Northeast Pacific Marine Heatwaves

Was the record-breaking 2013–2015 Northeast Pacific marine heatwave (MHW) event exceptional or merely the most pronounced of a group of similar events, and was its intensity and multiyear duration driven by internal extratropical processes or by the tropics? By analyzing the historical MHWs within the ERSST.v3 data set over the 1950–2019 period, we find that Northeast Pacific MHWs occurred over a continuum of intensities and durations, suggesting that these events are a recurrent Pacific phenomenon. These statistics and corresponding composite evolution are dynamically reproduced by a large ensemble simulation of a Pacific Linear Inverse Model, thereby providing a greater range of MHW expressions than the short observational record alone. Consistent with the 2013–2015 event's evolution, we find that overall the tropics influence MHWs primarily by increasing their duration, while MHW intensity is related to the initial extratropical anomalies.

Inner-shelf Real-time Forecast at Pt. Sal

An experimental forecasting system for the inner shelf circulations around Pt. Sal, California, was implemented using a multi-scale nesting configuration of the Regional Ocean Modeling System (ROMS). The system was operational from 09/2017 - 11/2017 to assist the observational campaigns of the Office of Naval Research Inner Shelf Dynamics DRI field experiment. Forecast of ocean conditions were conducted daily through the downscaling of several nested grids (3km → 1km → 600m → 200m), each forced with the COAMPS 2-days atmospheric forecasts at hourly resolution. By comparing the field observations to the model forecasts, we present an assessment of the forecast on the 200-meter scale. We generated ensemble simulations with different configurations of initial, boundary and surface forcing conditions. Using this ensemble, we quantify the sources of predictability (e.g. deterministic vs. internal variability): the initial conditions carry little skill beyond 2 days; the surface and boundary conditions dominate afterwards.