| Current Conditions | ||
| Temp |  | 2.3 C |
| RH | | 23 % |
| Wind | | NNE 2 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 633 FXHW60 PHFO 151330 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 330 AM HST Fri Jan 15 2021 .SYNOPSIS... Generally light winds and mostly dry weather is expected today as high pressure moves off far to the northeast of the area. A front is expected to approach and gradually dissipate just northwest of Kauai tonight and Saturday. Some increase in showers is possible over the western end of the state with this front. A much stronger front is then forecast to move into the area Sunday through Monday, possibly stalling out over the eastern end of the state through the middle of next week. Rainfall chances increase statewide with the passage of this front, with thunderstorms and locally heavy rainfall possible. Cool and breezy northerly flow is expected following the frontal passage. Trade winds may return late next week. && .DISCUSSION... Currently at the surface, a 1030 mb high is centered around 2000 miles northeast of Honolulu, with ridging extending southwestward and over the western islands. Meanwhile, a cold front is located around 475 miles west-northwest of Kauai. The resulting gradient is producing light to moderate east-southeasterly winds around the Big Island, while winds remain light and variable over the rest of the state. Infrared satellite imagery shows clear to partly cloudy skies across most of the state, although mostly cloudy skies conditions are in place over Kauai. Radar imagery shows a few showers moving through Kauai and into windward Big Island, with rain free weather over Oahu and Maui County. Main forecast concern continues to revolve around the potential for unsettled weather late in the weekend into early next week. Today through Saturday... The front far to the northwest of the state will track steadily southeastward toward the island chain today. Light to moderate trades will hold in place over the eastern islands during this time, while light and variable winds will allow for land breezes and sea breezes to develop over the western islands. The front will stall out and gradually dissipate around 100 miles northwest of Kauai tonight and Saturday, while a weak high builds eastward well to the north of the island chain. This should bring a brief return of trade winds to the area late tonight, with trades strengthening to moderate and locally fresh levels on Saturday. Relatively dry conditions will prevail through the period as deep layer ridging holds in place over the islands. Saturday night through next Thursday, The next cold front will approach from the west Saturday night, then move through Kauai late Sunday. The global models have come into better agreement with the 00z model cycle, showing the front pushing eastward through Oahu and Maui County Sunday night, then stalling out over or just east of the Big Island Monday through Wednesday. Cool and breezy conditions are expected following the frontal passage, at least over the western end of the state. A new strong high then appears to build northeast of the islands late next week, swinging the old frontal remnants back westward across the island chain, and bringing a return of trade winds. Confidence has increased on the potential for some locally heavy rainfall in association with this stronger front beginning late Sunday and continuing through at least Wednesday and possibly right through Thursday. At the moment, the models appear to be indicating a higher potential for a long duration heavy rainfall event would be over the eastern end of the state. Given that the models have just begun to come into better agreement however, prefer to wait another model cycle or two before ironing out the details. As a result, will continue to keep rain chances in the forecast statewide throughout the extended portions of the forecast. Will also maintain the mention of thunder and locally heavy rainfall along and in close proximity to the front as it moves through the area Sunday through Monday night when confidence in timing details is the highest. Future shifts may need to extend the mention of thunder and locally heavy rainfall to portions of the area through Wednesday and possibly next Thursday, so stay tuned. && .AVIATION... Showers will continue to threaten the southern half of Kauai until shortly after sunrise as the convergent southerly winds gradually become light and variable as the morning progresses. This light and variable wind pattern will favor an onshore sea breeze flow, but an inversion will be strong enough to hold down the convective showers to isolated. The return of the trades by tonight means there will be an uptick in showers favoring the windward and mountain areas. This shift in the winds is being caused by an approaching front from the northwest. The front is forecast to stall and fall apart a short distance from Kauai, but in doing so, some of this moisture may leak over to Kauai tonight. No AIRMETs in effect, and none are expected today. && .MARINE... Two cold fronts will move into Hawaiian waters over the next several days. Winds will veer from the southeast and weaken today ahead of a cold front approaching from the northwest. Another, stronger front is forecast to move down the island chain from the northwest Sunday through Monday, bringing strong northerly winds to the western half of the state and possible thunderstorms along the front as it passes through each island. A Small Craft Advisory (SCA) remains in effect for most coastal waters until Friday evening for elevated seas. An extra large northwest swell will build into the northwest waters by early Saturday morning with a return to SCA conditions for elevated seas. A series of large to extra large northwest swells will impact the state through early next week. The current northwest swell will slowly trend lower today. Surf heights will remain at advisory levels today for north and west facing shores of the smaller islands (north facing shores of Maui and the Big Island). The first extra large northwest swell will arrive this evening, quickly pushing surf well above warning levels by Saturday morning. This new northwest swell will potentially become the largest surf event of the season so far. Surf will trend slowly lower Saturday night through Sunday, but remain well above warning levels through the weekend. Another extra large northwest swell is expected to build into Hawaii waters on Monday, producing another round of warning level surf. This swell begins to diminish Tuesday as another north swell fills in, with moderate swell heights holding through Wednesday. Some larger surf may wrap into south and east facing shores exposed to large northwest swells. Otherwise, surf along south and east facing shores will remain small through the first half of next week. && .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-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-Kaiwi Channel-Maui County Windward Waters-Alenuihaha Channel-Big Island Windward Waters. && $$ DISCUSSION...Jelsema AVIATION...H Lau MARINE...Morrison Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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