| Current Conditions | ||
| Temp |  | 5.0 C |
| RH | | 34 % |
| Wind | | W 13 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 865 FXHW60 PHFO 091346 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 346 AM HST Mon Dec 9 2019 .SYNOPSIS... Light easterly winds will continue through the first half of the week as a front stalls and diminishes just north of Kauai. Outside of a few clouds and showers setting up over interior areas each afternoon due to sea breezes, mostly dry and stable conditions are anticipated. Increasing moisture associated with another front that is forecast to move into the area will bring increasing rainfall chances and the potential for gusty northeast winds by the end of the week. && .DISCUSSION... Water vapor imagery showed a ridge extending eastward across the region and a potent shortwave trough far northeast of the state driving a cold front toward the west coast. The surface analysis showed the tail-end of this frontal boundary beginning to stretch out from east to west north of Kauai and a weak ridge extending west- southwestward over the islands. Although mostly dry conditions remain in place, some moisture is beginning to bleed out ahead of this boundary near Kauai, which could be enough to trigger a few showers over the adjacent coastal waters of Kauai through the early morning hours today. Elsewhere, mostly dry and clear conditions will prevail due to the drainage flow associated with the early morning land breezes. The exception is over the southeast Big island waters, where isolated to scattered showers have begun to develop due to a passing trough to the south. The latest short-term (through Tuesday) guidance depicts the aforementioned frontal boundary stalling just north of Kauai today, before retreating northward and diminishing tonight through Tuesday. As this scenario materializes, a return of light trades is expected over the eastern end of the state by Tuesday as the ridge axis shifts back to the north. The land and sea breeze regime, however, remains likely over the western end due to the proximity of this ridge axis. Although dry conditions will prevail, a few clouds and showers setting up over interior areas can't be ruled out each afternoon due to the sea breezes, especially over Kauai where the better source of moisture remains. For the extended period (Wednesday through the weekend), guidance depicts lowering upper heights associated with a strong short wave trough approaching and moving into the area Wednesday through Friday. Although it remains too far out to determine any specifics due to persistent model differences, increasing moisture and rainfall chances along with gusty northeast winds remain a possibility Wednesday night through Friday as the attendant cold front approaches and moves into the area. Just how far down the island chain and how strong this boundary will be upon arrival will continue to be the main forecast challenge this week. && .AVIATION... The light trade wind pattern continues. Expect sea breezes today and land breezes tonight. This forecast period will be relatively dry again through this afternoon. Any showers we have will be isolated. There may be brief periods of MVFR conditions against the slopes but otherwise expect VFR conditions across most of the state. There are no AIRMETs currently in effect or expected. && .MARINE... There are no warnings or advisories in effect for the Hawaii coastal or offshore waters today. A ridge north of the area will maintain light to moderate winds over the area through tomorrow night. Winds will strengthen starting Wednesday as a front moves over the area from the northwest and a strong high builds behind the front. A new northwest swell now spreading into the area is forecast to product surf above the advisory threshold along north and west facing shores starting this evening and continuing through Wednesday morning. As this swell subsides on Wednesday, a new very large northwest swell is expected. Surf from that swell will produce surf well above warning levels along north and west facing shores of the smaller islands. This swell may be large enough to also produce advisory level surf along west facing shores of the Big Island of Hawaii. The swell is expected to gradually subside through Friday night && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Gibbs AVIATION...Chevalier MARINE...Donaldson Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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