Slight instability this weekend may lead to increased showers

HONOLULU (KHON2) – Trades will then acquire a decreasingly stable character as the aforementioned upper low opens up and shears east along the northern periphery of the subtropical jet.

The inversion is modeled to weaken and lift by a few thousand feet which will increase the depth of trade wind showers as they advance across the area.

This will facilitate slightly greater rain rates and increase leeward penetration of showers.

Waves of forcing rotating around the low will be responsible for periodically increasing shower coverage Saturday night through early next week.

During this time, the cold pool aloft will move directly overhead and is modeled to moderate to around -11C at 500mb.

Lapse rates will still be adequate for pockets of deep convection to develop Sunday night through Monday night, mainly during the overnight periods.

Isolated thunderstorms cannot be ruled out during this period, but confidence at this stage is too low to warrant explicit inclusion in the forecast.

Meanwhile, a separate thunderstorm threat may manifest over the Big Island where a plume of steep lapse rates on the order of 7C/km is modeled to extend northeastward over the eastern end of the state.

This will contribute to an increased probability of pockets of heavy showers and/or isolated thunderstorms Sunday and Monday afternoon, particularly as the upper jet provides maximum venting aloft on Sunday followed by the upper wave itself pivoting through on Monday.

Confidence at this stage once again falls short of inclusion in the forecast but will be given consideration in future forecast cycles.