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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 832 FXHW60 PHFO 182011 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 1011 AM HST Thu Jul 18 2019 .SYNOPSIS... High pressure far to the north will support locally breezy trade winds into next week, although winds will be a little less gusty by the weekend. Showers riding in with the trades will favor the windward and mountain areas, with showers most frequent during nights and mornings. An area of especially showery clouds will arrive later today, and bring numerous windward showers to all islands through tonight, with a few showers spreading leeward. The leeward side of the Big Island will have clouds and a few showers every afternoon and evening. && .DISCUSSION... High pressure will remain entrenched far N and NE of the islands over the next week, supporting a seasonable trade wind weather pattern. The high will support locally strong ENE trade winds initially, with wind speeds easing slightly over the weekend as it weakens a little. With trade winds blowing, we look for potential moisture sources and/or destabilizing features to anticipate shower coverage and intensity. While most showers affect windward areas, strong trades and instability can bring occasionally bring rainfall to leeward areas of the smaller islands. On the Big Island, this is the wet season for the leeward slopes, where increased instability usually leads to greater shower coverage and intensity. After a few morning showers that affected primarily Oahu and Maui, an area of mostly clear skies lies immediately upstream of the islands from Maui to Kauai, and windward showers are expected to be minimal the next couple of hours. The leading edge of an area of open-celled showery cumulus clouds is approaching from the E, and will soon arrive over windward Big Island, bringing an increase in shower coverage, especially as compared to the current mostly dry conditions. This area of showery low clouds will traverse the island chain later today and overnight, bringing categorical rain chances to windward areas, with a few showers occasionally spreading leeward with the gusty trade winds. This moisture will move W of the islands on Friday, with models depicting another slug of low level moisture (now near 27N 143W) arriving from the ENE late Saturday into Sunday. Current soundings indicate a strong subsidence inversion keeping a lid on low clouds at around 8000 feet or so, with elevated instability above about 12000-15000 feet. This instability is due to a slow-moving persistent low aloft centered several hundred miles N of the islands. Although the low aloft will drift N over the couple of days, the associated E-W oriented trough will become N-S oriented over the islands by tomorrow. Models do not depict significant destabilization of the lower portions island atmosphere, but incoming cumuli will be able to grow sufficiently tall to drop showers as the subsidence inversion is weakened into early next week. Additionally, the low will bring periods of high clouds, potentially becoming thick over parts of the state at times. A ridge aloft is expected to bring increased stability by the middle of next week. && .AVIATION... A high about 1100 miles northeast of the main Hawaiian islands will remain nearly stationary. The high will maintain locally strong east winds over the islands through Friday. AIRMET Tango is in effect for moderate turbulence below 7,000ft and this AIRMET will likely continue into Friday. The low level winds will carry some clouds and showers over east sections of the islands. The incoming clouds are currently rather sparse and stable and VFR conditions prevail. An area of showery broken low clouds just upstream of the Big Island of Hawaii will move over the islands later today and will likely produce MVFR conditions over east sections. Localized MVFR conditions are also possible over the west slopes of the Big Island this afternoon. AIRMET SIERRA for MTN OBSC could be required. The area of showery low clouds should clear the islands Friday afternoon. && .MARINE... High pressure north of the state will maintain fresh to strong trade winds through Friday. The high is expected to weaken some over the weekend, which will help the winds ease slightly. Trade winds may drop to moderate speeds early next week for a brief day or two. The Small Craft Advisory (SCA) continues through Friday afternoon for all waters in response to the trade winds. The forecast calls for the winds to start to weaken Friday night, which will drop the SCA back to the typical windier areas around Maui and the Big Island. This SCA will likely be extended through the remainder of the weekend. Rough and choppy surf is expected to hold steady along east facing shores at heights just below the advisory threshold through Friday. As the winds ease over the weekend, surf is expected to drop slightly. Some small background south and southwest swells are expected through the weekend. An increase in surf along south facing shores is possible early next week as a couple southwest swells arrive in the islands. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. Small Craft Advisory until 6 PM HST Friday for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Big Island Windward Waters. && $$ DISCUSSION...Birchard AVIATION...Donaldson MARINE...Kino Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office

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