| Current Conditions | ||
| Temp |  | 4.7 C |
| RH | | 7 % |
| Wind | | N 6 mph |
| Road | | Closed |
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Hawaiian Islands Synoptic Discussion and Guidance 308 FXHW60 PHFO 221332 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 332 AM HST Tue Oct 22 2019 .SYNOPSIS... High pressure northeast of the state will keep moderate to locally breezy trade winds in place through Wednesday. The trades will ease Thursday through Saturday as a series of fronts approach from the northwest. The trades are then expected to strengthen Sunday through early next week. Fairly typical trade wind weather will prevail, with showers favoring windward and mauka areas and a stray shower reaching leeward locales from time to time. && .DISCUSSION... Currently at the surface, a 1031 mb high is centered around 1775 miles northeast of Honolulu, while a cold front is located around 1275 miles west-northwest of Kauai. The resulting gradient is producing moderate to locally breezy trade winds across the island chain early this morning. Infrared satellite imagery shows partly cloudy skies in windward areas of the smaller islands, with mostly cloudy conditions in place over windward Big Island. Clear to partly cloudy conditions prevail in most leeward locales. Radar imagery shows isolated to scattered showers moving into windward areas, with shower coverage the greatest across windward Big Island. Mainly rain free conditions are in place in leeward locales. Main short term concerns over the next several days revolve around trade wind trends and rainfall chances. High pressure northeast of the state will keep moderate to locally breezy trade winds in place through Wednesday. A weakening cold front will approach from the northwest Wednesday night and Thursday, then stall out a few hundred miles north of Kauai through the weekend. A secondary cold front will approach from the northwest over the weekend and stall out in roughly the same position, a few hundred miles north of Kauai early next week. These fronts should ease the trades into the light to moderate range Thursday through Saturday, with localized land and sea breezes possible in the more sheltered locations. Moderate trade winds will try to make a return Sunday through early next week as the gradient across the island chain tightens up due to high pressure strengthening to the north of the state. As for forecast details, fairly typical trade wind weather should prevail during the next 7 days, with showers favoring windward and mauka areas, particularly at night through mid morning each day. A stray shower will also reach leeward areas from time to time. There could be a slight increase in leeward shower activity Thursday through Saturday as the trade winds ease, allowing for some sea breeze driven shower development as well. Overall, rainfall amounts are expected to remain on the light side through early next week. && .AVIATION... Passing, isolated areas of MVFR conditions on the windward side of the islands are expected through this forecast period. Will monitor and issue an AIRMET for mountain obscuration if necessary. Otherwise, the rest of the state will see VFR conditions. AIRMET Tango is in effect now for areas south and west of the mountains for low-level turbulence below 8,000 ft. Will probably continue this AIRMET through today. May be able to drop this AIRMET later tonight or Wednesday as winds are expected to weaken. && .MARINE... High pressure centered far northeast of the islands will maintain moderate to strong trades through Wednesday. The evening ASCAT pass revealed small craft advisory level (SCA) winds extending beyond its usual near-shore waters of Maui County and waters south of the Big Island. The SCA now includes the windward waters of Maui County and leeward waters of Oahu. These additional waters are good until late tonight. With this weakening trend, the last of the SCA, which include the typically windy areas of Maui County and waters south of the Big Island, is set to expire late Wednesday afternoon. The weakening of the trades is being caused by a front settling some 450 miles north of Kauai by Thursday. The front may linger near the northern extreme of our offshore waters into the upcoming weekend. Additionally, a weak area of surface low pressure is expected to form some 850 miles northwest of Kauai as well, which may help in maintaining moderate trades across the island waters over the weekend. Small surf will remain along all shores today. A series of northwest swells are then expected over the coming days with each bump being a little bit larger. A small bump first rolls in on Wednesday followed by a moderate northwest swell on Friday. Then, on Saturday night, a large northwest swell arrives, bringing advisory level surf to the north and west facing shores between Sunday and Tuesday. This swell will peak Monday before trending down slowly. Locally strong trade winds will maintain mainly moderate level surf along east facing shores through Wednesday, followed by slightly smaller surf during the second half of the week as the trades become lighter. A small background swell will maintain small surf for the south facing shores through the rest of the period. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. Small Craft Advisory until 6 AM HST Wednesday for Oahu Leeward Waters-Kaiwi Channel-Maui County Windward Waters. && $$ DISCUSSION...Jelsema AVIATION...Chevalier MARINE...H Lau Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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