Current Conditions | ||
Temp | ![]() | 4.7 C |
RH | ![]() | 54 % |
Wind | ![]() | SW 9 mph |
Road | ![]() | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 762 FXHW60 PHFO 172006 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 1006 AM HST Sun Jan 17 2021 .SYNOPSIS... A wet pattern is on tap for the islands during the first half of the coming week. This comes about as a front moves down the island chain this afternoon and tonight, then stalling around Maui and the Big Island between Monday and Tuesday. The front, or trough, is then slated to drift back to Oahu and Kauai between Tuesday afternoon and Wednesday. The front will have good support aloft from an upper level disturbance, resulting in heavy showers and isolated thunderstorms. On top of the rain, strong northerly winds will follow in behind the front. Moderate to strong easterly trade winds return to the region during the second half of the week with a bit of a wet flavor. && .DISCUSSION... The leading edge of a cold front is located about 160 miles northwest of Kauai this morning. This front is moving toward the state at around 20 mph. For rest of the day today, we will see light to moderate southerly winds ahead of the front which will bring clouds and scattered showers across the state. As the front nears Kauai this afternoon into evening, increasing chances of heavy rain and isolated thunderstorms are expected. A brief burst of heavy rain is likely as the front quickly makes its way through Kauai late this afternoon into the evening. As the front makes its way through Oahu and Maui County tonight, we should see the front slowing and eventually stalling near Maui and the Big Island on Monday. With the forward speed of the front slowing, this will bring a greater threat for flooding concerns, thus a Flash Flood Watch is in effect for Oahu and Maui County starting tonight and continuing through Tuesday. Behind the front, we will see strong (15 to 30 mph) northerly winds fill in and will likely lead to an issuance of a Wind Advisory by Monday for the smaller islands. Although the front looks to dissipate on Tuesday, moisture associated with the front will continue to linger near Oahu and Maui County. The strong northerly winds should taper off by then, and breezy trades should return. The trade winds should focus the showers across windward and mountain areas. A trade wind pattern is expected for the second half of the week but due to lingering moisture, we will likely see a more of a wet trade wind pattern. && .AVIATION... A front will reach Kauai and move down the island chain later today through tonight. While clouds and showers are associated with the frontal cloud band, showery prefrontal cloud areas are affecting the islands now. The bulk of this activity is confined to Kauai and adjacent waters but will gradually shift east. Prevailing VFR is therefore forecast for Oahu through Big Island for the balance of the daylight hours. For Kauai, the probability of MVFR will begin increasing over Kauai by this afternoon as low-level moisture increases. Issuance of AIRMET Sierra for tempo mountain obscuration is likely by this evening. The arrival of the cold front is expected for Kauai around 02z/4pm HST and around 06z/8pm HST for Oahu and will be marked by a greater coverage of showers, some locally heavy, followed by abrupt shift to gusty northerly winds. && .MARINE... An approaching cold front has pressed a ridge axis over the state. This has created weakly convergent, light to moderate south to southwesterly winds across the majority of the waters. The front will enter the nearshore Kauai waters late this afternoon and make it into Oahu's waters later this evening. The front is forecast to stall out over the central island chain going into early Monday. The approach and passage of the front will introduce locally heavy showers and the potential for isolated thunderstorms. The movement of the upper trough over the western islands through Tuesday will maintain this shower and thunderstorm potential. A High Surf Warning (HSA) is in effect for exposed north and west-facing shores through Monday night. Despite a brief lowering of surf below warning levels on Kauai this morning, along with surf falling below warning levels along the remaining smaller isles by tonight, the HSA will remain in effect to account for the next large northwest swell's arrival tonight. This powerful northwest swell will build tonight through Monday and push surf back up to warning levels along north and west-facing smaller island shorelines through Monday morning and north-facing Big Island shores Monday afternoon. Peak surf heights late Monday into early Tuesday are expected to be slightly lower than they were during this most recent weekend XL surf event. Strong north to northeast winds in association with an early week cold front will result in lesser quality wave shapes during the passage of the highest swell. While these most recent swell directions of around 330 degrees are not traditionally favorable for significant impacts within both Kahului and Hilo Bay Harbors (as with a more north swell direction), there is a Marine Weather Statement in effect to address the potential for some harbor surge impacts. A Small Craft Advisory (SCA) remains in effect for all waters except Maalaea Bay through the day as passing northwest swells continue to produce greater than 10 foot seas. Seas will diminish today with a slowly subsiding swell. Seas will again be on the rise tonight and Monday with a newly arriving northwest swell. A Gale Watch will be in effect beginning tonight for the Alenuihaha Channel and westward waters as strong post-frontal north to northeast winds may frequently gust to greater than gale force. && .HFO WATCHES/WARNINGS/ADVISORIES... Flash Flood Watch from 6 PM HST this evening through Tuesday afternoon for Oahu-Molokai-Lanai-Kahoolawe-Maui. High Surf Warning until 6 AM HST Tuesday for Niihau-Kauai Windward-Kauai Leeward-Waianae Coast-Oahu North Shore-Oahu Koolau-Olomana-Molokai-Maui Windward West-Maui Central Valley- Windward Haleakala. High Surf Advisory until 6 AM HST Tuesday for Kona-Big Island North and East-Kohala. Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters except Maalaea Bay- Gale Watch from 6 PM HST this evening through late Monday night for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters- Kaiwi Channel-Maui County Windward Waters-Maui County Leeward Waters-Maalaea Bay-Pailolo Channel-Alenuihaha Channel. && $$ DISCUSSION...Kino AVIATION...Powell MARINE...Blood Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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