| Current Conditions | ||
| Temp |  | 4.6 C |
| RH | | 20 % |
| Wind | | ENE 13 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 076 FXHW60 PHFO 051413 CCA AFDHFO Area Forecast Discussion...CORRECTED National Weather Service Honolulu HI 413 AM HST Sat Dec 5 2020 .SYNOPSIS... A cold front moving into the region from the northwest will continue to weaken the high pressure ridge north of the islands for the next few days. Trade winds will diminish as the front approaches the islands with winds becoming more variable land and sea breezes with a few interior showers each afternoon through Sunday. Higher pressure will build back in north of the state with moderate trade winds and passing showers forecast from Monday afternoon through Tuesday. Light and variable winds return on Wednesday and Thursday as yet another cold front moves into the region. && .DISCUSSION... This mornings satellite imagery shows stable conditions over the islands with scattered cloud cover in a light background southeasterly wind regime. The band of clouds associated with the old cold front has drifted northwest of the state. A cold front roughly 900 miles northwest of Kauai will approach the state over the next few days, decreasing wind speeds across the region. The short range forecast guidance shows the islands on the edge of the high pressure ridge axis through the weekend. Weaker large scale pressure gradients under this ridge will weaken wind speeds transitioning towards a light and variable wind pattern starting later this afternoon through Sunday. A background large scale light southeasterly flow will develop. In the absence of strong large scale winds we expect local scale light and variable land and sea breezes to form over the islands. Onshore sea breezes on Sunday will lead to clouds building up over mountains and island interior sections with a few showers in the afternoon to early evening hours. On Monday, the front stalls north of the islands and another migratory high moves into the Central Pacific basin from the west. High pressure building north of the islands will lead to a return to moderate trade winds from Monday afternoon through Tuesday. In the longer range forecast on Wednesday, light to moderate southeasterly winds will develop across the region ahead of the next approaching cold front northwest of the state. By Thursday we see increasing trends in passing showers due to an upper level trough moving across the state from west to east in a light to moderate southeasterly weather pattern. Weather models are in fair agreement with this changing weather pattern. The timing on these wind and weather conditions may change a bit as the 5 to 7 day forecast period gets shorter. && .AVIATION... High pressure northeast of the state will weaken during the next 24 hours as a cold front approaches from the northwest. As a result, the trades will diminish from east to west across the state today. Sea breezes are expected to develop in many areas by late this afternoon, with land breezes common statewide tonight. Rather dry weather is expected across the island chain, with only a few isolated showers affecting windward areas this morning, and interior sections this afternoon. AIRMET TANGO remains in effect for moderate low-level turbulence over and downwind of terrain of all islands. Conditions should improve by late this morning. && .MARINE... High pressure northeast of the state will maintain moderate to locally fresh trades through the morning hours. As the East Pacific high retreats a little further east in tandem with an approaching northwest front, the pressure gradient back across the chain should weaken later today and subtly weaken winds. The Small Craft Advisory (SCA) has been extended through today but scaled back to just include the Alenuihaha Channel and the waters surrounding the Big island. Trades will gradually fall off through early Monday, especially over the western end of the state in response to the approaching boundary. An SCA for building seas may be needed Sunday in association with an incoming larger, long period northwest swell. A quick-hitting moderate period northwest swell will come across during the day that will lift western island north and west-facing shoreline surf to near High Surf Advisory levels. A larger and longer period northwest swell is anticipated to fill in early Sunday. This swell is projected to drive surf heights along north and west-facing shores to above High Surf Warning levels. This swell will diminish from Monday on into the middle of the week. This will allow surf to fall below Surf Advisory levels on Wednesday. Relatively longer duration Surf Advisory to Warning-level surf along with higher than predicted water levels will only exacerbate ongoing coastal erosion issues. The best chance for water to reach vulnerable coastal properties and roadways will be around daybreak on Monday when the daily high tide could coincide with the peak of this early week large northwest swell. Surf along east-facing shores will remain small over the weekend, then trend up slowly next week as the trades fill in locally and upstream of the islands. Surf along south-facing shores will remain small with a mix of small, short period southeast and background south southwest energy moving up from the Southern Hemisphere. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST this evening for Alenuihaha Channel-Big Island Windward Waters-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Bohlin AVIATION...Jelsema MARINE...Blood Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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