Current Weather Status
Issued: 10/9/2021, 04:08 AM HST
A very windy trade wind pattern will hold in place during the next couple days, as strong high pressure builds north of the islands. Clouds and showers will favor windward and mauka areas with the strong trades sending brief passing showers over to leeward areas more regularly. A wet trade wind pattern will develop late Monday and continue through early Wednesday as a disturbance aloft combines with a plume of deep moisture moving in from the east. A drier and more typical trade wind pattern is forecast to return Wednesday afternoon through late next week.
Currently at the surface, a 1032 mb high is centered around 1250 miles north-northeast of Honolulu, while a trough of low pressure is located around 900 miles east-southeast of Hilo. These features are producing a very tight pressure gradient and windy conditions across the island chain early this morning. Infrared satellite imagery shows partly to mostly cloudy conditions across the state, with cloud cover most prevalent in windward areas. Radar imagery shows numerous showers moving into windward areas, with quite a few showers spilling over into leeward communities as well. Main short term concerns revolve around rain chances and trade wind trends during the next couple days.
A series of reinforcing highs building to the north of the islands will keep strong trade winds in place through most of the forecast period. The trades will remain very strong through the weekend, and the Wind Advisory has been extended through 6 PM Sunday. The gradient will ease ever so slightly early next week, but breezy to locally windy conditions will likely continue Monday through Wednesday. The trades should drop a notch lower by late next week, with moderate to locally breezy conditions expected Thursday and Friday.
As for the remaining weather details, we should see fairly showery conditions to start the morning, as a band of higher moisture with precipitable water (PW) values of 1.3 to 1.6 inches moves through the islands. Most of the showers will focus over windward and mauka areas, but the strong trades will allow these showers to reach leeward communities as well. After a showery start to the day, a more typical trade wind shower regime should take hold this afternoon and continue through Monday. Showers will continue to favor windward slopes and coasts, although the strong trades will also deliver passing showers to leeward areas at times. Moisture will remain deeper over the eastern islands during this time, and this should result in higher shower coverage over windward sections of Maui and the Big Island.
A plume of deeper tropical moisture should begin to slide into the eastern islands late Monday, then overspread the remainder of the island chain Monday night through Tuesday night, before exiting to the west Wednesday morning. PW values climb into the 1.5 to 2.0 inch range, with low level inversions getting eliminated as mid and upper level troughing to the southwest of an upper level low moves over the islands. This should result in wet trade wind weather across the islands, with some downpours likely, particularly over windward slopes and coasts. The strong trades will continue to carry showers into leeward communities more regularly as well. A more typical trade wind regime is then forecast to return Wednesday afternoon and continue through late next week.
