Forecast Analysis's blog

The casts done by the 3 boats in the north channel are very interesting, and the model-data comparisons revealed that the ocean forecast is frequently better than even the DA forecast, for salinity profiles ( DA vs. ocean forecast) and flow-thru ( DA vs. ocean forecast), and temperature flow-thru (DA vs. ocean forecast). This is due to the different transport algorithms used in the two forecast; in particular, the mass-conservative upwind scheme seems to lead to better results, although the salinity values around mid-estuary (am169) continue to be under-estimated by this algorithm. The comparisons indicate that if this difficulty can be resolved, the ocean forecast will the preferred forecast everywhere (and we can cut down the total number of forecasts).

Charles has fixed the problem with cruise comparison for the 7-day estuary forecast. The CT comparison in the north channel (c/o Barnes) reveals that while the bottom salinity is better than the ocean forecast, the surface salinity is consistently under-estimated thru'out the tidal cycle.

The plume has been subject to upwelling wind for a couple of days now and is tending southwest with a residual plume (from 2-day ocean forecast) west of Gray's Harbor.

The plume is starting to detach from the coast acccording to the 2-day ocean forecast and at the end of Aug. 25, the northern tip is west of the Gray's Harbor, and the most offshore extent of the plume is just north of Cape Meares line.

Inside the estuary, the 2-day ocean forecast is under-estimating the salinity in the north channel thourghout the tidal cycle, according to CT casts from Barnes.

The plume predicted by the 2-day ocean forecast continues to shift southwest. Inside the estuary, the neap-tide condition seems to more clearly expose the shortcoming of the forecasts: in particular, the under-estimation of ocean water intrusion, which can be seen in both salinity and temperature (as predicted by the 2-day ocean forecast).

The wind is changing to upwelling favorable, and the plume predicted by the 2-day ocean forecast is starting to detach from the coast and tend towards southwest. The comparison with Wecoma data largely confirmed this trend.

The tides are in the neap cycle now, and the 2-day ocean forecast in particular is under-esrtimating near-bottom salinity in the estuary .

The wind observed at CR buoy and predicted by NAM model has shifted from downwelling to upwelling. The comparison is not very encouraging: both components of the wind has errors; but at least the trend is picked up by NAM model.

The cruise data from Barnes and Forerunner is streaming in.
The comparison is not bad, e.g. on Aug. 20 from 2-day ocean forecast. The surface salinity and temperature are reasonably predicted by the 2-day ocean forecast.

The downwelling wind is gaining strength at the beginning of today but will relax and reverse to upwelling wind at the end of today, if the weather forecast is right:

Surface salinity and wind from 2-day ocean forecast

Cruise data from Wecoma indicates that the modelled plume salinity is generally too high. This may be due to a combination of factors: wrong wind for the last couple of days, model errors, and/or incorrect discharge information.

Inside the estuary, the salinity is generally under-estimated by the ocean forecast, e.g.

The 2-day ocean forecast (and short-range weather forecast) indicate that the plume at the end of today is still going north due to the downwelling wind , albeit relaxed as compared to a couple of days ago. As we said in yesterday's blog, the 7-day ocean forecast suggests that the plume should have started going south today.

The Barnes seems to be around am169 right now (2pm Monday).

The downwelling wind yesterday and today has pushed the plume passed GH, approximately 2 days earlier than the 7-day ocean forecast; the outer edge of the plume reached GH line early Sunday according to the 2-day ocean forecast:

surface salinity plume from 2-day ocean forecast
surface salinity plume from 7-day ocean forecast

The ocean forecast continues to show the plume turning northward today, with the outer edge of the plume passing the mouth of Grays Harbor by tonight.

Monday, the extended forecast predicts that the plume will reach WB-5 strongly, and WB-9 and GH-5 weakly.