July 22 Wed WRF and ROMS forecast summary

The low-pressure system dominating the weather pattern has moved little in the last 24 hours, but has filled a bit and is forecast to move slowly to the NE and weaken. This should allow pressure gradients across the PWS region to weaken and the strong east-to-southeast winds to decrease. While PWS-WRF model forecast wind speeds have been very accurate, the wind direction forecast has shown a larger southerly component to the winds than observed. Associated with the continued strong east to southeast surface winds, twenty-four hour mean ROMS forecast surface currents (HF radar observations are not available) show a strong inflow into the PWS through both the Hinchinbrook Entrance and Montague Strait. This inflow is forecast to weaken somewhat during the second 24 hours of the forecast. As a consequence of this inflow it appears that some higher salinity waters from outside are being advected into the Sound, primarily through the Montague Strait. A comparison of one of the SVP 10m drifter tracks with a cluster of ROMS simulated trajectories shows good qualitative agreeement. The drifter, released in the central Sound, undergoes a small excursion to the southwest, followed by steady movement to the northwest. Most of the simulated drifters in the cluster show the same movement, though a bit slower than the observed.

More detailed report with figures can be found at the JPL OurOcean/PWS portal, http://ourocean.jpl.nasa.gov/PWS.

-Yi (from Johannesburg airport)