Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 353 AM EDT Mon Oct 18 2021 Valid 00Z Tue Oct 19 2021 - 00Z Tue Oct 26 2021 The surface high that has been in place north of Hawaii is breaking down some as the result of a strong storm system passing well to the north, with a weakening cold front approaching the northern Islands, and another trough following behind it for mid-week. The surface high is expected to rebuild near 30-35 degrees north for the end of the week. Aloft, a weak upper level disturbance will likely track westward to the south of the state late in the week. There is good agreement among the ECENS and GEFS means on the evolution of the overall weather pattern. The features noted above are not expected to have much of an impact in terms of rainfall, with mainly dry conditions for leeward areas and trade wind showers for east-facing terrain. The heaviest rainfall should remain well south of the Islands. Some abatement in the trades is likely by Tuesday/Wednesday as the col develops and the pressure gradient weakens, and then increase again by next Friday/Saturday as the surface high becomes more firmly established. Hamrick