A normal trade wind pattern expected to prevail over the Island of Hawaii through Saturday (February 13th) with Kona wind pattern (light sea and land breeze conditions) will take over from late Saturday through the beginning of next week.
Published by: HIRSC - Weather Team
Rather dry and stable trade wind weather will prevail during the next couple of days as a ridge holds north of the islands. Winds will shift out of the east to southeast late Friday and over the weekend, when increasing moisture moving up from the southeast will lead to an uptick in showers. Unsettled weather may develop over the islands by the middle of next week.
Currently, at the surface, a 1023 MB high is centered around 950 miles northeast of Honolulu, while a cold front is located around 900 miles west-northwest of Kauai. Light to moderate trade winds prevails over the island chain this evening, with the trades strongest over the eastern end of the state. Infrared satellite imagery shows stable stratocumulus fanning out beneath a sharp low-level inversion depicted between 4.5 and 6.0 kft by the 11/00Z soundings from Lihue and Hilo. Clear to partly cloudy conditions prevail in most leeward areas, with mostly cloudy skies in most windward locales. Radar imagery shows a few light showers over windward sections of the Big Island, with very little rainfall elsewhere. Main short term concerns revolve around trade wind trends and rain chances through the weekend. Tonight through Sunday... High-pressure northeast of the state will edge further east during the next couple of days, then strengthen slightly while remaining nearly stationary around 1500 miles northeast of the state over the weekend. Moderate to locally breezy trades will prevail over the eastern islands, while the western islands see light to moderate trades. Some disruption to the trade flow appears likely across the western islands Friday through the weekend, however, which would bring localized sea breezes and land breezes, particularly to leeward areas. Rather dry conditions will prevail through Friday, although the air mass will gradually be modifying. Light showers will be confined to windward areas with very little shower activity expected to make it into leeward locales during this time. Precipitable water values will then climb back to normal levels Friday night through the weekend, while an upper low shifts east-southeastward to the south of the state. This should bring an increase in trade wind showers to windward areas, while also allowing for some sea breeze driven shower development in leeward areas each afternoon. Sunday night through next Wednesday, The GFS and ECMWF are in decent agreement with the large scale synoptic features, suggesting high pressure will remain anchored northeast of the state, while troughing develops to the west of the islands. Although details remain unclear at this time, the general pattern suggests southeasterly boundary layer flow bringing above normal precipitable water values over the state during this time. The southeasterly winds will keep winds light over the smaller islands, resulting in daytime sea breezes and overnight land breezes in most areas, while light to moderate southeast winds prevails on the Big Island. Showers will favor locations near the coast that are favored in southeast flow at night and during the morning, and interior and mauka locations during the afternoon and evening. There is the potential that the pattern could turn increasingly unsettled by the middle to late part of next week, so stay tuned.
Prevailing VFR areawide will be accompanied by moderate trades through the forecast period. Land breezes will likely develop over Kauai and Oahu tonight followed by a modified sea breeze regime for Oahu on Thursday. The chance for showers over Windward Big Island will increase late tonight. No AIRMETs in effect.
High-pressure northeast of the islands will maintain moderate trade wind flow across local waters for the next few days. Winds will veer a bit this weekend as a front far northwest of the islands pushes the high eastward. This front will reach northwest offshore waters next Tuesday, with north to northeast winds expected to move in behind the front. Northwest swell forecast to arrive late Friday into Saturday will likely generate warning level surf along smaller island north and west-facing shores by Saturday. A smaller reinforcing northwest swell will move on Sunday. This reinforcing swell will either support a weekend High Surf Advisory or continue low-end High Surf Warning conditions. High surf is expected to subside Monday. No other significant swells are expected through next Wednesday.