW60 PHFO 180132 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 332 PM HST Tue Jul 17 2018 .SYNOPSIS... High pressure north of the state will maintain moderate to breezy trade winds through the week, with the strongest winds holding through the next couple of days. Clouds and showers will favor windward and mauka areas, as well as the kona slopes of the Big Island each afternoon. A brief increase in shower activity is expected for the Big Island and possibly Maui tonight and Wednesday. && .DISCUSSION... A breezy and stable trade wind flow remains in place this afternoon as patches of high clouds pass overhead. A broad area of surface high pressure parked roughly 1,200 miles north of the islands is driving the gusty trade winds, and a strong mid level ridge sitting overhead is maintaining stable conditions with an inversion between 5,000 and 6,500 ft. An upper level trough parked several hundred miles north of the state is sending patches of high clouds over the state, and a mix of stable stratocumulus and shower-bearing cumulus clouds is moving along the trade wind flow, leading to modest rainfall across windward slopes and a few showers over the South Kona slopes of the Big Island. Breezy trade winds will hold tonight and Wednesday as portions of the state see an uptick in rainfall. The surface ridge to the north will remain nearly stationary as a weak tropical disturbance passes a couple hundred miles south of the state. As a result, the pressure gradient over the islands should tighten slightly, causing the trades to increase a bit. Enhanced moisture along the northern fringe of the tropical disturbance will affect the Big Island and east Maui. Shower activity will likely increase along windward slopes and along leeward slopes Wednesday afternoon. Although the mid level ridge will maintain stable conditions across the southern half of the island chain, we cannot rule out localized heavy showers flaring over and downwind of the active lava flow in the southeast Puna District. In addition, the upper level trough to the northwest will drift closer to Kauai. This feature is producing spotty thunderstorms about 275 miles northwest of Kauai, and as it shifts closer, thunderstorms could pop up closer to the state, while high clouds continue to stream overhead. Trade winds will back off a notch on Thursday as drier air settles back over the state. The result will be a moderate trade wind flow with modest shower activity. Another increase in rainfall is possible on Sunday and Monday. && .AVIATION... Breezy trade winds will continue over the next 24 hours with a persistent high pressure ridge far to the north of the Hawaiian Islands. While mostly VFR conditions will prevail into this evening, low clouds and scattered showers moving through the trade winds will bring periods of MVFR conditions along some of the windward slopes tonight. The windward slopes of the Big Island are expected to see more persistent MVFR conditions and increasing showers developing tonight through Wednesday morning as deeper moisture moves through from the east. Conditions are expected to improve throughout the afternoon as the moisture moves off to the west and passes south of the state. AIRMET Tango remains in effect for tempo moderate turbulence over mountains and south through west sections of each island including coastal waters. Breezy trade winds will keep these conditions through tonight and likely Wednesday as well. && .MARINE... High pressure to the north of the islands will maintain fresh to strong trade winds through the week. The strongest winds expected on Wednesday as a trough passing south of the state tightens the local pressure gradient. Starting tonight, the Small Craft Advisory (SCA) has been expanded from the typically windy waters around the Big Island and Maui County to cover waters around Oahu. Combined seas around the Big Island will also rise to near 10 ft. Winds will decline a notch on Thursday and Friday, and the SCA will likely be scaled back to the typically windy waters through the weekend. The fresh to strong trade winds will generate rough seas during the next couple of days. Local PacIOOS buoys are registering seas of 7 to 8 ft at 8 seconds this afternoon, and with an increase of a foot or two due tomorrow, rough surf along east facing shores will approach the High Surf Advisory (HSA) level. As winds decline on Thursday and Friday, east shore surf will drop back to seasonable levels. A series of reinforcing south and southwest swells will maintain small to moderate surf along south facing shores across the state through Friday. Slightly larger and longer period south-southwest swells spreading across the state this weekend may cause surf to approach the HSA threshold along south facing shores from Saturday into Monday. See the latest Oahu Surf Discussion (SRDHFO) for additional details on surf and swell. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Thursday for waters around the Big Island, Maui County, and Oahu. && $$ DISCUSSION...Wroe AVIATION...TS MARINE...M Ballard/Wroe 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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