| Current Conditions | ||
| Temp |  | 7.7 C |
| RH | | 29 % |
| Wind | | NE 22 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 882 FXHW60 PHFO 171945 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 945 AM 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 morning. 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 6,000 ft. A mix of stable stratocumulus and shower-bearing cumulus clouds is moving along the trade wind flow, leading to generally a quarter inch or less of rainfall across most windward slopes during the past 24 hours. Expect little change today, along with typical summertime clouds and scattered showers across the South Kona slopes of the Big Island during the afternoon hours. 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 may 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, an upper level trough currently sitting several hundred miles northwest of Kauai will drift closer to Kauai. This feature is produce spotty thunderstorms about 275 miles northwest of Kauai, and as it shifts closer, thunderstorms could pop up closer to the state. 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 showers activity. Another increase in rainfall is possible on Sunday. && .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 today, 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 will see persistent MVFR conditions and increasing showers tonight as deeper moisture moves in from the east. AIRMET Sierra is no longer in effect for mountain obscuration. Extensive mountain obscuration is not expected through this afternoon. 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 this evening. && .MARINE... High pressure to the north of the islands will maintain a locally breezy trade wind pattern over the islands through tomorrow. A trough to the southeast of the islands will continue to move west, passing south of the islands later this week. As it moves to the west, the pressure gradient particularly over the southern end of the islands will increase, causing another uptick in the winds. A Small Craft Advisory remains posted for a number of zones, and the SCA could be expanded to additional zones as the situation develops. This trough will also bring an increase in seas late tonight and tomorrow, that will bring seas in excess of 10 feet to some areas south of the Big Island. The locally breezy trade winds combined with a small short-period northeast swell may cause choppy surf along east facing shores to approach the High Surf Advisory criteria from Wednesday into Thursday. Surf along along east facing shores is expected to gradually subside from Friday through this weekend as the trade winds weaken. 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 High Surf Advisory 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 Kaiwi Channel- Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters- Big Island Southeast Waters. Small Craft Advisory from 6 PM this evening to 6 AM HST Thursday for Oahu Leeward Waters. && $$ DISCUSSION...Wroe AVIATION...TS MARINE...M Ballard Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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