| Current Conditions | ||
| Temp |  | -0.2 C |
| RH | | 39 % |
| Wind | | NNE 36 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 322 FXHW60 PHFO 150621 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 821 PM HST Fri Dec 14 2018 .SYNOPSIS... Mostly dry and pleasant weather can be expected over the weekend thanks to a stable trade wind air mass. Winds will gradually diminish over the weekend and on into early next week as the high weakens, due to a front approaching the islands. The front is expected to move down the island chain from late Tuesday through Wednesday with showers increasing with its passage. Cooler and breezy weather will fill in behind the front. && .DISCUSSION... The forecast package was updated to lower the overnight POPS for the smaller island and change the showers to light showers. Satellite imagery shows widely and randomly dispersed low clouds mainly across the island's windward waters. They are moving from east to west with a moderate to strong trade wind flow. Appearance of these clouds suggests stable stratocumulus with a few embedded light showers, especially upwind of the Big Island. Both the GFS and ECMWF, points to some light precip activity over windward Big Island through the weekend, so kept some scattered light nighttime showers in the grids for that area. There is a strong low level inversion at around 5k feet area- wide. This low level inversion is forecast to hold through Sunday, which means the continuation of the nice weather like today, and limiting the light showers. It should be noted, that a patch of radar returns now exiting Kauai County is false returns and not real precipitation. About 280 miles N of Kauai is surface ridge of high pressure. This ridge extends from a 1022 mb high pressure cell located 670 miles NW of Kauai. The two continues to supply the islands with sometimes windy trades. The center the high pressure will be moving east, passing N of the islands on Sunday with central pressure of 1023 mb. It is'nt a very strong high but will be strong enough to produce locally strong trades, felt especially in the more sensitive near-shore waters around Maui County and waters south of the Big Island. See the marine section below for more details. In the mean time, the trades will continue to slowly trend down. It looks like, based on the latest GFS model from this evening, the trades will lower to below Small Craft Advisory strength by Tuesday, with our winds becoming light and variable Monday night. A front is expected to be near the far NW offshore waters Monday night. Twelve hours later, the front weakens to where light northerly winds forge ahead of the actual front, which is just NW of Kauai, to over Kauai and Oahu. The front will be accompanied by some scattered showers as it work its way down the island chain. Expect the front to be east of the Big Island by Wednesday evening. Moderate to strong trades fill in behind the front along with a cool and dry air mass. && .AVIATION... A deep-layer ridge centered N of the islands will change little through Saturday, with stable trade wind weather prevailing. The moderate to locally fresh ENE trade winds will deliver stable low clouds that will favor windward areas, and a subsidence inversion based near 5500 feet will keep any rainfall very light. While brief and ISOL MVFR ceilings may occur, VFR conditions will prevail statewide. AIRMET Tango for low-level turbulence to the S and W of the mountains will remain posted into at least Saturday. && .MARINE... Trade winds are expected to ease some tonight and Saturday, with the typically windier areas near Maui and the Big Island continuing to see Small Craft Advisory (SCA) level winds. The current northwest swell continues to bring elevated seas, maintaining SCA level seas for other coastal waters near Molokai through tonight. With the trade winds easing, expect surf along east facing shores to lower. The High Surf Advisory (HSA) for east facing shores was thus cancelled. A new northwest swell will arrive late in the day Saturday, and rise rapidly to warning levels. It is expected to peak Sunday, and then subside some on Monday. An even larger northwest swell will build late Monday, once again peaking at warning levels. Exposed coastal waters will once again rise to over 10 feet as these swells come rolling through. Expect the current SCA to once again be expanded to most, if not all, the coastal waters for the first half of the new week as the new swells arrive. See the latest Oahu Surf Discussion (SRDHFO) for additional details on surf and swell. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. Small Craft Advisory until 6 AM HST Saturday for Kaiwi Channel- Maui County Windward Waters-Maui County Leeward Waters-Big Island Windward Waters. && $$ H Lau/Birchard/Kinel Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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