| Current Conditions | ||
| Temp |  | -0.3 C |
| RH | | 98 % |
| Wind | | SW 35 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 281 FXHW60 PHFO 191423 AAA AFDHFO Area Forecast Discussion...UPDATED National Weather Service Honolulu HI 423 AM HST Fri Oct 19 2018 .UPDATE... The zones were updated to include thunderstorms for the 2 Big Island summits this afternoon. && .SYNOPSIS... A rather light trade wind flow will persist through today before a gradual strengthening takes hold tonight through Saturday. A strong upper level disturbance will bring some unsettled weather to most of the islands over the weekend, but especially targeting the Big Island. This unsettled trade wind regime may linger into next week. && .DISCUSSION... The Kona area of the Big Island had an active evening with heavy showers and thunderstorms, resulting in rainfall totals of up to 1.16 inches recorded at Kona Airport. Some of the blow-offs spilled over to the summits of Mauna Kea and Mauna Loa with a light dusting of snow at the higher elevations. No real change to the reasoning behind the forecast. After the overnight showers and thunderstorms in the Kailua-Kona area, we suspect the weather will get more active especially over the Big Island this afternoon and evening. Thus, we dished out a Flash Flood Watch for the Big Island that is good through 4 pm HST Saturday afternoon. The approaching upper level disturbance will deepen the already establish upper trough over the islands. The deepened upper trough will moving eastward tonight starting from Kauai. In doing so, the weather will be getting rather active area-wide with heavy showers and a outside chance of a thunderstorm just about every where across the main Hawaiian Islands. The upper trough pinches off an upper low over the Big Island Saturday night and stays there through Monday. This is per the latest 06Z GFS run, which is now siding with the ECMWF (EC) solution. The new EC run still maintain its stance of an upper low over the Big Island through Monday before moving westward to Kauai by Wednesday. The GFS outlook is much friendly too. The upper low/trough continues to linger around the Big Island or the eastern part of the island chain, including Maui, through at least Wednesday. To probably make things look more bleak, the trades could be carrying some tropical moisture to the islands toward the middle of next week with the Big Island getting the brunt of the weather. Currently, the smaller islands are in O.K. shape with some minor trade wind showers. Multilayered clouds cover all the islands but Kauai. The layered clouds are also passing through the Big Island from the southwest, grazing the very top of the two summits at 13k feet in the process. There are a couple of thunderstorms, one located just beyond the coastal waters some 50 mile out from the Kona coast. A couple of thunderstorms are noted 30 miles east of Cape Kumukahi of the Big Island. Radar is just beginning to pick up higher tops from showers elsewhere outside the Big Island premise, a 25k foot top 20 miles south of Hawaii Kai Oahu. && .AVIATION... Light trade winds will hold through the day and into tonight. There will also be periods of daytime sea breezes and nighttime land breezes because of the weak overall flow. Brief MVFR ceilings and/or visibilities will mainly affect windward and mauka sections around the island chain, especially the Big Island where remnant moisture from an old front lingers. Too, statewide afternoon interior and leeward showers are possible when seas breezes become established. And a slight chance of thunderstorms will exist around the Island of Hawaii as well. No AIRMETs are currently in effect, though mountain obscurations are possible with afternoon cloud buildups and showers. && .MARINE... The arrival of a significant long-period S swell is anticipated today and tonight, with surf along S facing shores of all islands building to advisory levels by Saturday. A High Surf Advisory has been issued, with the swell expected to remain elevated for several days. Peak surf heights with this long-lived swell could approach the south shore High Surf Warning threshold (15 feet) over the weekend, and buoy observations will be monitored to fine tune the forecast. Elsewhere, surf heights will remain below advisory levels for at least the next several days, although a new short- period NNW swell is expected today. See the Oahu Surf Discussion (SRDHFO) for additional details. Light to locally moderate trade winds are expected through tonight, with a gradual increase in NE trade winds Saturday as high pressure builds NW of the islands. Winds should remain below Small Craft Advisory (SCA) speeds through Sunday, with moderate to locally fresh trade winds potentially requiring a SCA for the windier zones early to mid next week. Uncertainty with this portion of the forecast is due to forecast models increasing the low-level pressure gradient as a tropical disturbance passes S of the islands. A persistent upper-level trough over the area will develop a cut- off low this weekend, maintaining unstable conditions that will bring the threat of locally heavy showers and/or thunderstorms, especially over Big Island waters. && .HFO WATCHES/WARNINGS/ADVISORIES... High Surf Advisory from 6 PM this evening to 6 PM HST Monday for Niihau-Kauai Windward-Kauai Leeward-Oahu South Shore-Waianae Coast-Molokai-Lanai Makai-Kahoolawe-Maui Leeward West-Maui Central Valley-Windward Haleakala-Leeward Haleakala-Kona-South Big Island-Big Island North and East-Kohala. Flash Flood Watch through Saturday afternoon for Big Island. && $$ Lau/Kinel/Birchard Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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