| Current Conditions | ||
| Temp |  | 4.2 C |
| RH | | 83 % |
| Wind | | WNW 7 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 978 FXHW60 PHFO 172005 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 1005 AM HST Wed Oct 17 2018 .SYNOPSIS... Moderate trades will slowly weaken through Friday, then strengthen again on Saturday. Remnants of a front will linger near the Big Island for the next few days. A trough aloft will bring somewhat unstable conditions around the Big Island before moving away Saturday night. Drier weather will persist for the western half of the state this week. && .DISCUSSION... A weak surface ridge is centered around 600 miles north of Kauai this morning driving gentle to moderate trade winds across the island chain. Visible satellite shows a remnant frontal band lined upstream of the Big Island and Maui with trade winds carrying the clouds and showers over windward sections of these islands. The northern end of the shower band is also impacting windward Molokai and Oahu. Rainfall amounts and intensity has been light. Meanwhile, leeward sides of the islands are seeing mostly sunny skies this morning. Water vapor imagery shows a trough aloft over the western portion of the state. 12Z soundings show weak and elevated midlevel inversions at Hilo and Lihue. The upper trough will remain nearly in place through Saturday and will act to create more enhanced showers, particularly near the Big Island where moisture levels will continue to be a bit higher from the remnant front. There is also a slight chance of thunderstorms over the next several afternoons on the Big Island. Elsewhere, expect similar weather to continue, with windward and mauka clouds and a few passing showers. A front will pass by to the north of the island chain Thursday through Friday, weakening the high pressure ridge, and easing the trades slightly. Light trades should prevail across the entire island chain by Friday, with some of the more sheltered areas possibly seeing land and sea breezes develop. High pressure will become better established to the northwest of the state over the weekend, bringing a return of moderate trade winds to the island chain that will last through early next week. The upper trough is also forecast to move away to the east Saturday night. && .AVIATION... Light to locally brisk trade wind flow continues. Bands of showers embedded in the the flow will continue to impact mainly north and east facing slopes and coasts while leeward coasts and adjacent waters experience mostly clear skies. A thick band of low clouds continues to shroud the Windward coasts the Big Island and Maui. AIRMET Sierra remains in effect for north through east facing slopes of both the Big Island and Maui. Conditions are expected to gradually improve from the west, so Maui will likely be removed from Sierra later today. Mostly clear skies over Leeward Big Island this morning will give way to sea-breeze driven cumulus build ups in the afternoon. Shower activity should be limited to mountainous areas while the coast remains excellent VFR. The airmass over Maui and the Big Island remains moderately unstable. Slight chance of thunderstorms again over interior Big Island late this afternoon and early evening. Over the remainder of the state, the air mass is becoming increasingly stable. High based stratocumulus tops are not expected to exceed about 8000 ft west of Molokai. Shower activity will be light and limited. && .MARINE... A check of the nearshore buoys this morning show the current north-northwest swell is still at its peak, but is starting to show signs of declining. The High Surf Advisory (HSA) for north and some west facing shores continues today, and will be monitoring the swell decline today to see if surf will indeed drop below advisory levels by sunset. The swell continues to produce some seas in excess of 10 feet over waters exposed to the northwest, but are expected to drop below 10 feet this afternoon. The trade winds are already on the decline, with most areas below Small Craft Advisory (SCA) levels already. The current SCA is in effect until 6pm, but may be able to cancel that a little earlier if the winds and seas continue to subside. Trade winds will continue to weaken through the end of the week. After the current SCA event ends, no SCA is anticipated through the weekend. The next north-northwest swell is expected to arrive this weekend, but remain below advisory levels. Surf along south facing shores will continue to decline today, with a new south swell expected to arrive Friday, peaking Saturday into Sunday at high end advisory or low end warning levels. See the latest collaborative surf discussion (SRDHFO) for more details. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory until 6 PM HST this evening for Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley- Windward Haleakala-Big Island North and East. Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters-Alenuihaha Channel-Big Island Windward Waters. && $$ DISCUSSION...Foster AVIATION... MARINE... Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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