| Current Conditions | ||
| Temp |  | 2.2 C |
| RH | | 57 % |
| Wind | | SW 11 mph |
| Road | | Open (4x4) |
|
Menu of Text Products for the Hawaiian Islands and the Tropical Pacific/Atlantic Oceans: |
|
Narrow the Menu List Select Time Limit: 12 hours | 24 hours | 48 hours | 72 hours | No time limit Select Product Type: All | Routine Bulletins/FCSTS | Warnings/Watches/Advisories | HAWN Weather | Tropical | Marine | Aviation | Daily Obs | Special |
|
|
Hawaiian Islands Synoptic Discussion and Guidance 753 FXHW60 PHFO 181334 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 334 AM HST Thu Oct 18 2018 .SYNOPSIS... Light to moderate trades will continue through the remainder of the work week. The trades will then strengthen to moderate levels over the weekend and possibly reach locally breezy levels next week as high pressure builds north of the islands. Clouds and showers associated with and old front will linger near the Big Island and Maui through the weekend, keeping a showery trade wind pattern in place. Meanwhile, drier conditions should prevail across the western half of the state with mainly windward and mauka showers through Saturday, with a more showery trade wind pattern expected Sunday through early next week. A disturbance aloft will bring unstable conditions and the potential for heavy rain and thunderstorms to Maui and the Big Island Friday night through Sunday as well, which could continue into early next week. && .DISCUSSION... Currently at the surface, a weak ridge of high pressure is centered around 500 miles north of Honolulu, and is driving light to moderate trade winds across the island chain early this morning. Meanwhile, a weakening cold front is located around 450 miles northwest of Kauai. Aloft, an upper level trough is evident in water vapor imagery over Kauai, with a sharper and more potent shortwave trough digging southward around 400 miles north- northwest of Kauai. Infrared satellite imagery shows partly to mostly cloudy skies across the state, with cloud cover most prevalent over windward sections of Oahu eastward to the Big Island. Radar imagery shows scattered showers moving into windward areas, with shower coverage the highest across Maui County and the Big Island. A few showers are also making the trip over the terrain into leeward areas of the smaller islands, with a few showers near the coast of leeward Big Island as well. Main short term concern revolves around the potential for some locally heavy rainfall and thunderstorms associated with a digging upper level trough over the weekend. The ridge of high pressure north of the state will continue to erode over the next couple of days as a cold front passes by well to the north of the island chain. Light to moderate trades are expected to prevail today, then ease slightly tonight through Friday night with local land and sea breezes possible in some of the more sheltered areas. A ridge of high pressure will then become re-established north of the state over the weekend, bringing a return of moderate trade winds, with the trades strengthening to moderate and locally breezy levels early next week. As for sensible weather details, a plume of deep moisture associated with the remnants of an old front, will linger over the Big Island through the weekend and possibly into early next week. In the near term through Friday, showery trade wind weather is expected to persist over the Big Island, with drier trade wind weather expected across the smaller islands. Clouds and showers will favor windward and mauka areas, but we should see some interior and leeward shower development as a result of the weakening trades, particularly on Friday. Additionally, with the airmass remaining unstable over the Big Island, will keep a slight chance of thunderstorms in the forecast each afternoon. The models are advertising quite a different scenario than they were 24 hours ago during the weekend and into early next week. Both the GFS and ECMWF now show a sharp upper trough digging southward over the western islands Friday night, then closing off over the central and eastern islands Saturday through Sunday. The models to differing degrees, then show the weakness aloft lingering over on in the vicinity of the island chain through the first half of next week. Deep moisture associated with the frontal remnants is expected to linger over the eastern end of the state through the middle of next week, so this should keep a showery trade wind pattern in place here. Across the western islands the moisture won't be quite as deep through Saturday night, so expect the shower coverage to not be as great here at least initially. This will likely change on Sunday as the deeper moisture begins to lift back across western islands, making for a more showery trade wind pattern which could continue through the middle of next week. The upper trough/low overhead could also create a fairly unstable airmass Friday night through Sunday, particularly across Maui County and the Big Island. The main hazards would likely be heavy rainfall and thunderstorms. We'll need to monitor model trends closely over the next couple days however, as there is the potential that we could see some severe weather particularly Saturday afternoon and evening as the coldest air aloft rotates overhead. At this time the main severe weather threats, if they materialize, appear to be strong gusty winds and hail. && .AVIATION... Light to occasionally moderate trade winds will continue across the island chain through the day. Brief to TEMPO MVFR conditions will mainly affect windward and mauka sections over all isles. This will especially be the case over the Big Island, and, to a lesser extent, Maui and Molokai. Low level remnant moisture from an old front will affect those isles. Elsewhere VFR will hold sway. An AIRMET for mountain obscuration remains in effect for the windward areas of the Big Island. && .MARINE... Trade winds are forecast to remain weak through Friday night. The trades may gradually strengthen from Saturday into early next week. The current forecast does not have Small Craft Advisory (SCA) conditions over any of the coastal waters or channels through Sunday night. SCA conditions may develop across the typically windy waters adjacent to the islands of Maui County and the Big Island early next week. Unstable atmospheric conditions are forecast to develop over parts of the state toward the end of the work week. This may cause locally heavy downpours, and allow thunderstorms to form across some areas from Friday night into this weekend. Mariners should monitor future weather forecasts as this situation evolves. The current north-northwest swell is gradually declining early this morning. Therefore, the High Surf Advisory (HSA) has been cancelled. The north-northwest swell will continue to slowly subside through this weekend. The weak trades will cause surf to slowly decrease along most east facing shores. However, some east facing shores with a northerly exposure may continue to see small breakers from the north-northwest swell energy during the next couple of days. A new long-period south swell arriving Friday, is expected to peak this weekend. Based on the latest guidance, surf will likely reach the HSA criteria along south facing shores starting Saturday. There is also a possibility surf may approach the High Surf Warning threshold along south facing shores this weekend, before the swell begins to gradually decline early next week. See the latest Collaborative Nearshore Swell and Wind Forecast for Oahu (SRDHFO), which was updated earlier Wednesday afternoon, for more details on swells and surf. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Jelsema AVIATION...Kinel MARINE...Houston Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
|