Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 711 AM EST Tue Feb 13 2018 Valid 00Z Wed Feb 14 2018 - 00Z Wed Feb 21 2018 Today's guidance continues to suggest that mean troughing aloft will support a lengthy period of unsettled weather, along with a persistent north-south trough axis at the surface preventing any semblance of trade flow. Within the overall mean trough aloft the first feature of interest will be a deep upper low northwest of the state. Guidance consensus shows this upper low tracking southeast to position north of Kauai by Thursday followed by a rapid turn to the north in response to upstream flow. Exact details vary by model but in principle there is decent agreement that this evolution will likely generate enhanced focus of deep moisture with an axis of heavy rainfall potential drifting from west to east across the islands during Wednesday to Thursday night. With the northward departure of the upper low, the axis of greatest deep moisture may stall near the Big Island into the late week/weekend time frame. Thus the Big Island may continue to see some rainfall while western islands see a period of relatively drier weather. Then over the weekend upstream energy reloading the mean upper trough may pull some moisture back to the west leading to another period of enhanced rainfall potential. There is somewhat more spread for the precise evolution during this part of the forecast versus the prior episode though. By next Monday most guidance indicates that the trough energy will close off another upper low near the islands. The 00z CMC track ends up south of most other solutions while the 00z/06z GFS are deeper than other models/means. Looking at the ensembles, as might be expected 00z GEFS members offer more support for the GFS depth (on a percentage basis) than do ECMWF members. This feature will likely keep the area fairly unstable but at least push the axis of high precipitable water values farther to the east away from the state. Rausch