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Issued: Feb 13, 2013 8:05 PM HST
Synopsis
High pressure to our north will strengthen over the next several days. Trades will start to increase Friday and continue strengthening Saturday. Strong trades will persist Sunday through Tuesday. The weather should stay fairly dry for the next couple of days. An upper level trough developing near the islands this weekend will produce a small increase in showers.
Discussion
The forecast is looking solid to get the night shift started. Not expecting any significant changes to the ongoing forecast reasoning from prior shifts. Strengthening high pressure over latitudes N of Hawaii signals increasing trades locally over the next several days. A developing trough aloft will produce less stable conditions and better vertical development of any showers, however moisture will remain limited. Expect short lived yet isolated downpours at times along windward zones. A brief increase in coverage is possible Fri night-sat afternoon as an axis of higher PW crosses the area.
Next week enpac high pressure will become even stronger resulting in sustained fresh-strong trades locally. Wind advisories and perhaps warnings for some of notoriously windy areas are possible Sun through mid week.
Previous discussion
/issued 345 pm HST Wed afternoon/ moderate trades will continue through the next 24 to 36 hours under the influence of a 1038 mb high pressure system roughly 1800 miles northeast of the islands. Friday into Saturday the high will move closer to the islands and strengthen. This combination will tighten up the gradient over the islands and produce strong trades across the state Sunday through at least Tuesday. A few of the windier locations may require wind advisories.
Afternoon soundings show a healthy subsidence inversion at 5000 ft over Lihue and 6000 ft over Hilo. The inversion, in addition to a relatively dry airmass, kept showers to a bare minimum today. Do not anticipate much change through tomorrow and have decreased the amount of showers statewide accordingly.
The airmass over the islands is forecast to become much less stable as mid-level troughing develops near the islands over the weekend. This destabilization is countered by the fact that moisture levels are expected to remain quite low during the same time period. There may be a modest increase in trade wind showers, and what showers do occur will likely be fast-moving and heavier. The increasing showers will not be limited to windward/mauka areas. The strong trades will ensure leeward areas get their fair share.
Weather radar data from the Molokai WSR-88D will be unavailable through February 23 2013. The radar is undergoing both a software and hardware upgrade featuring dual-polarization technology. The Molokai radar is the last of the four weather radars in Hawaii to receive this upgrade.
Aviation
Vfr will be the rule for terminals through the period. Only brief MVFR cigs are possible along windward sections. Airmet tango is in effect for llvl lee turb and will likely be sticking around for quite some time as trades will only be getting stronger.
Marine
Small craft advisories are posted for the typically windy coastal zones of maui/hawaii counties through tomorrow. As trades continue to increase this will be expanded likely covering all waters this weekend with gales likely in the windiest channels. Little change is expected into next week as trades increase further.
Surf for N and W facing beaches will stay modest tomorrow but likely reach advisory levels again Fri pushing 15-20 ft. A larger swell will probably exceed 20 ft again by Sun at high-end advisory levels. Trade swell along windward reefs/beaches will build steadily into the weekend with advisories for exposed windward shores possible by Sun, and definitely Mon.
Watches/Warnings/Advisories
Small craft advisory until 6 pm HST Thursday for the Pailolo and Alenuihaha channels, Maalaea Bay and waters south of the Big Island.
PUBLIC/MARINE/AVIATION...DEJESUS
SYNOPSIS...TANABE
PREVIOUS...TANABE/BURKE