Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 713 AM EST Fri Feb 08 2019 Valid 00Z Sat Feb 09 2019 - 00Z Sat Feb 16 2019 ...Unusually deep and southward low pressure brings a threat of strong/damaging winds, high waves and precipitation to the state Sunday into next week... An initial upper shortwave crossing the region is now supporting an area of low pressure to the north-northeast of the main islands. A trailing cold front passing through the state is ushering in brisk northerly winds and drier air, with an axis of lowest precipitable water values (1-2 standard deviations below climatology) passing through from northwest to southeast on Saturday. Models/ensembles still show a dramatic amplification of central Pacific energy leading to a closed low forming just north of 30N latitude by Saturday that digs southward to around 25N by Monday. At the low's most extreme combination of depth and southward extent, latest GFS/ECMWF runs and their ensemble means suggest that 500mb/850mb heights could reach as low as 4-6 standard deviations below normal. In response to this upper low there is good consensus the surface low north of the state will deepen and loop back to the south, possibly getting as close to the islands as 24N Sunday/Monday. The upper low will be slow to open up next week in a pattern within a persistent upper trough that gradually weakens. Expect surface low pressure to persist just north of the state through midweek that may sag into the state later week, maintaining some forms of unsettled weather. Confidence in the specific scenario surface/aloft (along with associated sensible weather effects) decreases into Wednesday-Friday. Despite smaller scale differences that increase over time, the 00 UTC GFS/ECMWF and GEFS/ECMWF ensemble means forecasts are well clustered in this threatening pattern with above normal predictability. In constrast, the 06 UTC GFS seems an outlier solution with more questionable northern stream phasing next week. There is a threat for strong northerly/northwesterly winds and high waves on the western side of this system, with multiple periods of heavier rains embedded within the flow starting Sunday and lingering well into next week. There is also enough cold air aloft in this pattern to also support wintry weather at the higher summits. The Honolulu WFO has already issued a Special Weather Statement (SPSHFO) to discuss all these upcoming weather threats. Schichtel