Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 730 AM EST Sat Feb 25 2017 Valid 00Z Sun Feb 26 2017 - 00Z Sun Mar 05 2017 The current setup across the central Pacific continues to support a blocking regime with a stagnant upper ridge anchoring the region just south of the Aleutians. To its south, a pair of closed lows will slide away from one another which helps establish mid-level southwesterly flow across the Hawai`ian island chain. Models depict a shortwave evolving west of the state with the feature slowly migrating eastward with the trough passing overhead by the middle of next week. After this exits the region, a rather robust closed low tracks east of the International Dateline with model differences in the amplitude of this system. This includes some spread among the ensemble means as well. Fortunately, most of the action should remain far enough north and west to not significantly influence the islands. For the first few days of the period, east-northeasterly trade winds should be the norm with the intensity picking up by the early part of next week. This is in response a large surface anticyclone settling over the east-central Pacific. The larger change in the weather will be an increase in the threat for moderate to locally heavy rainfall as a surface wave passes across Hawai`i. Low-level winds are forecast to shift to the more south-southwesterly direction which will usher in rather high precipitable water to the southern most islands. The guidance are in agreement in the potential for heavy rainfall over the Big Island during the Tuesday/Wednesday timeframe. After this system departs, the wind should generally maintain a southerly component in response to warm advection ahead of the next band of mid-level height falls. However, the pattern should generally remain dry as noted in much of the guidance. Rubin-Oster